ML20236S989
| ML20236S989 | |
| Person / Time | |
|---|---|
| Issue date: | 06/30/1998 |
| From: | Doug Broaddus, Camper L, John Pelchat, Deborah Piskura NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | |
| References | |
| NUREG-1631, NUDOCS 9807270358 | |
| Download: ML20236S989 (250) | |
Text
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l NUREG-1631
- Source Disconnects Resulting From Radiography Drive Cable Failures Final Report Manuscript Completed
- May 1998 Date Published: June 1998 Prepared by L.W. Camper, D. A. Broaddus, J.M. Pelchat, D.A. Piskura Division of Industrial and Medical Nuclear Safety Office of Nuclear Material Safety and Safeguards U.S. Nuclear Regulatory Commission Washington, DC 20555-0001
ABSTRACT From November through December 1997, the NRC received three reports of drive cable failures associated with the Amersham Model 660B radiography system. All three failures occurred imiaediately behind the male connector and appeared to be -meric in nature. Although drive cable failures have occurred periodically within the indus' :ography industry,it was uncommon to experience so many apparently identical frf u , hin such a briefperiod of time. The events were reviewed by the NRC to determine if the rau .a met the criteria in NRC Management Directive 8.3, "NRC Incident Investigation Program," for initiating an inspection as either an Augmented Inspection Team (AIT) or a Incident Investigation Team (IIT). It was decided that the reported failures did not satisfy all of the criteria for initiating these categories of inspections, but the apparent generic nature of the events, the potential for serious exposure to radiographer, and the possibility that the issue went beyond NRC jurisdiction thus affecting Agreement States warranted NRC's attention. As a result, a Special Team Inspection was initiated on December 22,1997. The Team, led by a Senior Executive Service (SES) executive, included members with a broad knowledge in health physics, mechanical engineering, and industrial radiography operations. The inspection involved interaction with three Agreement States including close coordination ofinspection activities conducted within theirjurisdiction. This report describes the investigation of the initially reported drive cable failures, other failures identified during the inspection, the methodology used in the inspection, and presents the Team's findings, conclusions, and recommendations. iii NUREG - 1631
\
CONTENTS A BSTRACF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . til EX ECUTIVE S UMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 I ACKNOWLEDG MENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xv TEAM M EM BERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvil ABBREVIATIONS AND ACRONYMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xit
- 1. INTRO D U CTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 - 1
1.1 BACKGROUND
INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1 1.2 INSPECTION OBJECTIVE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 -4 1.3 METHODOLOGY AND INSPECTION SCHEDULE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4
- 2. S EQ U ENCE O F EVENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1 I 2.1 M QS EVENT NO. 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ~ . . . . . . . . . 2- 1 2.2 MQS EVENT NO. 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2 2.3 CALUMET TESTING SERVICES EVENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . 2-3 2.4 OTHER FAILURES IDENTIFIED DURING THIS INSPECTION . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4 2.4.1 GENERAL DYNAMICS, ELECTRIC BOAT CORPORATION, GROTON, CONNECTICUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4 2.4.2 GLITSCH FIELD SERVICES /NDE, INC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5 2.4.3 INDT................................................................2-6 2.4.4 MQS HOUSTON, TEXAS FIELD OFFICE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6 2.4.5 H & G INSPECTION, HOUSTON, TEXAS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7 2.4.6 GLOBAL X-RAY, MORGAN C.lTY, LOUISIANA . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7 2.4.7 LONGVIEW INSPECTION, LAPORTE, TEXAS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7 2.4.8 APPLIED STANDARDS INSPECTION, INC. (ASII), BEAUMONT, TEXAS . . . . . . . 2-8 2.5 LICENSEE AND VENDOR RESPONSE TO INCIDENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8 2.6 DOS E A SSESS MENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8 3 DESCRIPTION OF EQUIPMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1 3.1 RADIOG RAPHIC SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3- 1 3.2 CAMERA.......................................................................3-2 3.3 GUIDE TUBES /END STOP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2 3.4 CONTROLS AND PLUG S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3 3.5 DRIVE CA B LE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -. . . . . . . . . . . . . . . . . , 3-3 3.5.1 TELEFLEX 522 2 CAB.LE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3 3.5.2 MALE CONNECTOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5 3.5.3 CABLE STOP (COIL SPRING) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6 3.6 SOURCE ASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 -6 3.6.1 CABLE...............................................................3-7 L
3.6.2 FEMALE CONNECTOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7 3.6.3 LOC K B ALL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 7 3.6.4 SOURCE CAPSULE . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . 3-7 l l l l v NUREG - 1631 i l l l L______..__._ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _ _ _ _ _ _ . _ _ _ _ . _ _ . _ _ _ _ _ _ _ . _ _ _ _ _ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _ _ _ . ._ _ _ . _ _ _ _ _ _ _
CONTENTS 3.7 OTHER EQUIPMENT , ......................................................... 3-8 3.7.1 COLLIMATOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . 3 8 3.7.2 GO/NO-GO GAUG E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 8 4 EQUIPMENT PERFORMANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1 4.1 MAINTENANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2 4,1,1 LUBRICATION . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3 I 4.1.2 CLEANING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4 1 4.1.3 INSPECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 5 -j 4.2 ENVIRONMENTAL AND OPERATIONAL CONSIDERATIONS . . . . . . . . . . . . . . . . . . . . . . . . . 4-7 4.3 MANUFACTURING PROCESSES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-10 4.3.1 CABLE..............................................................4-10 4.3.2 MALE CONNECTORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 10 4.3.3 SWAGING AND ASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-11 4.3.4 QUALITY ASSURANCE AND QUALITY CONTROL . . . . . . . . . . . . . . . . . . . . . . . . 4-12 4.4 AMERSHAM FAILURE ANALYSIS REPORT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 13 4.5 POTENTIAL ROOT CAUSES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4- 18 4.5.1 INADEQUATE MAINTENANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-18 4.5.2 ABUSIVE HANDLING BY RADIOGRAPHY PERSONNEL . . . . . . . . . . . . . . . . . . 4-18 4.5.3 BRITILE FAILURE DUE T 0 FATIGUE AS A RESULT OF NORMAL LOADS ENCOUNTERED IN A RADIOGRAPHIC SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . 4-19 4.5.4 DUCTILE FAILURE AS THE RESULT OF TENSILE LOADS CREATED BY DRIVE CABLE ASSEMBLY CONTROLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-20 4.5.5 FATIGUE AS THE RESULT OF TENSILE LOADS INDUCED BY FLEXIBLE CONDUIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 20 4.5.6 CABLE DEFECTS OR WEAKNESSES AS THE RESULT OF CHANGES IN THE MANUFACTURING PROCESS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 21 4.6 HUMAN FACTORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-21 4.7 OTHER OBSERVED FAILURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 23 4.8 ' OBSERVABLE AND POTENTIAL FAILURE PRECURSORS . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 23 5 REG ULATORY AS PECTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1 5.1 APPLICABLE REGULATIONS (30.32(g),32.210,34.20,34.31 & REQUIRED LEVEL OF AGREEMENT STATE COMPATIBILITY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1 5.2 ONGOING RULEMAKING EFFORTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2 5.3 SEALED SOURCE & DEVICE REVIEW PROCESS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2 5.4 NRC LICENSING PROCESS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3 5.5 NRC INSPECTION PROCESS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4 5.6 NRC INFORMATION NOTICE PROCESS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5 5.7
SUMMARY
AND PROPOSED CHANGES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 5 6 FINDINGS AND CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1 6.1 ROOT CAUSE ANALYSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6- 1 6.2 MOST PLAUSIBLE FAILURE MODE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7 NUREG - 1631 vi
CONTENTS 6.3 OTHER FINDINGS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 13 6.4 CONCLU SIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6- 14 7 RECOMMEND ATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1 7.1 RULEMAKING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7- 1 7.1.1 PART 3 0 (3 0.32(g)) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1 7.1.2 PART 3 4 (3 4.20(c)) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1 7.2 LICEN SING GUIDANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1 7.3 INSPECTION GUIDANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-2 7.4 S S&D REVIEWS . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-3 7.5 INFORMATION NOTICE PROCESS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3 7.6 INDU STRY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-3 7.6.1 MANUFACTURERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-5 7.6.2 RADIOGRAPHY LICENSEES / RADIOGRAPHER . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-5 l 7.7 REGULATORY AGENCIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-6 i APPENDICES A Special Team Inspection Chaner . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1 B Information Notice No. 97-91 . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B 1 C Amersham Analysis Report Dated February 6,1998 . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C 1 D Amersham Metallurgical Analysis Reports . . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-1 E Commonwealth of Massachusetts Inspection Report Dated March 5.1998 . . . . . . . . . . . . . . . . . . . . . . . . . . . E-1 F Drive Cable Cleaning Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F 1 l G G lo ssary . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . G 1 H Re ference s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 ..................H-1 l FIGURES Figure 1.1 Drive Cable Failure Behind Male Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3 Figure 2.1 Partial Cable Failure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 5 Figure 3.1 General Arrangement of Radiography Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1 Figure 3.2 Internal View of Camera . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2 Figure 3.3 5222 Cable Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4 Figure 3.4 Drive Cable Connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6 Figure 3.5 Connector and Source Assembly Detail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 7 Figure 4.1 Examples of Observed Bends and Kinks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 i i Figure 4.2 Radiographer Connecting / Disconnecting Drive Cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7 vil NUREG - 1631 l
- l. - - __ _- _ _ _ _ _ _ _ . . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
i i i 1 4 l CONTENTS l Figure 4.3 Drive Cable with Bent Neck on Male Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-11 Figure 6.1 Detail of Control Crank . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-10 1 TABLES Table 1.1 Inspection Field Activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 -6 Table 4.1 Summary of Amersham Drive Cable Failures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 14 I i i 1 1 L l l l l i i l l l i I NUREG - 1631 viii !
EXECUTIVE
SUMMARY
From November through December 1997, three drive cable failure events, involving Amersham Model 660B radiography systems, were reported to the NRC. On November 16,1997, a cable failure event took place while a radiography crew, based out of the MQS Inspection, Inc., Rochester Hills, Michigan, field office was performing work at a temporary job site. The drive cable broke approximately 3.2 to 6.4 mm (1/8 to 1/4 inches) behind the male connector. The crew was working with a radiography camera containing a 3.6 TBq (98 curie) iridium-192 source. The crew notified their local Radiation Safety Officer (RSO) about the incident who responded to thejob site and recovered the source. The RSO experienced difficulty retrieving the source and received an exposure of 15.3 mSv (1530 millirem). The field office reported the incident to the NRC later that day. On November 19,1997, the Region III Office conducted a special inspection to review the circumstances of this cable failure and related exposure. During this inspection, the NRC learned of two prior instances where the drive cable had failed while in use with the Amersham 660B camera from 1995 to 1996. MQS experienced another drive cable failure (involving Amersham equipment) on December 8,1997. The drive cable broke in the same approximate location as the first cable. A radiography crew based out of the Wilmington, Delaware Field Office was performing work at a temporary job site in Pennsylvania. The crew was working with a camera containing a 2.2 TBq (60 curie) iridium-192 source. The crew notified their field office about the incident who contracted with Amersham to recover the source. Region I conducted a special inspection to review the circumstances of this cable failure and observe the source recovery operations. Region III learned of another drive cable failure on December 5,1997, experienced by Calumet Testing Services, Inc. that had occurred on November 21,1997. This drive cable broke in the same approximate location as the previous occasions. The radiography crew was using a 2.6 TBq (70 curie) iridium-192 source. The circumstances of this drive cable failure were reviewed during the Team's on-site inspection on December 22,1997. Due to these five drive cable failures, the NRC issued Information Notice 97-91, "Recent Failures of Control Cables Used on Amersham Model 660 Posilock Radiography Systems," on December 31,1997, informing all NRC radiography licensees of these incidents and reminding l them of NRC incident reporting requirements. The IN also discussed methods to identify a source disconnect situation. The NRC conducted a review ofits Nuclear Materials Event . Database (NMED) and identified as many as 15 additional cable breaks that had occurred in the , past, the majority occurring in the States of Louisiana and Texas. The NMED review also revealed that these additional cable breaks involved other radiography equipment vendors and models including the Source Production and Equipment Corporation (SPEC) Model 150 and the Industrial Nuclear Corporation (INC) Model IR-100. Due to the potential generic implications of these known drive cable failures, the NRC implemented a Special Team Inspection and initiated its investigation on December 22,1997. On January 21,1998, the Special Team Inspection Charter was formally established in coordination with Agreement States. The involved Agreement States,(the Commonwealth of ix NUREG - 1631 L_ _ _ _ _ _ _ . _ _ _ _ _ _ _ _ _ _ _ _ _ _
EXECUTIVE
SUMMARY
t Massachusetts, and the States of Louisiana and Texas) took the lead role in their respective j states. ' Appendix A is the memorandum establishing the Team and defining its charter. The Team was to gather facts and make appropriate recommendations from their conclusions. The - Team, led by an SES executive, included members with a broad knowledge in health physics, mechanical engineering, and industrial radiography operations. On January 22 and 23,1998, representatives from the Commonwealth of Massachusetts, Department of Public Health, Radiation Control Program conducted a special inspection at the Amersham QSA (Amersham), Burlington, Massachusetts, facility to investigate the reported cable failures. The Team accompanied the Commonwealth Massachusetts inspectors and participated in the inspection. This included a review of Amersham's "Retumed Materials Authorization" (RMA) reports and their manufacturing and maintenance processes. Amweham presented the Team with an example of a " failure in progress" where a cable had partially failed. This failure was initially discovered by the RSO at Electric Boat Corporation, Groton, . Connecticut. Subsequently, on February 26,1998, the Team met with this licensee to discuss the circumstances surrounding the cable failures. The licensee provided the Team a second example of a " failure in progress." This sample was provided, in tum, to Amersham for analysis. On January 30,1998, the Team met with representatives of Triumph Controls, Inc. (TCI) the manufacturer / supplier of the radiography drive cable. TCI provided the Team with information regarding the manufacture, cleaning, and maintenance of the cable. - A significant finding was that the cable was manufactured utilizing a quenching oil that TCI representatives characterized as an essential component of the cable. A member of the Commonwealth of Pennsylvania, Department of Environmental Protection observed the Team's activities during this meeting. The Team met with representatives from the State of Louisiana, Department of Environmental Quality on February 4,1998. On February 5,1998, the Team led by the State of Louisiana representatives inspected the Amersham, Baton Rouge, Louisiana, Customer Support facility. The inspection Scluded a review of the facility's RMA reports with emphasis on a previous drive cable failure that was believed to have been sent to this facility in 1996, as well as a discussion about cable maintenance practices. On February 5,1998, the Team's inspection activities were conducted at a radiography company and two after-market equipment manufacturers. On' February 6,1998, the Team met with representatives of SPEC, St. Rose, Louisiana. These inspections concentrated on the manufacture, use, and maintenance of radiography drive cables, and observations about the drive cable failures. On February 9,1998, the Team met with representatives from the State of Texas, Bureau of Radiation Control and reviewed several licensees' incident reports. On February 10 and 11, 1998, the Team, led by representatives of Texas, discussed drive cable failures with four Texas licensees who had experienced these failures. These inspections also concentrated on the use and maintenance of radiography drive cables. NUREG - 1631 x
EXECUTIVE
SUMMARY
All drive cable failure incidents investigated by the Team, required a source recovery, and it appears that licensees followed their operating and emergency procedures. The majority of the radiation exposures received by the individuals who performed the source recoveries was I minimal (typically 0-150 millirem). One individual received an exposure of 15.3 mSv (1530 millirem). No occupational worker received a radiction dose above the NRC annual occupational limit of 50 mSv (5 rem) Total effective dose equivalent (TEDE), previously referred to as whole body dose. A significant portion of this inspection focused on examining the drive cable (Model 5222) manufactured by TCI. The 5222 carbon steel drive cable is an off-the-shelf component used by all radiography equipment manufacturers and has been provided to the radiography industry since the early 1960s. TCI primarily manufactures controls for the aerospace industry which contain the cable within enclosed casing or transport tubes for use in airplanes or helicopters. TCI found no similar failures reported in the aerospace industry. The cause of the drive cable failures was investigated by Amersham and their contractor Analytical Associates, Inc., who performed metallurgical analysis on the failed cables. Amersham concluded these drive cable failures were due to a combination of wear, corrosion, and lack oflubrication, all indications ofimproper maintenance. Amersham further concluded that these failures were not a result of a design or manufacturing defect and thus not Part 21 reportable events but were attributed to corrosion and fatigue. The Team identified several significant concerns regarding drive cable maintenance practices and identified several root causes, secondary causes, and contributing factors. In addition, the Team has made recommendations to the cable manufacturer, the radiography equipment manufacturers, radiography licensees, the radiography industry, and to regulatory agencies that license industrial radiography. In summary, the Team concluded the following root causes for the radiography drive cables failures:
- The cable is not designed for use in industrial radiography.
It is designed for use in the aerospace, marine, and other industries as a component in cable control systems. These systems are vecifically designed for their intended operating environment and use conditions, which are markedly different than the those of the industrial radiography industry.
. The importance of radiography drive cabies is not sufficiently emphasized.
Manufacturers, the radiography industry and regulatory agencies have not adequately emphasized the importance of observing and evaluating the condition of radiography drive cables. As a result, opportunities to detect precursor events may have been missed due to incomplete or ineffective visual examinations and/or maintenance. xi NUREG - 1631
i EXECUTIVE
SUMMARY
l t l The Team also found the following secondary causes for drive cable failures:
- Industrial drive cable assemblies are subjected to harsh operational conditions that include the following:
- Impact loads
- Excessive and frequent bending loads
- Poor transportation and storage practices
- Drops and externalimpacts.
. Field industrial radiography is conducted in a wide variety of settings many of which expose radiography personnel and their equipment to extreme environmental conditions. Conditions for field radiography may involve exposure to the following:
- A wide range of temperatures ranging from arctic to desert
- High humidity .
- Salt water
- Corrosive chemicals !
- Dirt, dust, and sand.
As a result ofindustrial radiography operations performed under these conditions, radiography , personnel are frequently sequired to clean the drive cable assembly to remove various ; contaminants and keep the controls operational.
- Based on statements by the cable manufacturer, many cleaning processes commonly used in the j radiography industry have the potential to remove the quenching oil from the cable, allowing accelerated corrosion and wear to cause a loss in flexibility, eventually leading to fatigue and i possible failure of the cable, j Drive cables may require periodic lubrication after cleaning as a result of exposure to harsh I environmental conditions. Similarly, inappropriate re-lubrication also has the potential to significantly impact the cable's integral lubricant, thus reducing flexibility, accelerating corrosion, and increasing wear.
In addition, the team identified the following contributing factors as having a role in the ! radiography cable failures listed below: I
- Some radiography licensees continue to use drive cables in poor condition.
i i NUREG J1631 xii i
EXECUTIVE
SUMMARY
. Both the radiography industry and the regulatory community need an increased awareness of the importance of the cable's quenching oil on the flexibility, corrosion resistance, and the wearability of the cable. The industry and regulatory community also did not understand the
- potential detrimental impacts of various cleaning and lubricating materials on this quenching oil nor the susceptibility of the cable to various environmental conditions.
- Radiographer frequently failed to completely retract the drive cable and failed to use protective coverings thus exposing the drive cable to dirt and grit, physical damage, and corrosive attack from various sources, including chemicals typically found in mobile radiographic darkrooms.
The indastry and the regulatory community apparently do not understand that maintenance of associated equipment is as critical as maintenance of radiography cameras themselves. Radiographer and other personnel maintaining radiographic eqmpment need to understand the importance of proper cable care and inspection. Although the Team concluded that the 5222 cable was not designed for use in the industrial radiography industry, they did not recommend discontinuance ofits use. However, if used for this purpose, it will require greater emphasis on monitoring its condition and properly maintaining it for safe use. Drive cable failures are an important issue that warrants timely attention by the radiography industry and regulatory agencies. The actual number of drive cable failures is unknown since all of them may not have been reported, nor is the total number of cycles that drive cables experience known. Therefore, the frequency of such failures cannot be accurately determined. Because this type of failure has the potential for significant exposure of radiography personnel and members of the public, the Team developed several recommendations that address maintenance. xiii NUREG - 1631
ACKNOWLEDGMENTS The Team wishes to thank the Commonwealth of Massachusetts, the Commonwealth of Pennsylvania, the State of Louisiana, and the State of Texas for their support and participation in this inspection. The Team wishes to thank the following individuals for providing technical and production assistance: Mary Lou Roe, Regulatory Products Development Center Coordinator, NMSS Gina Thompson, Document Coordinator, Computer Sciences Corporation Steve Schawaroch, Groupware Administrator, Computer Sciences Corporation Judy Boykin, Graphic Artist, Computer Sciences Corporation In addition the Team would also like to thank the following individuals for their invaluable technical assistance and insight: Inna Lazarev & Hank Limper, Houghton International Michelle Burgess, Mechanical Engineer, NMSS Dennis Serig, Human Factors Specialist, NMSS l L j xy NUREG - 1631
TEAM MEMBERS The inspection was conducted in several Agreement States and within NRCjurisdiction. The involved Agreement States assumed the lead role for that aspect of the inspection conducted within theirjurisdictions. As part of this process, the Agreement States identified, arranged, and coordinated all inspection activities. Agreement State participants also contributed to the preparation of this report. Members of the NRC Special Inspection Team for the radiography drive cable failures included: Larry W. Camper, Team Leader, USNRC, HQ Douglas A.Broaddus, USNRC, HQ John M. Pelchat, USNRC, RII Deborah A.Piskura, USNRC, RIII The Commonwealth ofMassachusetts, Department ofPublic Health, Radiation Control Program Robert M. Hallisey, Director Salifu Dakubu, Ph.D. Richard B. Fairfull Agostino J. Savastano The Commonwealth ofPennsylvania, Department ofEnvironmental Protection Michael Cosgrove The State ofLouisiana, Department ofEnvironmental Quality William H. Spell, Administrator Thomas H. Patterson, Assistant Administrator Joseph Nobel Michael Fontenot xvii NUREG - 1631
TEAM MEMBERS Richard Penrod Michael Henry The State of Texas, Department ofHealth, Radiation Control Program Arthur C. Tate, Division Director. Brad Caskey David Smith i l l l l l I l l L
)
I NUREG - 1631 xviii
ABBREVIATIONS AND ACRONYMS ALARA As Low As Reasonably Achievable ANSI American Nr.tional Standards Institute C Coulonbc CFR Code of Federal Regulations ID Inner Diameter IN Information Notice INC Industrial Nuclear Corporation IP Inspection Procedure ISO International Organization for Standardization Ibf pounds force MC Manual Chapter N Newtons NDT Non-Destructive Testing NMSS Nuclear Materials Safety and Safeguards (Office of) NRC United States Nuclear Regulatory Commission OD Outer Diameter OEM Original Equipment Manufacturer OSP Office of State Programs Pa Pascal PSI Pounds per Square Inch QA Quality Assurance QC Quality Control RMA Returned Materials Authorization RSO Radiation Safety Officer S/N Serial Number SPEC Source Production and Equipment Corporation TCI Triumph Controls, Inc. TEDE Total Effective Dose Equivalent xix NUREG - 1631
l 1 INTRODUCTION BACKGROUND INFORMATION 1.1. On November 16,1997, MQS Inspection, Inc., reported that a radiography source disconnect incident occurred while a radiography crew was performing work at a temporary job site in
- Lima, Ohio. The drive cable broke approximately 3.2 mm (one-eighth inch) behind the swage of the male connector, leaving the source pigtail, with the male connector attached, inside the collimator. The radiography crew was performing industrial radiography using an Sentinel / Amersham Model 660B exposure device containing a nominal 3.6 TBq (98 curies) iridium-192 source. After completion of an exposure, the radiography crew attempted to retract the source but observed that the survey meter reading did not decrease as expected. The radiographer also noticed that the color indicator on the automatic locking mechanism did not change. The radiographer again attempted but was unsuccessful in returning the source assembly into the fully shielded and secured position within the camera. The radiography crew then implemented their emergency procedures, maintained surveillance of the restricted area and contacted their field office Radiation Safety Officer (RSO) for assistance.
The RSO responded to the job site to perform the source recovery. However, he experienced difficulty recovering the source because he dropped the pigtail and it rolled unseen into a seam between two concrete slabs. The RSO searched the area for approximately 2 to 3 minutes at a distance of approximately 1.5 to 1.8 m (5 to 6 feet) from the source. During this time his alarming ratemeter continuously sounded and he noted that his pocket dosimeter was off-scale (greater than 51,600 nC/kg (200 mR)). The RSO located the source after approximately 6 minutes and placed it in a shielded shipping container. The RSO's film badge was sent for emergency processing and the vendor reported a TEDE of 15.3 mSv (1,530 mrem). The pocket dosimeter readings for the radiographer and the assistant , were 9,030 nC/kg and 2,580 nC/kg (35 mR and 10 mR) exposure respectively. l On December 5,1997, Calumet Testing Services, Inc. reported an incident involving a radiography source disconnect that occurred on November 21,1997. The drive cable broke approximately 3.2 mm (one eighth inch) behind the swage of the male connector, leaving the source pigtail, with the male connector attached. The incident occurred while a radiography crew was performing ind istrial radiography using an Amersham Model 660B exposure device , with a nominal 2.6 TBq (70 curies) iridium-192 source. Following an exposure, the radiographer { noticed less resistance while he attempted to retract the source into the camera. The radiographer l cranked the source back and forth several times in an effort to retum the source to the safe ) shielded position inside the camera. He observed that the survey meter readings at the crank did j not decrease as expected and concluded that the source was stuck inside the collimator, thus j l remaining exposed in the unsecured position. The radiography crew implemented their j emergency procedures, maintained surveillance of the restricted area, and contacted their RSO for assistance. I l1 NUREG - 1631 i
IN1RODUCT10N The RSO and the former RSO, who was qualified to perform source recovery operations, responded to thejob site and successfully recovered the source. The radiation exposures received form this incident were minimal. The individual who performed the source recovery received an approximate TEDE of 0.25 mSv (25 mem) and the radiographer assisting in the source recovery operations received an approximate TEDE of 0.10 mSv (10 mrem). Subsequently, on December 8,1997, MQS Inspection, Inc. experienced another radiography source disconnect event occurring at a temporaryjob site in Trainer, Pennsylvania. Similar to the November 161997 (Rochester Hills, Michigan, field office) drive cable failure event, this drive cable also broke approximately 3.2 mm (one-eighth inch) behind the swage of the male t ccmector, leaving the source pigtail, with the male connector attached, inside the collimator. The licensee described the appearance of the failed end of the drive cable as being sheared off with a few strands of the frayed cables sticking out. The incident occurred while the field office assistant RSO was performing an audit of a radiographer. The radiographer was using an Amersham Model 660B exposure device containing a nominal 12.2 TBq (60 curies) iridium-192 source. The radiographer did not experience any difficulty exposing the source. However, he noticed difficulty when he retracted the source into the camera. The radiographer cranked the source back and forth several times until it returned to the safe shielded position inside the camera. This exposure concluded his work for the day and the assistant RSO, a qualified radiographer, resumed operations. The assistant RSO experienced difficulty cranking out the source. At the conclusion of the exposure, he attempted to retract the source into the camera. He observed that the color indicator on the locking mechanism did not change and the survey meter readings did not decrease, as expected. The assistant RSO concluded that the source remained in the unshielded position, informed his management at the Wilmington, Delaware, field office of the situation, and maintained surveillance of the restricted area. The field office management retained the services of the device manufacturer who was authorized to perform source recovery operations. Representatives from the equipment manufacturer responded to the job site and successfully recovered the source. The manufacturer brought their failed drive cable and the male connector to its facility for evaluation. The radiation exposure received as a result of this incident was minimal. The radiography personnel involved in the recovery operations received TEDEs ranging from 0.05 mSv (5 mrem) to 0.20 mSv (20 mrem). The NRC Region I Office learned of this incident upon receipt of a reciprocity request from the device manufacturer to perform a source retrieval operation. This prompted NRC Region I to perform a special inspection on December 8,1997, to review the source disconnect incident and observe the source recovery. NUREG - 1631 12
INTRODUCTION porengy y73 . ;;7 4 m $ ta.- cw c .. #, ' 1.&
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h:I'&' 'N ' ' ' ' FigG6 tynp Figure 1.1 Drive Cable Failure Behind Male Connector During this inspection, through discussions with radiography equipment manufacturers and licensees, the Team learned of other drive cable failures which have occurred recently. Some of these failures were viewed by the Team as information only, due to their age or scarcity of details, but some of them became the primary focus of the inspection effort. In addition, the Team leamed of drive cable failures "in progress" which had been discovered by licensees. As a result, the primary population of drive cable failures examined during this inspection includes the three original failures initiating this inspection, a failure occurring in Canada in August 1997, a failure discovered in 1995 by the RSO at MQS Inspection, Inc., and two failures "in progress" discovered by the RSO at General Dynamics Electric Boat Company, for a total of seven recent failures examined. A significant portion of this inspection focused on examining the drive cable manufactured by TCI, which is an off-the-shelf component used by all radiography equipment manufacturers involved in all failures examined during this inspection. TCI primarily manufactures controls for the aerospace industry which contain the 5222 cable within enclosed casing or transport tubes for use in airplanes or helicopters. The 5222 cable is a carbon steel cable which has been provided to the radiography industry since the early 1960s. TCI indicated that there have been no similar failures reported in the aerospace industry. However, the inspection Team noted that the conditions of use for the cable within the radiography industry is markedly different than that of the aerospace industry and this fact plays a major role in the identifying the root cause for the drive cable failures. Throughout this inspection, the Team observed that in general, radiography cameras examined appeared to be in good working order, showing no evidence of damage, abuse, or lack of maintenance. By contrast, control mechanisms, including drive cables, often appeared in disrepair, lacking maintenance, or damaged. This indicated failures due to lack of attention to proper inspection and maintenance of associated equipment including drive cables by the radiography industry. I 1-3 NUREG - 1631
1 INTRODUCTION The Team's report of the drive cable failures and related f'mdings is organized into the following sections and appendices:
. Section 2 presents the sequence of events for the initiating drive cable failures and subsequent failures identified during the inspection. . Section 3 describes radiography equipment including drive cables. . Section 4 discusses equipment performance including operational issues and human factors considerations. . Section 5 discusses the regulatory aspects of the overall issue of drive cable failures and summarizes proposed regulatory actions. . Section 6 presents the Team's findings and conclusions for the initial events, all other drive cable failures identified during the inspection, and issues of drive cable failures in general. . Finally, Section 7 presents the Teams recommendations to the NRC, industry, licensees and radiographer, and the Agreement States. . Appendix A is a copy of the Special Team Inspection Charter for investigating the drive cable failures; Appendix B contains Information Notice 97-91, "Recent Failures of Control Cables Used on Amersham Model 660 Posilock Radiography Systems"; Appendix C is a copy of Amersham's February 6,1998 report; Appendix D contains copies of Analytical Answers, Inc., metallurgical reports prepared for Amersham; Appendix E is a copy of the Commonwealth of Massachusetts' inspection report; Appendix F is a copy of the State of Louisiana inspection report and Appendix G presents drive cable specifications.
1.2 INSPECTION OBJECTIVE On January 21,1998, a Special Team Inspection was chartered to conduct inspection follow-up of the Amersham QSA (Amersham) radiography failures involving MQS, Calumet Testing Services, Inc., and possibly other licensees' facilities. The inspection was to also focus on other drive cable failures over the past several years and determine if a generic problem exists and to determine the root causes of the failures. The special inspection team charter and inspection schedule is described in Appendix A. 1.3 METHODOLOGY AND INSPECTION SCHEDULE In its investigation of unanticipated failures ofindustrial radiography drive cable, the members of the Team collected information from documentation, photographs, engineering drawings, measurements, metallurgical tests, and meetings and interviews, in person and by telephone. The Team collected this information to determine the sequence of events for these failures, to determine the possible radiation exposures to involved individuals, to establish the circumstances NUREG - 1631 1-4
[ l INTRODUCTION of any similar events, and to determine the root causes and secondary causes for the failures, as well as any other potential factors that may have contributed to the cable failures. ! Because various events related to these failures ~ occurred in several different states, the Team closely coordinated its inspection activities with the cognizant Agreement State authorities in the Commonwealth of Massachusetts and in the States of Louisiana and Texas. When inspection activities took place in those states, personnel from the respective radiation control offices assumed the lead for that part of the inspection. After completing its field activities, the Team assembled at NRC headquarters in Rockville, Maryland, to compile the inspection findings, conduct follow-up inspection activities, and prepare the inspection report. This report was prepared by Team with input being provided by various Agreement State representatives. In formulating its inspection methodology, the Team relied heavily on the inspection guidance and procedures described in NRC Manual Chapter 2800, " Materials Inspection Program" and Inspection Procedure 87120, " Industrial Radiography Programs." In addition, the Team reviewed and adopted appropriate guidance from Inspection Procedure 43001, " Reactive ; Inspection of Nuclear Vendors," Regulatory Guide 6.9, " Establishing Quality Assurance l Programs for the Manufacture and Distribution of Scaled Sources _and Devices Containing . Byproduct Material," and, Appendix A of Regulatory Guide 6.9," Checklist for Auditing QA l Programs." The Team primarily obtained information about the circumstances and possible causes of the l radiography drive cable failures through interviews with involved individuals, through the review ! of operational and manufacturing information and records, and through the review of metallurgical reports prepared by an independent testing laboratory contracted by Amersham. The team also collected information through the review oflicensee reports to the NRC and Agreement States as well as inspection reports prepared by NRC and Agreement State Inspectors. ] l The Team ~also gathered information by physical examination and measurement of various l radiographic equipment components, observation of the cable manufacturing and drive cable l assembly processes, observation of radiographic equipment inspection and maintenance techniques, and examination of some of the actual components that were involved in the failures documented in this report. During the inspection, the Team conducted or supervised several measurements to obtain data needed to ana!yze these failures. The Team made the following observations:
. Visually examined, measured, and photographed various radiography drive cable assemblies to determine their condition including flexibility and resilience.
- Requested and observed the pull tests of drive cable samples and swaged drive cable male connectors at various cable and equipment manufacturers.
15 NUREG - 1631 L.
INTRODUCTION
. Identified a second example of a drive cable that had experienced a partial failure in the possession of a licensee and made arrangements for the transfer to and the analysis of the sample by an independent testing laboratory contracted by Amersham to provide metallurgical analysis of cables that had experienced failures.
The following table summarizes the sequence of the Team's field activities. Table 1.1 inspection Field Activities Osymmksdom Leenden -
. OrguminationType 4 Calumet Testing Services,Inc. Calumet,IN Radiography Firm ElkGmve Village,ILi M] ,h8QS Inspections,'Inc.
8 "$-,yFinnj g, Mammachusetts Radiation Control Burlington, MA Agreement State Program Staff
'Asnesuluun,'QSAL 1. ' J' ' , Budington,TF T EquipmentManudinnemmar* - {,
. ahKT Triumph Controls,Inc. North Wales, PA Cable Manufacturer
;LauisimmaRadiadosProtsedosgff BetonRouge,LA$ f Agenoment State
, Division Staffy QJ4M%@f "; :QggMQy l., : jf y'y 7 'J 4 @M 'ij Rg f s_q .
Amersham, QSA Baton Rouge, LA Equipment Maintenance and , Repair [SobelX-Ray & Testing Comp.sQ Ausslin,LApg @ Radingsplyh fNM l Industrial Radiography Maintenance Amelia, LA Radiography Firm )
' & Supply Co.
l3EKRapeirSonyies & Supply,l lac); M LA5 M j ? Equipment h)g l Source Production and Equipment St. Rose, LA Equipment Manufacturer Company,Inc. ylisuus RussauofRadindes ;yL Austin,TX; fri Agmsensat StateCoatmlStudf; Longview Inspection,Inc. La Porte, TX Radiography Firm FW9tendsedsinspondon,ils's.Q B eesu m a ns, T>l: @ ^ Raeoguphy Pins) 'R p H & O Inspection Company Houston, TX Radiography Firm g 3supondens, Inn.] ' IF W 'TX@@.4 - RadiogeplyFinal " 4 < J Electric Boat Corporation Groton, CT Radiography Firm NUREG - 1631 1-6
INTRODUCTION f After completion ofits field activities, the team requested additional technical information be provided by the drive cable manufacturer and several radiography equipment manufacturers. The results of the Team's review of the resultant submissions are included in this report. l l l I l l I l l.7 NUREG - 1631 w_-______________-____ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ - _ _ _ - _ _ _ _ _ _ _ _ _ - _ _ _ _
, 2 SEQUENCE OF EVENTS 2.1 MQS EVENT NO.1 l l On November 16,1997, the licensee reported a radiography source disconnect incident that i occurred while a radiography crew (based out of the Rochester Hills, Michigan, field office) was performing work at a temporary job site in Lima, Ohio. The drive cable broke approximately 3.2 mm (one-eighth inch) behind the swage of the male connector, leaving the source pigtail, with the male connector attached, inside the collimator. The crew was performing industrial radiography using an Amersham Model 660B exposure device containing a nominal 3.6 TBq (98 curies) iridium-192 source. The radiography crew took eight exposures of piping without incident. After completion of the ninth exposure, the radiography crew attempted to retract the source and noticed that the survey meter readings did not decrease, as expected. The radiographer also noticed that the color indicator on the automatic locking mechanism did not change. He attempted to retract the source again, but did not succeed in returning the source assembly into the fully shielded and secured position within the camera. He noted that the survey meter readings were 10,000 nC/kg/hr (40 mR/hr) at the crank and concluded that the source was stuck inside the collimator, and remained exposed in the unsecured position. The radiography crew implemented their emergency procedures, maintained surveillance of the restricted area, and called their field office RSO for assistance. The RSO responded to thejob site to perform the source recovery. The RSO experienced difficulty recovering the source because he dropped the pigtail and it rolled unseen into a seam between two concrete slabs. The RSO searched the area for about 2 to 3 minutes at a distance of approximately 1.5 to 1.8 meters (5 to 6 feet) from the source. During this time his alarming ratemeter continuously sounded and his survey meter was reading off-scale. The RSO located the source and placed it in a shielded shipping container. The entire source recovery operation took approximately 6 minutes. Following the source recovery, he noted that his pocket dosimeter was off-scale (greater than 51,600 nC/kg (200 milliroentgen)). The RSO sent his film badge to the vendor for emergency processing on November 17,1997. The vendor reported a recorded TEDE of 15.3 mSv (1530 millirem). The pocket dosimeter readings for the radiographer and the assistant were 9000 nC/kg and 3000 nC/kg (35 mR and 10 mR), respectively and on the basis of these readings, their film badges were not sent in for emergency processing. The RSO sent an 20.3 cm (8-inch)1ength section of the failed drive cable (including the male connector) to Amersham for analysis. Amersham forwarded the broken cable assembly to a third party testing firm for metallurgical analysis. The licensee notified NRC Region III of the source disconnect, off scale dosimeter, and the reported 15.3 mSv (1530 millirem) TEDE on November 16,1997. This notification prompted a special inspection conducted by Region III on November 19,1997. Conversations with MQS, Rochester Hills, Michigan, Field Office representatives during the November 19,1997, 2-1 NUREG - 1631
SEQUENCE OF EVENTS inspection revealed that there were two prior instances where the drive cable had failed while in use with the Amersham Model 660B camera. From approximately 1995 to 1996, the licensee was conducting work at a job site and completing the last exposure for the day. The crew cranked in the source into the camera and the drive cable broke as the source was secured inside the camera. The licensee found this cable in December 1997, and sent it to the equipment manufacturer for analysis. A second drive cable failure also occurred during approximately the same time period. The cable failure was discovered during the daily equipment inspection prior to conducting radiography. The licensee described the cable as frayed with a couple ofinner core wire strands connected to the male connector. The licensee believed that this cable was sent to the Amersham Baton Rouge, Louisiana, office for evaluation. However, Amersham was unable to locate this item. Unfortunately, the whereabouts of this cable are unknown. No violations of NCR requirements were identified during this inspection. One potential generic problem regarding the drive cable failures was identified and considered as an unresolved item for follow up during this special Team inspection. 2.2 MQS EVENT NO. 2 The same licensee (operating out of the Wilmington, Delaware, field office) experienced another radiography source disconnect event on December 8,1997, occurring at a temporary job site in Trainer, Pennsylvania. Similar to the November 16,1997, (Rochester Hills, Michigan, field office) drive cable failure event, this drive cable also broke approximately 3.2 mm (one-eighth inch) behind the swage of the male connector, leaving the source pigtail, with the male connector attached, inside the collimator. The licensee described the appearance of the failed end of the drive cable as being sheared off with a few strands of the frayed cable sticking out. The event occurred while the field office assistant RSO was performing an audit of a radiographer. The radiographer was using an Amersham Model 660B exposure device containing a nominal 2.2 TBq (60 curie) iridium-192 source. The radiographer did not experience any difYiculty exposing the source. However, he noticed difficulty when he retracted the source into the camera. The radiographer cranked the source back and forth several times until the source retumed to the safe shielded position inside the camera. This exposure concluded the radiographer's work for the day. The assistant RSO, who was a qualified radiographer, resumed operations. The assistant RSO experienced difficulty cranking out the source. At the conclusion of the exposure, he attempted to retract the source into the camera. He noted that the color indicator on the locking mechanism did not change and the survey meter readings did not decrease, as expected. He concluded that the source remained in the unshielded position, informed his management at the Wilmington, Delaware, field office of the situation, and maintained surveillance of the restricted area. The field office management retained the services of the device manufacturer who was authorized to perform source recovery operations. Representatives from the equipment manufacturer responded to the job site and successfully NUREG - 1631 22
SEQUENCE OF EVENTS I l recovered the source. The manufacturer brought the failed drive cable and the male connector to its facility for evaluation. Amersham forwarded the broken cable assembly to a third party testing firm for metallurgical analysis. The radiation exposure received as a result of this incident was minimal. The radiography licensee personnel involved in the recovery operations received TEDEs ranging from 0.05 to 0.20 mSv (5 to 20 millirem). , The NRC Region I Office teamed of this incident upon receipt of a reciprocity request by the device manufacturer to perform a source retrieval operation. This prompted NRC Region I to perform a special inspection on December 8,1997, to review the source disconnect incident and observe the source recovery effons. No violations of NCR requirements were identified during this inspection. l 2.3 CALUMET TESTING SERVICES EVENT On December 5,1997, the licensee reported an incident involving a radiography source disconnect that occurred on November 21,1997. The drive cable broke approximately 3.2 to 6.4 mm (one-eighth to one-quarter inch) behind the swage of the male connector, leaving the source pigtail, with the male connector attached. The incident occurred while a radiography crew was performing work at a temporary job site (indoors) in Hammond, Indiana, using an Amersham Model 660B exposure device containing a 1 nominal 2.6 TBq (70 curies) iridium-192 source. Upon completion of the ninth exposure, one ! radiographer noticed less resistance while he attempted to retract the source into the camera. He cranked the source back and forth several times in an effort to return the source to the safe shielded position inside the camera. He noted that the survey meter readings at the crank did not decrease as expected and concluded that the source was stuck inside the collimator, and remained exposed in the unsecured position. The radiography crew implemented their emergency procedures, maintained surveillance of the restricted area, and called their RSO for assistance. The RSO and the former RSO, who was qualified to perform source recovery operations, responded to the job site and successfully recovered the source. The licensee sent the failed cable (not the male connector) to the device manufacturer for evaluation. Amersham forwarded the broken cable to a third party testing firm for metallurgical analysis. The radiation exposures received from this incident were minimal. The individual who performed the source recovery, received an approximate TEDE of 0.25 mSv (25 millirem). The radiographer who assisted in the source recovery operations receive an approximate TEDE of 0.10 mSv (10 millirem). l f 2-3 NUREG - 1631
SEQUENCE OF EVENTS I l 2.4 OTHER FAILURES IDENTIFIED DURING THIS INSPECTION During the inspections of the Amersham and SPEC facilities, the Team leamed of additional drive cable failures. Both vendors had observed drive cable failures near the male connector, as well as other locations (i.e.,13 cm (5 inches) from the male connector,6.4 meters (21 feet) from the male connector). They have also seen drive cables that showed " failure in progress." During the inspection at the Amersham, Burlington, MA facility, an example of one of these " failures in progress" was discovered and brought to the Team's attention. Both vendors presented the Team with numerous examples of frayed and failed drive cables. In addition, the Team observed examples of other connector failures such as broken necks, bent necks, and cracks. These equipment manufacturers further indicated that numerous cables were received from licensees that were corroded and lacking sufficient flexibility as determined by the manufacturer. Furthermore, the Team leamed of a drive cable failure occurrence with INC equipment. The Team subsequently discussed this event with a representative of INC who indicated that he was unaware of this incident. The next sections describe additional drive cable failures and a summary of the circumstances (if known) surrounding each cable failure event. 2.4.1 GENERAL DYNAMICS, ELECTRIC BOAT CORPORATION, GROTON, CONNECTICUT On August 4,1995, a radiography crew (comprised of four radiographer) was performing work (during the third shift) at the licensee's property using an Amersham Model 660B exposure device containing a nominal 425 GBq (11.5 curies) iridium-192 source. The radiography crew had completed several exposures without incident. The radiography crew had completed a second exposure, of three required on a pipe joint, and proceeded to retract the source into the camera. The radiographer cranked the source back and forth in an effort to return the source to the safe shielded position inside the camera. He noted that the color indicator on the automatic locking mechanism did not change or " click." He approached the exposure device with a survey meter and determined that the source remained unshielded. The radiography crew implemented their emergency procedures, maintained surveillance of the area, and contacted the RSO for assistance. The RSO responded to the site and determined that the drive cable broke approximately 6.4 meters (21 feet) behind the male connector (still attached to the pigtail). The RSO successfully recovered the source by manually pulling the broken drive cable through the camera unit the source was secured within. The licensee's engineering department examined the failed drive cable and attributed the failure to corrosion and fatigue of the materials. In addition, the RSO sent this drive cable to Amersham for evaluation. Amersham forwarded the broken cable assembly to a third party testing firm for metallurgical analysis. In response to this cable failure, the licensee conducted a physical examination of all drive cables in an effort to identify other possible failures. NUREG - 1631 2-4
SEQUENCE OF EVENTS I The radiation exposure received as a result of this incident was minimal. The radiography team members involved in the recovery operations received 0 mSv (0 millirem) TEDE and the RSO received 0.05 mSv (5 millirem) TEDE. In 1995, following this event, the RSO conducted an examination of all drive cables in their possession. During this equipment inspection, the licensee discovered two partial drive failures in progress (See Figure 2.1 for one example of these partial drive cable failures). This special equipment inspection was prompted by the licensee's investigation of a previous source hang-up incident and included all cameras and control assemblies in the licensee's possession at that time. The RSO attributed these failures in progress to improper maintenance and poor equipment inspection technique. These failures were available for examination by the Team and were extremely useful because they allowed examination of the cable break prior to complete failure. These drive cables were sent to Amersham who in turn, forwarded the cables to a third party testing firm for metallurgical analysis. i Fgo2 bmp Figure 2.1 Partial Cable Failure 2.4.2 GLITSCH FIELD SERVICES /NDE, INC. On December 7,1994, the licensee reported a radiography source disconnect incident involving an Amersham 660 Camera containing a nominal 1.9 TBq (51 curies) iridium-192 source. The incident occurred while a radiography crew was performing work at a temporary job site in Erie, Pennsylvania. The radiography crew took several exposures without incident prior to the drive cable braking approximately 13.3 cm (51/4 inches) from the swage of the male connector, leaving the source pigtail, with the male connector attached outside of the camera. Upon completion of the tenth exposure, the radiographer approached the camera, surveyed the area, and determined that the source was not secured within the camera. The radiographer implemented their emergency procedures, maintained surveillance of the area, and contacted the RSO for assistance. The RSO responded to the site and verified that the source position did not change when he attempted to retract the source. He noted that the drive cable appeared to move freely in the expose and retract positions without any change in survey meter response. This free movement indicated to the RSO that the incident involved a condition other than a pig-tail disconnect because the male connector should not retract past the safety connector assembly. l The RSO disassembled the crank assembly (at the crank), manually withdrew the drive cable l from the housing, and examined the male connector end. He determined that the drive cable I broke somewhere behind the male connector (perhaps still attached to the pigtail). He 2-5 NUREG - 1631 l
i SEQUENCE OF EVENTS reassembled the crank assembly and fully extended the cable to push the source to the end stop. The RSO successfully recovered the source. The drive cable and the male connector were sent to Amersham who in turn, forwarded the broken assembly to a third party testing firm for metallurgical analysis. The radiation exposure received es a result of this incident was minimal. The radiographer involved in the recovery operations cceived 0.55 and 0.20 mSv (55 millirem and 20 millirem) TEDE respectively and the RSO received 0.50 mSv (50 millirem) TEDE as a result of this incident. 2.4.3 INDT Amersham informed the Team of a drive cable failure incident that occurred in Canada involving a Canadian radiography firm. This drive cable failure took place in August 19,1997, and involved Amersham radiography equipment. In September 1997, the company sent a 6.4 mm (1/4 inch) portion of the drive cable (including the broken end) to Amersham for evaluation. Amersham forwarded the broken cable piece to a third party testing firm for metallurgical analysis. Unfortunately, the circumstances of this drive cable failure event are unknown to the Team. 2.4.4 MQS HOUSTON, TEXAS FIELD OFFICE The Team also leamed of a drive cable failure involving a late model radiography camera containing a nominal 1.0 TBq (26 curies) cobalt-60 source used in a fixed cell. This radiography system normally remained in-house and it was typically not used in the field. The set of controls were dedicated to the same camera and were typically laid out straight. While in house, the controls remained connected all the time, eliminating connection and disconnection as a source of stress. The drive cable broke offin the male connector and strands of the cable remained in the connector. The licensee successfully retrieved the source. The maximum exposure as a result of this source recovery was 1.5 mSv (150 millirem) TEDE. This failure appears to be similar to the drive cable failures prompting this inspection. However, details surrounding this event were dated and vague. The failure occurred November 25,1992, but the system had been in use for several years prior. The male connector used in this system was an older model compared to those in all other failures examined during this inspection. As a result of the incident, MQS removed this equipment from service and sent it to Amersham for disposal. The circumstances associated with this particular failure appear to be substantially different than other failures and as a result, was viewed by the Team as an outlier event. NUREG - 1631 2-6
l i SEQUENCE OF EVENTS 2.4.5 H & G INSPECTION, HOUSTON, TEXAS i This radiography firm had exp rienced two drive cable failures within the last 5 years. The j company also experienced failures in the male connector, specifically cracks or breaks at the base of the neck of the male connector. No further details about these failures were available. 2.4.6 GLOBAL X-RAY, MORGAN CITY, LOUISlANA This radiography firm had experienced several failures from one after-market equipment manufacturer but no drive cable failures. The company experienced failures in the male connector, specifically involving cracks or breaks at the base of the neck of the male connector. They showed the inspection Team numerous examples of male connector failures that exhibited breaks at the base of the neck, bent necks, and cracks. In some examples, the male connector was attached to a section of drive cable. The Team observed rust, loss of flexibility, and kinks in the drive cable samples. l 1 2.4.7 LONGVIEW INSPECTION, LAPORTE, TEXAS ! l The company experienced a drive cable failure event on December 9,1996. The incident occurred while a radiography crew was performing work at a temporary job site in Baytown, Texas, using an Amersham Model 660B containing a nominal 3.5 TBq (96 curies) iridium-192 source. The drive cable broke approximately 6.4 mm (one-quarter inch) behind the swage of the male connector, leaving the source pigtail, with the male connector attached inside the collimator. Upon completion of the first exposure, the radiographer noticed that as he was , retracting the source, the raotion felt too easy. He approached the camera, surveyed the area, and l determined that the source was not secured within the camera. He also noted that the color ; indicator on the automatic locking mechanism did not change. The radiographer implemented I their emergency procedures, maintained surveillance of the area, and contacted the RSO for assistance. The RSO successfully recovered the source. The drive cable and the male connector were sent to Amersham who forwarded them to a third party testing firm for metallurgical analysis. The radiation exposure received as a result of this incident was minimal. The radiographer involved in the recovery operations received 0.50 mSv and 0.20 mSv (50 millirem and 20 millirem) TEDE respectively and the RSO received 0.55 mSv (55 millirem) TEDE as a result of this incident. l Upon further investigation of the incident the RSO determined tM A radiographer did not perform the required daily equipment inspection prior to perfan. nF v. rk on the day of the cable break. The RSO attributed this failure to improper maintenwr ch ng use ofinappropriate lubricants and cleaning agents, inappropriate use and storage y and poor equipment inspection technique. l 2-7 NUREG - 16H
SEQUENCE OF EVENTS 2.4.8 APPLIED STANDARDS INSPECTION, INC. (ASil), BEAUMONT, TEXAS This radiography firm had experienced one drive cable failure that involved an INC radiography system. The incident occurred at a temporaryjob site on September 20,1993, while a radiography crew was using an INC Model IR-100 radiography camera containing a nominal 2.7 TBq (74 curies) iridium-192 source. The RSO successfully recovered the source. The radiation exposure received as a result of this incident was minimal. The radiographer involved in the recovery operations received less than 0.10 mSv (10 millirem) TEDE each and the RSO received 0 mSv (0 millirem) TEDE as a result of this incident. 2.5 LICENSEE AND VENDOR RESPONSE TO INCIDENTS The Team reviewed the operating and recovery procedures followed during response to the disconnects for the NRC licensees that experienced cable failures during the November to December 1997 time frame. It appears that the licensees followed their operating and emergency procedures, including the proper use of survey meters, minimizing personnel radiation exposure throughout the events (i.e., from source disconnect through retrieval). In addition, the individuals who performed the source recovery operations had previous training and experience in performing source retrievals, thus aiding in keeping personnel exposures to a minimum. The Team also reviewed the circumstances surrounding several other cable breaks that occurred in the past within Agreement States and found similar results. 2.6 DOSE ASSESSMENT Several individuals were exposed to unsecured radiography sources as a result of drive cable failures. In the known drive cable failures investigated by the Team, all incidents required emergency source recovery. The majority of the individuals who performed source recovery, received minimum to low exposures 0 to 1.5 mSv (0 tol50 millirem) TEDE. However, one individual received a higher TEDE,15.3 mSv (1530 millirem). No individual's TEDE exceeded the 50 mSv (5 rem) annual occupational limit. Re-enactments of the MQS November 16,1997, incident were performed during the NRC Region III inspection on November 19,1997. The RSO set up the same source recovery equipment that was used during the actual event and he demonstrated the use of safety equipment used during the source recovery. He used a survey meter and wore a whole body film badge pocket dosimeter and an alarming ratemeter during the actual source recovery and the re-enactment. The Re-enactments of the source recovery showed that it would take about 10 seconds to pick up the source and place it in the shielded container under ideal circumstances. l The licensee estimated that the individual spent 2 to 3 minutes in the restricted area looking for l NUREG - 1631 2-8
l l SEQUENCE OF EVENTS the unseen source and a total time of 6 minutes to recover the source and place it in a shielded I container. ! l According to calculations performed by the NRC, TEDE from a 3.6 TBq (98 curies) iridium-192 source, at an approximate distance of 2 meters (6 feet), for a maximum time of 6 minutes would have been approximately 14 mSv (1,400 millirem). The licensee's calculations indicated a TEDE of 14 mSv (1,416 millirem) for 6 minutes at 6 feet and the individual's film badge exposure demonstrated 15.3 mSv (1,530 millirem) TEDE. As a result, estimated and recorded exposure i closely aligned. This individual's recorded exposure from the source retrieval plus his 0.60 mSv (60 millirem) TEDE year-to-date exposure did not exceed the NRC's regulatory limits (50 mSv or 5 rem TEDE). However, the licensee considered the exposure to be higher than expected. Based on the licensee's past experience in performing source recoveries, the licensee expected the individual to receive less than 1 mSv (100 millirem) TEDE for the task. The Team calculated the individual's expected exposure based on an approximate distance of 6 feet for a maximum time of 10 seconds, resulting in an anticipated exposure of approximately 0.40 mSv (40 millirem) TEDE. Unfortunately, the individual experienced difficulty locating the source after he removed it from the collimator and spent 2 to 3 minutes looking for it. This amount of time spent in such close proximity to the source significantly contributed to the individual's exposure. l t i , 4 29 NUREG - 1631 L _ ______ _ _ _ _ _ _ _ _ _ _ _ _
l l ! 3 DESCRIPTION OF EQUIPMENT 3.1 RADIOGRAPHIC SYSTEM l Radiographic systems, for the purposes of this document, include all components necessary to perform a radiographic exposure. These include the camera (exposure device), guide tubes, end 4 stops and collimators, controls, and the source assembly (see Figure 3.1). Each component is l important to the safe use of the radiographic system and must be used properly to minimize exposures. To perform radiographic operations, the source assembly is driven out of the camera by cranking the controls which drive the cable until the source assembly reaches its fully extended position. The source assembly is left in the exposed position for the pre-determined time and then cranked back into the fully retructed position. This expose / retract operatica represents one complete cycle. The designs of radiographic systems reviewed during the inspection preclude during noni al operations creating tensile forces on the drive cable sufficient to cause a tensile overload failure of the drive cable, without other contributing factors such as fatigue or corrosion. l ( Source Gukte Tube Lock AssernNy / 1
/ -
I End Stop Crar* g cortra sn atn. l V l ortv. contre 1 am. m l- Figure 3.1 General Arrangement of Radiography Section ( 3-1 NUREG - 1631 L_____
DESCRIPTION OF EQUIPMENT 3.2 CAMERA A radiographic camera (exposure device) is a shielded storage and, in some cases, transport container that allows the controlled exposure and retraction of a source assembly (see Figures 3.1 and 3.2). When fully retracted in the camera the source capsule is shielded such that external radiation levels on the surface of the camera are less than 51,600 nC/kg/hr (200 mR/hr). Primary shielding materials include lead, depleted uranium, and tungsten. Typically, an S-tube is centrally positioned through the shielding so that, when fully retracted, the source capsule is positioned at the center of the S-tube, providing maximum shielding. Cameras also contain a locking mechanism used to secure the source assembly in the fully shielded position, and connections at either end of the S-tube used to connect guide tubes and controls.
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j>g %f [ . hh . . - pp- pf } s' lf i-'fa< qw f odlet Fittire Typical Radiography Camera , j ownse Figure 3.2 Internal View of Camera l 3.3 GUIDE TUBES /END STOP 1 Guide tubes are conduit that is attached to the front of the camera to provide a controlled path ! through which the source assembly may travel to and from the exposure position. Typical guide tube construction is flexible yet durable. One end of the guide tube contains a connector 1 matched to the outlet connector of the camera and the other end contains an end stop (exposure , head). End stops are typically constructed of metal, are crimped or swaged on the guide tube, ; I \ l l l NUREG - 1631 3-2
DESCRIPTION OF EQUIPMENT and are intended to contain the source assembly in the guide tube and prevent it from passing out I its end. j 3.4 CONTROLS AND PLUGS Controls refer to the mechanisms used to transport the source assembly from its shielded position in the camera to the exposed position at the end of the guide tube. These mechanisms include the crank, gear box, control sheath, drive cable, and connectors. The controls are used to move the source assembly by attaching the drive cable to the source assembly, attaching the control sheath i I to the camera, unlocking the source and rotating the crank which in turn drives the cable. A plug is supplied with each set of controls that is placed over the control sheath connector (outlet of the controls) when not in use. This plug provides protection from the ingress of dirt, fluids, grit and other foreign material that may damage the drive cable or prevent proper operation. The manufacturer of the drive cable recommends that the maximum inner diameter of conduit for 5222 cable should not exceed 6.35 mm (0.250 inch) to prevent flexing which could lead to fatigue of the cable. Samples of control sheaths examined during the inspection revealed inner diameters measuring approximately 5.31 mm (0.209 inch) which is consistent with the cable i manufacturer's recommendations. However, samples of guide tube examined during the inspection revealed inner diameters ranging from 9.14 to 9.65 mm (0.360 inch to 0.380 inch) which exceeds the cable manufacturer's recommendations. The larger diameter is to allow the lock ball to pass through the guide tube. The inner diameter of a typical S-tube is essentially the same as that of the guide tube and measures approximately 9.65 mm (0.380 inch). 3.5 DRIVE CABLE Drive cable is the cable that is connected to the source assembly and is used to transport the source assembly to and from the camera and the exposure position. Drive cable consists of three components: 5222 cable; a male connector; and an end stop (coil spring). 3.5.1 TELEFLEX 5222 CABLE l The 5222 cable is an off-the-shelf product supplied by TCI (formerly Teleflex, Inc.) which is used by all radiography equipment manufacturers reviewed during the inspection. TCI 5222 cable is also used by some radiography equipment manufacturers with their source assemblies. It is made from high carbon content steel wire consisting of a lx19 (1-6-12) core, an intermediate compression wrap and a two-part exterior helical winding (See Figure 3.3). The core, ( compression wrap, and outer helix are constructed from wires of differing diameters. The nominal diameter of complete 5222 cable is 4.75 mm (0.187 inch). After the cable is assembled, it is heated to 300 to 350 C (572* to 662 F) to relieve manufacturing stresses and then oil quenched. The quench oil used by TCI is Houghton Quench G which is a medium / fast quench oil containing petroleum-based anti-oxidants, employed to retard degradation of the oi! via 3-3 NUREG - 163I w__-____--
DESCRIPTION OF EQUIPMENT oxidation during the heating process. This process provides the cable with its ultimate material properties (e.g., hardness) and serves to lubricate the individual wire strands. The cable is not subjected to a tempering process following quenching. Due to the type of carbon steel used in its construction, subjecting the cable to this heating and quenching process without additional tempering could result in a cable with high ultimate strength, low ductility, and high hardness. A cable with these characteristics would be relatively susceptible to fatigue and would not be ideal for applications where cyclic loads would be expected. l 1 X19 Core 9 Helix Spacers Intermediate Convesskn Wap 1X19 Cora King Wre
^
5222 Cable Construction
.._g Figure 3.3 5222 Cable Construction TCI characterized the quenching oil as an integral component of the cable,just as important as other components of the cable. TCI also characterized the quenching oil as essential for providing cable flexibility and corrosion resistance. The absence of this oil in the inner core of the cable (i.e., through extraction by solvent based cleaners) would allow a " wicking" effect whereby liquids may be drawn into the structure and inner core of the cable. This would reduce the flexibility of the cable and allow the onset of corrosion of the wire strands. TCI indicated that without a protective coating, the carbon steel would exhibit signs of corrosion in a matter of hours. However, the manufacturer of the quench oil indicated that although Houghton Quench G quench oil will provide some level oflubrication and corrosion resistence to the cable, it is not ideally suited for these purposes.
TCI is the sole source of this cable to the radiography industry. The 5222 cable is normally sold to customers contained in a TCI manufactured control system however, TCI sells cable in raw form to the radiography industry. Radiography equipment manufacturers process the raw cable into drive cable assemblies which are used in their own or in other radiography equipment manufacturers' controls. A number of radiography equipment manufacturers have attempted to identify suitable alternative cables, including stainless steel cables. In all cases, identified NUREG - 1631 34
DESCRIPTION OF EQUIPMENT alternative cables were determined to be unsuitable for various reasons (cost, flexibility, hardness, similar susceptibility to corrosion in the intended environments). Discussions with radiography equipment manufacturers indicated that no formal procets was ever employed to l determine the cable's suitability for use in the radiography industry. These discussions further 1 l indicated that 5222 cable was selected for the following reasons:
- Its availability l
- The ability ulthe cable manufacturer to supply cable and control mechanisms as complete
! systems
- The historice.1 use of the cable and control systems in the aerospace industry
- The cables and control mechanisms could easily be suited for use in the radiography industry ;
l l The 5222 cable has been provided to the radiography industry since the early 1960s. TCI stated [ l that there have been e changes in the cable manufacturing process or in the vendors supplying materials for the cable. However, a limited review ofincoming certification data sheets for steel l wire shipments !dentified that a shipment did not meet TCI's specifications for minimum tensile strength. Specifically, TCI's current material specifications call for steel wire to have a minimum
- tensile strength of I827 MPa (265,000 psi), but the wire shipment indicated a minimum tensile l
strength of 1800 MPa (261,000 psi). Upon further investigation, TCI determined that the steel ! wire supplier had been providing wire based on an earlier version of TCI's material specifications which indicated a tensile strength range of 1724 to 2%9 MPa (250,000 to 300,000 psi). In l addition, TCI determined that changes in the acceptable tensile strength range contained in later versions of their steel wire materials specifications had not been adequately conveyed to the steel l wire supplier. i L TCI reviewed all incoming material certification records with dates after the effective date of the ! tensile strength increase, and determined that only 30 shipments of steel wire had tensile strength below I827 MPa (265,000 psi) and no shipments were less than 1724 MPa (250,000 psi). TCI l' indicated that it was their engineering judgment that shipments received w; th a tensile strength below I827 MPa (265,000 psi) do "not impair the performance of the cable and is not important to the reported failure mode. The greater concem is the obvious evidence of corrosion fatigue j that initiated and progressed to the point that the smallest diameter wires (0.014 inch and 0.013 inch) making up the inner strand experienced complete failure first before the rest of the wires in the cable separated and failed in tensile overload." i , 3.5.2 : MALE CONNECTOR A male connector is attached (typically by swaging) to one end of the drive cable and is used for connection to the female connector on the source assembly. This connector is typically constructed of stainless steel and is of the ball and shaft type (See Figure 3.4). The design of 3-5 NUREO - 1631 l l
DESCRIPTION OF EQUIPMENT I l some male connectors allow a 90 degree freedom of movement between the male and female connectors for maximum flexibility of the connection. Female connector 1'E)
@R i >
oc10 ppt Figure 3.4 Drive Cable Connectors 3.5.3 CABLE STOP (COIL SPRING) A cable stop is a coil spring that is installed between the wrappings of the helix of the drive cable, opposite the male connector end. The cable stop is intended to keep that end of the drive cable from being extended beyond the gear box by preventing the gears from engaging the helix. 3.6 SOURCE ASSEMBLY The source assembly consists of a source capsule, female connector, and lock ball attached, typically by swaging, to a cable (See Figure 3.5). Source assemblies are stored in the camera or a I source changer when not in use. I 1 NUREG - 1631 3-6
l DESCRIPTION OF EQUIPMENT Remotope sourm capeue ox* Bm
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, r, source catse Spring ta*ing Sleeve Ro8 Pin San Connector Ned Dtve Catne
*=>acg Figure 3.5 Connector and Source Assembly Detail 3.6.1 CABLE Source cables are typically constructed of 5222 cable or stainless steel aircraft cable.
3.6.2 FEMALE CONNECTOR Female connectors are typically cylindrical, constructed of stainless steel, and have a slot which is designed to accept the ball and shaft of the male connector. Modem female connectors are spring loaded to reduce the possibility of unintentional disconnection from the male connector. 3.6.3 LOCK BALL Lock balls are typically spherical and measure approximately 7.62 mm (0.3 inch) outer diameter. The purpose of the lock ball is to actuate the locking mechanism of the camera and secure the source assembly in its stored and shielded position. In addition, the lock ball prevents the source i assembly from being withdrawn out of the back of the camera. 3.6.4 SOURCE CAPSULE The source capsule consists of the radioactive material sealed in a stainless steel encapsulation. This encapsulation is designed to prevent leakage or escape of the radioactive material. 37 NUREG 163I l
DESCRIPTION OF EQUIPMENT 3.7 OTHER EQUIPMENT 3.7.1 COLLIMATOR A collimator is a small radiation shield used in radiographic operations to shape or restrict the radiation beam during exposures. Typically, the collimator is constmeted oflead, tungsten, or other shielding material and is placed over the end stop of the guide tube or connected directly to a guide tube. 3.7.2 GO/NO-GO GAUGE A "go/no go" gauge is not part of a radiography system, but is a tool supplied by Amersham for checking the critical areas of their model 550 connector. This gauge allows the radiographer a quick check of the male / female connectors and connection to determine if excessive wear or damage of the connectors has occurred. Amersham recommends the "go/no go" gauge be used as part of a radiographer's daily inspection, and that if the male / female connectors or connection fail any of the "go/no go" tests, the equipment should not be used, but should be serviced or replaced. The "go/no go" gauge checks only the connectors and does not check the condition of the cables. I NUREG - 1631 38 i
4 EQUIPMENT PERFORMANCE In general, examined radiography cameras appeared to be in good working order, showing no evidence of damage, abuse, or a lack of maintenance. However, control mechanisms, including drive cables, often appeared in disrepair, lacking maintenance or damaged. A number of cables j examined by the team demonstrated observable bends and/or kinks within 30.5 cm (12 inches) of I the male connector, many at similar locations along the length of the cable. Several cables also exhibited evidence of wear to the outer helical strand apparently the result of kinked cables being worn by various radiography system components. In addition, corrosion was observed on most drive cables examined with the greatest amount occurring over the 15.2 to 20.3 cm (6 to 8 inches) directly behind the male connector. In some cases, the corrosion continued, to a lesser extent, up to a distance of 0.91 to 1.83 meters (3 to 6 feet) behind the male connector. See Figure 4.1. t r oos e-p _ i Fgotbmp ((hj_4 d aqH h i M7:- *j l l
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, ; 1 r c emp l Figure 4.1 Examples of Observed Bends and Kinks l 1
1 4-1 NUREG - 1631 1
EQUIPMENT PERFORMANCE 4.1 MAINTENANCE Proper maintenance and inspection of radiographic equipment is crucial to its safe operation. In particular, interviews and discussions with representatives of the radiography industry indicate that proper maintenance of drive cables is essential for maintaining cable integrity and preventing cable failures, and proper inspection of drive cables is crucial for early detection of failure precursors. Proper maintenance of drive cables includes appropriate lubrication, cleaning, and periodic inspection. . Choice of cleaning and lubrication materials, or the lack thereof, may have a significant impact on the drive cable's integrity. Several maintenance and inspection practices were observed during the inspection, ranging from little to no maintenance or inspection of the drive cable, to a rigorous program by which drive cables are cleaned and lubricated monthly and thoroughly inspected during daily inspections and at maintenance intervals. Discussions with radiography indust'y personnel indicate that the radiography industry and regulatory community apparently have failed to emphasize the importance of maintenance and inspection of associated equipment, including drive cables, and there is a misperception that maintenance and inspection of associated equipment is not as crucial as maintenance and inspection of the camera. In addition, there seems to be an apparent lack of understanding of: (1) the importance of the quenching oil on the flexibility, corrosion resistance, and wearability of TCI's 5222 cable; (2) the potential detrimental impact of various cleaning and lubricating materials on the quenching oil; and (3) the limitations of 5222 cable when subjected to the harsh environmental and operating conditions of use in the radiography industry. There are currently no standard procedures or recommendations for maintenance and inspection of drive cables. Maintenance and inspection recommendations vary greatly between radiography equipment manufacturers as well as service providers of radiography drive cables. In addition, previously the cable manufacturer made no recommendation regarding suitable cleaning agents for its cable, nor routinely provided lubrication recommendations to the radiography industry. The choice of cleaning agents and lubrication was, therefore, left to the radiography equipment manufacturers or the radiographer / licensees. In early 1997, one radiography equipment manufacturer requested TCI to provide information concerning cleaning and lubrication of 5222
. cable. At that time, TCI provided the equipment manufacturer with information concerning lubrication of the cable during and after the manufacturing process and a recommended cleaning process. The equipment manufacturer developed these recommendations into a cleaning and lubrication procedure that was subsequently reviewed and commented on by TCI. See Appendix G for a description of the basic procedure as developed by this manufacturer.
A dirty and/or unlubricated cable will be subjected to elevated stress, excessive wear, and accelerated corrosion. Under these conditions, corrosion will likely result from several processes i including stress corrosion, oxidation, and galvanic reactions. These conditions also serve to I reduce the cable's ultimate strength. Combined with the cyclic and impact forces to which drive NUREG - 1631 4-2
\ l EQUIPMENT PERFORMANCE l cables are routinely subjected, this reouction in strength may be significant, possibly up to 90 ! percent. I j 4.1.1 LUBRICATION
- A variety oflubricants are used by the radiography industry on drive cables and are selected for
. various reasons including: cost, availability, perceived suitability for the use conditions, and preference. Lubricants used by radiography licensees included: light penetrating oil (e.g., WD- I 40), diesel fuel, Dow Corning DC-33 siliconc lubricant, MIL SPEC MIL-G-23827B grease, and LPS1 greaseless lubricant. In some cases, licensees indicated that they did not apply any lubricant to drive cables because of environmental conditions such as sand or grit that could cling to the lubricant and create a gumming effect in the gear box.
- Radiography equipment manufacturers use and recommend several different approaches to lubrication, including the following:
l' !
. Using MIL SPEC MIL-G-23827B grease
- Using diesel fuel (this vendor stated that the use of diesel fuel was a local industry standard) l
. Not making any recommendations conceming drive cable lubrication due to the wide variety of use conditions and differing lubrication requirements. Instead, this vendor provided its customers a lubrication and cleaning procedure that was developed based on the materials and )
L lubricating process employed and recommended by the cable manufacturer (e.g., using the .l
. same quenching oil and lubricant as the cable manufacturer, but not subjecting the cable to the 'I heating and quenching process). See Appendix G for a description of the basic procedure as !
l developed by this manufacturer.
. Not making any recommendations conceming cleaning solutions or drive cable lubrication other than lubrication of the drive gear. This vendor recommends against lubrication of the drive cable as the lubricant would attract dirt and debris and serve to clog and bind their controls. !
l TCI, the ' cable manufacturer, stated that certain lubricants should not be used with 5222 cable as
- they could serve to replace or extract the quenching oil from the cable, thereby reducing the cable's flexibility and corrosion resistant properties. These lubricants include paraffm-based !
greases and light penetrating oil. The only lubricant recommended by TCI is Dow Coming DC- 1 ! 33 silicon-based grease. In addition, TCI stated that "if an unlubricated cable is used, the softest j material (be it the cable itself or a gear box, etc.), ~will see excessive wear. The addition of environmental conditions that expose the cable to salt, sand, dust, etc., will only compound the ! problem by simulating the wear effects of a piece of sandpaper." i l 1 l l 43 NUREG - 1631 !
.r - . . . .
- _ _ _ _ _ _ - - - - _ - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ - _ _ _ - _ _ _ _ - _ _ _ _ _ = _ _ _ _ _ _ _ _ _ _ _ _ - _ _ _ - . _ - EQUIPMENT PERFORMANCE 4.1.2 CLEANING Industrial radiography use environments are typically harsh and require periodic cleaning of the drive cable to remove dirt, sand, grit, grime, and other contaminants from the cable. A variety of . cleaning materials are used by the radiography industry on drive cables and are selected for various reasons including the following:
- Cost .
- Availability
- Perceived suitability for the use conditions
. Preference.
Cleaning materials used by radiography licensees (and in some cases recommended by radiography equipment manufacturers) included the following:
- Gasoline
. Naphtha
. Mineral spirits (e.g., Varsol)
- Kerosene
. Light penetrating oil (e.g., WD-40)
- Dieselfuel
. Trichloromethane
- Perchloroethylene (e.g., ARDROX K410-A)
- Aqueous solvent (e.g., EPA 2000)
The cable manufacturer initially identified certain cleaning materials that should not be used with 5222 cable.' These included light penetrating oils, any degreasing materials, and gasoline. These materials would be especially harsh to the quench oil and could result in complete removal of the quenching oil and drying out the cable. The cable manufacturer further indicated that all of the
, cleaning solutions identified as being used by radiographer may remove the quenching oil from the cable in varying degrees, allowing accelerated corrosion and wear to occur and causing a loss in cable flexibility.
As discussed above, the cable manufacturer previously did not typically make recommendations as to appropriate cleaning solutions for its $222 cable. TCI cable, including 5222 cable used in the aerospace industry, is typically used in environments where the cable would require little or NUREG - 1631 4-4
EQUIPMENT PERFORMANCE no periodic cleaning. In addition, a TCI engineering representative stated he was " uncomfortable with cleaning of the 5222 cable." However, the cable manufacturer indicated that when cable is returned to it for evaluation, it may be cleaned only by immersion in AquaWorks . AquaWorks is a non-toxic aqueous cleaning solution that is designed to clean many types of oils, greases, dirt and grime, would not tend to remove the quenching oil from the cable during cleaning, is compatible with many metals including many stainless steels and high carbon steels, and would not tend to attack or degrade 5222 cable. TCI indicated that reusable ceble is relubricated with DC-33 grease to protect it from corrosion. However, as discussed above, one equipment manufacturer requested information and recommendations concerning cleaning and lubrication from TCI in early 1997. The Team noted that the cleaning solution and cleaning process used by TCI for refurbishing cable is different from the cleaning solution and process indicated to have been recommended to the radiography equipment manufacturer. Specifically, the cleaning process recommended by TCI to the equipment manufacturer suggested using a degreaser on the cable and drying the cable with compressed air. It was further recognized that this process would remove the quenching oil, and that this oil would subsequently need to be replaced. When questioned by the team on this previously recommended procedure and cleaning material, TCI indicated that this procedure is appropriate and would, if properly followed, be adequate to replace the quench oil and protect the l cable from accelerated corrosive attack. It is very important in this procedure that following the cleaning, the cable be completely dried and the quench oil be replaced. In addition, any cleaning agents which leave a residue on the cable or which cannot be readily dried (e.g., light penetrating oil) would reduce the efficiency of the quench oil replacement. If the quench oil is not completely replenished or is replaced by another solution, corrosive attack of the cable, l especially the core, may proceed or be accelerated. l Representatives of Houghton indicated that, although Houghton G quench oil will provide some level oflubrication and corrosion resistance, it is not ideally suited for these purposes. In addition, the representatives agreed that solvent-based cleaning agents would break down their quench oil and extract it from the cable, and indicated alternative products could pmvide better corrosion resistance as well as lubrication of the cable. Further discussions with the quench oil ' manufacturer indicated that several of these alternatives could be applied as an af ter-market product following cleaning of the cable. In fact, one of these products was indicated to have the ability to clean, lubricate, and provide enhanced corrosion resistance to the cable. 4.1.3 INSPECTION Radiography equipment inspections were identified as a key element for detecting potential failures early and avoiding equipment problems due to improperly operating equipment. It was further identified that inspections of radiography associated equipment, including drive cables, is l just as important as inspections of radiography cameras. In several cases, radiography licensees indicated they had identified cable failures in progress (see Figure 2.1 in Section 2.4) during equipment inspections. In one case, the failure in progress was identified during a daily 4-5 NUREG - 1631
EQUIPMENT PERFORMANCE inspection. In each of the other cases, the failure in progress may have been identified during a daily inspection if the first several inches of the distal end of the drive cable had been inspected. However, in these cases, the failures in progress were identified during special equipment inspection audits performed by the RSO on equipment in use, rather than during the daily inspection or quarterly maintenance. The RSO who identified these failures in progress indicated that radiographer continued to use the drive cables, even though they exhibited obvious signs of impending failure that could easily have been identified during daily inspections. RSOs from several radiography licensees stated that it was important for radiography licensees to develop formal equipment inspection procedures, including the use of checklists. In addition, a number of RSOs also emphasized the importance of providing adequate instruction and training to individuals performing radiography equipment inspections and maintenance. Several suggestions were received on means to provide this training including the following:
- Increased emphasis during initial training on the proper care of associated equipment
. Adding maintenance and inspection related questions to the radiographer's certification exams . Emphasis during periodic refresher training
- Revision of radiographer audit practices to include inspection and maintenance
. Development of additional inspection and maintenance guidance to enhance awareness of the importance ofinspections and proper maintenance.
Radiography cameras examined were generally in good condition and seemed to be adequately maintained. In addition, radiography licensee maintenance programs for cameras were generally thorough and adequate to properly maintain the cameras. In general, an emphasis on inspection of radiography cameras was noted throughout the radiography industry and in the regulatory community. Conversely, the Team observed that inspections of associated equipment varied greatly, were not consistent from one licensee to another, and generally there seemed to be an underemphasis on inspection of associated equipment. This un Dremphasis was demonstrated by the fact that associated equipment, including drive cables, often showed signs of disrepair and many were in poor condition. This underemphasis may result from a lack of emphasis by the { regulatory community. For example, previously 10 CFR Part 34 section 34.28," Inspection and . Maintenance of Radiographic Exposure Devices, Storage Containers, and Source Changers," did not address inspection and maintenance of associated equipment. However,10 CFR Part 34 was { amended (effective June 27,1997) to identify inspection and maintenance requirements for j associated equipment. This may help to increase the awareness of the importance ofinspection I of associated equipment.
) l TCI, the cable manufacturer, indicated that 5222 cable that is inspected and found to have evidence of corrosion should not be used because this would indicate that degradation had already occmred. It is impossible to determine the amount ofinternal degradation of the cable from an external visual examination. In addition, tests that are intended to evaluate overall cable NUREG - 1631 4-6
l EQUlPMENT PERFORMANCE flexibilig may be able to give a general indication of overall cable condition and amount of internal corrosion, but would fail to give any indication of cable condition and amount ofinternal corrosion at, or near, the male connector. 4.2 ENVIRONMENTAL AND OPERATIONAL CONSIDERATIONS Radiographic operations are, by nature, harsh to radiographic equipment. For example, radiographic systems, including drive cables, may be subjected to extreme temperatures, high humidity, salt water, corrosive chemicals, dirt, dust, sand, inappropriate storage, drops, and other external impacts. In addition, drive cables may see additional harsh conditions such as impact loads at each limit of travel, excessive, frequent and cyclic bending loads, and repetitive compressive and tensile loads. Drive cables appear to be subjected to the greatest stresses at the juncture between the cable and the male connector. These stresses result, in part, from the following:
. Handling in this area for connection / disconnection e impacts from objects hitting or falling on the connector and subsequent field repair to straighten . A stress concentration resulting from the change in material flexibility between the cable and the male connector . The amount of corrosion occurring in this region. Radiographer were observed handling about 4 inches of the distal end of the drive cable when connecting / disconnecting the male and female connectors. In addition to increasing the stress on the cable, this action serves to remove cable lubricant and may enhance corrosion by the addition of bodily oils and salts to .
the cable. (see Figure 4.2) l
, @F E 9 3 a,.
+1 b A .s
. 'p FgDS tap Figure 4.2 Radiographer Connecting / Disconnecting Drive Cable 47 NUREG - 1631
EQUIPMENT PERFORMANCE 1 There are several ways in which the drive cable may be exposed to excessive and/or frequent j bending loads. These include flexing in the guide tube at the limit of travel under compressive ! loading, passing through the S-tube, bending during connection and disconnection of the male i connector, and external impacts on the male connector end of the drive cable. As discussed earlier, guide tube inner diameters in excess of the 0.635 cm (0.250 inch) maximum specified by the cable manufacturer were observed with all radiographic equipment manufacturers' equipment. The cable manufacturer indicated that this extra diameter would allow excessive flexing of the cable when subjected to compressive loads at the limit of travel which would increase the fatigue of the cable, thereby reducing its ultimate strength. This flexing was observed in a demonstration model of a radiography exposure device, with the maximum flexing occurring near the male connector. Radiography industry practice is to rapidly extend and retract the source to keep radiation exposures ALARA. This results in increased compressive impact loads at full extension of the source to the endstop. Such flexing and impact loading could be expected to occur each time the drive cable assembly was used to extend the source to the exposed position. Impact loading also serves to decrease the useful life of the cable by reducing its ultimate strength. Additional bending loads were observed as a result of the manner in which the drive cable is sometimes handled by radiographic personnel. Several radiographer and RSOs demonstrated methods by which the male connector on the drive cable could be connected to the female connector with the use of only one hand, and methods to disconnect the male connector from the female connector by means of a whipping action. The connection technique subjects the drive cable immediately behind the male connector to 60 degrees to 90 degrees bends. The whipping disconnect technique involved bending the cable at an angle greater than 90 degrees immediately behind the male connector to compress the spring loaded pin in the female connector, and then pulling sharply on the drive cable to extract it from the female cennector. Continual use of such techniques would also result in additional fatigue of the cable near the male connector. While some individuals stated that such a technique was practically possible only with connector designs that allow 90 degree freedom of movement between the male and female connectors, another RSO stated that it was possible with connectors from any of the radiography equipment manufacturers. Drive cable is also subjected to cyclic bending loads when it passes through the S-tube during extension and retraction. Some of the connector designs examined during the inspection allowed 90 degree freedom of movement between the male and female connectors. The positive aspect of this design is that it would relieve stress on the drive cable as it travels through the S-tube. However, the team later leamed through discussion and demonstration that this same feature may allow the whipping disconnection. Other connector designs only allow limited flexibility between the connectors, thereby increasing the bending load stress placed on the cable immediately adjacent to the connector. This stress is further increased by a concentration factor resulting from the transition between the rigid connector and the flexible cable. NUREG - 1631 4.g
l-EQUIPMENT PERFORMANCE 1 I Numerous instances were observed where radiographer failed to completely retract the drive cable and failed to use protective coverings exposing the distal portion of the drive cable to dirt l and grit, physical damage, and corrosive attack from various sources, including chemicals l typically found in mobile radiographic darkrooms. Exposed drive cable could also be damaged by falling objects (e.g., tools or collimators). It is common industry practice to store and , transport drive cable assemblies in these mobile darkrooms and the team observed instances I where up to 30.5 cm (12 inches) of drive cable was extended out to the control assembly during storage and transport. The team also observed instances where protective covers were not
. installed on the control assembly and control assemblies stored on the floor of radiography darkrooms, thereby exposing the end of the drive cable to the corrosive chemicals typically found in these darkrooms. Fully retracting drive cables and use of the vendor supplied protective cover would greatly reduce the exposure of the drive cable to the corrosive chemicals found in j radiography darkrooms, and dirt and grit found on the floors of these darkrooms.
l Radiography is often performed in locations that are in high and relatively inaccessible locations where the radiographic system must be operated on scaffolds, catwalks, and other similar , structures. In addition, radiographic operations are frequently perforrned under these structures, as well. As a result, the radiographic system, including the drive cable assembly, is at a greater risk to be damaged as the result of falling or having other objects fall on it. The drive cable may be subject to bending forces when other objects fall on the controls or the camera falls in a orientation where the connection between the controls and the camera is impacted. In addition, the drive cable may be subject to tensile and kinking forces when the camera falls from a high location, but the controls remain fixed at the location such that the controls (including the drive l cable) absorbs the entire force of the fall. Discussions with the radiography industry indicate that
- some radiographer continue radiographic operations after such an event because of operational
! and/or economic pressures and have performed field repair to straighten severely bent cables and l connectors. These drops and impacts may subject the cable to significant stress and plastic !' deformation of the metal. This would be compounded by field repairs. Drive cables ! encountering recurring bends and straightening would be subject to accelerated fatigue, possibly l leading to ultimate failure. A review of utilization records and interviews with radiography personnel at one of the NRC
- licensees that experienced a drive cable failure indicated that the cable had experienced more than 20,000 cycles, and likely as many as 35,000 cycles. Throughout the inspection, discussions
- with numerous licensees and radiography equipment manufacturers indicated that some drive cables may be subjected to in excess of 100,000 cycles. Radiography licensees and equipment manufacturers stated that utilization rates can be very high; as high as 100 shots per shift,3 shifts per day,7 days per week. It should be noted that ANSI N432-1980 specifies prototype radiographic systems must be subjected to 20,000 cycles, and ANSI N43.9-1991 and ISO 3999 - specify prototype testing to 50,000 cycles. Each of these standards require that the prototype device remain operational following the test and that the integrity of the source assembly not be compromised. No current radiographic industry standards require prototype testing to 100,000 cycles or more. At least one of the radiography equipment manufacturers indicated that they had 4-9 NUREG 1631
EQUIPMENT PERFORMANCE tested their equipment to in excess of 100,000 cycles with no failure of the drive cable. However, the equipment manufacturer indicated that they did not have complete documentation of the test or the test conditions. No basis exists to establish defendable age or utilization limits on drive cables. This would have to be based on a known set of environmental and operational conditions. Without the additional factors of corrosion and excessive bending stresses from impact and bending loads, it is likely that drive cables would consistently withstand in excess of 100,000 operational cycles without failure. However, since environmental and operational conditions vary greatly from site to site in industrial radiography, the operational and age limit of the cable would also vary greatly and would be indeterminate. 4.3 MANUFACTURING PROCESSES 4.3.1 CABLE TCI 5222 cable is basically manufactured using a three-step process including: stranding, stress relief, and oil quenching. Cable stranding is accomplished through a three-step process including:
. A single wire strand is wrapped by 18 wires to create the lx19 core
. The core is wrapped by intermediate compression windings
. Outer helix and spacer wire windings complete the process.
The winding process creates manufacturing stresses in the cable. Following the winding process, the cable is heated to 300 degrees to 350 degrees C (572 degrees to 662 degrees F) to relieve these stresses and oil quenched to provide the cable with its ultimate material hardness properties. The quench oil used is Houghton Quench G which is a medium / fast quench oil containing petroleum-based antioxidants, employed to retard degradation of the oil via oxidation during the heating process. The manufacturer of the quench oil indicated that the quench oil is not intended to be a primary lubricant or corrosion inhibitor, but its sole purpose is as a quench oil. Following manufacture, the cable is inspected for quality and workmanship, excess quench oil is removed and the cable is coiled into 122 to 305 meter (400 to 1000 foot) lengths (depending on customer requirements). Samples from each end of the coil are removed for quality checks and the remaining ends are deburred. 4.3.2 MALE CONNECTORS Male connectors are constructed from stainless steel (typically 316L) and may be cast or milled, with the majority of vendors using milled connectors. One vendor interviewed continues to use NUREG - 1631 4-10
EQUIPMENT PERFORMANCE l cast connectors. During a 6-month period in1995, the male connectors of this vendor experienced an increase in failures in which the neck of the connector broke off at its base. (See Figure 43) The failures apparently occurred due to a stress concentration at thejuncture of the connector body and the neck due to a sharp angle at the transition. To prevent additional failures, the vendor modified its design to make the transition less abrupt, thereby reducing the stress concentration. Failures of this type with the vendor's male connector have significantly reduced since the modification was implemented. All current designs of male connectors examined during the inspection had smooth transitions in the areas where the connector body and neck met.
--a Figure 43 Drive Cable with Bent Neck on Male Connector l Several vendors' designs included rounded edges of the body of the male connector. The purpose of these rounded edges was to provide additional freedom ofmovement between the male and female connectors, in some cases greater than 90-degree freedom of movement.
l Variations identified in the construction of the male connectors would likely not compromise the , integrity of the cable. 4.3.3 SWAGING AND ASSEMBLY Visual examination of several drive cables and manufacturing processes indicate that there are differences in male connector construction, the processes used to swage male connectors onto drive cables, and the quality of the end product. Certain observed swaging processes appear to have the potential to compromise the integrity of the connector and/or drive cable at or near the male connector. For example, the Team observed one cable swaging technique utilizing a ! manually pumped hydraulic press with a capacity of 154 kN (17.5 tons). The press was not equipped with a pressure gauge and the operator p.:mped the press until it could not be pumped
- any longer. As a result, the actual applied pressure was unknown. The Team observed that a ,
! potential existed for the cable to be crushed in the process. The consequences to the cable of l applying such pressure are uncertain, although the Team observed a newly swaged connector where its inner surface had been cracked by the swaging force. In all swaging processes examined, the force of the pn:ss on the connector caused plastic deformation of the connector metal, forming " ears" en the connector. Mon of the " ears" were , small, but one vendor's swaging process caused " ears" large enough to cause a drive cable hang-up. This vendor would remove the " ears" with a grinding wheel. The Team observed that the outer helix wire of a newly-swaged cable from this vendor was inadvertently nicked in this 4 11 NUREG - 1631
1 EQUIPMENT PERFORMANCE process. The nicked cable had been installed in a set of controls and was awaiting shipment to a customer. Upon inquiry by the Team, the vendor indicated that the cable was considered unsatisfactory and would be reterminated. While at another licensee's fecility, the Team observed a drive cable on which the outer helical wire showed signs of being nickedjust behind the male connector. A nick in the helix would cause a stress concentration at the nick, a reduction in wire cross-section, and the nick and surrounding area would be more vulnerable to corrosive attack. Swaging dies are subject to deterioration from use. The Team observed that some equipment mav.facturers periodically examined swaging dies to determine their ongoing conformance with design requirements. At one vendor's facility, the Team found that the swaging dies were not routinely examined. Rather, the vendor indicated that swaging dies were replaced when pull test failures were detected. This technique increases the potential for inconsistent swage quality. 4.3.4 QUALITY ASSURANCE AND QUALITY CONTROL During cable manufacture, TCI performs several tests to ensure proper cable quality control including the following:
- A check ofincoming wire strands for conformance to design specifications including wire diameter, composition, tensile strength, and workmanship a
Pull testing of samples from incoming shipments of wire
. Measurement of completed cable inner core and outer helix diameters Measurement of helix pitch (helix wrappings /mch)
. Pull testing samples of each cable batch to destruction The cable manufacturer demonstrated the pull testing with a random sample of cable. The specified minimum tensile force necessary to pull the helix and core of the cable to failure was 1780 N (400 lbf) and 2135 N (480 lbf), respectively. The cable sample tested for the team failed at 2113 N (475 lbf) for the helix and in excess of 2224 N (500 lbf) for the inner core.
In addition, TCI indicated that several samples of wire of each batch received from their supplier are pull tested to failure to demonstrate compliance with the tensile strength requirements. In addition, every 2 years samples of wires received from the supplier are sent out for chemical analysis to demonstrate compliance with TCI material specifications for metal composition. TCI indicated that no incoming shipments of steel wire from their vendor have ever been rejected. Radiography equipment manufacturers use different equipment, techniques, and criteria when j conducting pull tests to evaluate swage quality (556-890 N (125-200 lbf) applied for 25 seconds to 5 minutes). It should be noted that the tensile test specified in ANSI N43.9-1991 for NUREG - 1631 4-12
l l EQUIPMENT PERFORMANCE l to 5 minutes). It should be noted that the tensile test specified in ANSI N43.9-1991 for i production source assemblics requires a minimum tensile force of 445 N (100 lbs) be applied ! within 10 seconds and held for 5 seconds. However, no standard test methodology is specified. 4.4 AMERSHAM FAILURE ANALYSIS REPORT On February 6,1998, Amersham submitted a report (Appendix C) to the Commonwealth of Massachusetts addressing its review of the six drive cable failures identified up to that point. The review addressed the sequence of events, subsequent evaluation, and a Part 21 assessment. Amersham assessed the drive cable failures following its procedures, SOP-Q030 " Product . i Complaint Handling-Returned Material Authorization," and SOP-Q002, "Part 21 Procedure." Amersham characterized the drive cable failures following its Retumed Material Authorization (RMA) process and assigned RMA numbers as follows: 775,780,780-A,782,784 and 788. In addition, in March,1998, Amersham received a seventh cable failure (another " failure in progress"). Table 4.1, " Summary of Amersham Drive Cable Failures" adapted from the i Amersham report, includes this seventh drive cable failure. 1 4-13 NUREG - 1631
i l i
. EQUIPMENT PERFORMANCE Table 4.1 Summary of Amersham Drive Cable Failures RMA 775 780. .780-A 782 > 784. .788 788-A Date Failed 8/19/97 11/16/97 1995 11/21/97 12/8/97 ~ 1995 ~ 1995 (Date Reported 9/15/97 11/17/97' 11/17/97 11/26/97 12/8/97 1/21/98 2/26/98 Date Analyzed 9/97; 11/97.. 12/97 12/97 12/97 1/30/98 3/19/98 !
11/97 s- , Conspements Retern 4 Cable Yes Yes No Yes Yes Yes Yes (Connector No ~ ~ Yes: Yes No; Yes Yes Yes Cable Unknown 0.186" Unknown 0.187" 0.183" 0.185" 0.1855" Diameter . Imeian of Unknown 1/8" from 1/8" fm m Unknown 1/4" from 1/8" from 1/8" from;
- Break connector connector connector connector connector.
Asymmetrical Yes Yes Yes Yes Yes Yes N/A Wear at Break D, ; Corrosion on Fracture Surfaces Inner Wires Yes Yes Yes No Yes Unknown No
- Intennediate No No: No No? No: Unknown No-4 Wire ?
Outer Wire No No No No No Unknown No l , :n Conssion en Wire Surfaces Inner Wires Yes Yes Yes Yes Yes Yes No Intennediateu Yes . Yes - Yes : Yes - Yes ' Yes No-Mue; Outer Wire Yes Yes Yes Yes Yes Yes No B , Kimidag Location Unknown 5/25" Unknown 5.5" from 2.5" and None None from connector 5.0" from noted on noted on connector connector sample sample
;Wearat Kink Unknown Yes Unknown Yes Yes N/A N/A NUREG - 1631 4-14
l EQUIPMENT PERFORMANCE 1 The Amersham evaluation examined five customer complaints of drive cable failures and one customer-identified event. All of the failures involved drive cables which had been in service for at least 5 years. Preliminary review of the RMAs conducted by the Amersham Engineering and Regulatory Affairs department concluded that the failures were potential Part 21 issues and an evaluation was initiated. The Amersham Part 21 Review Board met in December 1997, and agreed to the following actions:
. Order metallurgical analysis of the retumed materials with additional testing of materials if necessary.
. Review RMA logs to determine trends.
. Determine the age, service history and usage patterns of the failed components, as well as any j special environmental factors. l l
. Review the manufacturing process for contributing factors.
. Discuss the drive cable failures with service personnel.
- Measure the drive cable diameters and examine the conditions of the cables and the male connectors.
. Retrieve the male connectors from customers.
. Analyze the components for similarities and differences.
All six of the drive cable failures were subjected to an analysis performed by Analytical Answers, Inc. (See appendix D). Analytical Answers identified the cause of the drive cable breaks as a combination of tensile overload, fatigue and corrosion fatigue. Inspection of the fracture faces demonstrated plastic deformation on some strands, indicating tensile failure, and smooth breaks on others, indicating brittle failure mode. Corrosion fatigue was characterized as l the simultaneous action of corrosion and fatigue, with the endurance limit under attemating stress such as flexing, being lowered as a result of exposure to a corrosive environment. The fracture surfaces of the inner wires of the drive cables were corroded, indicating that these wires probably failed before the failure of the entire cable, j Analytical Answers also analyzed drive cable and individual wire strands provided by TCI, by l pulling them to failure in order to examine the fracture surfaces to confirm characterization of the l tensile and brittle failure modes. This examination indicated that the cable and wires demonstrated fracture surfaces generally more consistent with tensile overload failure than the RMA fracture surfaces. The examination also revealed that stresse.; induced during cable manufacture i.e., winding, may contribute to fatigue failure but cycle testing demonstrated that this stress by itselfis not significant. Amersham reviewed the service history of the subject drive cables and determined that the age and number of cycles for the failed cables could not be accurately determined but that they were i 4-15 NUREG - 1631 1
EQUIPMENT PERFORMANCE all at least 5 years old. Maintenance history for all of the failed cables varied significantly revealing different frequencies, e.g., quarterly and annually etc., for maintenance and numerous different materials used for cleaning and lubrication. The service history was not available for two of the RMAs. The manufacturing process (for the Amersham model 660 radiography system) was reviewed and no manufacturing procedures were identified which could have contributed to the drive cable failures. Amersham has previously subjected the drive cable to I endurance testing at 50,000 cycles and found no evidence of breaking thus validating the design , and manufacturing process. The failed drive cables were visually examined and revealed corrosion and lack oflubrication. The diameter of the drive cables ranged from 4.65 to 4.75 mm (0.183 to 0.187 inches) with several of the cables presenting kinks and presence of wear at the kinks and at the break indicating that the cables had been in use for some time with the kinked condition. Male connectors were retrieved from all but two failures with the four returned connectors revealing l that the break occurred directly behind the connector. The location of the break on the other two cables could not be confirmed but the Amersham customers reported the breaks as being close to , the male connector. Lot numbers were not visible on the retumed connectors confirming that the l cable had been in field use for a long time. ! The Amersham analysis also addressed several operational issues and administrative factors. The operational issues focused on observations by Amersham service personnel and input from the field dealing with the manner in which drive cables are handled and transported. The administrative factors dealt with possible reasons for the increase in the number of reported drive cable failures including enhan=4 NRC reporting requirements and factors resulting from the 1992 changes to 10 CFR Part 34. Amersham's assessment based upon metallurgical analyses and inspection of the retumed drive cables concluded that wear and corrosion were the principal causes of the failures. Their conclusion was based on the following indicators: . Corrosion of the outside of every wire. . Corrosion on the fracture faces of the inner wires . Kinks in the cables five to six inches form the male connector in three of the six RMAs. .' Asymmetrical wear at the point of the break. . Fatigue is the principal failure mechanism. i NUREG - 1631 4-16
EQUIPMENT PERFORMANCE Amersham determined that this evidence suggest two probable scenarios: Scenario A:
- 1. An initial event fractures some or all of the inner wires and/or causes a kink in the cable.
- 2. The damage goes undetected and the cable continues to be used as evidenced by the asymmetrical wear at the point of the break and at the kink and the corrosion on the fracture faces of the inner wires.
- 3. After a sufficient number ofcycles, the intermediate wires and the outer wire fail because of fatigue, along with any inner wires that did not break with the initial event.
Scenario B:
- 1. Regular lubrication of the cable is not maintained, or a solvent or penetrating oil is used as a lubricant, stripping the cable ofits protective lubricant and allowing corrosion to take place.
- 2. Over time, the cable wires oxidize. Concurrently, the cable is flexed during connections, disconnections, and normal operations.
- 3. Wire strands fail individually due to corrosion fatigue.
In the final analysis, Amersham concluded that based on their review and analysis, the drive cables failed due to a combination of wear, corrosion, and lack oflubrication, indicative of improper maintenance. The failures were not due to a design or manufacturing defect of the cable and were not reportable under 10 CFR Part 21. The Team commends Amersham on conducting a thorough analysis of the failed drive cables and the compilation of their findings in the February 6,1998, report submitted to the Commonwealth of Massachusetts. It is a high quality report and represents a great deal of effort on Amersham's part to understand the causes of the drive cable failures and other related concerns such as manufacturing processes, operational issues and administrative factors. Metallurgical analyses conducted by Analytical Analysis, Inc. for Amersham provided useful insight into the specific nature of the drive cable failures and a number of technica! parameters associated with the failures. Examination of other RMAs associated with earlier drive cable failures and service history records helped to establish the scope of the problem and to gain a better insight into the difficulties associated with establishing the age of affected cables. In addition, examination of the manufacturing process and discussions with Amersham service personnel aided in the determination that the problem is likely a use-issue rather than a mrmufacturing problem. 4-17 NUREG - 1631
EQUIPMENT PERFORMANCE Amersham's findings that the drive cables failed due to a combination of wear, corrosion, and lack oflubrication, indicative ofimproper maintenance are consistent with the Team's observations. However, this conclusion addresses only technical and operational causes for the failures and does not attempt to address a root cause. In addition, the Team views the two probable scenarios suggested by Amersham as problematic. Essentially, this concem results from Amersham's two-scenario approach in which there are three distinct elements for each scenario pathway. The inspection observations and findings lead the Team to conclude that some or all of the distinct elements contained in either of the Amersham scenarios occur in some or all of the drive cable failures under review. As a result, the either/or conclusion for the two scenarios does not seem plausible for the cable failures that are the subject of this report. 4.5 POTENTIAL ROOT CAUSES As the Team collected and considered findings during the course of the inspection, several possible root causes of radiography drive cable failures were considered. Some causes that were initially considered were later characterized as secondary causes or contributing factors while others were rejected as potential reasons for the drive cable failures. A discussion of all potential root causes in contained in Section 6 of this report. 4.5.1 INADEQUATE MAINTENANCE A major radiography equipment manufacturer stated that it was their view that the cause of the drive cable failures was strictly related to a lack of proper and adequate maintenance by radiography equipment operators. As is documented in several sections elsewhere in this report, the 5222 cable used as drive cable can be subject to degradation and ultimately failure, ifit is improperly used, cleaned, or lubricated. The Team determined that this factor alone was not a root cause for the cable failures that are the subject of this report. 4.5.2 ABUSIVE HANDLING BY RADIOGRAPHY PERSONNEL A major equipment manufacturer felt that abusive work practices by radiography personnel may have been a significant factor in the failure of the drive cables. Specifically, it was felt that radiography crews working with Amersham model 660 radiography systems would partially disconnect the controls by releasing the outerjaws of the connector on the controls, leaving only the drive cable connected. The connector would then hang by the drive cable and place additional bending force on the drive cable in the immediate vicinity of the male connector. The crews would then relocate the radiography system from one set-up site to the next by dragging the radiography camera by the drive cable assembly. This would result in the drive cable experiencing higher tensile and bending loads than during normal radiography. This would also { create the potential for the drive cable to be subjected to tensile impact loads as the camera is dragged across uneven surfaces. This practice reportedly allowed radiography personnel to move j more rapidly between one set-up and the next, while ensuring that the source could not be NUREG - 1631 4-18
l l l EQUIPMENT PERFORMANCE l extended from the shielded position, by not taking the time to completely disconnect the drive l cable assembly from the camera. The Team asked numerous individuals employeu by equipment manufacturers and radiography firms about this possible practice. Interviews with radiographic personnel indicated that this was not normal practice, and most indicated that they had ever heard of or witnessed it. Most i individuals stated that they did not understand the benefit this procedure would provide, and they believed it was unlikely that this was a common industry practice. l In discussions with several representatives of the radiography community, it became apparent that radiography equipment is frequently subjected to unintentional abuse as the result of being l operated in various industrial environments such as refineries. These situations frequently require that radiography system components to be set up on scaffolds, catwalks, and other similar
- structures and that as a result, these components are at a greater risk to falling. The team concluded that this type of scenario was more likely to result in a sudden tensile overload on the drive cable. The resultant damage could then create a site for the cable to undergo corrosive attack and be further weakened over time until it ultimately failed.
l 4.5.3 BRITTLE FAILURE DUE TO FATIGUE AS A RESULT OF NORMAL LOADS ENCOUNTERED IN A RADIOGRAPHIC SYSTEM In order for the 5222 cable to fail in a brittle mode due to fatigue, the endurance limit of the carbon steel would need to be exceeded. Endurance limits for metals are not precise, but are a j function of the alternating stresses resulting from the force of the cyclic loads applied, and the l number of cycles the member is subjected to. Data supplied by the cable manufacturer indicates l that new cable subjected to loads similar to those encountered in a typical radiographic system, would not be expected to exceed its endurance limit and should maintain its integrity for at least
- 100,000 cycles. The performance test data supplied by TCI was for a similar model cable used in TCI manufactured controls. However, similar results would be expected for 5222 cable used in a typical radiography system.
Interviews with several radiography equipment manufneturers indicated that prototype testing of radiography systems had been performed where the drive cables were subjected to in excess of L 100,000 cycles, and in one case, up to 400,000 cycles, without failure. In each case, the drive l cable was new and had not been subjected to corrosion or other damage prior to the test. Specific data concerning these tests were not available for the Team to review. However, this test data is consistent with the test data of the cable manufacturer. The metallurgical analyses performed by Analytical Answers for Amersham of the failed drive I cables indicated that corrosion was evident in all cases and that corrosion fatigue was a key factor in all failures. However, none of the analyses indicated that fatigue alone was the 4-19 NUREG - 1631
EQUIPMENT PERFORMANCE l principle cause of the failures. Based on these analyses and the test data provided by the cable manufacturer and the radiography equipment manufacturers, it does not seem probable that fatigue was the primary failure mode for these cables, absent other contributing factors. 4.5.4 DUCTILE FAILURE AS THE RESULT OF TENSILE LOADS CREATED BY DRIVE CABLE ASSEMBLY CONTROLS Several Amersham RMAs indicated that some drive cables appear to have ultimately failed under tensile overload. The Team's discussions with the cable manufacturer and a review of documented design specifications indicated that 5222 cable would fail under tension in a two-step process. The cable's outer helical winding is designed to withstand a minimum tensile force of 1779 N (400 lbf) and the inner cable core is designed to withstand a minimum tensile force of 2135 N (480 lbf). This was verified by reviewing a representative sample of pull test results where the drive cable was pulled to destruction by the cable manufacturer. Discussions with radiography equipment manufacturers indicated that the maximum tensile load that could be exerted on a drive cable by the crank mechanism would not be sufficient to cause tensile overload and ductile failure of the cable. The Team attempted to estimate the maximum steady-state tensile force that could be applied to the drive cable, based on the physical limitations of a typical human and of the radiography system. Based on data from actual human trials, this force was calculated to be no greater than 356 N (80 lbf), neglecting frictional losses, efficiency losses, and partial absorption of the force by other members of the system (i.e., the worst-case scenario). This force is significantly less than the tensile force required to cause ductile failure of 5222 cable that has not been subjected to corrosion or other contributing factors. Therefore, it does not seem possible that sufficient force could be applied to the controls, and transferred to the drive cable, to cause tensile overload and ductile failure of the drive cable. 4.5.5 FATIGUE AS THE RESULT OF TENSILE LOADS INDUCED BY FLEXIBLE CONDUlT A radiography firm representative stated that he believed the likely cause of the drive cable failures was the result of tensile loads imposed on the cable as the result of using flexible conduit in the construction of drive cable assemblies. The representative arranged a demonstration using a radiography camera (with an inactive source) equipped with a drive cable assembly constructed with flexible conduit, as supplied by the original equipment manufacturer (OEM). The demonstration was then repeated using a drive cable assembly constructed with non-flexible (non-standard) conduit. The demonstration showed that greater force had to be applied to the crank on the controls in order to actuate the source locking mechanism of the camera equipped with the OEM flexible conduit as compared to one with the non-flexible conduit. The Team evaluated this issue and, on further examination, determined that no additional force was being exerted on the drive cable at the male connector. This is because the less flexible the conduit, the NUREG - 1631 4 20
7 EQUIPMENT PERFORMANCE greater would be the transmission efficiency of the applied force on the cable. The additional force required with more flexible conduit was in fact compressing the conduit, which acted similar to a spring and absorbed the additional force. L 4.5.6 CABLE DEFECTS OR WEAKNESSES AS THE RESULT OF CHANGES IN THE MANUFACTURING PROCESS - The cable manufacturer has been producing 5222 cable since at least 1959. Interviews with representatives of the cable manufacturer indicated that there have been no changes in the cable manufacturing process. In addition, there have been no changes in the specifications for, or the vendors providing the materials used in the manufacture of 5222 cable. Part of the cable manufacturer's quality assurance program is to require that the vendor supplying wire used to produce the cable, provide a certificate documenting that the wire satisfies the cable manufacturer's materials specifications. The cable manufacturer added that there had been no reported failures of their cable products in the aerospace industry which is the primary application for the cable. l The specified minimum tensile strength of the wire used in the manufacture of 5222 cable is ! 1827 MPa (265,000 psi). . As discussed elsewhere in this report, during the inspection, a review of these vendor-supplied certificates revealed that until February 1998, wire supplied to the cable manufacturer had an actual minimum tensile strength ranging from 1724 to 2069 MPa (250,000 psi to 300,000 psi). The cable manufacturer stated that it was its engineering judgment that L component wire with a tensile strength as low as 1724 MPa (250,000 psi) would not impair the performance of the cable and would not be important in the corrosion-induced fatigue failure mode. 4.6 HUMAN FACTORS Radiographer continue to use drive cables in poor condition. The Team examined several drive ; l cables in use, including several in poor condition, i.e., cuts, broken fittings, breaks, excessive or uneven wear, fraying, unraveling, nicks, kinks, bends, stiffness, loss of flexibility, stretching, excessive grit and grime and flaking. One failed cable was severely corroded and worn to the extent that only half of the nominal cable diameter remained. Another drive cable was also wom and corroded and the outer helix showed signs of unwrapping. The RSO who identified the failure stated that he was able to bend and break the cable by hand. Another RSO identified two drive cables that were experiencing breaks in progress. These breaks were readily apparent, however they have not been observed by radiographer during daily inspections. The breaks were identified during a special equipment audit conducted by the RSO following a source hang-up. Some examined cables had experienced failures, others had not. Radiographer do not always follow established operating procedures or recommendations provided by equipment manufacturers. For example, numerous instances were observed where I' 4 21 NUREG - 1631 e
EQUIPMENT PERFORMANCE radiographer failed to completely retract the drive cable and failed to use protective coverings exposing the distal portion of the drive cable to dirt and grit, physical damage, and corrosive attack from various sources, including chemicals typically found in mobile radiographic darkrooms. Discussions with some members of the radiography community indicated that the current level of attention during equipment inspections of the condition of the drive cable appears inadequate in l ! many cases to identify precursors. In one case, the RSO determined that the radiographer failed to perform the daily inspection of the drive cable on the day of the failure. Several other i licensees indicated that they identified cable breaks in progress; however, these breaks in progress were not identified during daily inspections, but were identified during quarterly maintenance or as a result of a special audit. This indicates that equipment inspections are either not performed or inadequately performed as a result of emphasis on production schedules or other time and cost incentives. Discussions during the inspection with representatives of the radiography industry and State regulators indicated that there appears to be a prevailing omd set that drive cable failures are going to occur as a result of conducting industrial radiography operations. This perception is compounded by the fact these failures seem to occur infrequently given the number of cycles to which the' drive cables are typically subjected. As a result, breaks are anticipated, assumed to be insignificant, and may result in a lack of reporting and insufficient emphasis on measures to reduce or prevent their occurrence. A former radiographer said that as a result of emphasis on production schedules or other time-related incentives, some radiographer may use incompatible drive cables and cameras potentially compromising the designed safety functions. Other individuals said that these pressures would also cause radiography crews to attempt unauthorized field repairs on bent drive cables. Amersham has received numerous (40 to 50) calls regarding the NRC Information Notice (IN) 97-91: "Recent Failures of Control Cabl-s Used on Amersham Model 660 Posilock Radiography
. Systems." A majority of the callers mistakenly believed that the IN referred to failed male connectors rather than to drive cable failures. Other individuals interviewed during the inspection had a similar misconception. The Team observed that some members of the radiography industry were accustomed to connector failures of the type occurring in 1995 in which the neck of the male connector ball broke off at its base. As a result, they did not realize that the IN addressed drive cable failures occurring immediately behind the male connector.
Many members of the radiography community (managers, RSOs, vendors, and owners of radiography companies) thought that radiographer were not prone to devote a great deal attention to the condition of drive cables in an ongoing manner, but rather they focused on meeting production schedules or accomplishing their assignments as quickly as possible for various work and non-work related reasons. Resolution of this problem would require training NUREG - 1631 4 22
EQUIPMENT PERFORMANCE radiographer to devote greater attention to drive cable condition rather than attempting to change their behavior through prescriptive regulatory requirements. 4.7 OTHER OBSERVED FAILURES Radiography licensees have also observed male connector failures in the past. For example, several licensees indicated that during a 6-month period around 1995, they experienced an increase in failures in which the neck of the male connector broke off at its base. (See Figure 4.5 in Section 4.3.2 of a damaged male connector prior to failure at the base of the neck) The i licensees indicated that all of these failed male connectors were supplied by one vendor and were the result of a design and/or material incompatibility. These failures were reviewed by the State of Louisiana and an independent contractor. As a result, the vendor subsequently modified its design. There have been no known similar failures involving the vendor's male connector since the modification was implemented. 4.8 OBSERVABLE AND POTENTIAL FAILURE PRECURSORS A cable break in progress may be detectable. Several licensees indicated that they identified, during equipment inspections, cable breaks in progress and removed these drive cable assemblies from service prior to failure. In several cases, these breaks in progress were not identified during daily inspections, but were identified during quarterly maintenance or as a result of a special audit. No definitive precursors wem identified by radiography personnel involved in events reviewed as part of this inspection before the complete breaks in the drive cables. These precursors may include fraying of cable strands, corrosion, loss of flexibility, stretching, and obvious physical damage such as bending. In one case, the RSO determined that the radiographer failed to perform the daily inspection of the drive cable on the day of the failure. Discussions with other members of the radiography community indicated that the current level of attention during equipment inspections of the condition of the drive cable appears inadequate in many cases to identify precursors. These discussions indicated that such inspections are either not performed or inadequately performed as a result of emphasis on production schedules or other time and cost incentives. < l The Team observed bends and/or kinks within 30.5 cm (12 inches) of the male connector and j corrosion on the distal 15.2 to 20.3 cm (6 to 8 inches) behind male connector on most cables involved in examined failures. Although these features may not be definitive precursors, they , i may indicate damage to the drive cable which could result in ultimate failure. Drive cables exhibiting these features may warrant enhanced observation or replacement. I 1 4-23 NUREG - 1631 ) (-
! 5 REGULATORY ASPECTS Industrial radiography utilizes sealed sources containing large quantities of radioactive material j and presents many opportunities for significant exposures to radiographer and members of the public. As a result, the NRC and Agreement States have a long and established history of regulatory oversight in order to ensure the safe use of these materials. The specific regulatory l requirements for industrial radiography are set forth in 10 CFR Part 34," Licenses For l Radiography And Radiation Safety Requirements For Radiographic Operations" and equivalent Agreement State regulations.10 CFR Part 34 recently underwent a major revision that became effective on June 27,1997, that placed an increased emphasis on several important safety-related issues for all aspects ofindustrial radiography including requirements for radiography equipment. Much of this rule change was an item of compatibility for Agreement States. NRC l and Agreement State regulations for industrial radiography place a significant emphasis on j radiography cameras but also address, to varying degrees, associated equipment, including drive cables involved in producing radiography images. ,
- i 5.1 APPLICABLE REGULATIONS (30.32(g),32.210,34.20,34.31 &
REQUIRED LEVEL OF AGREEMENT STATE COMPATIBILITY l 10 CFR Part 30.32(g) requires that an application for a specific license to use byproduct material in the form of sealed sources, or in devices containing a sealed source, to either identify the source or device by manufacturer and model number as registered with the NRC or an ) Agreement State or contain the information identified in 10 CFR Part 32.210(c). These j requirements are designed to ensure that only those sources and/or devices which have ; l undergone an adequate safety review and approval are used by licensees. 10 CFR Part 32.210 states that any manufacturer or initial distributor of sealed sources or devices containing sealed sources whose products are intended for use by a specific licensee may submit
- a request to the NRC for evaluation of radiation safety infonnation about its product and for its registration. The term may is used in this regulation since licensees, as well as manufacturers or distributors, may also submit such information seeking review and approval of sealed sources. In addition, under the authority in 10 CFR Part 33, licensees of broad scope may also review and approve sealed sources and/or devices provided the requirements in 10 CFR Part 33.13(c)(3)(ii) l are satisfied.
- 10 CFR Part 34.20 specifies requirements for industrial radiography equipment performance and l use. The regulation specifies that all radiographic exposure devices, source assemblies or sealed l sources and all associated equipment must meet the requirements specified in American National Standard Institute, ANSI N432-1980, " Radiological Safety for the Design and Construction of l
l Apparatus for Gamma Radiography." In addition to the requirements specified in the ANSI standard, all radiographic exposure devices, source changers, source assemblies and sealed sources must satisfy a number of other requirements specified in 10 CFR Part 34.20 such as labeling, automatic locking mechanisms and testing requirements, etc. l 5-1 NUREG - 1631 l
i REGULATORY ASPECTS 10 CFR Part 34.31 requires radiography licensees to perform visual and operability checks on survey meters, radiographic exposure devices, transport and storage containers, associated equipment and source changers before each day of use. In addition, inspection and maintenance requirements for this equipment are specified along with related record keeping requirements. In addition to these specific regulatory requirements for industrial radiography, the requirements in 10 CFR Part 20, " Standards For Protection Against Radiation," and the general requirements in 10 CFR Part 30, " Rules Of General Applicability To Domestic Licensing Of Byproduct Material," are applicable to radiography licensees. All Agreement States have equivalent regulatory requirements. 5.2 ONGOING RULEMAKING EFFORTS The 1990 revision to 10 CFR Part 34.20 required that all radiographic exposure devices and all associated equipment must comply with the requirements in ANSI N4232-1980 and other specific requirements such as labeling, automatic locking devices and testing requirements. Problems have surfaced with these requirements because much of the associated equipment used for conducting radiography operations was not designed to the ANSI standard but can be used safely. However, the existing regulations do not contain provisions for dealing with the unique items of associated equipment. Amersham has petitioned the NRC to address this and other issues dealing with the use of associated equipment. Currently, the NRC staffis addressing the petition and has interacted with the industrial radiography about possible solutions. Modifications to the current requirements in 10 CFR Part 34 are anticipated. 5.3 SEALED SOURCE & DEVICE REVIEW PROCESS 10 CFR Part 30.32(g) requires all specific licensees, including radiography licensees, using sealed sources or devices containing sealed sources, to identify the source or device by manufacturer and model number as registered with the NRC under 10 CFR 32.210, or with an Agreement State or submit the information specified in 32.210(c) in order to use the source or device. 10 CFR Part 32.210 provides for the registration of a product (sealed source and/or device) and provides a means for having a single safety evaluation of the product performed. This process allows applicants, licensees and NRC or Agreement license reviewers to reference the evaluation when licensing the product for use or distribution without having to perform a complete evaluation of the product for each licensing action. Furthermore, this process ensures that only sealed sources and/or devices which have undergone an adequate safety review and approval are used by licensees including those within the radiography industry. : The NRC maintains a registry of radiation safety information on sealed sources and devices containing byproduct material. Agreement States also provide information on their radiation safety evaluations to the NRC for inclusion within the registry. Both the NRC and Agreement States use the registry. Thus a vendor (or licensee) needs to provide detailed information NUREG - 1631 5-2
7_ _ l REGULATORY ASPECTS describing its sealed source and/or device only to a single regulatory agency, and the results of the radiation safety evaluation is available for use in granting licensing approval to users of the. source or device throughout the United States. L 5.4 NRC LICENSING PROCESS Persons authorized by the NRC to perform industrial radiography using byproduct materials are licensed in accordance with the regulations in 10 CFR Part 30," Rules of General Applicability l to Domestic Licensing of Byproduct Material" and 10 CFR Part 34, " Licenses for Radiography and Radiation Safety Requirements for Radiographic Operations." Persons authorized by one of Agreement States to perform industrial radiography using byproduct materials are licensed in accordance with correspondingly similar statutory and administrative requirements in place in
. that particular state, In addition to the regulations, the NRC previously provided industrial radiography licensees and applicants supplemental information published in Proposed Revision 2 to Regulatory Guide 10.6., " Guide for the Preparation of Applications for the Use of Scaled Sources and Devices for l
Performing Industrial Radiography (October 1984)." This guide was recently replaced by NUREG 1556, Volume 2, " Program-Specific Guidance About Industrial Radiography Licenses." These guides contained a compilation of the information that an applicant would need to submit to be able receive an NRC license authorizing industrial radiography, including use, inspection, and maintenance of radiography equipment such as drive cable assemblies. The NRC staff has reviewed industrial radiography license applications using, in part, the criteria published in these documents. As noted above, Part 34 specifically requires daily inspections of radiographic equipment. Exhibit 2 of Regulatory Guide 10.6 and Appendix P of NUREG 1556, Volume 2 describe model checklists to be followed by radiographic personnel while performing required daily inspections of radiography equipment. In reviewing a license application, NRC staff generally accept a licensee's statement that they will follow this model checklist or accept a licensee-created daily , checklist as long as it contained the same elements in the model procedure. In both documents, j the first checklist item states: " Inspect the cables for cuts, breaks, and broken fittings." Careful examinations of the visual condition and the flexibility of the drive cable may identify broken ! strands or cable stiffness that would have wamed radiographic personnel of an impending drive l cable failure. Similarly, the third checklist item in both documents states: " Check operation of the control for freedom of drive cable movement." Frayed or otherwise damaged drive cables may create drag or hang up in the radiography controls that could also warn radiography l personnel of an impending drive cable failure. j Regulatory Guide 10.6 does not address required quarterly inspection and maintenance of radiography equipment . Section 8.18, Item 10 of NUREG 1556, Volume 2, describes the requirements for a radiography equipment inspection program in general terms. However, this i 1. 5-3 NUREG - 1631
REGULATORY ASPECTS I part of the document provides no specific information regarding the inspection or upkeep of drive cables. 5.5 NRC INSPECTION PROCESS The NRC and the Agreement States perform routine inspections ofindustrial radiography licensees to determine iflicensed activities are performed in a manner that will protect the health and i.afety of workers and the general public and to determine iflicensed programs are conducted in accordance with applicable regulatory requirements and license conditions. NRC Manual Chapter 2800 describes the requirements for the inspection of most of NRC's materials licensees. The NRC's specific procedures for perfonning inspections of persons licensed to conduct industrial radiography are described in Inspection Procedure 87120. IP 87120 directs inspectors to do the following:
. Verify that equipment in use meets the requirements described in 10 CFR 34.20, and is inspected and maintained;
. Verbally confirm that licensees are aware that associated equipment needs to comply with 10 CFR 34.20;
. Verify that the licensee has implemented written procedures for the insoection and routine maintenance of associated equipment.
However, the inspector is specifically directed not to attempt to confirm that associated equipment used by the licensee complies with 10 CFR 34.20, except under the following conditions:
. When an incident or event results from equipment failure;
. The use of an associated equipment component would create an apparent public health and safety threat;
- A component is being used with a non-compatible system;
. Ifit is clearly obvious to the inspector that an associated equipment does not comply (e.g., use of a non-typical drive system or guide tube (a garden hose) or an end stop taped to a guide tube).
The inspection procedure contains no specific references to the condition of the drive cable nor 1 does it direct the inspector to physically examine the drive cable to determine its present condition. NUREG - 1631 5-4
l I REGULATORY ASPECTS 5.6 NRC INFORMATION NOTICE PROCESS The Nuclear Regulatory Commission will from time to time issue written Information Notices (IN) to various groups oflicensees to alert them of a particular issue that has come to the attention of the NRC and that has the potential to impact large groups oflicensees. These notices , typically include a description of circumstances introducing the issue, and a discussion of the ! details, safey e isiderations, and relevant regulatory requirements. ins do not impose new regulatory req sments, nor do they require any specific action or written response. Licensees are typically advised to review their radiation safety programs and adjust them as necessary in ; response to the information notice. On December 31,1997, the NRC published Information Notice 97-91, "Recent Failures of Control Cables Used on Amersham Model 660 Posilock Radiography Systems." This IN described three of the cable failures that were evaluated in this report. The IN stated that all of the described cases, the control cable failed at a point approximately 0.33 to 1.25 centimeter (0.125 to 0.5 inch) behind the male connector. The notice noted that in each case, radiography personnel avoided serious radiation exposures by performing proper surveys and by following the appropriate emergency procedures. The notice also discussed the importance of reporting such events to the NRC so potential generic problems could be identified and evaluated. During the inspection, Amersham representatives stated that they had received numerous (40 to
- 50) calls regarding IN 97-91. Reportedly, a majority of the callers mistakenly believed that the IN referred to failed male connectors rather than to drive cable failures. Other individuals interviewed during the inspection had a similar ndsconception. The Team observed that some members of the radiography industry were accustomed to connector failures of the type occurring in 1995 in which the neck of the male connector ball broke off at its base. As a result, they did not realize that the IN addressed drive cable failures occurring immediately behind the male connector.
5J
SUMMARY
AND PROPOSED CHANGES The issues raised by this inspection of the drive cable faihires generate a number of challenging questions in the context of necessary changes to existing regulations, licensing guidance, or the , inspection pmcess for industrial radiography. The Team has identified several changes needed for the licensing and inspection process which are set forth under Section 7, " Recommendations" j of this report. These changes are recommended in order to enhance the existing regulatory ! program from an operational perspective, while not imposing overly prescriptive requirements { whose efficacy is unknown. l l I The Team is recommending a relatively minor adjustment to 10 CFR Part 30 to emphasize the importance oflicensees' understanding and committing to the operating and use conditions specified by the manufacturers of sealed sources and/or devices. This is important because 5-1 NUREG - 1631
REGULATORY ASPECTS manufacturers have evaluated their products for use under certain operating conditions which, if exceeded, may compromise the safety and reliability of the product. Based on suggestions from members of the radiography industry (RSOs and managers), another regulation change is reconunended for 10 CFR Part 34.20 to clarify that safety plugs or covers must be applied to associated equipment such as drive cables. This could be accomplished through a relatively minor change to 10 CFR Part 34.20(c)(3), which currently requires that - outlet fittings, lock box and drive cable fittings on each radiographic exposure device must be equipped with safety plugs or covers which must be installed during storage and transportation to protect the source assembly from water, mud, sand, or other foreign matter. . Throughout this inspection, members of the radiography industry (managers, RSOs, vendors, or owners of radiography companies) expressed the sentiment that new prescriptive regulatory requirements would not materially improve the current conditions of use for drive cables or enhance their maintenance. In addition, there was a general sentiment that no basis exists to establish defensible age or utilization limits on drive cables. Establishment of such limits would have to be based on environmental and operational conditions which vary greatly from site- to-site and with differing applications. The Team agrees with these conclusions and has not recommended such changes of to the regulations. NUREG - 1631 5-6
6 FINDINGS AND CONCLUSIONS 6.1 ROOT CAUSE ANALYSIS In arriving at the root causes, the Team attempted to identify all potential causes, analyzed each potential cause in view of the results, and eliminated those causes that would not result in a failure without other contributing factors. The focus of this evaluation was to identify the fundamental causes from which all the potential causes, secondary causes, or contributing factors evolved. Refer to Section 4.5, " Potential Root Causes" for a detailed discussion of the various l potential causes that were evaluated and eliminated in arriving at the following root causes: l
= The cable being used is not designed for use in industrial radiography. l TCI 5222 cable is designed for use in the aerospace, marine, and other industries as a component in cable control systems. These systems are specifically designed for their intended operating environment and use conditions which are markedly different and less harsh than the those of the industrial radiography industry.
- There is an underemphasis on the importance of radiography drive cables.
Manufacturers, the radiography industry, and regulatory agencies do not adequately l emphasize the importance of observing, maintaining and evaluating the condition of radiography drive cables. As a result, opportunities to detect precursor events may be missed. Discussions with all major radiography manufacturers indicated that the TCI-produced 5222 drive cable has been used throughout the industry since the early 1960s. However, there is no l evidence that a systematic evaluation was performed in selecting the 5222 cable for use in industrial radiography, even though the drive cable was originally designed for use in the aerospace industry. In addition, drive cable failures seem to have become an accepted occurrence within the radiography industry. Apparently, the drive cable was selected "because it worked" and no cost-effective alternative has been identified, although other cables have been evaluated and rejected. The lack of critical review and the subsequent acceptance of drive cable failures appears to have created a mind set within a substantial portion of the industry that such cable failures are inevitable. This has resulted in a reduction of the attention paid to the condition of the drive cable and related maintenance, preventing early detection of drive cable failures in some cases. l l Although the Team concluded that the 5222 cable was not designed for use in the industrial radiography industry, the Team is not recommending the discontinuance ofits use. Using it however, requires greater emphasis, on monitoring its condition and properly maintaining it for ( safe use within the industrial radiography industry. l 6-1 NUREG - 1631 L-___---- _ - - - - - - - - _ - - . - - - -
MNDINGS AND CONCLUSIONS Secondary Causes The kWon revealed several secondary causes that appear to contribute to the failure of industrial radiography drive cables Operational Conditions
- Industrial radiography equipment including drive cable assemblies, is subjected to a wide variety of harsh operational conditions that include:
-- Impact Loads Radiography drive cables experience impact loads at each limit of travel in the drive cable assembly. Radiography personnel are traipad to crank sources out to the collimator and
. back into the camera as quickly as possible, minimizing the time that the source is present in the unshielded guide tube, and as a result, keeping exposures to radiography personnel as low as possible.
Observations of drive cable in a transparent demonstration model of a radiography exposure device, demonstrated that the drive cable experiences compressive impact loads as the source assembly is driven against the collimator or end stop at the fully extended position. It was also observed that the drive cable experiences tensile impact loads when the source is retracted into the shielded position within a camera. These tensile loads occur as the radiographer turns the controls and when the lock ball on the source assembly is engaged by the cameras locking device and continue during the brief period between the lock ball engagement and the radiographer releasing back pressure of the controls.
- Excessive and Frequent Beriding Loads There are several ways in which the drive cable may be exposed to excessive and frequent bending loads. As noted earlier, the nominal outer diameter of new 5222 cable is 4.75 mm (0.187 inches). The cable manufacturer recommends that the maximum inner diameter of conduit for 5222 cable should not exceed 6.35 mm (0.250 inches) to prevent flexing which could lead to fatigue of the cable. The Team measured several samples of drive cable assembly conduit at an Amersham facility and found that the inner diameter measured 5.31 mm (0.209 inches). Measurements of the inner diameter of guide tube' samples ranged from 9.14 to 9.65 mm (0.360 to 0.380 inches). This is to allow the 7.8 mm (0.308
; inch) lock ball on the source assembly to pass through the guide tube. Observing a demonstration model of a radiography exposure device revealed that the drive cable experienced flexing, especially near the male connector, as the source assembly was driven against the collimator or end stop at the fully extended position. The greater internal diameter of guide tubes'will allow excessive drive cable flexing when it is subjected to compressive loads that occur when the source assembly reaches full extension NUREG - 1631 6-2
FINDINGS AND CONCLUSIONS at the end stop, which would increase the fatigue of the cable, thereby reducing its ultimate strength. Excessive and frequent bending loads could also be the result of how radiographic personnel handle the drive cable. Several radiographer and RSOs demonstrated methods by which the male connector on the drive cable could be connected to the female connector on the source assembly using only one hand. These techniques place 60 to 90 degree bends in the drive cable immediately adjacent to the male connector. Continual use of such techniques could result in cable fatigue near the male connector. (see Figure 4.2) Several RSOs and radiographer also demonstrated a " whipping" disconnect that allowed a very fast disconnect using only one hand. This technique involved bending the cable to an angle greater than 90 degrees immediately behind the male connector to compress the pin in the female connector and then pulling sharply on the drive cable. Continual use of such techniques could also result in cable fatigue near the male connector. While some individuals stated that such a technique was possible only with connector designs that allow 90 degree freedom of movement between the male and female connectors, another RSO stated that it was possible with connectors from any of the radiography equipment manufacturers.
- Poor Transportation and Storage Practices Through observations and discussions with radiography personnel, the Team found that drive cable assemblies were frequently transported and stored in the mobile darkroom mounted on or behind the radiography crew's vehicle. The Team determined that this practice is widespread . This practice would expose the drive cable assemblies to the water and to the various chemicals, including acids, both in vapor and in liquid forms, present in the darkroom. These chemicals could subject any exposed drive cable to corrosion.
The potential for corrosion is further increased by the common practice of some radiography crews to store the drive cable assembly with as much as 30.5 cm (12 inches) of the drive cable extended out of the control assembly. The Team also observed several failures to install the manufacturer-provided protective covers on the drive cable assembly and several instances in which the covers were missing. These covers are intended to protect the drive cable from the intrusion of dirt, dust, abrasives and corrosive materials.
- Drops and ExternalImpacts Because radiographic images must be made in difficult and inaccessible locations such as refineries, radiographic equipment must frequently be operated on scaffolds, catwalks, and other similar structures. As a result, the radiographic system, including the drive cable assembly, is at risk ofdamage by falling or having other objects fall on it. For example, collimators (which because of their intended use have a high density) occasionally fall back on the drive cable assembly, crimping the conduit and damaging the drive cable either through cutting or bending.
6-3 NUREG - 1631
FINDINGS ANDCONCLUSIONS Several individuals throughout the radiography industry stated that some radiography crews continue radiographic operations after such an event because of operational and/or economic pressures. Crews have reponedly straightened out severely bent cables and connectors risking metal fatigue and continued operations, rather than stopping to replace equipment and incurring economic or operational penalties inherent in nondestructive testing industry. Environmental Considerations Field industrial radiography is conducted in a variety of settings which expose radiography personnel and their equipment to extreme environmental conditions. Such conditions may involve exposure to:
. A wide range of temperatures ranging from arctic to desert
. High humidity
. Salt water
. Corrosive chemicals
- Dirt, dust, and sand.
Given these conditions, radiography personnel are frequently required to clean the drive cable assembly to remove various contaminants and keep the controls operational. Because field radiography is frequently performed at great distances from the radiography crew's home base the drive cable assembly cannot be returned to the home base for maintenance in a controlled environment. This results in the drive cable assembly being cleaned in the field using whatever materials are available. Based on statements by the cable manufacturer, many cleaning processes commonly used in the radiography industry have the potential to remove the quenching oil from the cable, allowing accelerated conosion and wear and causing a loss in flexibility, eventually leading to fatigue and ! possible failure of the cable. Cleaning processes include the use of the following materials:
. Gasoline
. Naphtha
. Mineral-spirits products, including Varsol
'. Kemsene ' l
. Light penetrating oil products, including WD-40
. Diesel fuel NUREG - 1631 64
L l FINDINGS AND CONCLUSIONS 1
- j. : . Trichloromethane l
. ; Perchloroethylene products including ARDROX K410-A 1
l .
. Aqueous solvents such as EPA 2000 l
~
L . As previously discussed, most of these materials can significantly impact the quench oil l- component of the drive cable's structure. l There are currently no standard procedures or recommendations for cleaning drive cables. Previously, the cable manufacturer made no recommendation regarding suitable cleaning agents for its cable, nor routinely provided lubrication recommendations to the radiography industry. t This was probably because all other applications involved using the cable in a sealed conduit, so
; it required no cleaning.- As a result radiography equipment manufacturers and radiographer / licensees had to choose their own cleaning agents and lubrication.
L In early 1997, one radiography equipment manufacturer requested TCI to provide information conceming cleaning and lubrication of 5222 cable. TCI provided with information on lubricating the cable during and after the manufacturing process and recommended a cleaning process. The equipment manufacturer developed these recommendations into a cleaning and lubrication - procedure that was subsequently reviewed and commented on by TCI. '(See Appendix G for a basic description of this procedure.) Drive cables may require periodic lubrication because of exposure to the conditions described above that necessitate the cleaning of drive cables. Inappropriate re-lubrication can also compromise the cable's integral lubricant, thus reducing flexibility, accelerating corrosion, and increedng wear. The only lubricant recommended by the cable manufacturer is Dow Coming DC-33 silicon-based grease. l Radiography equipment manufacturers use and recommend different approaches to lubrication, including: !:
- Using only MIL SPEC G-23827B grease.
. Not making any recommendations concerning drive cable lubrication due the wide variety in use conditions and differing lubrication requirements. This manufacturer has developed a procedure that it follows during drive cable assembly and refurbishment which uses the same quenching oil and lubricant used by the cable manufacturer but does not subject the cable to i
the same heating and quenching process. In addition, they have supplied this' procedu:e to its existing as well as new customers. L L = Lubricating drive cables with diesel fuel. This vendor stated that the use of diesel fuel was a L local irulustry standard and that the use of other lubricants would attract abrasive and corrosive I materials that could damage the cable.- ' L 6-5 NUREG Il631 l l
1 l FINDINGS AND CONCLUSIONS l
- Not make any recommendations about appropriate cleaning solutions or lubricants. In fact, j this vendor recommend that drive cables not be lubricated because this would attract dirt and {
debris and would clog and bind the drive cable control mechanism. There are a wide variety oflubricants used by radiography licensees, including:
. Light penetrating oil products such as WD-40
. Diesel fuel a Dow Corning DC-33 silicone lubricant
= MIL SPEC MIL-G-23827 B grease
- LPSI graceless lubricant These lubricating materials are selected for various reasons including: cost, availability, perceived suitability for the use conditions, and preference. Again many radiographer stated that under certain conditions that they did not apply any lubricant to drive cables because of environmental conditions, such as sand or grit, that could cling to the cable and make operation of the system more difficult.
Contributing Factors In addition to the root cause and secondary causes, several factors may have contributed to the failure of radiography drive cables, including:
- Cable Condition Representatives of both radiography firms and radiography equipment manufacturers report that some radiography crews continue to use drive cables in poor condition. Among the drive cables examined by the Team, several were found to be in poor condition. Some had experienced failures, while others had not. For example, one failed cable was severely corroded and worn to the extent that only % of the nominal cable diameter remained. Another drive cable was also worn and corroded and the outer helix showed signs of unwrapping. The RSO who identified the failure was able to bend and break the cable by hand.
Deferred Maintenance According to several equipment manufacturer representatives some radiography companies sent one component of the drive cable assembly for repair and were advised that the drive cable showed excessive wear and should be replaced. In some instances, the customer directed that the equipment be retumed without repair. The cost of a replacement drive cable I for a 7.6 m (25 foot) long set of controls was indicated to be about $260.00. NUREG - 1631 6-6
I , FINDINGS AND CONCLUSIONS
- Emphasis on Radiography Cameras Rather Than Associated Equipment Based on statements by equipment manufacturers, RSO's, and radiographer, individuals in the radiography industry and the regulatory community apparently believe that maintenance of
- associated equipment is not as critical as maintenance of radiography cameras. 'Ihe inspection found that the radiographer and other personnel maintaining radiographic equipment may not i understand the importance of proper cable care and inspection. This is especially true regarding the importance of ensuring that drive cable is in good condition and of the cable's quenching oil on the flexibility, corrosion resistance, and wearability of the cable. The industry and regulatory community also did not understand the potential detrimental impacts I
of various cleaning and lubricating materials' on this quenching oil as well as the susceptibility of the cable to various environmental conditions. Many industry representatives indicated that this probably contributed to some radiography crews either not performing daily inspections or performing them so perfunctorily that they would fail to detect a potential problem that could lead to cable failure. An RSO cited an example of debriding a radiographer after a drive cable failure and discovering that he or she had in fact not performed the required equipment inspections prior to beginning work that day. Another RSO identified two drive cables that were close to complete failure, as evidenced by breakage, fraying, and unwinding ofinner wire strands, breakage of the outer helix, and pulling apart of the cable. (See Figure 2.1.) Despite that these readily apparent signs of i impending failure, they had not been discovered by radiographer during daily inspections. These signs may also have been missed during quarterly maintenance but were identified during a special equipment audit conducted by the RSO following a source hang-up event. The RSO indicated that the responsibility for maintenance and upkeep of radiography cameras j 1 and associated equipment had previously been assigned to an individual with no work experience as a radiographer. The licensee's investigation determined that the individual had not given sufficient attention to the maintenance of radiography equipment and was relieved of all radiography-related duties. Subsequently, responsibility for maintenance had been j assigned to members of the licensee's radiography staff. 6.2 MOST PLAUSIBLE FAILURE MODE The discussion of the most plausible failure mode identified by the Team is based on data concerning the identified failures, analyses performed, radiographic equipment design (including drive cable), typical use scenarios, and environmental use considerations. To verify the failure
- mode presented, it is recommended that samples of drive cable be subjected to a testing regime that would simulate worst case actual use conditions for the drive cable.
6-7 NUREG - 1631
FINDINGS ANDCONCLUSIONS l L Various failure modes of drive cable presented throughout this report include fatigue, corrosion, corrosion-enhanced fatigue, tensile overload, and wear. Several contributing factors have been identified that may have caused, singly or in conjunction with other factors, these failure modes including the following:
. Normal forces encountered in the radiography system (tension, compression, and impact and cyclic forces)
. Drive cable being exposed to especially harsh and/or corrosive environments
. Absence of corrosion and/or wear inhibitors afforded the cable either throu;;h a Icck of application or removal
. External initiating events such as severe impacts on the cable
. Age
. Long term or very high rates of use Testing data supplied by TCI and several radiography equipment manufacturers demonstrate that new cable would likely not fail catastrophically due to fatigue, tensile overload, or excessive wear, when the cable was:
. Subjected to forces encountered in typical industrial radiographic operations
. Not subjected to external initiating events
. Properly lubricated
. AITorded appropriate protection from corrosive attack As manufactured, the design of current radiographic equipment precludes the generation of forces sufficient to exceed the fatigue limit or ultimate strength of 5222 cable. However, with the addition of corrosion, excessive wear or external initiating events, forces on the cable may lead to the fatigue limit and/or ultimate strength being exceeded.
Based on data gathered during the inspection, a failure would most likely occur on the drive cable at or near the point where the 5222 cable enters the male connector. The following factors lead to this conclusion:
. This portion of the cable is handled to a much greater extent than the rest of the cable during connection and disconnection, resulting in additional stress on the cable and removal of lubrication and/or corrosion inhibitors.
. This portion of the cable is exposed to the environment (harsh or otherwise) to a greater extent because access to the male connector is required for connection and disconnection given the NUREG - 1631 6-8
l FINDINGS AND CONCLUSIONS i 1 l common radiographer' use practice (e.g., leaving the end of the drive cable exposed or not L using the end cap).
- The point at which the 5222 cable enters the male connector is a stress concentrator in the cable.
I
. Dissimilar metals used in the construction of the male connector (stainless steel) and cable
. (carbon steel) could, when subjected to certain environments, create a galvanic cell in which the carbon steel would tend to be subject to the anodic reaction (reduction of material).
- The design of certain radiographic equipment would tend to increase stresses in the cable in this area (e.g., one design allows only limited freedom of movement between the male and female connectors. This type design would serve to increase axial forces in the cable near the connectors when passing through the "S-tube" and when the cable deflects due to the impact with the endstop at its limit of travel).
It is recognized that cable failures have occurred at locations other than at or near the juncture of the cable and male connector. However, the majority of the failures examined that occurred at other locations were determined to be caused, in part, by an external initiating event or significant occurrence. These included bends or kinks in the cable caused by impacts to the cable, drops of the camera where the drive cable absorbed the primary force of the drop, and severe corrosion and embrittlement of the cable at the location of the failure or of the entire cable. In these cases, the extemal initiating event created a weakness of the cable, at the failure location, where factors such as fatigue, tensile overload, and corrosion would be accelerated. These types of failures could likely be avoided by removing the cable from service following the external initiating event. In most cases where the cables were severely corroded, the corrosion was not concentrated near the male connector, but was essentially evenly distributed throughout the cable. In this case, a failure may occur at any point along the cable, but would be more likely to occur at or near the male connector or where the cable is subjected to the highest bending forces (e.g, as it passes through the gear box or "S-tube"). Although an external initiating event would tend to accelerate failure in this region, the majority of drive cable failures (including failures in progress) examined during the inspection that occurred near the male connector (within the first 1.27 cm (0.5")) did not show obvious signs of an external initiating event in the failure region. In addition, although evidence of an external j initiation event could become obliterated due to corrosion products, failed cables that did not have sufficient corrosion for this to' occur also did not have evidence of an external initiating I event in the failure region. This indicates that these failures were not triggered by an external initiating event. Metallurgical analyses indicated failure modes of tatigue (in some cases enhanced by corrosion) and tensile overload. However, it is unlikely that either of these were the initiating event in any of these failures but rather that corrosion was the initiating factor in these ) cases. As indicated previously, cyclic loading of drive cable in current radiographic systems is j l
~ insufficient to cause a fatigue failure without other contributing factors. In addition, the design . of current radiographic systems in use precludes exerting a tensile force sufficient to exceed the f
l 6-9 NUREG - 1631
)
FINDINGS AND CONCLUSIONS ultimate strength of the cable (in excess of 2.78 kN (625 lbf)). This is demonstrated in the following example: Typical radiographic systems have cranks approximately 20 cm (8") long (See Figure 6.1) connected to the gear box. Typical drive gears in radiographic systems measure approximately 8 cm (3") in diameter. The design of radiography system controls would likely limit a typical human to exert no greater than 133 N (30 lbf) to the crank and handle of the controls, which would equate to approximately 27.2 Nm (20 ft-lbs) torque (based on actual human trials). Assuming no losses in the system, this would equate to approximately 356 N (80 lbf) on the cable. Detve Cable
/
^ ^
(??? ^ i
; :==
/
- cree Hanee seae>wic.
Figure 6.1 Detail of Control Crank In addition, several drive cable vendors demonstrated that the force necessary to overcome the swage on the male connector, causing extraction of the cable from the male connector, is significantly less (in the range of 890 N (200 lbf)) than that needed to cause failure of the core of 5222 cable (in excess of 2.14 kN (480 lbf)) or deflection (slipping) of the helix (in excess of 1.78 kN (400 lbf)). Since corrosion is the most likely initiating event for cable failures near the male connector, it is important to understand how corrosion begins and progresses in this region. As indicated previously, corrosion may occur by several processes including oxidation, stress corrosion, and I galvanic c;11s. In each case, conditions must allow corrosion to proceed. Normal oxidation requires the metal be exposed to oxygen (atmospheric is sufficient) and the absence of corrosion NUREG - 1631 6-10
l FINDINGS AND CONCLUSIONS inhibitors. However, an oxidation-type concentration cell may also occur in areas where oxygen is depleted. The inner core of the cable may have a depletion of oxygen, possibly causing this type of concentration cell. In concentration cells, corrosion may be dramatically increased. Stress corrosion occurs rapidly.in areas of metal that have been stressed and higher stresses increase the rate of corrosion. Examples include metal fatigue, tensile overload, and surface damage such as scrapes or nicks. Metallurgical analyses performed on some of the failed cables I showed signs of stress corrosion. Galvanic cells occur when dissimilar metals are brought into ( contact with each other. The galvanic potential between the metals depends on the individual
. electrode potential of each metal. In general, carbon steels are more anodic than sainless steels and, therefore, will tend to lose material as a result of the galvanic cell. As the point where the carbon steel helix wire and the stainless steel male connector come into contact is en the exterior of the drive cable, this corrosion process would be expected to accelerate corrosion only on the exterior of the cable. In addition, if drive cables are cleaned such that the lubricant is removed from the inner core, and no suitable lubricating oil or corrosion inhibitor is reapplied, corrosion would be expected to proceed rapidly in the core, even if a lubricant, such as a grease, was applied to the extemal surfaces of the cable. This corrosion could not be readily detected, and, therefore, would likely proceed unimpeded. However, corrosion of the outer surfaces of the cable could be easily seen and would be impeded by the application of extemally applied lubricants or corrosion inhibitors.
l The primary load carrying members of 5222 cable are the inner core and external helix. (See Figure 3.3.) For this reason, these members would, in general, be subjected to the highest stree.ses and fatigue in the 5222 cable, with the inner core encountering the highest . Cyclic loading and fatigue of metals may reduce their ultimate strength in the range of 40 percent to 60 l percent . The effects of corrosion on a metal's ability to resist fatigue are well known and serve l also to drastically reduce (possibly up to 90 percent) the ultimate strength of a metal subjected to cyclic loading. Therefore, as the inner core becomes corroded, its strength may be dramatically l reduced to the point where cyclic and impact loadings generated during typical radiographic operations may exceed the endurance limit ofindividual wire strands in the core, ultimately resulting in brittle fracture. As individual strands fail, stress will be concentrated at the point of failure, increasing the stress in surrounding strands, and remaining strands in the core will be required to carry an increasing percentage of the total load on the cable. In addition, as the stress ofindividual strands increases, corrosive attack of these strands would likely similarly increase. As this process pr-ded, it would also accelerate. Tensile overload ofindividual core wires may occur when only a few wires remain. The smallest individual wire strands in the core were demonstrated by the cable manufacturer to be pulled to failure at tensile forces in the range of 156 to 178 N (35 to 40 lbf). Corrosion and fatigue of these wires would reduce the force necessary to pull them to failure. Based on the likely . maximum forces generated in radiographic systems (calculated above), the only few individual { wire strands remaining in the core could be pulled to failure by these forces; however, as core ! I wire strands fail, the outer helix would carry an increasing percentage of the total load. As the inner core approaches complete failure, the helix would carry a large percentage of the load, and, 6 11 NUREO - 1631 l
FINDINGS AND CONCLUSIONS therefore, it is expected that the resulting load carried by the remaining core strands would not be sufficient to cause tensile overload and resulting ductile failure of those strands as long as the helix remains. This is because the outer helix wire is coiled about the inner core and compression wrap and acts like a spring that would tend to resist unraveling and straightening adequate to allow the inner core wires to be subjected to an axial force sufficient to cause tensile overload. The inner core provides the principle axial strength of the cable, and as it fails axial strength of the cable would be dramatically reduced. As this occurs, the coiled helix wire would provide some axial strength and respond much like a spring and become compressed and stretched with each loading of the cable. This would dramatically increase cyclic loading of the helix and thus alternating stresses of the helix wire, especially at the stress concentrator where the helix comes into contact with the male connector. This stress concentration would be further compounded by the loss of core material. Many cables examined during the inspection showed signs of wear on the outer helix and male connector. Wear of the helix wire would reduce the force necessary to pull it to failure. The cable manufacturer demonstrated that new, undamaged helix wire has an ultimate strength sufficient to preclude failure due to tensile overload and requires more than 2.11 kN (475 lbf) to pull it to failure. However, increased cyclic loading, stress concentration factors, and damage due to corrosion and wear of the helix could reduce its ultimate strength enough that its endurance limit could be exceeded, leading to ultimate brittle fracture of the helix wire. In fact, forces exerted on the helix, combined with these other factors, may be sufficient to cause it to fail before all the core wires have completely failed. Once the helix wire completely fails, it would no longer provide axial strength for the cable and any remaining inner core wires would again take the primary load in tension. Therefore, without the helix, any remaining inner core wires could then fail in either a ductile mode or a brittle mode. Even with complete failure of the inner core and helix wire, the drive cable could continue to be used withjust the intermediate compression wrap and spacer wires. After failure of the helix wire, the entire load on the cable would be carried by the intermediate compression wrap and spacer wires. These wires would provide little axial strength in compression, but would continue to provide axial strength in tension. For example, ifonly undamaged intermediate compression wires remained, the tensile force required to pull the wires to failure would exceed 445 N (100 lbf); however, in compression, any remaining wires would collapse like an accordion, causing severe overstressing and fatigue of the wires. Observations of radiographic operations demonstrate that control mechanisms are operated rapidly in the expose and retract direction. Rapid extension would cause a significant compressive force in the drive cable at the limit of travel when the source assembly impacts the endstop. This compressive impact force would serve to greatly increase the overstressing and fatigue of the remaining wires. This overstressing and fatigue of the remaining wire strands would be compounded by rapid retraction of the cable, following the exposure, and the resulting tensile impact force applied when the lock ball
" bottoms-out" in the camera. This cyclic compressive and tensile force application could cause fatigue failure (brittle fracture) of the remaining wires in relatively few cycles due to the extreme bending forces caused by this compression / tension cycling. However, since relatively few wires NUREG - 1631 6-12 l
1 _ _ _ - _ _ - - _ - _ _ - - - - - - - - _ - - - _ - - - - - - - --- _ a
FINDINGS AND CONCLUSIONS remain, tensile overload could also occur in individual wires during the tension cycle, especially if the strength of the wire had already been reduced due to fatigue. In fact, the tensile impact load on the cable during retraction could cause ductile failure of multiple wires all at once if either there are only a few wires remaining or multiple wires remain, but their ultimate strength has been reduced by fatigue, corrosion, or some other destructive mechanism. 1 i When ultimate failure of the remaining wires occurs in one of the modes described above (ductile l or brittle), each would feel different to a radiographer operating the equipment. In the case of tensile overload (ductile failure), the radiographer may retract the source assembly to the fully 4 l shielded position without incident. However, typical practice is to give the controls a final pull after the source assembly if fully retracted to ensure the locking mechanism is fully engaged. Either the act of retraction or this final pull may cause the tensile overload failure of the remaining wires. In this case, the radiographer may notice the system give (i.e., little or no resistance) after the failure occurs, but may have no other indications of the failure. In the case of brittle fracture due to fatigue from the compressive load, the radiographer would likely have no visible or physical indications of the failure as it occurs. This type failure would likely occur during the compressive load when the source assembly impacts the endstop at full extension and { the wires are subjected to the maximum bending forces. However, at the point when this failure j occurs, the frayed wires may intertwine such that the source assembly could be partially retracted, possibly even through the entire guide tube. However, as the radiographer retracts the l source, the broken wires would likely pull apart and either leave the source exposed in the guide tube or partially exposed in camera. The source would likely not be able to be fully retracted as I the bending forces encountered in the S-tube would likely separate any intertwined wires, not l allowing full retraction. A radiographer could identify this type failure mode by noting that radiation levels had not reduced to the expected levels and the lock ball had not engaged the l camera locking mechanism. In addition, making several attempts to retract the source assembly by extending and retracting the drive cable would be to no avail. In fact, this type action could result in the source assembly being left out in the fully extended position. Based on the data gathered during the inspection and interviews conducted with radiographer , involved in the failures, the above described failure mode seems most plausible to the Team. I However, verification of this hypothesis would require testing under controlled conditions. i 6.3 OTHER FINDINGS The team was informed by a licensee RSO that the current version of the NRC-produced radiography training video entitled Taking Control, Safety Proceduresfor Industrial l Radiographer, contained several errors, one germane to the it.spection's objective. Specifically, the RSO stated that it was obvious that the radiographer portrayed in the video were spraying l light penetrating oil (WD-40), on portions of the radiography controls. As this inspection indicated, this type oflubricant is not suitable for 5222 cable. Further, the RSO noted that one of the radiographer apparently tested his alarming ratemeter while the device was tumed off. l 6-13 NUREG - 1631 l
6 FINDINGS AND CONCLUSIONS
'Ihe team reviewed a copy of the 1;# ring v!deo and confirmed the RSO statements. While the two radiographer did not actually spray light penetrating oil on the drive cable itself,it was
- shown being sprayed on various other components of the radiography controls. This practice could ultimately lead to the light penetrating oil coming into contact with the drive cable since the cable traverses through the controls. The Team also noted that it seemed that one of the radiographer did apparently test his alarming ratemeter while the device was tumed off.
The team also noted that the video reinforced the industry practice of training radiography personnel to crank sources out to the collimator and back into the camera as quickly as possible, minimidag the time that the source is essentially unshielded in the guide tube, keeping exposures to radiography personnel ALARA. As noted.in the discussion of secondary causes, this practice imparts an impact load on the drive cable when it reaches its limits of travel. However, this load by itself would not be expected to result in a drive cable failure provided appropriate maintenance, inspection and other compensatory measures are implemented for the drive cable. In view of the important ALARA savings this practice provides, the team does not believe modification of this practice is necessary. 6.4 - CONCLUSIONS The 5222 cable was not designed for use within industrial radiography. Given that no viable alternative exists for the 5222 cable, and the radiography industry will continue to use this cable for the foreseeable future, a greater emphasis must be placed on the condition and maintenance of the cable by radiography licensees, the radiography industry, and the regulatory agencies. Drive cable failures are an established fact within the industrial radiography industry. The actual number of drive cable failures is unknown since all failures may not have been reported. In addition, the typical total number of cycles that drive cables may experience before failure is unknown. Therefore, the frequency of drive cable failures cannot be accurately determined. Regardless of the actual frequency, this type of failure has the potential for significant exposure of radiography personnel and members of the public. As a result, the Team has developed several recommendations addressing the issue ofindustrial radiography drive cable failures. The Team concluded that such failures are an important issue and warrants timely attention by the radiography industry and regulatory agencies. NUREG - 1631 6 14
l 7 RECOMMENDATIONS 7.1 RULEMAKING 7.1.1 PART 30 (30.32(g)) The current rulemaking effort to modify 30.32(g)(1) should be broadened to include a requirement that licensees commit to the limitations, specifications, and operating and use conditions as specified in the registration certificate. Otherwise, licensees must submit applicable information as required by 10 CFR 32.210(c). The Statements of Considerations supporting this rule change should clarify that when licensees intend to use radiography equipment in a manner which deviates from the recommendations provided by the manufacturer (e.g., cleaning and lubrication) under the certification process, the licensee mustjustify the deviation. 7.1.2 PART 34 (34.20(c)) The current rulemaking effort to address associated equipment issues should .be broadened to include a modification to 10 CFR Part 34.20(c) to make it clear that associated equipment includes drive cables. This could be accomplished by adding the term " including drive cables" following the existing term " associated equipment." This would clarify that drive cables require the same level of attention to protective covers as specified later in this part for the radiographic exposure device.10 CFR Part 34.20(c)(3) should be modified by replacing the existing term "each radiographic exposure device" with "each piece of radiographic equipment." This change would address the apparent existing confusion whereby drive cable protective coverings are only 3 applied when connected to radiographic exposure devices. While it may be argued that the i current language addresses this issue, it was apparent to the Team that there is confusion on this ! point, and several members of the radiography community (RSOs and managers) suggested that this issue warrants a rule change. 7.2 LICENSING GUIDANCE j Revise the daily radiography inspection checklist described in Appendix P of NUREO 1556,
. Volume 2, to specifically direct radiography personnel to carefully inspect approximately one l foot of the drive cable immediately next to male connector. The radiographer should take care ;
not to introduce any di:t or dust on the drive cable during this inspection. The examination of the l cable should look for any of the following: \
. Cuts . Broken fittings . Breaks . Excessive or uneven wearing 7-1 NUREG - 1631
INPSECTION GUIDANCE
- Fraying e . Unraveling
- Nicks! '
( Kinks or bends i Loss of flexibility (abnormal stiffness)
- Excessive grit or dirt a Stretching
' Revise the description of a radiography equipment inspection and maintenance program in Section 8.18, Item 10 of NUREG 1556, Volume 2, to state that radiography drive cable assemblies should be cleaned and lubricated (when operationally appropriate) according to the recommendations of the equipment manufacturer or the cable manufacturer, or with any lubrication and cleaning recommendations established by the industrial radiography community.
Inspections of drive cables should emphasize looking carefully for any evidence of cable fraying, unwinding, or stretching, as well as any bends, kinks, or corrosion. Item 10 of Appendix C of NUREG 1556, Volume 2, should be amended to make it clear that the procedures and maintenance of radiographic equipment procedures include associated equipment, including drive cables. License myiewers should ensure that these elements are included in any radiography equipment inspection and maintenance procedures submitted by an applicant or licensee. The NRC should provide a description of these licensing program changes to the Agreement States and suggest that the Agreement States consider incorporating these changes. 7.3 INSPECTION GUIDANCE Revise Inspection Procedure 87120 to direct inspectors to physically examine a representative sample of drive cable assemblies to determine the condition of the drive cable and the male connector as well as the overall condition of the drive cable assembly. The examination should
- be sufficiently thorough to detect any of the conditions described in the suggested revision of NUREG 1556, Volume 2. Should a damaged cable be found, the inspector should notify an appropriate licensee representative and then expand the scope of his examination. The inspector should monitor what actions if any, the licensee takes in response to this discovery. Should the licensee elect to take no action, the inspector should consult with his or her regional management.
The NRC should monitor the progress of the equipment manufacturers in developing a practical
- j. field test for assessing cable flexibility. Once such a field test is developed, IP 87120 should be modified to include this test into the inspector's physical examination of drive cable condition.
NUREG - 1631 72
INSPECTION OUIDANCE i ( l The NRC should provide a description of these inspection program changes to the Agreement States and suggest that the Agreement States consider incorporating these changes. l 7.4 SS&D REVIEWS The NRC and the Agreement States that review sealed sources and devices in accordance with 10 l CFR Part 32.210 or equivalent state regulations should monitor industry changes to standards and review the need for corresponding changes or modifications to this review process. 7.5 INFORMATION NOTICE PROCESS 1 The NRC should perform a critical review of the Information Notice preparation piccess to identify what changes, if any, are required to ensure that information notices more clearly and successfully communicate (e.g., by using diagrams or photographs) with their intended target audiences. The NRC should also consider what other methods (e.g., enhanced use of the Intemet, articles in professional periodicals, and increased participation in professional meetings) or alternatives might be developed to ensure that safety-critical issues are communicated to licensees clearly so that the target audience understands the issue. 7.6 INDUSTRY The existing industry consensus standards (i.e., ANSI and ISO) establish criteria to properly design and construct various components, including cameras, controls, and source assemblies, to ensure a high degree of radiation safety. The endurance requirements contained in these standards specify that devices remain operational after 20,000 and 50,000 cycles, respectively. However, it was observed that drive cables are often subjected to more than 20,000 cycles, and in some cases, exceed 100,000 cycles. In addition, current industry standards require consideration to conditions that gamma radiography equipment may encounter which could adversely effect safe operation. For example, ANSI N43.9-1991 states "The design of the apparatus shall assure continued operation under the environmental conditions of moisture, sand, mud, and other foreign matter that the apparatus is likely to encounter in use." In addition, ISO-3999 states that the apparatus shall be designed with due consideration to their " durability and resistance to corrosion." However, these standards do not specify testing for these conditions or indicate means to enhance corrosion resistance. As a result, there appears to be substantial disparity between the testing criteria specified in these industry consensus performance standards and actual use for radiography equipment. This may be particularly meaningful in view of the fact that drive cables used in radiography systems were not designed for use in this industry, and ) cannot withstand, absent proper maintenance, the enviromnental and operational conditions to which they are subjected in this industry. The radiography industry should re-examine the - relationship between the performance and testing criteria specified in current industry consensus standards, and actual life cycle data and use conditions for each component of a radiography system to establish more representative performance and testing criteria. 7-3 NUREG - 1631 i i
INPSECTION GUIDANCE Radiography equipment manufacturers use different equipment, techniques, and criteria when conducting pull tests to evaluate swage quality (556-890 N (125-200 lbf) applied for 25 seconds to 5 minutes). The tensile test specified in ANSI N43.9-1991 for production source assemblies requires a minimum tensile force of 445 N (100 lbs) be applied within 10 seconds and held for 5 seconds; however, no standard test methodology is specified. The radiography industry should consider increasing the test criteria to conform with current industry practice, and specify standard test methodology for tensile testing of source assemblies. At least one drive cable failure occurred in a radiography system that was not typically used in harsh operating and/or environmental conditions (i.e., cobalt 60 in a fixed cell). Therefore, the radiography industry should consider the possibility of failures occurring in the absence of these
. contributing factors.
The radiographic industry should conduct a workshop to develop maintenance criteria. (especially cleaning, lubrication, and inspection) based on drive cable construction and industry operational and environmental conditions of use. For example, the industry should consider the need for differing recommendations for differing work environments such as coastal, desert, and arctic environs. Participants of the workshop should include representatives from radiography equipment manufacturers and vendors, licensees, service companies, the cable manufacturer, and the regulatory community including NRC and the Agreement States. In addition, they should consider consulting with, or including as participants of the workshop, representatives from lubrication and/or corrosion protection manufacturers or suppliers, and a metallurgist familiar with high carbon content steel wire cable and the effects on the cable of corrosion, cyclic loading, and the harsh environmental and other operational conditions to which the cables are subjected in industrial radiography. Because the Team observed that drive cable inspections by radiographer varied significantly and lacked consistency in approach, the radiography industry should consider developing standardized inspection procedures and accompanying checklists for radiographer. Until consensus is reached on acceptable and appropriate maintenance requirements, the Team recommends that radiography licensees consider using the cleaning and lubrication procedures developed by SPEC in conjunction with the cable manufacturer and contained in Appendix H. This recommendation is based on the conclusion that until an industry consensus is developed, these procedures will likely provide an acceptable interim level of protection and lubrication to the drive cable. As noted earlier in the report, there may be preferable alternatives to the Houghton G quench oil or equivalent for field use. As a result, the Team has made a recommendation to the radiography industry that this issue be addressed as part of a workshop designed to develop an industry standard. Radiography licensees should closely monitor the development of the industry standard and make appropriate c%nges to their maintenance procedures. NUREG - 1631 7-4
l INSPECTION GUIDANCE ! ) 7.6.1 MANUFACTURERS i { Manufacturers and vendors of drive cable should consider modifying their operations and use l l manuals, furnished to customers, to include instructions for proper inspection of drive cables and l male connectors in the equipment inspection procedures, or equivalent, section. In addition, l drive cable suppliers should consider developing a simple in-field testing apparatus to assess drive cable condition. A suggested approach would be to develop a modified go/no go gauge similar to the one currently supplied by Amersham. This gauge could include the ability to assess cable flexibility and elasticity, diameter, and helix pitch. Possible means to assess cable flexibility and elasticity include the following: l . Attach a known weight to the cable and compare its deflection to a standard for appropriate flexibility.
. Deflect the cable a known distance, release the cable, and measure the degree to which it retums to its original position as compared to a standard for appropriate elasticity.
The flexibility test could be accomplished if the gauge had sufficient weight to perform the test and a means to easily attach it to the tip of the male connector. The elasticity test could be accomplished by marks placed on the gauge's length for initial deflection and acceptable return distance. Cable that failed to deflect or retum the proper distance would not be considered acceptable. To measure cable diameter, the gauge could have cut-outs sized to the minimum criteria of cable diameter at the helix and inner wrappings. A cable that could fit into these cut-outs would not be considered acceptable. Finally, as a measure of cable integrity, the helix pitch could be measured to identify stretching of the cable or helix wrapping. This could be accomplished by cutting notches into one side of the gauge at intervals that, when placed against a cable, would align with helix of the correct pitch. If the gauge would not properly align with l the helix, the cable would not be considered acceptable. These tests could likely provide sufficient opportunity to detect a cable failure in its early stages. Manufacturers and vendors of drive cable should reexamine the appropriateness of the TCl 5222 cable in industrial radiography systems as currently used and designed. This should include an examination of altematives to the use of this cable and an evaluation of other methods for conducting industrial radiography which would substantially reduce fatigue and corrosive attack on the cable, or eliminate entirely the need for the use of 5222 cable. In addition, manufacturers and vendors of drive cable should take a lead role in establishing appropriate maintenance and inspection procedures and recommendations. l 7.6.2 RADIOGRAPHY LICENSEES / RADIOGRAPHER Licensees should emphasize the importance of adequate inspections and maintenance of all associated equipment, including drive cables. This function should be emphasized during 7-5 NUREG - 1631 l
INPSECTION GUIDANCE training of radiographer, radiographer's assistants, and maintenance personnel. This could include an increased emphasis during initial training, related questions on certification examinations, and during periodic refresher training. Radiographic equipment inspection procedures should be modified to include checklists which include all associated equipment, including drive cables. Emphasis should be placed on identifying any evidence of cable fraying, unwinding or stretching, as well as any bends, kinks or corrosion within 30.5 cm (12 inches) of the male connector. Although these features may not be definitive precursors, they may indicate damage to the drive cable which could result in ultimate failure. Drive cables exhibiting these features may warrant enhanced observation or replacement. 7.7 REGULATORY AGENCIES Monitor and work with the radiography industry to develop changes to applicable standards, practices and to develop guidance for radiographer and individuals who may perform inspections or maintenance. If appropriate, these should be evaluated for inclusion within 10 CFR Part 34 and equivalent Agreement State regulations. The NRC should revise the current version of the radiography training video entitled Taking Control, Safety Proceduresfor industrial Radiographer to correct the apparent testing of an alarming rate meter while the device was off, to delete the use of a light penetrating oil, and to demonstrate proper cleaning and lubrication materials and techniques. Because of time constraints on this inspection, the Team was not able to conduct independent verification analyses of the drive cable failures in order to substantiate the failure pathways and applicable conclusions. The Team relied on the analyses conducted by Analytic Answers,Inc. on behalf of Amersham. The results appear to be accurate and reliable. However, the NRC should determine ifindependent testing is warranted. The NRC in cooperation with the Agreement States and the industrial radiography industry, should develop a poster-style NUREG similar to the fixed gauge poster developed in cooperation with the Atomic Energy Control Board of Canada. The poster should clearly and simply describe how the cable functions, discuss how to detect impending cable failures, include images depicting examples of drive cable failures, and incorporate guidelines developed by the industry describing the proper lubrication and cleaning methods for drive cables. The NRC and Agreement States or organizations such as the Conference of Radiation Control Program Directors or the Organization of Agreement States should consider participating an industry workshop to address the inspection and maintenance issues for drive cables and other key findings addressed in this report. NUREG - 1631 9 7-6
i l l l Appendix A l Special Team inspection Charter i l l l i l
l g [ g i UNITED STATES l s" j t NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20566.0001
\ . . . . . ,o# January 21, 1998 MEMORANDUM TO: Larry W. Camper, Chief Medical, Academic, and Commercial l Use Safety Branch Division ofIndustrial and Medical Nuclear Safety, NMSS FROM: Donald A. Cool, Director ,
Division of industrial and / C Medical Nuclear Safety, NMSS
SUBJECT:
SPECIAL INSPECTION TEAM CHARTER (AMERSHAM RADIOGRAPHY DRIVE CABLE FAILURES) This memorandum confirms the establishment of a Special Inspection Team to conduct
- inspection follow up of the Amersham radiography drive cable failures, involving MQS, Calumet
{ Testing Services, Inc, and possibly other licensees and/or facilities. The inspection will review not only these failures, but reports of drive cable failures over the past several years to i determine if a generic problem exists and the root cause(s) of the failures. You are hereby designated the team leader and should report status directly to me. Your team members are: John Pelchat (Region 11 Senior inspector), Debbie Piskura (Region lll Senior inspector), Douglas Broaddus (NMSS Mechanical Engineer). Portions of the inspection fol. low up that occur in Agreement States (e.g., Louisiana, Texas, and the Commonwealth of Massachusetts) will include representatives from their respective regulatory bodies. For inspections conducted in an Agreement State, the applicable regulatory body will retain the lead for these activities and follow up. The special inspection team shall integrate theses findings with the results of its own inspections to complete the assigned task. A Special Inspection Charter has been prepared in accordance with NRC Management Directive MD 8.3 and Inspection Manual Chapters 0325 and 93800. A copy of the Charter, MD, 1 and Chapters are attached for your use. The objective of the team is to gather information and i I make appropriate findings and conclusions in the areas listed in the Charter. These will then be used as a basis for any necessary follow up actions. The inspection will be conducted in two
. phases. The initial phase commenced on December 22,1997, focusing on inspection of the NRC licensees reporting cable failures. The second phase of the inspection will take place
- during January and February 1998 and will focus on site visits to Amersham manufacturing and t
customer service facilities, interface with Agreement State licensees and/or regulators who j have l CONTACT: Douglas Broaddus, NMSS/IMNS (301)415-5847 e-mail DAB @NRC. GOV l A1 NUREG - 1631
L. Camper reviewed similar drive cable failures, review of the Nuclear Materials Event database and 10 CFR Part 21 reports, and review of the failure analyses performed for Amersham. I While assigned to this inspection, all team members are relieved of their normal duties. The team's report should be issued within about 30 days of the time the team completes all inspection and review activities. You should serve as the on site NRC spokesperson. - Attachments: 1. Special Inspection Team Charter
- 2. Proposed inspection Schedule
- 3. MD 8.3 l l
- 4. IMC 0325
- 5. IMC 93800 I
cc w/atts: H. Thompson, EDO l C. Paperiello, NMSS - D. Cool, NMSS l T. Martin, AEOD 1 D. Bangart, OSP j l 1 NUREG - 1631 A-2
l l i Amersham Special Insoection Team Charter ! A. Basis MOS inspection, Inc. (MQS), an NRC radiography licensee, reported that on November . 16,1997, the drive cable on one of their Arnersham Model 660 exposure devices had { broken, separating the source assembly from the cable. On December 8,1997, MQS J reported an additional instance where the source became separated from the drive cable. A record search of the Nuclear Materials Event Database (NMED) indicated that as of December 11,1997, MOS had reported a total of four drive cable failures. The two additional failures occurred in 1995 (broke off in the camera during retraction) and in 1996 (identified during periodic maintenance). Calumet Testing Services Inc. (CTSI), also a radiography licensee, reported an additional cable break that occurred on November 21,1997. All cable failures have occurred 0.125" to 0.5" (0.64 cm to 1.27 cm) behind the male connector. All these events / failures involved an Amersham Model 660 radiography system. All cables were subsequently sent to Amersham, either in Massachusetts or Louisiana, for analysis. A review of the NMED data and Part 21 reports indicate that as many as 15 additional repsrts of cable breaks have aurred in .ae past. The majority of these tailures have occurred in the States of Texas and Louisiana. These cable breaks have occurred with Amersham Model 660 equipment as well as with SPEC Model 150 and INC Model IR-100 radiographic exposure devices. This data may indicate that the scope of the problem is broader than originally suspected and support the possibility of a generic issue. Amersham, the manufacturer of the Model 660 radiography system, is located in Massachusetts, an Agreement State, and operates a customer service facility in Louisiana . The Commonwealth of Massachusetts has authority over material licensees and sealed source and device certificate holders within its borders, including those certificates issued for Amersham equipment. The State of Louisiana has equivalent authority within its borders, but has no registration certificates issued to Amersham. Massachusetts has been following up with the analysis of the broken cables and has been providing NRC with their results. NRC has volunteered assistance for inspections and other functions to assist them with their review of the failures. A contractor has performed , metallurgical analyses on all five of the recent failed cables. . l Amersham has received reports from the contractor for all of these analyses and has shared the findings with NRC. Amersham expects to complete its analysis of the reports by the end of January,1998. j Triumph Controls, the manufacturer of the drive cable, is located in Pennsylvania. i Triumph is not an NRC licensee, but is a supplier of basic component equipment intended for use in devices used by NRC licensees. Triumph supplies its cable to all three radiography equipment manufacturers in 500-1000 foot lengths that are cut to the desired length by the manufacturers. Use of this "off-the-shelf" component by all three major radiography camera manufacturers increases the likelihood that the cable failures are of generic consequence. i A-3 NUREG - 1631 i
- The basis of the Special Inspection is that this may be indicative of generic product problems that may present significant health and safety concerns. Further investigation is necessary to evaluate this issue, determine the root cause(s) for the failures, and recommend an appropriate course of regulatory action.
B. Scope in order to evaluate whether there is a generic product problem, develop the safety significance of the failures, and recommend an appropriate course of action, the team should address the following:
- 1. Evaluate the root cause(s) of the failures and associated problems with manufacturing processes and user procedures. This should include:
(a) inspection of licensees reporting cable failures and the circumstances surrounding the failures; This would include MQS, Calumet,' and a sample of Louisiana and Texas licensees - (b) adequacy of user mainter ance of the cables, including visualinspections, cleansing, and lubrication (c) review of the licensee's (user's) radiographic operations to evaluate if the use conditions and/or environment contributed to the cause(s) of the failures and any similar use conditions (trends) associated with each of ' the failures (d) inspection of the Amersham's customer service records located in MA and LA to help bound the scope of the failure and determine if similar problems have occurred resulting in the same or similar failures (e) . an interface with Louisiana and Texas regulators responsible for reviewing previous reports of drive cable failures (f) the design and actual condition of the cables (including an appropriate independent evaluation of the cable condition) to determine the failure mode (g)- Amersham's and Triumph's production process for the cables to determine if any significant changes have occurred with the cable construction and evaluate if any of the processes could cause stress concentrations that could lead to the failures
- 2. Evaluate the failure analysis report performed by Amersham's contractor for the five recent cable failures.
- 3. Evaluate whether early waming of these types of failures could be detected during maintenance or periodic user inspection.
- 4. Evaluate the adequacy of the Amersham's investigation of the event and corrective actions.
NUREO - 1631 A-4
t-I l
- 5. Determine the cause of the failures of the (approximately 15) other cable failures 4 that were identified in NMED and the Part 21 reports and if they occurred in the same manner and under similar conditions as the MQS and CTSI failures. I I
j 6 Determine, through inspection, if the other manufacturers (SPEC and/or INC) of l radiographic equipment are experiencing sirr.3ar failures and evaluate the design ( ! and use conditions of the other manufacturer's equipment to identify any ' ! similarities. l 7l Determine if Triumph Controls has had reoorts of similar failures with other users f of their cable when subjected to similar conditions in other industries. 6 Evaluate the adequacy of MQS's and CTSI's dose evaluations.
- 9. Determine / evaluate the generic aspects of the above. l
- 10. Thoroughly evaluate any other technical or regulatory issues associated with the cable failures which may arise during the inspection, but are currently unknown.
- 11. - Provide recommendations for technical and regulatory adjustments based upon the inspection findings.
i l l l I ! A5 NUREG - 1631 l l w _ ___ - ______-_____
')
Proposed Schedule for inspections: I January 22 23,1998 (firm)
.- Meeting with Massachusetts Radiological Staff
. Inspection of Amersham Manufacturing facility in Burlington Massachusetts ,
January 29,1998 (tentative) Inspection Team meeting at NRC HQ to review Amersham Inspection findings and plan upcoming inspection activities January 30,1998 (firm) Inspection of Triumph Controls in North Wales, Pennsylvania
. February 4-6 (firm)
Review of Louisiana licensee event data with the State of Louisiana radiological staff in Baton Rouge, LA, and site visits to sample Louisiana licensees who have experienced failures. Inspection of Amersham Service facility in Baton Rouge, LA, to review earlier cable failures Review of evant data at Source Production and Equipment Company (SPEC) in St. Rose,11. February 9-11 (firr.1) Review of Texas licensee event data with the State of Texas radiological staff in Austin,
- TX, and site visits to sample Texas licensees who have experienced failures February 17-27 Complete review and analysis of all NMED data on drive cable failures
- Complete review of all Part 21 reports of drive cable failures Review and evaluate Amershain contractor analyses of cable failures 1 March 9-20
'. Compile inspection findings and prepare report NUREG - 1631 A-6
l i i l 1 1 i I l
- i l
l l I 1 i 1 Appendix B l Information Notice No. 97-91 , 1 i I I t 1 l
l UNITED STATES l NUCLEAR REGULATORY COMMISSION l OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS WASHINGTON, D.C. 20555 i December 31,1997 i i l I NRC INFORMATION NOTICE 97-91: RECENT FAILURES OF CONTROL CABLES USED ON l AMERSHAM MODEL 660 POSILOCK RADIOGRAPHY ! ! SYSTEMS l Addressees I All industrial radiography licensees. Puroose The U.S. Nuclear Regulatory Commission (NRC) is .asuing this information notice to alert addressees to potential failures of control (drive) cables used on Amersham Model 660 Posilock radiography systems. It is expected that recipients will review this information for applicability to their radiographic equipment and consider actions, as appropriate, j to avoid similar problems. However, suggestions contained in this information notice are not ] NRC requirements; therefore, no specific action nor written response is required. l l Description of Circumstances , Recently, NRC became aware of several instances where the control cables used on Amersham Model 660 Posilock radiography systems became disconnected from the source , assemblies. In each instance, the control cable broke at the male end of the control cable, and ! emergency procedures were implemented to retum the source to the fully shielded and secured position. Three recent cases are described below: 1 Case 1: On November 16,1997, a licensee was perfvrming routine radiographic operations at j a temporary job site. At the completion of the ninth radiographic exposure, the radiographer attempted to retract the source assembly into the radiography camera, using the remote drive assembly. The radiographer observed that his survey meter reading did not change as expected as the control cable was being retracted. Furthermore, the radiographer noted that
' the self-locking mechanism on the radiography camera had not actuated. The radiographer operated the remote drive assembly again, but did not succeed in retuming the source assembly to the fully shielded and secured position. The radiographer and his assistant then l implemented emergency procedures, maintained control of the area, and contacted their l radiation safety officer (RSO). The RSO responded to the temporary job site and successfully recovered the source assembly, placing it into an Amersham 650L source changer. The licensee then reported th) source disconnect to the NRC Operations Center. The licensee also submitted a 30-day report to the NRC.
9712310254 B-1 NUREG 1631 l
IN 97-91 December 31.1997 Page 2 of 4 Case 2: On December 8,1997, this same licensee reported another source disconnect, also at a temporary job site, where the control cable failed in the same manner. In this instance, an Amersham representative retrieved the disconnected source assembly. The licensee reported the source assembly disconnect on the same day of the event. In addition to these two source disconnects, this licensee reported to NRC that it had two previous source assembly disconnects on Amersham Model 660 Posilock radiography systems, both having similar failures of the control cable. These disconnects occurred in 1995 and 1996. Case 3: On November 21,1997, another licensee was performing routine radiographic operations at a temporary job site. The radiographer noted that the source assembly had not retracted to the fully shielded and secured position, implemented emergency procedures, and notified their RSO. The RSO and a former RSO responded to the temporaryjob site and successfully recovered the source assembly, returning it to the radiography camera. The control cable failed in a similar manner to the previous two cases. Normal operations were resumed using anothe control cable. The licensee did not report the source disconnect to the NRC Operations Center within the 24-hour timeframe, as required by 10 CFR 30.50(b)(2), but did submit a 30-day report. Discussion in all the cited cases, the control cable failed at a point approximately 0.33 - 1.25 centimeter (0.125 - 0.5 inch) behind the male connector. The failed equipment from each instance has been returned to the manufacturer for failure analysis. A metallurgical analysis has been completed on two of the control cables with the results indicating failure from fatigue and failure due to corrosion and/or fatigue. The cause of the remaining failures is still under investigation by the manufacturer. Due to these failures, it is recommended that the control cable be carefully checked before each day's use and during the quarterly maintenance checks, as required by 10 CFR 34.31(a) and (b), for indications of corrosion, metal fatigue, or other early indications of cable failure. It is important to note that these control cables can be purchased off-the-shelf and may be used on radiography systems manufactured by various companies, and, therefore, these failures may not be limited to control cables used on Amersham Model 660 Pmilock radiograpN systems. Each of the source disconnects discussed above required the radiographer to implement emergency procedures to return the source assembly to the fully shielded and secured position. Implementation of emergency procedures is crucial to successful source assembly retrieval as well as to ensuring that exposure of radiographer and members of the public remain as low as is reasonably achievable. In all three cases, after identifying that the source assembly had become disconnected from the control cable, the radiographer adequately secured and controlled the area surrounding the disconnected source assemblies. In addition, the exposures to the individuals involved in the source assembly retrievals were well within regulatory limits. Therefore, it is important to implement and adhere to emergency procedures when source assembly disconnects are identified. i NUREG - 1631 B-2
IN 97 91 December 31.1997 Page 3 of 4 A source assembly disconnect on the Amersham Model 660 radiography system can be identified by two methods. First, upon completion of retracting the control cable, the self-locking mechanism should engage, revealing a green dot. This can be identified by observing the indicator (lock slide) on the locking mechanism. Failure of the self-locking mechanism to ) engage would cause the red dot to remain visible on the lock slide, thus indicating the source l was not secured in the fully shielded position, although not necessarily indicating a source assembly disconnect. Second, when the survey to verify that the source assembly has been returned to its shielded position is performed after each radiographic exposure, as required by ) 10 CFR 34.49(b), typical dose rates around the radiography camera and the guide tube should be observed. However, if the dose rates observed are not typical for a fully shielded source ; assembly (e.g., the dose rates may be lower if the source assembly remained in the collimator { or the dose rates may be higher if the source assembly is located within the guide tube), then , the situation should be further investigated. Therefore, it is important to use the survey meter and to pay careful attention to its readings and the self-locking mechanism indicator to identify ' circumstances that are not normal. j in cases of unintentional disconnection of the source assembly from the control cable or the inability to retract the source assembly to its fully shielded and secured position, licensees must notify NRC within 24 hours, ptJsuant to the regulations in 10 CFR 30.50(b)(2). The notification must be made to the NRC Operations Center. In addition to making a notification within 24 hours, the licensee must also submit a written report to NRC within 30 days, as required by 10 CFR 30.50(c)(2) and 10 CFR 34.101(a). One report can satisfy both of these requirements, l but it must include: (1) a description of the equipment problem; (2) cause of each incident, if known; (3) manufacturer and model number of equipment involved in the incident; (4) place, time, and date of the incident: (5) actions taken to establish normal operations; (6) corrective actions taken or planned to prevent recurrence; and (7) qualifications of personnel involved in the incident [10 CFR 34.101(b)). Additional information on reporting requirements for industrial radiography licensees can be found in Information Notice 96-04, " incident Reporting Requirements for Radiography Licensees? Reporting such problems to NRC is important because it provides the opportunity for NRC to verify that the material has been properly secured and has not been released into the public domain. If notified early, NRC can help ensure that all necessary regulatory actions are completed. In addition, NRC reviews this information to determine if trends or generic safety issues exist that have the potential to cause a significant safety hazard. If a generic safety issue is identified, those licensees that may be affected will be notified and informed of the proper actions to reduce or eliminate similar incidents in the future and to protect the health and safety of both the occupational workers and the public. It is important to point out that these failures have not been identified as a generic safety issue at this point in time, but that the recommendations provided in this information notice should be considered by those licensees who use Amersham Model 660 Posilock radiography systems. The Commonwealth of Massachusetts (hereafter, Commonwealth) has been informed of all the l cases discussed above and is working with Amersham on the determination of whether these i B-3 NUREG - 1631
IN 97-91 December 31.1997 Page 4 of 4 failed control cables ' represent a generic safety issue. NRC will coordinate with the Commonwealth to determine if any actions are necessary, based on the findings from the failure analyses being performed by Amersham. This information notice requires no specific action nor written response. If you have any questions about the information in this notice, please contact the technical contact listed below or the appropriate regional office. i f, u 2 , n-i- \ Donald A. Cool, D'r ector Division of Industrial and Medical Nuclear Safety Office of Nuclear Material Safety and Safeguards Technical contact: Larry W. Camper, NMSS 301-415-7231 E-mail: lwc@nrc. gov Attachments: l
- 1. List of Recently issued NMSS Information Notices
- 2. List of Recently issued NRC Information Notices i
l NUREO - 1631 B-4 i
Attachmsnt 1 IN 97-91 December 31.1997 Page 1 of 1 LIST OF RECENTLY ISSUED NMSS INFORMATION NOTICES Information Date of Notice No. Subject issuance issued to - 97-89 Distribution of Sources and 12/29/97 All sealed source and device Devices Without Authorization manufacturers and distributors 97-87 Second Retrorit to Industrial 12/12/97 Allindustrial radiography
. Nuclear Company IR100 licensees Radiography Camera, to Correct inconsistency in 10 CFR Part 34 Compatibility 97-86 Additional Controls for Transport 12/12/97 Registered users of the Model of the Amersham Model No. 660 No. 660 series packages, and Series Radiographic Exposure Nuc! ear Regulatory Commission Devices industrial radiography licensees l ~ 97-75 Enforcement Sanctions issued 09/24/97- All U.S. Nuclear Regulatory as a Result of Deliberate Commission licensees Violations of NRC Requirements 97-72 Potential for Failure 09/22/97 All holders of OLs or cps of the Omega Series for nuclear power reactors Sprinkler Heads and fuel cycle facilities 97-65 : Failures of High-Dose- 08/15/97 All high-dose-rate remote i Rate Remote Aftenoading afterloader licensees Device Source Guide Tubes,
. Catheters, and Applicators 97-64 Potential Problems 08/13/97 All U.S. Nuclear Regulatory Associated with Loss Commission medical tele-of E'ectrical Power therapy licensees in Certain Teletherapy j Units :
97 6.1 U.S. Department of 08/06/97 All U.S. Nuclear Regulatory Health and Human Commission rnedical Services Letter, to licensees, veterinarians, i Wiedical Device Manu- and manufacturers /distri- ; facturers, on the butors of medical devices Year 2000 Problem Be5 NUREG - 1631 ; l
Attachment 2 IN 97-91 December 31,1997 Page 1 of 1 LIST OF RECENTLY ISSUED NRC INFORMATION NOTICES Informabon Date of Notce No. Subject issuance issued to 97-90 Use of Nonconservative 12/30/97 All holders of OLs for nuclear Acceptance Criteria in power reactors except those Safety-Related Pump who have ceased operatons Surveillance Tests and have certified that fuel has been permanently removed from the vessel 97-89 Distnbuten of Sources and 12/29/97 All sealed source and device Devices Without Authorization manufacturers and distributors 97-88 Experiences During Recent 12/16/97 All holders of OLs for pressurized-Steam Generator Inspectons water reactors except those who have permanently ceased operations and have certified that fuel has been permanently removed from the reactor 97-87 Second Retrofit to 12/12/97 Allindustrial radiography ladustrial Nuclear Company licensees IR 100 Radiography Camera, to Correctinconsistency in 10 CFR Part 34 Compatibility 97-86 Additional Controls for 12/12/97 Registered users of the Model Transport of the Amersham No. 660 series packages, and Model No. 660 Series Nuclear Regulatory Commission Radiographic Exposure Devices industrial radiography licensees 97-85 Effects of Crud Buildup 12/11/97 All holders of Ols for pressurized-and Boron Deposition on water reactors, except those Power Distribution and licensees who have permanently Shutdown Margin ceased operations and have certified that the fuel has been permanently removed from the reactor vessel OL = Operatmg License CP = Constructed Permit NUREG - 1631 B-6
i i 1 1 i l l l l { l Appendix C l Amersham Analysis Report Dated l February 6,1998 I I l i I
I SENTINEL Amersham Corporation 40 North Avenue Burlington, MA 01803 tel (781) 272-2000 tel (800) 815-1383 fax (781) 273-2216 Mr. Bob Ha!!isey Radiation Control Program Department of Public Heahh grAmerSham The Commonwealth ofMassachusetts 305 South Street QSA Jamaica Plain, MA 02130 Fax: 617-727-2098 6 February 1998
Dear Mr. Hallisey:
Enclosed please find a copy of the report of our analysis for the drive cable breaks that have occurred recently. The report covers the sequence of events and the subsequent evaluation and Part 21 assessment. This covers our Returned Material Authorization (RMA) numbers 775,780,780-A,782,784 and 788. RMA numbers are assigned to equipment related customer complaints and are investigated and documented under our procedures SOP-QO30, " Product Complaint Handling - Returned Material Authorization" and SOP-QOO2,"Part 21 Procedure". Please let me know ifyou require any additional information. Sincerely, Cathleen Roughan V Regulatory Affairs and Safety Manager C-1 NUREG - 1631
SENTINEL Part 21 Evaluation: Drive Cables 4 Amersham Corporation February 6,1998 l Burlington, Massachusetts Page 1 of 11 Part 21 Evaluation Report: Projector Drive Cables February 6,1998 This document reports on the analysis of failed projector drive cables performed by Amersham as required under 10 CFR 21. The evaluation was conducted in accordance with Amersham SOP-Q002 and SOP-Q030. Drive Cables The drive control units used on Amersham projectors consist of either a welded tubular frame with a hand-crank or a pistol-grip hand-crank which drives a flexible carbon steel cable. The cable moves inside a flexible housing (sheath) of helical-wrap steel lined with Teflon and covered in bright yellow PVC. The cable consists of a commercially available winding made up of multip;e wires with a ball connector at one end. The drive cable itselfis a 3/16-inch diameter Teleflex cable manufactured by Triumph. The cables are comprised of three wraps ofwire: The inner core consisting of the smallest diameter wires An intermediate wrap of wires
+
A single large-diameter wire that forms an outer helical wrap This cable has been used extensively in the radiography industry since the 1960s. The cable connects to the source wire with a swivel coupling. The male connector is swaged onto the drive cable; the female, onto the source wire (Figure 1). pgg Female and Male Swivel Coupling
?
[ .p. _gp- - - Source Stop Ball Drive Cable Figure 1: Drive Ceble-Source Connection NUREG - 1631 C-2 1
l SENTINEL Part 21 Evaluation: Drive Cables Amersham Corporauon February 6,1998 Burlington, Massachusetts Page 2 of 11 l l When the cable is coupled to a radiographic source in a projector unit and a guide tube is fitted to the projector outlet, counterclockwise rotation of the hand crank in the EXPOSE direction propels the source out of the projector through the guide tube to the exposure position. Rotation in the RETRACT direction moves the source back into the projector. Source Wire y Connector ., m
.~ ,
l Dnve Cable Connector Figure 2: Drive Being Connected to the Source Wire at the Lock Assembly A cable break during operation of the projector or during field replacement of the source could pose a significant safety risk as the source cannot be returned to the projector. Chronology This evaluation examined five customer complaints of drive-cable failure and one customer-identified event. The instances are summarized in Table 2, " Returned Materials Summary," on page 7. All of the failures occurred with drive cables that , had been in the field for at least five years. l 1 The first complaint, Returned Materials Authorization (RMA) 775, was received ) on September 15,1997. A preliminary review and a customer-initiated ! i rnetallurgical analysis that accompanied the complaint indicated no need for a Part 21 Evaluation. The projector and equipment had been purchased used, and the age and maintenance history were not known. Only a small portion of the cable was provided and no connector was returned. The cable itself was heavily corroded. The preliminary review determined that the failure was due to corrosion and wear, and that the failure was not Part 21. When the Pan 21 Evaluation was initiated for cable failures reported in November, RMA 775 was included in the study due to potential similarities. Failures at two different customer locations were reported on November 16 (RMA 780) and November 21,1997 (RMA 782). RMA 780 included a repon of a failure that occurred in 1995. That connector was returned to Amersham in December for analysis as RMA 780-A. C-3 NUREG - 1631
SENTINEL Part 21 Evaluation: Drive Cables ; Amersham Corporation February 6,1998 l Burhngton, Massachusetts Page 3 of 11 j Preliminary review of the new RMAs conducted by Engineering and Regulatory Affrirs concluded that the breaks were potential Part 21 issues and an evaluation was initiated. A Part 21 Review Board met in December 1997, by which time a fifth failed cable was received (RMA 784). De board agreed to the following actions: Order metallurgical analysis of the returned materials with additional testing of materials if necessary. The analysis was performed by an outside laboratory using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and other non-destructive tests.
. Review RMA logs to determine trends.
Determine the age, service history and usage pattems of the failed components, as well as any special environmental factors. Review the manufacturing process for contributing factors. Discuss the drive cable failures with service personnel. Measure the drive cable diameters and examine the condition of the cables and the male connectors. Retrieve the male connectors from customers. Analyze the components for similarities and differences. A sixth drive cable (RMA 788) was received on January 21,1998, and was also included in the study. The damaged cable was discovered in 1995 during routine radiography and was pulled from service by the customer's RSO. The cable sample, which was approximately seven inches long, had been cleaned and extensively handled between the failure and the time of delivery to Amersham. At the request of the NRC, no destructive tests were performed on this sample. Findings ne actions produced the following results: Metallurgical Analysis ne outside test laboratory identified the cause of the cable breaks as a combination of tensile overload, fatigue and conosion fatigue. Inspection of the fracture faces showed plastic deformation on some strands, indicating tensile failure, and smooth breaks on others, indicating brittle failure mode. Corrosion fatigue refers to the simultaneous action of corrosion and fatigue. In this situation, the endurance limit under alternating stress such as flexing is lowered when a specimen is subjected to a corrosive environment. The fracture surfaces of the inner wires were corroded, indicating that these wires probably failed before the failure of the whole cable. NUREG - 1631 C-4
SENTINEL Part 21 Evaluation: Drive Cables Amersham Corporebon February 6.1998 Burlington, Massachusetts Page 4 of11 The test lab also analyzed Teleflex cable and individual wires supplied by the manufacturer. The wires were pulled to failure, and the fracture surfaces were examined to confirm the characterization of the tensile and brittle failure modes. This study showed that individual wires and cables pulled to tensile failure had fracture surfaces that were generally more consistent with tensile overload failure than the RMA fracture surfaces. However, this study also revealed that stresses ' induced during cable manufacture (that is, winding) may contribute to fatigue failure. (Cycle testing shows this stress by itselfis not significant.) Review of RMAs A review of previous RMAs back to 1991 showed five cases of cable breaks. Four of the breaks occurred on cables with significant corrosion and wear, and diameters reduced to 0.150 to 0.181 inches. As manufactured, the cable diameter is 0.187 inches nominal. The fifth failure was independently analyzed and determined to be caused by corrosion and wear. The cables were broken at different distances from the male connector (6 inches to 21 feet) as shown in Table 1. Table 1: Previous Cable Break Instances RMA Year Description Cause 482 1992 Cable was dirty and had oxide particles; Fatigue cable diameter was 0.150" 537 1993 Break 6" from the drive wheel; cable Age, wear diameter was 0.177" at the break; pitted at break point. 601 1994 Cable diameter 0.179"; break 6" from the Age, wear connector; significant corrosion and rust; the cable was stiff. 639 1995 Break was 21 feet from the connector. Corrosion, wear l Independently analyzed. l 1 703 1996 Cable diameter 0.181"; seven to five years Age, wear old; break at 1/2 the cable length; excessive wear on coils; stretching of outer coils indicated that the break was not spontaneous. Service History None of the customers could accurately determine the age and number of cycles of the failed cables, but all agreed that the cables were at least five years old. Based j on customer input, there were no unusual operating environments, and only one setup that might have contributed to the failure. C-5 NUREG - 1631
SENTINEL Part 21 Evaluation: Drive Cables Amersham Corporation February 6,1998 Burlington, Massachusetts Page 5 of 11 Cable maintenance was performed annually by the customer that experienced three failures (RMAs 780,780-A and 784). The customer that returned RMA 782 said that they performed maintenance quarterly. That customer reported using the penetrating oil WD-40, which is not the lubricant recommended in the Model 660 l Series manual. In addition, we had previously sent a notice to all customers that penetrating oils such as WD-40 should not be applied to the cables. The maintenance histories for RMAs 775 and 788 are unknown. The Model 660 Series operating manual requires quarterly maintenance of the drive cables including: Removing the drive cables form the controls Inspecting for kinks and rust Inspecting thejuncture of the cable and male connector for signs of wear or damage Cleaning and lubricating the cables with Mil. Spec. grease before reassembly Manufacturing Procedures The manufacturing process was reviewed and we found no manufacturing procedures that could contribute to the failure. None of the failures (in this review or in the five previous RMAs) occurred with new cable. All breaks occurred on caHe that had been in the field for several years. Amersham has previously subjected the cable to endurance testing in excess of the 50,000 cycles and found no evidence of breaking, validating the design and manufacturing process. Discussion with Service Personnel Based on experience and history, Amersham service personnel indicated the following factors that may influence drive-cable failures: Transporting the drive assembly without the protective cover on the cable end and having a length ofcable exposed. This exposes the cable to adverse environmental conditions and physical damage, for example, when the drive cable is in the back of a truck containing film-developing chemicals. Lack oflubrication and maintenance.
- Based on their condition, the returned cables should have been removed from service.
NUREG - 1631 C-6
l l' l ' SENTINEL - Part 21 Evaluation: Drive Cables ! Amersham Corporshon February 6,1998 Burlington, Massachusetts Page 6 of11 l l Cable Conditions-Corrosion and a lack oflubrication was evident on all of the returned cables. The diameter of the cables ranged from 0.183 inches to 0.187 inches. Several cables L
' were kinked approximately five inches from the male connector, and the coils of l Teleflex were worn at the kink and at the break indicating that the cable had been used for some time with the kinked condition.
l Male Connectors The male connectors were retrieved from all but two sites. The four returned connectors showed that the breaks occurred directly behind the connector. The - t location of the break relative to the connector could not be confim.J in the other two cases because the connectors were not available. However, the customers l repoited the breaks as being close to the connector. Lot numbers west _not visible on the returned connectors, confirming that the cables had been in the field for a long time. l~ Similarities and Differences A comparison of the six RMAs is provided in Table 2. I C-7 NUREG - 1631 L - - ____ _ _ _ _ _ _ _ _ _ - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ \
SENTINEL Part 21 Evaluation: Drive Cables Amersham Corporation February 6,1998 Burlington, Massachusetts Page 7 of 11 Table 2: Retumed Materials Summary RMA 775 780 780-A 782 784 788 Date Failed 8/19/97 11/16/97 1995 11/21/97 12/8/97 ~1995 Date Reported 9/15/97 11/17/97 11/17/97 11/26/97 12/8/97 1/21/98 Date Analyzed 9/97;11/97 11/97 12/97 12/97 12/97 1/30/98 Components Returned Cable Yes Yes No Yes Yes Yes Connector No Yes Yes No Yes Yes Cable Unknown 0.186 inches Unknown 0.187 inches 0,183 inches 0.185 inches Diameter Location of Unknown 1/8" from 1/8" from Unknown 1/4" from 1/8" from Break connector connector connector connector Asymmetrical Yes Yes Yes Yes Yes Yes Wear at Break Corrosion on Fracture Surfaces Inner Wires Yes Yes Yes No Yes Unknown Intermediate No No No No No Unknown Wire Outer Wire No No No No No Unknown Corrosion on Wire Surfaces Inner Wires Yes Yes Yes Yes Yes Yes Intennediate Yes Yes Yes Yes Yes Yes Wire Outer Wire Yes Yes Yes Yes Yes Yes Kinking Location Unknown 5.25" from Unknown 5.5" from 2.5" and None noted connector connector 5.0" from on the connector sample Wear at Kink Unknown Yes Unknown Yes Yes N/A i 1 i NUREG - 1631 C-8
SENTINEL Part 21 Evaluation: Drive Cables Amersham Corporation February 6,1998 Burlington, Massachusetts Page 8 of 11 Table 2: Retumed Materials Summary i i' RMA 775 780 780-A 782 784 788 Fracture Type (TO = Tensile Overload; F = Fatigue; CF = Corrosion Fatigue Inner Wires TO/F/CF F TO/F/CF TO/F/CF TO/F/CF Unknown Intermediate TO/F/CF F TO/F/CF TO/F/CF TO/F/CF Unknown Wire Outer Wire TO/F/CF F TO/F/CF TO/F/CF TO/F/CF F OperationalIssues When the projector is fully assembled with controls and guide tubes, the source wire cannot be subjected to a bend of sufficient degree to produce a kink similar to those seen in the retumed cables. Input from the field identified several operational factors:
- When the drive assembly is transported without the required protective cover on the cable, the cable can be moved out from the housing and be exposed to damage.
- The locking assembly on the Model 660 Series projector is conveniently located at the top of the rear panel where it is above mud, dirt and other debris at the site. This placement does require that the user support the controls while connecting and disconnecting the cable.
- Some customers disconnect the controls from the projector, but leave the drive cable connected to the source wire, allowing the weight of the controls to settle on the cable approximately five inches from the male connector on the cable (Figure 3).
l l l l l l C-9 NUREO - 1631 L______-_-______-__-__-_____--__-__-_
l l SENTINEL Part 21 Evaluation: Drive Cables Arr -#,sm Corporation February 6,1998 Burlington, Massachusetts Page 9 of11 f [ ) Drive Cable Connected to Source
, -C':
[y s( (:: Disconnected Locking Collar Bears Down on
'(
# the Drive Cable C 'M, c C kC ' / .,~~ " - ,
l_ - _ c_ Drive Cable Kinked 5" to 6" from Connector Figure 3: Possible Cause for Drive Cable Kinks Connecting and disconnecting the cable to source wire without the depressing the connector roll pin can fatigue the cable directly behind the male connector. Administrative Factors The following administrative factors may influence the apparent increase in the number of cable breaks: RMAs were recently applied to cover damaged equipment. More documentation is now kept for what was previously considered routine damage. The NRC reporting requirements have been enhanced and better enforced, resulting in more reports, even though actual incidents may not have increased. The industry was required to have new equipment after 1992 due to 10 CFR Part 34 changes. A surge of associated equipment was put into use in 1992 to support this new equipment. As all of the equipment was put into service at roughly the same time, we are perhaps now seeing and documenting the effects of wear showing up at the same time. Teleflex is used extensively in the field by all manufacturers and there have been reports of breaks on drive cables not supplied by Amersham. NUREG - 1631 C-10
l SENTINEL Part 21 Evaluation: Drive Cables Amersham Corporation February 6,1998 Burlington, Massachusetts - Page 10 of11 Assessment Based on the metallurgical analyses and inspections of the returned materials, we conclude that wear and corrosion were the principal causes of the failures. The conclusion is based on the following indicators: Corrosion on the outside of every wire.
. . Corrosion on the fracture faces of the inner wires.
Kinks in the cables five to six inches from the male connector in three of the six RMAs. Asymmetrical wear at the point of the break. Fatigue is the principal failure mechanism. This evidence suggests two probable scenarios: Scenario A: l-
- 1. An initial event fractures some or all of the inner wires and/or causes a kink in the cable.
- 2. The damage goes undetected and the cable continues to be used as evidenced by the asymmetrical wear at the point of the break and at the kink and the corrosion on the fracture faces of the inner wires.
- 3. Afler a sufficient number ofcycles, the intermediate wires and the outer wire fail because of fatigue, along with any inner wires that did not break with the initial event.
I Scenario B: 1.' Regular lubrication of the cable is not maintained, or a solvent or I penetrating oil is used as a lubricant, stripping the cable ofits pro-tective lubricant and allowing corrosion to take place.
- 2. Over time, the cable wires oxidize.' Concurrently, the cable is flexed during connections, disconnections and normal operations.
- 3. Wire strands fail individually due to corrosion fatigue.
L Part 21 Conclusion ! Based on our review and analysis, the cables failed due to a combination of wear, corrosion and lack oflubrication, indicative ofimproper maintenance. The failures are not due to a design or manufacturing defect of the cable, and are not Part 21 reportable events under Amersham SOP Q002. I 1 C.11 NUREG - 1631
; SENTINEL Part 21 Evaluation: Drive Cables Amersham Corporation February 6.1998 Burlington. Massachusetts Page 11 of 11 Recommendations The following recommendations are based on the results of this evaluation:
- 1. Users should inspect drive cables regularly for kinks and exces-sive wear. Kinked or worn cables must be removed from service immediately.
- 2. Users must adhere to the quarterly maintenance requirements for cables as described in the manual.
- 3. Amersham should establish a recommended life for cables, most likely based on wear measurements.
- 4. Users must use the protective covers on controls as originally sup-plied to keep the drive cables within the control housing and pro-tected, and to remain in compliance with regulatory requirements.
- 5. The industry and regulators should review the use of the ANSI standard as a reference for the drive cable and ensure that the test-ing being conducted simulates real use, that is, repeated connec-tion and disconnection in dirty environments.
- 6. Cables need proper lubrication at regular intervals.
- 7. Amersham should provide more detailed information in the in-spection and maintenance sections of the operating manuals to identify preventive measures and precursor events, and to empha-size that users not apply penetrating oil as a cable lubricant.
l NUREO - 1631 C-12
l SENTINEL Ptrt 21 Evaluation: Drive Cables Amersham Corporaten February 6.1998 Burhngton, u ..,husetts Page 11 of11 L ' Recommendations
- The following recommendations are based on the results of this evaluation:
l 1. Users should inspect drive cables regularly for kinks and exces-sive wear. Kinked or wom cables must be removed from service ! immediately. l
- 2. Users must adhere to the quarterly maintenance requirements for cables as described in the manual.
- 3. Amersham should establish a recommended life for cables, most i likely based on wear measurements.
l
- 4. Users must use the protective covers on controls as originally sup-plied to keep the drive cables within the control housing and pro-
!- _ tected, and to temain in compliance with regulatory requirements. l l 5. The industry and regulators should review the use of the ANSI standard as a reference for the drive cable and ensure that the test-l . ing being conducted simulates real use, that is, repeated connec-tion and disconnection in dirty environments.
- 6. Cables need proper lubrication at regular intervals.
- 7. Amersham should provide more detailed information in the in-
- l. spection and maintenance sections of the operating manuals to i identify preventive measures and precursor events, and to empha-size that users not apply penetrating oil as a cable lubricant.
C-13 NUREG - 1631 1
l l l l l l l I l r i l l l Appendix D Amersham Metallurgical Analysis Reports ( s I i 1
} AVA\ac. Analytical Answers,l The information you need...when you need it
- i November 26,1997 Mr. Steve Grenier Amersham Sentinal 40 North Avenue Burlington,MA 01803 1
Report No: 33636 P.O. No: P1728 l PURPOSE OF ANALYSIS: j Scanning Electron Microscopy Spectroscopy (SEM) examination of a cable wire to determine the metallurgical failure mode. l SAMPLES: One broken cable assembly with RMA # 780 l METHOD OF ANALYSIS: Optical Microscopy (OM) Scanning Electron Microscopy (SEM) CONCLUSIONS In the absence of any clear evidence of the four primary fracture failure modes i.e. tensile overload, decohesive rupture, cleavage, or fatigue, the most probable cause of the wire fracture was fatigue. The fracture features for tensile overload, decohesive rupture, and cleavage are always present when metals fail for these reasons. Fatigue striations do not always develop, but the precursor marbled appearance was visible on these wire strands. This leads to the conclusion that the unit failed due to fatigue. l RESULTS: I The fracture faces on the two ends of the sample were photographed as received (See micrographs M1 and M2). The debris on the fracture surface was removed with acetone in a ultra sonic cleaner. The fracture surface were then examined in the SEM. Both large and small diameter wires were examined (See photographs M3 to M8 for typical examples of what was found). l 0-1 4 Arrow Drive, Woburn, Massachusens 01801 A Telephone:(617)9384)300 A Fax:(617) 935-5087 l w__ _-__
Report #33636, Page 2 In all but very hard alloys, tensile overload fractures generally exhibit plastic deformation and microvoid coalescence. This sample did not have these features and therefore did not fail as a result of tensile overload. Embrittled or decohesive ruptured samples will exhibit distinctive grain structure features. This sample did not have these features and therefore did not fail as a result of embrittlement or decohesive rupture. There was no evidence of cleavage. This sample did not fail as a result of high impact loading or high triaxil stress. The only remaining failure mode is fatigue. Although there was no evidence of fatigue striations (they do not always develop), this sample did exhibit the precursor marbled appearance associated with fatigue. The enclosed data sheet further describes the SEM analytical tecimique.
. b; Char es F. Tuson Failure Analyst / Microscopist CFT/jmh
Enclosures:
Samples: 1 Micrographs: 8 Data Sheet: 1 Evaluation: 1 D-2
> Analytical Answers. Inc.
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, MI 12X Opticalmicrograph t x of the connector end of the g broken cable. This is an optical
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t Note that the wires appear blunt and not tapered due to plastic Ii deformation. y l ;- w l M2 12X Optical micrograph of the mating broken cable wire. This is an optical image
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$ ha, M3 74X SEM micrograph of the connector end of the broken cable. This a SEM image of f '/' the large diameter cable wire.
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/ tensile overload.
l l M4 1.09KX SEM micrograph of the connector end of the broken cable. This is a SEM image of the large diameter cable wire. In the absence of a . e. f[l-(1. . 4 y vy%;f (
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+ 1 of the connector end of the broken cable. This is a SEM image of a small diameter cable
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wire. Note the blunt appearance of the wire, this g^ , indicates that the failure was not the result of tensile overload. l .___- _ l \ M6 1.15KX SEM micrograph of the connector end of the broken cable. This is a SEM image of a small diameter cable
, wire. In the absence of any ;+ ,y - '- .
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gy"y)Vg d s ,p = ;;g)dmh,j; a ),... M7 136X SEM micrograph of the connector end of the yjbf 1 : broken cable. This is a SEM image of a small diameter cable wire. Note the blunt appearance of the wire, this indicates that the failure was not the result of tensile overload. M8 1.04KX SEM micrograph of the connector end of the broken cable. This is a SEM image of a small diameter cable wire. In the absence of any 4 :. - clear evidence of the four
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A%\c. Anal,tlical Answers.In The information you need...when you need it
- SCANNING ELECTRON MICROSCOPY (SEM)
Scanning Electron Microscopy (SEM) is a high resolution, great depth of field imaging technique. It shows topographical, structural and some elemental information at magnifications of 10X to 300,000X. SEM Applications include:
- 1. Materials Evaluation:
Grain size distribution Surf te roughness and porosity Particle sizing Materials homogeneity Intermetallic distribution Characterization of elemental diffusion
- 2. Failure Analysis:
1 Contaminat on location Examination for mechanical damage Electrostatic discharge determination Microcrack detection I
- 3. Quality Control Screening: l Comparison of good to bad samples Material thickness determination Dimension verification MIL-standard screening Principle of Operation:
A finely focused electron beam is scanned across the surface of the sample generating secondary electrons, backscattered electrons and x-ray signals. These signals are collected by specific detectors and displayed on a viewing cathode ray tube. The raster on the cathode ray tube corresponds to the raster on the sample, while the brightness on the cathode ray tube corresponds to the amount of signal generated at each point on the sample. D-7 4 Arrow Drive.Woburn. Massachusetts 01801 A Telephone:(617)938-0300 A Fax: (617) 935-5087
i Secondary Electron Imaging (SEI) shows the topography of surface features as small as 6 nm. The production of the SEI signal is primarily dependent on surface roughness. High Resolution Secondary Electron Imaging (IIRSEI) shows the topography of features as small as 3 nm. HRSEI can also image films and stains is thin as a few atomic monolayers. An HRSEI equipped SEM can evaluate electron beam sensitive and charging sensitive materials at magnifications up to 300,000X, often without the need for sample coating and without sample damage. Cryogenic Secondary Electron Imaging (CSEI) shows the size, structure, and shape of wet materials such as hydrated polymens, slurries, oils, biological materials and food products. an SEM equipped with a cryo-preparation system will allow all SEM imaging and analysis capabilities without the need for drying the sample or extensive extraction procedures. Backscattered Flectron Imaging (BEI) shows 6e lateral distribution of elements or compounds within the top micron of the sample. An SEM equipped with a high resolution Robinson type detector (RBEI) can analyze features as small as 10 nm and composition variations of as little as 0.2 percent. The production of the RBEI signal is primarily dependent on surface composition. The Robinson Backscattered Electron Signal is sorted by intensity to produce images which show the distribution of elements and compounds within the top 0.5 microns of the sample's surface. Electron Beam Induced Current (EBIC) Imaging shows the location of sub-surface opens or shorts in microelectronic devices. It is a useful failure analysis diagnostic tool. Voltage Contrast (VC) Imaging shows presence of applied bias on the surface of a circuit or device. It identifies opens or shorts as well as voltage drops across a circuit. Electron Channeling Patterns (ECP) show localized crystallinity in a 3 micron area. It can analyze the crystalline structure of a material on a microscale and locate defects within structures. Data Output: The SEM images are viewed on a TV screen and photographed from a high resolution (2000 lines per inch) cathode ray tube with positive or positive / negative Polaroid film. Sample Constraints: The sample can be up to 15 cm x 10 cm x 7.5 cm in size. The sample must be compatible with a 104 torr vacuum; i.e., non-volatile and not susceptible to electron beam induced damage. D-8
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- December 15,1997 l
Mr. Greg Fields ! Amersham Sentinal ! 40 North Avenue Burlington, MA 01803 1 i Report No: 33733 P.O. No: 1745 ; PURPOSE OF ANAINSIS: I Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDS) ! examination of a cable wire to determine the metallurgical failure mode. ; SAMPLES: j One cable connector (RMA # 780-A) with broken cable wires protruding. METHOD OF ANALYSIS: l Optical Microscopy (OM) Scanning Electron Microscopy (SEM) Energy Dispersive X-Ray Spectroscopy (EDS) CONCLUSIONS The cables are fabricated with three different diameter iron wires. The optical examination of the fractured wire strands indicated that all the fracture faces of the small diameter wires were corroded. Although the outside surfaces were all corroded, the medium and large diameter wire fracture surfaces were not corroded. These conditions indicate that the failure occurred over a period of time and that the small diameter wires failed first. The fracture features found on each individual strand (whether large, medium, or small) varies with the strands. Certain strands failed in a ductile failure mode (tensile overload) and others with a brittle failure mode (possibly fatigue or corrosion fatigue). Conclusive evidence for the possible modes on the small diameter wires were obliterated by the corrosion bi-products on the fracture surfaces of those wires. The evidence for fatigue on the medium and large diameter wire strands is not conclusive. Although not conclusive the fracture features on certain strands does suggest that fatigue was a factor in the failure of specific strands. 4 Anow Drive.Wobum. Massachusetts 01801 i Telephone:(617)938-0300 A Fax:(617) 935-5087
The elemental spectrum on the corrosion products found on all the wires indicates that corrosion fatigue could have contributed to the in service failures. RECOMMENDATIONS: Small, medium, and large diameter wires from new material and from material with a long service history should be pulled to failure and the fracture features produced compared to the in i service failures to determine conclusively that fatigue contributed to the in service failures. RESULTS: The unit was photographed as received. The cables are fabricated with three different diameter iron wires. The optical examination of the fractured wire strands indicated that all the small i diameter wires were corroded. Although the outside surfaces were all corroded, the medium and large diameter wire fracture surfaces were not corroded (See micrographs M1 and M2). The fracture faces of the wires were examined in the SEM. The fracture features found on each individual strand (whether large, medium, or small) varies with the strands. Certain strands failed in a ductile failure mode (tensile overload) and others with a brittle failure mode (possibly fatigue or corrosion fatigue). Conclusive evidence for the possible modes on the small diameter wires were obliterated by the corrosion byproducts on the fracture surfaces of those wires (See micrographs M3 to M8). In all but very hard alloys, tensile overload fractures generally exhibit plastic deformation and microvoid coalescence. In this sample some wire strands had evidence of plastic deformation some did not. However, strands with no plastic deformation did have evidence of microvoid coalescence at magnifications above 2000 X. This is perplexing. Test samples prepared under controlled failure conditions should be examined to resolve the nature of these mixed failure modes found on the in service failure. The evidence suggests that the in service sample is fatigued and then overloading. The enclosed data sheets further describes the SEM and E S analyti al techniques.
- N, Char;es . Tuson Failure Analyst / Microscopist CFT/jmh
Enclosures:
Samples: 1 Micrographs: 10 Spectra: 2 Data Sheet: 2 Evaluation: 1 D-10
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- 1 I
l l ENERGY DISPERSIVE X-RAY SPECTROSCOPY (EDS) l Energy Dispersive X-Ray Spectroscopy (EDS) is an analytical technique that qualitatively and quantitatively identifies the elemental composition of materials analyzed in an SEM. EDS analyzes the top two microns of the sample with a spatial resolution of one micron. Beryllium windowed EDS detects all elements with atomic numbers greater than oxygen at concentrations greater than 0.1%. " Windowless" EDS detectors can also detect carbon, nitrogen and oxygen at concentrations greater than 1.0%. EDS displays the distribution of elements as either dot maps or line profiles with a spatial resolution of one micron. l EDS Applications Include:
- 1. Materials Evaluation Contaminant location and identification Alloy and intermetallic identification Material composition verification Discrimination between electroless and electroplated nickel Elemental diffusion profiles Multiple spot analysis of areas from 1 micron to 10 centimeters
- 2. Failure Analysis Contaminant identification Identification and quantification of unknown materials Stringer location Cosmetic stain identification
- 3. Quality Control Screening Material verification Alloy identification Certifying platings to specification D-11 4 Arrow Drive, Wobum, Massachusetts 01801 A Telephone:(617)938-0300 A Fax:(617) 935-5087
Principle Of Operation: When the electron beam of the SEM is scanned across the sample, it generates x-rays from the atoms in the top two microns. The energy of each x-ray is characteristic of the atom from which it escaped. The EDS system collects the x-rays, sorts them by energy and displays the number of x-rays versus their energy. This qualitative EDS spectrum can be either photographed or plotted. This data can then be further analyzed to produce either an area elemental analysis (displayed as o dot map) or a linear elemental analysis (displayed as a line scan) showing the distribution of a panicular element within the top two microns of the surface of the sample. The EDS data can be compared to either known standard materials or computer-generated theoretical standards to produce either a full " quantitative" or a " semi-quantitative" analysis. Data Output: EDS dot maps and line scans may be smoothed, background corrected and overlaid to show the distributions of several elements together. EDS systems also produce color dot maps which show each element's distribution in a different color. These systems also compute concentration line profiles displaying exact composition in steps as small as 1 micron across the sample. Qualitative EDS data is typically presented as color photographs or as full-page spectral plots while quantitative EDS data is typically presented as tables. Sample Constraints: The sample can be up to 15 cm x 10 cm x 75 cm in size. The sample must be compatible with a 4 10 torr vacuum, i.e., non-volatile and not susceptible to electron beam induced damage. D-12
i l l M A \nc. AnalyticalAnswers,I i The information you need...when you need it
- FLOW CHART for FAILURE ANALYSIS SERVICES ;
1 l 1. External Microscopic Examination Optical Microscopy & Scanning Electron Microscopy l
- Electrical leakage due to contamination between leads
- Fractures in package seam
- High depth of field imaging
- Identifymg elemental constituents of contamination
- 2. Radiography (X-ray) Examination
- Viewing device construction prior to de-encapsulation
- Viewing wire bond integrity
- Viewing die placement
- 3. Electrical Failure Verification Functional & Pin-to-Pin Curve Tracing l - Verify operation ofdevice l - Test device to specification
- Characterize a device
- - Compare to known good device
- 4. High Temperature Bake (biased / unbiased)
- Identify the presence of mobile ions
- 5. De-lid /De-encapsulate :
Mechanical and/or Chemical
- 6. Cross-sectioning Abrasive Disk
- Package construction
- Bond wires and die attach l - Plating thickness and uniformity
- - Junction depths t
- 7. Internal Microscopic Examination l
l Optical Microscopy & Scanning Electron Microscopy
- Metallization/ Oxide defects
- Contamination and/or corrosion
- 8. ElectricalProbing
- Localize electrical faults at die level D-13 4 Arrow Drive,Woburn, Massachusetts 01801 A Telephone:(617)938-0300 A Fax:(617) 935-5087
l
- 9. Voltage Contract Imaging in SEM
- Visualize voltage levels in a semiconductor
- Locate opens, shorts or hot spots
- 10. Electron Beam Induced Current (EBIC) Imaging in the SEM
- Visual examination of current flow in a semiconductor
- Locate opens or shorts
- 11. Liquid Crystal Fault Detection
- Thermal characteristic of a semiconductor surface
- 12. Bond Strength Pull Test
- Verify bond integrity
- 13. Angle Lapping & Staining
- View semiconductorjunc' ions
- 14. Metallization Removal
- 15. Oxide Removal Chemical Plasma Etch
- 16. Other Analytical Techniques Scanning Auger Microscopy (SAM)
- Corrosion analysis
- Stainidentification
- Lifted lead bond evaluation
- Material delamination analysis
- Metal embrittlement evaluation Secondary Ion Mass Spectrometry (SIMS)
- Location oflow level ionic contamination
- Inversion studies
- Dopinglevelinvestigation Fourier Transform Infrared Spectroscopy (FTIR)
- Identification of contaminants on micro electronic packages and devices
- Identification of organic stains
- Identification of contaminants in process fluids
- Inspecting for component chemical degradation or decomposition i
D-14
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'. corroded. Although the large
% diameter wire fracture face is
, ( not visible here, it was not corroded either.
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(( 34g M3 18.5X Sample: RMA 780-A l7a This is a SEM image of the hi. failed cable. The unit is shown [.j . as received for this analysis. L Note the blunt appearance of the large and medium diameter wire visible at the arrows. The 3 lack of plastic deformation suggests a brittle failure mode
?r rather that a ductile tensile
*y, overload.
M4 77X Sample: RMA 780-A This is a SEM image of the failed large diameter wire. The wire strand is shown as
^J'- received for this analysis. The ' ( *i, , e ,' ^ 3, J, % arrow indicates a non-corroded
[ # 3 area where spectrum 33733 A was taken. Photographs M5 and M6 were taken in this area too. c5.. Q
- +g a
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- D-16 > Analytical Answers,Inc.
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M5 1.10KX Sample: RMA 780-A
, s This is a SEM image of the failed large diameter wire. The
. wire strand is shown as received for this analysis. The
'r _
arrow indicates a non-corroded
, area where spectrum 33733A was taken. Photograph M6 were taken in this area too.
- ~
M6 2.00KX Sample: RMA 780-A This is a SEM image of the failed large diameter wire. The wire strand is shown as received for this analysis. This s, - surface is characteristic of the entire fracture surface. There is evidence of very small dimples associated with tensile
' overload. The overall blunt appearance of the fracture suggest a brittle fracture mode rather than tensile over load.
=
Empirical fault simulation test evidence should be examined to determine if this evidence suggests fatigue as a component
. related to the failure.
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? This is a SEM image of one failed medium diameter wire.
- 4
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! received for this analysis. Note
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. c. ,
M8 1.31KX Sample: RMA 780-A This is a SEM image of one failed medium diameter wire. The wire strand is shown as
'jjs (
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Micrograph M9 was taken in this area. This surface is
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. This is a SEM image of one
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-; ,+ ; > % overload are visible at this j ; magnification.
.. ;X e
, , y? ? M10 48.5X Sample: RMA 780-A This is a SEM image of the failed small diameter vires. Most of the small wires have
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' the failure mode has been
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MA\nc. AnalyticalAnswers,I The infonnation you need...when you need it
- December 16,1997 Mr. Greg Fields Amersham Sentinal 40 North Avenue Burlington, MA 01803 Report No: 33737 P.O. No: 1745 PURPOSE OF ANALYSIS:
Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDS) examination of a cable wire to determine the metallurgical failure mode. SAMPLES: One broken cable assembly with RMA # 775. METIIOD OF ANALYSIS: Optical Microscopy (OM) Scanning Electron Microscopy (SEM) Energy Dispersive X-Ray Spectroscopy (EDS) CONCLUSIONS The cables are fabricated with three different diameter iron wires. De optical examination of the fractured wire strands indicated that all the fracture faces on the small diameter wires were corroded. Although the outside surfaces were all corroded, the medium and large diameter wire fracture surfaces were not corroded. These conditions indicate that the failure occurred over a period of time and that the small diameter wires failed first. The fracture features found on each individual strand (whether large, medium, or small) varies with the strands. Certain strands failed in a ductile failure mode (tensile overload) and others with a brittle failure mode (possibly fatigue or corrosion fatigue). Conclusive evidence for the possible modes on the small diameter wires were obliterated by the corrosion byproducts on the fracture surfaces of those wires. D-22 4 Arrow Drive,Wobum, Massachusetts 01801 A Telephone:(617)938-0300 A Fax:(617) 935-5087
The evidence for fatigue on the medium and large diameter wire strands is not conclusive. Although not conclusive the fracture features on certain strands does suggest that fatigue was a factor in the failure. The elemental spectrum on the corrosion products found on all the wires indicates that corrosion fatigue could have contributed to the in service failures. RECOMMENDATIONS: Small, medium, and large diameter wires from new material and from material with a long service history should be pulled to failure and the fracture features produced compared to the in service failures to determine conclusively that fatigue contributed to the in service failures. RESULTS: The unit was photographed as received. The cables are fabricated with three different diameter iron wires. The optical examination of the fractured wire strands indicated that all the small diameter wires were corroded. Although the outside surfaces were all corroded, the medium and large diameter wire fracture surfaces were not corroded (See micrographs M1 and M2). The fracture faces of the wires were examined in the SEM. The fracture features found on each individual strand (whether large, medium, or small) varies with the strands. Certain strands failed in a ductile failure mode (tensile overload) and others with a brittle failure mode (possibly fatigue or corrosion fatigue). Conclusive evidence for the possible modes on the small diameter wires were obliterated by the corrosion byproducts on the fracture surfaces of those wires (See micrographs M3 to M8). In all but very hard alloys, tensile overload fractures generally exhibit plastic deformation and microvoid coalescence. In this sample some wire strands had evidence of plastic deformation some did not. Ilowever, strands with no plastic deformation did have evidence of microvoid coalescence at magnifications above 2000 X. Test samples prepared under controlled failure conditions should be examined to resolve the nature of these mixed failure modes found on the in service failure. The evidence suggests that the in service sample is fatigued and then overloading. The enclosed data sheets further describes the SEM and E S analytical techniques. 1 . son g Failure Analyst / Microscopist CFT/jmh
Enclosures:
Samples: 1 Micrographs: 15 Spectra: 4 Data Sheet: 2 Evaluation: 1 0-23 > Analytical Answers. Inc.
AVA\c. Analytical Answers,In The information you need...when you need it ' ENERGY DISPERSIVE X-RAY SPECTROSCOPY (EDS) l
)
\
Energy Dispersive X-Ray Spectroscopy (EDS) is an analytical technique that qualitatively and quantitatively identifies the elemental composition of materials analyzed in an SEM. EDS analyzes the top two microns of the sample with a spatial resolution of one micron. I Beryllium windowed EDS detects all elements with atomic numbers greater than oxygen at concentrations greater than 0.1%. " Windowless" EDS detectors can also detect carbon, nitrogen . and oxygen at concentrations greater than 1.0%. EDS displays the distribution of elements as either dot maps or line profiles with a spatial resolution of one micron. EDS Applications Include:
- 1. Materials Evaluation Contaminant location and identification Alloy and intermetallic identification Material composition verification Discrimination between electroless and electroplated nickel Elemental diffusion profiles Multiple spot analysis of areas from 1 micron to 10 centimeters
- 2. Failure Analysis Contaminant identification Identification and quantification of unknown materials Stringer location Cosmetic stain identification
- 3. Quality Control Screening Material verification Alloy identification Certifying platings to specification D-24 4 Arrow Drive,Wobum, Massachusetts 01801 A Telephone:(617)938-0300 A Fax: (617) 935-5087
l l l l t Principle Of Operation: When the electron beam of the SEM is scanned across the sample, it generates x-rays from the l I atoms in the top two microns.. The energy of each x-ray is characteristic of the' atom from which
- l. it escaped. The EDS system collects the x-rays, sorts them by energy and displays the number of
- l. x-rays versus their energy. This qualitative EDS spectrum can be either photographed or plotted.
' This data can then be further analyzed to produce either an area ~ elemental analysis (displayed as a dot map) or a linear elemental analysis (displayed as a line scan) showing the distribution of a particular element within the top two microns of the surface of the sample. The EDS data can be compared to either known standard materials or computer-generated theoretical standards to .
produce either a full " quantitative" or a " semi-quantitative:" analysis. l l Data Output: j EDS dot maps and line scans may be smoothed, background corrected and overlaid to show the distributions of several elements together. EDS systems also produce color dot maps which
~
show each element's distribution in a different color. These systems also compute concentration line profiles displaying exact composition in steps as small as 1 micron across the sample. Qualitative EDS data is typically presented as color photographs or as full-page spectral plots while_ quantitative EDS data is typically presented as tables. Sample Constraints:
- The sample can be up to 15 cm x 10 cm x 75 cm in size. The sample must be compatible with a o 104 torr vacuum, i.e., non-volatile and not susceptible to electron beam induced damage.
l l l t I , . I i D-25
MA\nc. Analytical Answers,I The information you need...when you need it
- l FLOW CHART for FAILURE ANALYSIS SERVICES
- 1. ExternalMicroscopic Examination j Optical Microscopy & Scanning Electron Microscopy
)
- Electrical leakage due to contamination between leads
- Fractures in package seam
- High depth of field imaging
- Identifying elemental constituents of contamination ,
- 2. Radiography (X-ray) Examination f
- Viewing device construction prior to de-encapsulation
- Viewing wire bond integrity
- Vi wing die placement
- 3. Electrical Failure Verification Functional & Pin-to-Pin Curve Tracing
- Verify operation of device
- Test device to specification
- Characterize a device
- Compare to known good device
- 4. High Temperature Bake (biased / unbiased)
- Identify the presence of mobile ions
- 5. De-lid /De-encapsulate Mechanical and/or Chemical
- 6. Cross-sectioning Abrasive Disk
- Package, construction
- Bond wires and die attach
- Plating thickness and uniformity
- Junction depths
- 7. Internal Microscopic Examination Optical Microscopy & Scanning Electron Microscopy
- Metallization/ Oxide defects (
- Contamination and/or corrosion j
- 8. ElectricalProbing
- Localize electrical faults at die level D-26 !
4 Anow Drive, Wobum, Massachusetts 01801 A Telephone:(617)938-0300 A Fax:(617) 935-5087 l l
- 9. Voltage Contract Imaging in SEM
- Visualize voltage levels in a semiconductor
- Locate opens, shorts or hot spots
- 10. Electron Beam Induced Current (EBIC) Imaging in the SEM
- Visual examination of current flow in a semiconductor
- Locate opens or shorts
- 11. Liquid Crystal Fault Detection
- Thermal characteristic of a semiconductor surface
- 12. Bond Strength PullTest
- Verify bond integrity
- 13. Angle Lapping & Staining
- Vicv semiconductorjunctions
- 14. Metallization Removal
- 15. Oxide Removal Chemical Plasma Etch
- 16. Other Analytical Techniques Scanning Auger Microscopy (SAM)
- Corrosion analysis
- Stainidentification
- Lifted lead bond evaluation
- Material delamination analysis
- Metal embrittlement evaluation Secondary Ion Mass Spectrometry (SIMS)
- Location oflow level ionic contamination
- Inversion studies -
- Dopinglevelinvestigation Fourier Transform Infrared Spectroscopy (FTIR)
- Identification of contaminants on micro electronic packages and devices
- Identification of organic stains
- Identification ofcontaminants in process fluids
- Inspecting for component chemical degradation or decomposition D-27
M1 10X Sample: RMA 775 This is an optical image of the unit as received. t j . . - l M2 15X Sample: RMA 775 This is an optical image of the unit as received for this analysis. Note that the fracture faces of the small diameter wires are corroded. The medium diameter and large diameter wires are not corroded. y-
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D-28
> Analytical Answers,Inc.
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Sample: RMA 775 f This is a SEM image of the
. .27gg${- "FN failed cable. The unit is shown f
2[J
- fjYir$ ,;;g'Mird p as received for this analysis.
Note the jagged appearance of e Mij j , **"? the large and medium diameter k- wires visible at the arrows. [@3'(:% Mk ?,
. [(d This appearance is f{9 k
f ' $ characteristic of plastic deformation due to tensile
% )
- y. overload.
1 L l l M4 86X Sample: RMA 775 1 This is a SEM image of the failed large diameter wire. The wire strand is shown as received for this analysis. The arrow 1 indicates a non-corroded area where g{ , spectrum 33737A was taken. i j ~ ~ Micrographs M5 and M8 were taken in this area too. g '
,7 Micrographs M9 and M10 were
/' taken in the area indicated by 3
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, s A '
0-29
> Analytical Answers,Inc.
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M5 1.07KX
;, f Sample: RMA 775 H :: This is a SEM image of the
. failed large diameter wire. The k -
I wire strand is shown as received for this analysis. The arrow indicates a non-corroded area where spectrum 33737A -
. was taken. To the right of the
. arrow is a fiberous fracture area that had positive evidence of 2 tensile overload. An area similar to this can be seen in M6 M6 2.57KX Sample: RMA 775 This is a SEM image of the failed large diameter wire. The eq wire strand is shown as vy%1 i7f.
4y received for this analysis. This t %k AM , surface is characteristic of the 1 pp - T . %; *g .-{- large flat fracture surfaces seen
~~
- in M4. There is evidence of
^;* p#e. very small dimples associated with tensile overoad.
%4 D-30 > Analytical Answers,Inc.
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,. m ,. . + ,- . . . . .. . , - M7 1.00KX g $15c .',;.2., M n ; - Sample: RMA 775 kl kk[L. 7-2 :.., J ' .- 4 This is a SEM image of the
'g :
*?. $i[t. . sQ .
c ;' - failed large diamete: 'vire. This h p%}.M. ':' ;.-. C.J.1. . '
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- y.. ?.-,
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+ sa is a mixture of small
.. \ 2 dimples due to tensile overload
~
, ' , )'
and features which suggest a s second failure mode. Although l~ f' ' the evidence is not conclusive,
~
. ,. '.~ j because the features are not t -
7 characteristic of decohesive
'4 .
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.% Ag ,,k
~
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, 'N .hh area designated by arrow 2 in
*f .- ' Q, . g.,h j g fK \ M4. Although is not
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. *s, depressions are characteristic of 1w e s ~< , ,e microvoid coalescence, f .s.
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Sample: RMA 775 VO' .] j */ , ' This is a SEM image of one 5p failed medium diameter wire. t ( / The wire strand is shown as
., . received for this analysis. Note
.y^ ; the very blunt appearance of the
~
s . wire. Micrographs M12 and
~
- p. J. M13 were taken in area
) / gR indicated by the arrow. l_ g % A s4 , T!A$ , " le, t 225 YO. 7000 M12 1.22X Sample: RMA 775 This is a SEM image of one failed medium diameter wire. The wire strand is shown as
.; ~
received for this analysis. Micrograph M13 was taken in this area. This surface is J,, y-. -
- 4 characteristic of the entire
' ' i g ..
fracture surface. There is evidence of very small dimples Y . ; k' '~ ,.
- ^
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, y - , y .,; . -. evidence should be examined to E
h p[' V; ' 1,\; ,bYh k ,v j determine if this evidence suggests fatigue as a component
,c j <..s .. o q.. s. , , .!* g* >c.**.-
> u related to the failure. D-33
> Analytical Answers,Inc.
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- Sample: RMA 775 This is a SEM image of the cJ/ .
failed small diameter wires. 1 Most of the small wires have t i evidence of plastic deformation (tapered neckdown of the wire diameter) however, some do not. Conclusive evidence for i the failure mode has been
-. I obscured by corrosion
) byproducts on the sample.
i 0-34
> Analytical Answers. Inc.
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M13 2.94X
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4, , failed medium diameter wire.
~
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.. D4 4b.- 3 received for this analysis.
1M% . - g),$'\M '
- Small micro voids I.k
- c
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.s t.
~
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overload are visible at this
,-<w..g.,,'- ., 3. . -
=- ,.N .i magnification.
i; ; .fW .' s .7, C *% I' *,[ 9 15& 2 94 . . . . 5 ._. 7 ,:, ,:4 1 l I l M14 30X Sample RMA 775 This is an optical image of the failed small diameter wires. Many of the small diameter wire have corroded fracture faces. Many of these small diameter wires have evidence of plastic deformation that can be seen in M15.
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MA\c. Analytical Answers,In The information you need...when you need it
- December 16,1997 Mr. Greg Fields Amersham Sentinal 40 North Avenue Burlington,MA 01803 >
Report No: 33738 P.O. No: 1745 PURPOSE OF ANALYSIS: Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDS) examination of a cable wire to determine the metallurgical failure mode. SAMPLES: One broken cable with RMA # 782. METHOD OF ANALYSIS: Optical Microscopy (OM) Scanning Electron Microscopy (SEM) Energy Dispersive X-Ray Spectroscopy (EDS) CONCLUSIONS The ca~ oles are fabricated with three different diameter iron wires. The optical examination of the fractured wire strands indicated that although the outside surfaces were corroded, none of the fracture faces on the wires were corroded. The fracture features found on each individual strand (whether large, meditun, or small) varies with the strands. Certain strands failed in a ductile failure mode (tensile overload) and others with a brittle failure mode (possibly fatigue or corrosion fatigue). The principle failure mode on most of the wire strands regardless of diameter was tensile overload. Although not conclusive the fracture features on certain strands does suggest that fatigue was a factor in the failure. The elemental spectrum on the corrosion products found on all the wires indicates that corrosion fatigue could have contributed to the in service failures. D-40 4 Anow Drive,Wobum, Massachusetts 01801 A Telephone:(617)938-0300 A Fax:(617) 935-5087
l RECOMMENDATIONS: 1 Small, medium, and large diameter wires from new material and from material with a long service history should be pulled to failure and the fracture features produced compared to the in { service failures to determine conclusively that fatigue contributed to the in service failures. RESULTS: The unit was photographed as received. The cables are fabricated with three different diameter iron wires. The optical examination of the fractured wire strands indicated that although the outside surfaces were all corroded, fracture surfaces of all the wires were not corroded (See micrographs M1 to M2). The large diameter wire and several medium diameter wires were moved to permit visual examination of all small diameter wires (See micrograph M3). The fracture faces were examined in the SEM. The fracture features found on each individual strand (whether large, medium, or small) varies with the strands. Certain strands failed in a ductile failure mode (tensile overload) and others with a brittle failure mode (possibly fatigue or corrosion fatigue)(See micrographs M4 to M13). In all but very hard alloys, tensile overload fractures generally exhibit plastic deformation and i micravoid coalescence. In this sample some wire strands had evidence of plastic deformation some did not. However, wire strands with no plastic deformation did have evidence of microvoid coalescence at magnifications above 2000 X. Test samples prepared under controlled failure conditions should be examined to resolve the nature of these mixed failure modes found on the in service failure. The evidence suggests that the in service sample is fatigued and then i overloading. The enclosed data sheets further describes the SEM and S analytical techniques. son Um Failure Analyst / Microscopist l l CFT/jmh l
Enclosures:
Samples: 1 Micrographs: 13 l Spectra: 2 Data Sheet: 2 Evaluation:' 1 D-41
> Analytical Answers.Inc.
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M1 2.25X Sample: RMA 782 This is an optical image of the unit as received. M2 15X Sample: RMA 782 This is an optical image of the unit as received for this analysis. The small diameter and medium diameter wire fracture faces are not corroded. Although the large diameter wire fracture face is not visible here, it was not corroded either.
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l l l I I M4 21.3X l Sample: RMA 782 This is a SEM image of the failed cable. The unit is shown as received for this analysis.
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, ,, i1 Note the blunt appearance of l .n.w.O,q the large diameter wire visible l %,['[hhj at the arrow. The lack of plastic deformation suggests a
( ^ xg[4Q 9$fEj brittle failure mode rather that a ductile tensile overload. The 6: l - ? four medium diameter wires all I had evidence of plastic deformation. This is a good u
- indication that these wires failed due to tensile overload.
D-43 I > Analytical Answers,Inc.
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, suggests fatigue as a component related to the failure.
A D-44
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) g, 4 received for this analysis. The gj, e tapered side walls as well as the O
3 cone and cup shape of the fracture mdicate these wires j failed due to tensile overload. Micrographs M8 to M10 were taken in area indicated by the arrow. t l l f 1 M8 389X Sample: RMA 782 This is a SEM image of one l failed medium diameter wire. l g-y g < j. , The wire strand is shown as l W received for this analysis.
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- ~ _ _ _ _ __ _ _ _ _ _ . _ _ __ - - - - -
l > Analytical Answers,Inc. l
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.I M9 1.02KX l - Sample: RMA 782 This is a SEM image of one
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l l hil2 1.34KX Sample: RhiA 782 This is a SEhi image of a fracture face on one small diameter wire. The fracture face is relatively flat with little or no conclusive evidence of the failure mode. A similar
, f .. situation was found on a second wire seen in hil3. Empirical
^'
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M13 1.76KX Sample: RMA 782 This is a SEM image of a fracture face on a second small diameter wire. The fracture face is relatively flat with little
, or no conclusive evidence of the failure mode. Empirical fault simulation test evidence
.f should be examined and be compared to this structure to determine if this evidence truly
.. indicates fatigue was a component related to the failure or is the result of pure tensile overload.
D-48
> Analytical Answers.Inc.
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MA\ac. Analytical Answers,l - The information you need...when you need it
- January 30,1998 Mr. Steve Grenier Amersham Sentinal 40 Nonh Avenue Burlington,MA 01803
Dear Mr. Grenier:
I have reviewed report #33636 in the context of the work done (subsequent to this original report) on samples of wire and assembly cables that were intentionally pulled to failure. The conclusion stated in report #33636 that fatigue was the most probable cause of this failure remains unchanged. k Charles F. Tuson Failure Analyst / Microscopist CFT:dmh D-51 4 Arrow Drive,Wobum, Massachusetts 01801 A Telephone:(617)938-0300 A Fax:(617) 935-5087
MA\nc. Analytkal Answers,I December 16,1997 Mr. Greg Fields Amersham Sentinal 40 North Avenue Burlington,MA 01803 Report No: 33739 P.O. No: 1745 PURPOSE OF ANALYSIS: Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDS) examination of a cable wire to determine the nietallurgical failure mode. SAMPLES: One cable connector (RMA # 784) with broken cable wires protruding. METHOD OF ANALYSIS: Optical Microscopy (OhQ Scanning Electron Microscopy (SEM) Energy Dispersive X-Ray Spectroscopy (EDS) CONCLUSIONS The cables are fabricated with three different diameter iron wires. The optical examination of the fractured wire strands indicated that all the fracture faces on the small diameter wires were corroded. Although the outside surfaces were all corroded, the medium and large diameter wire fracture surfaces were not corroded. These conditions indicate that the failure occurred over a period of time and that the small diameter wires failed first. The fracture features found on each individual strand (whether large, medium, or small) varies with the strands. Certain strands failed in a ductile failure mode (tensile overload) and others with a brittle failure mode (possibly fatigue or corrosion fatigue). Conclusive evidence for the possible modes on the small diameter wires were obliterated by the corrosion byproducts on the fracture surfaces of those wires. D-52 4 Arrow Drive, Wobum, Massachusetts 01801 A Telephone:(617)938-0300 A Fax:(617) 935-5087
The evidence for fatigue on the medium and large diameter wire strands is not conclusive. Although not conclusive, the fracture features on certain strands does suggest that fatigue was a factor in the failure. The elemental spectrum on the corrosion procets found on a!; the wires indicates that corrosion fatigue could have contributed to the in service fatiures. RECOMMENDATIONS: Small, medium, and large diameter wires from new material and from material with a long service history should be pulled to failure and the fracture features produced compared to the in service failures to determine conclusively that fatigue contributed to the in service failures. RESULTS: The unit was photographed as received. The cables are fabricated with three different diameter iron wires. The optical examination of the fractured wire strands indicated that all the small diameter wires were corroded. Although the outside surfaces were all corroded, the medium and ( large diameter wire fracture surfaces were not corroded (See micrographs M1 and M2). The { fracture faces of the wires were examined in the SEM. The fracture features found on each individual strand (whether large, medium, or small) varies with the strands. Certain strands failed in a ductile failure mode (tensile overload) and others with a brittle failure mode (possibly fatigue or corrosion fatigue). Conclusive evidence for the possible modes on the small diameter wires were obliterated by the corrosion byproducts on the fracture surfaces of those wires (See micrographs M3 to M8). In all but very hard alloys, tensile overload fractures generally exhibit plastic deformation and microvoid coalescence. In this sample some wire strands had evidence of plastic deformation 1 some did not. However, strands with no plastic deformation did have evidence of microvoid ! coalescence at magnifications above 2000 X. Test samples prepared under controlled failure ! conditions should be examined to resolve the nature of these mixed failure modes found on the in service failure. The evidence suggests that the in service sample is fatigued and then overloading. The enclosed data sheets further describes the SEM and DS analytical techniques.
. uson%
f Failure Analyst / Microscopist i CFT/jmh r
Enclosures:
Samples: 1 Micrographs: 9 Spectra: 2 Data Sheet: 2 Evaluation: 1 0-53
> Analytical Answers.Inc.
l
Anal)tical Anwers. Inc. The information you need...u hen you need it
- i ENERGY DISPERSIVE X-RAY SPECTROSCOPY (EDS)
Energy Dispersive X-Ray Spectroscopy (EDS) is an analytical technique that qualitatively and quantitatively identifies the elemental composition of materials analyzed in an SEM. EDS analyzes the top two microns of the sample with a spatial resolution of one micron. j l Beryllium windowed EDS detects all elements with atomic numbers greater than oxygen at concentrations greater than 0.1%. " Windowless" EDS detectors can also detect carbon, nitrogen and oxygen at concentrations greater than 1.0%. EDS displays the distribution of elements as either dot maps or line profiles with a spatial resolution of one micron. EDS Applications Include:
- 1. Materials Evaluation Contaminant location and identification Alloy and intermetallic identification Material composition verification Discrimination between electroless and electroplated nickel Elemental diffusion profiles Multiple spot analysis of areas from 1 micron to 10 centimeters
- 2. Failure Analysis Contaminant identification Identification and quantification of unknown materials Stringerlocation Cosmetic stain identification
- 3. Quality Control Screening Material verification Alloy identification Certifying platings to specification D-54 4 Arrow Drive, Wobum, Massachuseus 01801 A Telephone:(617)938-0300 A Fax:(617) 935-5087
l Principle Of Operation: When the electron beam of the SEM is scanned across the sample, it generates x-rays from the atoms in the top two microns. The energy of each x-ray is characteristic of the atom from which it escaped. The EDS system collects the x-rays, sorts them by energy and displays the nmnber of x-rays versus their energy. This qualitative EDS spectrum can be either photographed or plotted. , This data can then be further analyzed to produce either an area elemental analysis (displayed as a dot map) or a linear elemental analysis (displayed as a line scan) showing the distribution of a particular element within the top two microns of the surface of the sample. The EDS data can be l compared to either known standard materials or computer-generated theoretical standards to produce either a full " quantitative" or a " semi-quantitative" analysis.
. Data Output:
EDS dot maps and line scans may be smoothed, background corrected and overlaid to show the distributions of several elements together. EDS systems also produce color dot maps which show each element's distribution in a different color. These systems also compute concentration line profiles displaying exact composition in steps as small as I micron across the sample. Qualitative EDS data is typically presented as color photographs or as full-page spectral plots while quantitative EDS data is typically presented as tables. L l Sample Constraints: l The sample can be up to 15 cm x 10 cm x 75 cm in size. The sample must be compatible with a 4 10 torr vacuum, i.e., non-volatile and not susceptible to electron beam induced damage. D-55
MA\nc. Analytical Answers,I The information you need...when you need it
- FLOW CHART for FAILURE ANALYSIS SERVICES
- 1. External Microscopic Examination Optical Microscopy & Scanning Electron Microscopy
- Electrical leakage due to contamination between leads
- Fractures in package seam
- High depth of field imaging
- Identifymg elemental constituents of contamination
- 2. Radiography (X-ray) Examination
- Viewing device construction prior to de-encapsulation
- Viewing wire bond integrity
- Viewing die placement
- 3. Electrical Failure Verification Functional & Pin-to-Pin Cun'e Tracing
- Verify operation of device
- Test device to specification
- Characterize a device
- Ccmpare to known good device
- 4. Iligh Temperature Bake (biased / unbiased)
- Identify the presence of mobile ions
- 5. De-lid /De-encapsulate Mechanical and/or Chemical
- 6. Cross-sectioning Abrasive Disk
- Package construction
- Bond wires and die attach
- Plating thickness and uniformity
- Junction depths
- 7. Internal Microscopic Examination Optical Microscopy & Scanning Electron Microscopy
- Metallization/ Oxide defects
- Contamination and/or corrosion 1
- 8. ElectricalProbing
- Localize electrical faults at die level D-56 4 Arrow Drive,Wobum, Massachusetts 01801 A Telephone:(617)938-0300 A Fax:(617) 935-5087
- 9. Voltage Contract Imaging in SEM
- Visualize voltage levels in a semiconductor
- Locate opens, shorts or hot spots
- 10. Electron Beam Induced Current (EBIC) Imaging in the SEM
- Visual examination of current flow in a semiconductor
- Locate opens or shorts
- 11. Liquid Crystal Fault Detection
- Thermal characteristic of a semiconductor surface
- 12. Bond Strength Pull Test
- Verify bond integrity
- 13. Angle Lapping & Staining s
- View remiconductorjunctions
- 14. Metallization Removal
- 15. Oxide Removal Chemical Plasma Etch
- 16. Other Analytical Techniques Scanning Auger Microscopy (SAM) i i
- Corrosion analysis j
- Stainidentification !
- Lifted lead bond evaluation Material delamination analysis
- Metal embrittlement evaluation !
Secondary Ion Mass Spectrometry (SIMS)
- Location oflow level ionic contamination
- Inversion studies
- Dopinglevelinvestigation l l
l Fourier Transform Infrared Spectroscopy (FTIR) ; i - Identification of contaminants on micro electronic packages and devices
- Identification of organic stains
- Identification of contaminants in process fluids
- Inspecting for component chemical degradation or decomposition 1
i D-57 L_--__-__-_____-_--______-_____________.
f 9 9
- 1. M1 2.25X Sample: RMA 784 f[ This is an optical image of the i.. unit as received.
l l
- n. l
[ I l l M2 20X Sample: RMA 784 This is an optical image of the
)
unit as received for this analysis. Note that the fracture faces of the small diameter wires are corroded. The (d, e
.f medium diameter wires are not corroded. Although the large diameter wire fracture face is not visible here, it was not 2 corroded either.
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D-58
> Analytical Answers. Inc.
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* ":fil This is a SEM image of the j failed cable. The unit is shown k i as received for this analysis.
7 .:. 4 s Note the blunt appearance of the large and medium diameter wire visible at the arrows. The lack of plastic deformation suggests a brittle failure mode rather that a ductile tensile overload. l l M4 64X Sample: RMA 784 This is a SEM image of the failed large diameter wire. The wire strand is shown as l . (fQ% d 6 i 'UF"M received for this analysis. The c$&
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M5 1.24KX
. Sample: RMA 784 This is a SEM image of the
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~
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.. wire strand is shown as
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. area where spectrum 33739A was taken. Micrograph M6 j s ( . .
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I i 1 i M6 2.99KX Sample: RMA 784 This is a SEM image of the failed large diameter wire. The
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~ '
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.- - j '
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> Analytical Answers,Inc.
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i h 858D6 5i h h.L The wire strand is shown as received for this analysis.
- 4 - Micrograph M9 was taken in
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. L, <<w surface in this area. There is
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D-61
> Analytical Answers,Inc.
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MA\nc. Analytical Answers,I The information you need...when you need it
- January 30,1998 Greg Field Amersham Sentinal 40 North Avenue Burlington, MA 01803
[(hdih6 Report No: 34051 P.O. No: 1777 PURPOSE OF ANALYSIS: Scanning Electron Microscopy (SEM) examination of one (1) failed cable assembly to determine the metallurgical failure mode. SAMPLES: One failed cable assembly. METHOD OF ANALYSIS: Optical Microscopy (OM) Scanning Electron Microscopy (SEM) CONCLUSION: l The fracture features on the large diameter wire in the assembly gave clear evidence that fatigue is the primary metallurgical failure mode. RECOMMENDATIONS: Adhering to the clients instructions not to damage the sample, this assembly was not dissected to I' allow examination of all individual wire ends. It is recommended that the unit be dissected. Although many of the wire ends are damaged and will not yield useful information, some are undamaged. The undamaged wires should be removed, thoroughly cleaned, and degaussed for SEM examination, i l I l RESULTS: l The unit was examined optically as-received. Dirt and debris covered most of the fracture faces. The fracture area was cleaned and rinsed with acetone and alcohol. The fracture face of the large diameter wire in the assembly was clearly visible (See photographs M1 and M2). The failed 1 D-65 l l 4 Arrow Drive,Wobum, Massachusetts 01801 A Telephone:(617)938-0300 A Fax:(617) 935-5087 l u___ ;
assembly was then examined in the SEM. The large diameter wire was examined (See photographs M3 to MS. The six inch cable made examination of the remaining broken wire l impractical. Flexing the still attached wire to examine the smaller wire fracture faces would have ! stressed and possibly broken the remaining wires. The enclosed data present the results. The enclosed data sheet further describes the Scanning Electron Microscopy (SEM) analytical technique. k Charles F. Tuson Failure Analyst / Microscopist i
Enclosures:
Samples: 1 Micrographs: 5 l I
'1
)
l D-66
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r M1 3X Opticalimage of the cable 773 assembly. The unit is shown L. w .
~t after cleaning to remove q heavy deposits ofdebris and b[ _ e dirt from the assembly. The ? S;L, ,. 3 4 arrow indicates the fracture y
i-f f e, l , l M2 3X Opticalimage of the cable assembly. The unit is shown after cleaning to remove heavy deposits of debris and 5- dirt from the assembly. The I arrow indicates the large I s v diameter fracture area. There appears to be secondary cracks perpendicular to the i fracture face. SEM images of this area can be seen in M3 to
%7, M5
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' y----{,
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D-67
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M3 18.6X g myy Secondary electron image of
,q .- .
7
- g. g ;
Mg;7 3#n.- , the failure. The arrow indicates the large diameter
, T .4, ' ,;
. ..c.
wire fracture seen in M2.
-p g%m.g %g b,A :: ? .'
j Secondary cracks
- g. ,. .. cq9:n 3.N g perpendicular to the fracture on # ,# sd M M face are clearly visible at the e
%n e - v
- x eqvp ;3;'j al*:
m 2
-#7 fM i]%. c arrow.
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.py .
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i c . . .
.\
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.t.. 4 M4 65X
, Secondary electron image of m 5.w.. f f'---m.x ?g ? ,', .. the failure. This is the large sp r " ' ?@y.f.
. diameter wire fracture seen in
$yfi g%p f .4 w h t ..;g??g?)
b_ M. d[
" 'S . ..
ni M2. Secondary cracks are clearly visible. Note also that
. g W.4., 4 A... ~ c .. .1 pp: 4 i the wire diameter is not g10 /F ,. q g :
E, ;.. necked down. This indicates y .:. , ?, y(,. J. J;t. e%
,a. . v. . ..,, s ..
- Y, a brittle failure mode rather 5>
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'I
.-] . The area to the right of the arrow and the secondary s );C crack has evidence ofimpact hammering that occurred aner the fracture initiated.
_.,.. Although the sample is
. , wf magnetized and debris A obscures some of the surface, at the leR of the arrow there is an area that strongly suggests that fatigue was the primary failure mode.
D-68
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i
MS 302X Secondary electron image of the failure. This is the large diameter wire fracture seen in M2. Secondary cracks are clearly visible at the arrows. Although the sample magnetism prevented high magnification observation, there is what appears to be fatigue striations to the left and right of the secondary crack. This wire should be removed from the assembly and prepared for higher magnification observation. 1 l l l I l l i D-69
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i NA( Analytical Answers,Inc. The information you need...when you need it
- SCANNING ELECTRON MICROSCOPY (SEM) i Scanning Electron Microscopy (SEM) is a high resolution, great depth of field imaging technique. It shows topographical, structural and some elemental information at magnifications of 10X to 300,000X.
SEM Applications include:
- 1. Materials Evaluation:
Grain size distribution Surfa;:e roughness and porosity Particle sizing Ma'erials homogeneity Intermetallic distribution Characterization of elemental diffusion
- 2. Failure Analysis:
Contamination location Examination for mechanical damage Electrostatic discharge determination Microcrack detection
- 3. Quality Control Screening:
Comparison of good to bad samples Material thickness determination Dimension verification MIL-standard screening Principle of Operation: A finely focused electron beam is scanned across the surface of the sample generating secondary electrons, backscattered electrons and x-ray signals. These signals are collected by specific detectors and displayed on a viewing cathode ray tube. The raster on the cathode ray tube corresponds to the raster on the sample, while the brightness on the cathode ray tube corresponds to the amount of signal generated at each point on the sample. D-70 4 Anow Drive, Wobum, Massachuseus 01801 A Telephone:(617)938-0300 A Fax:(617) 935-5087
i Secondary Electron Imaging (SEI) shows the topography of surface features as small as 6 nm.
- The production of the SE1 signal is primarily dependent on surface roughness.
liigh Resolution Secondary Electron Imaging (HRSEI) shows the topography of features as small as 3 nm. HRSEI can also image films and stains as thin as a few atomic monolayers. An HRSE1 equipped SEM can evaluate electron beam sensitive and charging sensitive materials at magnifications up to 300,000X, often without the need for sample coating and without sample damage. Cryogenic Secondary Electron Imaging (CSEI) shows the size, structure, and shape of wet materials such as hydrated polymers, slurries, oils, biological materials and food products. an SEM equipped with a cryo-preparation system will allow all SEM imaging and analysis capabilities without the need for drying the sample or extensive extraction procedures. Backscattered Electron Imaging (BEI) shows the lateral distribution of elements or 1 compounds within the top micron of the sample. An SEM equipped with a high resolution { Robinson type detector (RBEI) can analyze features as small as 10 nm and composition ! variations of as little as 0.2 percent. The production of the RBEI signal is primarily dependent { on surface composition. The Robinson Backscattered Electron Signal is sorted by intensity to produce images which show the distribution of elements and compounds within the top 0.5 microns of the sample's surface. 4 Electron Beam Induced Current (EBIC) Imaging shows the location of sub-surface opens or . shorts in microelectronic devices. It is a useful failure analysis diagnostic tool. Voltage Contrast (VC) Imaging shows presence of applied bias on the surface of a circuit or device. It identifies opens or shorts as well as voltage drops across a circuit. Electron Channeling Patterns (ECP) show localized crystallinity in a 3 micron area. It can analyze the crystalline structure of a material on a microscale and locate defects within structures. l Data Output: ; The SEM images are viewed on a TV screen and photographed from a high resolution (2000 lines per inch) cathode ray tube with positive or positive / negative Polaroid film. 4 l Sample Constraints: l The sample can be up to 15 cm x 10 cm x 7.5 cm in size. The sample must be compatible with a f 104 torr vacuum; i.e., non-volatile and not susceptible to electron beam induced damage. l D-71
! A%\nc. Analytkal Answers,I The information you need...when you need it
- March 19,1998 Mr. Greg Field Amersham Sentinal 40 North Avenue Burlington,MA 01803 gg y 788d Report No: 34376 P.O. No: 2202 PURPOSE OF ANALYSIS:
Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), and Micro-Fourier Transform Infrared Spectroscopy (FTIR) analysis of a broken cable assembly SAMPLES: One damaged cable assembly METHOD OF ANALYSIS: Optical Microscopy (OM) Scanning Electron Microscopy (SEM) Energy Dispersive X-Ray Spectroscopy (EDS) Micro-Fourier Transform Infrared Spectroscopy (FTIR) CONCLUSIONS: Not all of the wires in the cable were broken, but more than one wire was fractured. The fracture features on each individual strand of wire varied from wire to wire. Large diameter wire. Impact damage occurred on the large diameter wire after it had initially failed. Because of this impact damage on the fracture faces of the large diameter wire, the failure mode on this wire was obscured. Therefore, the cause of the large diameter wire failure could not be determined. Medium and small diameter wires. The one broken medium diameter wire and all of the broken small diameter wires had evidence of plastic deformation and tensile overload. The physical evidence suggests that the large diameter wire failed first and then the smaller wires were unable to sustain the load applied and failed due to tensile overload. D-72 4 Arrow Drive, Woburn, Massachusetts 01801 A Telephone: (781) 938-0300 A Fax: (781) 935-5087
Report 034376, Page 2 There was evidence of debris in the area of the failure. SEM/EDS and FTIR analysis of the debris indicated that the bulk of the debris was lubricant. The primary elements identified EDS were by order ofintensity silicon, magnesium, oxygen and carbon. Although there was no evidence of extensive corrosion, there were trace amounts of . other elements i.e., phosphorous, sulfur, calcium, sodium, chlorine and iron by order of x-ray intensity.
- RESULTS
OptkalMkroscopy The unit was photographed as received (see photographs M1 to M4). Subsequent to the initial i examination samples, debris were removed for SEM/EDS and FTIR analysis. After these l sample were collected, the fracture region was washed and rinsed with acetone and alcohol and the fracture area of the cable assembly was rephotographed (see mircographs M5 and 6). [ l Scanning Electron Mkroscopy (SEM) After cleaning debris from the fracture area the fracture features of the large diameter wire, one medium diameter wire and four small diameter wires were examined. The large diameter wire was extcined first. The primary fracture features on the large diameter wire was due to impact damage on the fracture faces that occurred after it initially failed. The cause of the large diameter wire failure could not be' determined because of the damage to the . fracture face (see micrographs M7 and M8). I One fractured medium diameter wire and four small diameter wires examined in the SEM. The primary failure mode on these wires was tensile overload (see micrographs M9 through M12). l Energy Dispersive X-Ray Spectroscopy (EDS) Debris samples were analyzed. The primary elements identified EDS were by order ofintensity silicon, magnesium, oxygen and carbon. Although there was no evidence of extensive corrosion, there were trace amounts of other elements i.e., phosphorous, sulfur, calcium, sodium, chlorine and iron by order of x-ray intensity. Mkro-Fourier Transform Infrared Spectroscopy (FTIR) Small portions of the residue associated with the cable were placed on an infrared transparent pellet for analysis. All spectra were collected in transmission mode at a resolution of 4 wavenumbers over the mid-IR region of 4000-700 wavenmnbers. The absorption band doublet l at 2340 wavenumbers, when present, is due to atmospheric carbon dioxide. I Although five different samples were examined, the bulk composition of each sample was similar. The residues, which were characterized in spectra 34376_1, _3, _4, _5, and _6, are I 1
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Rcport #34376, Page 3 mixtures of hydrocarbon / ester oils and magnesium silicate or tale. These two components suggest that grease was applied to the surface of the cable. A droplet of dichloromethane (DCM) was able to separate the oily component from the filler or thickener. The hydrocarbon /esteiportion was examined in spectrum 34376_7. Oils with similar FTIR spectra are Castor Oil and dioctyl sebacate. Printouts, which compare spectra of the residue with the two known materials, are attached. The thickener, which was examined in spectrum 34376_8,is a magnesium silicate or talc material. A printout which compares the spectra of the DCM washed residue and tale is attached. The enclosed data sheets further describes the SEM, EDS and FTIR analytical techniques. dleb.7% Charles F. Tuson Failure Analyst / Microscopist CFT:jmh
Enclosures:
Samples: 1 Micrographs: 12 Spectra: 1 EDS and 10 FTIR Data Sheet: 3 Evaluation: 1 D-74
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M1 Reduction 2:1 I The unit is shown as received.
\
l M2 Magnification 3X Opticalimage of the cable connector and the area of the broken wire. The unit is 3 . di (( shown as received. Arrows l L1 and L2 designate the large diameter wire fracture faces. l .
. , g. 4 v J g =,.T D-75
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l
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M3 Magnification 10X Opticalimage of the cable e connector and the area of the
. 2% ,
-F broken wire. The unit is shown as received. Arrows 43 L1 and L2 designate the large
" 'LA ,.. ; !* diameter wire fracture faces.
The arrows MI and M2 designate a " medium" diameter wire fracture. v;e , 1 k t.
.- l V
M4 Magnification 10X Opticalimage of the cable
, . , .gw""r connector and the area of the aI;id 75/ c p broken wire. The unit is
~ a. #"ap' c - shown as received Arrow L1 designates the large diameter wire fracture faces.
. Not seen in M3.
, j i g},lYh
, y;.y -
- f. .,.-
$. 4 I D-76
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M5 Magnification 15X
, <m..
Opticalimage of the cable wy,y 3 fracture area. The arrow (L1) indicate one end of the large diameter wire fracture and the two remaining arrows (M1 and M2) show the location of the two ends of the medium diameter wire that was fractured. Small
-g diameter wire in the background are also broken.
f However these are out of Q focus because the camera lens depth of focus has been exceeded. t l l M6 Magnification 15X l Optical image of the cable fracture area. The arrows indicate the small diameter wires not visible in M5. p. D-77
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,mg ' -- M7 Magnification 75X Secondary electron image of Jd ,6
,,nV" g,F a n.N the L1 end of the large m."E My+e y.
'y; g . , diameter wire fracture. Most
'q%gNLgE . . , ,
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l L2 end of the large diameter wire fracture. Most of the
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- were obliterated by impact
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I i 1 M9 Magnification 34.2X 1 . cam 7 ' ' ' y .
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. w, w try_,g. -
Secondary electron image. s[* ng Arrow M2 shows one end of S4- the medium diameter wire.
>Al,i q v The other arrows indicate cy!Qy.gg four small diameter wires.
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ftEf,Q Qfl %~ , ' The primary fracture feature pp:'e% 3% %w, 9 seen hear is the plastic p NK mppn defonnation of the wire due
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.% M11 and M12 were taken.
The fracture features
, , . ' $. QC, aV . . l.A) {
7:f@ photographed here are typical N %5NA. g ... of those on the small
^
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i, 1 D-79
> Analytical Answers. Inc.
Mll Magnification 900X Secondary electron image. This is a higher magnification image of the fracture seen in
~..' - " -
- M10. The small dimple like
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- g., - P.,#. .
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A%nswers,Inc. AnalyticalA The information you need...when you need it
- SCANNING ELECTRON MICROSCOPY (SEM)
Scanning Electron Microscopy (SEM) is a high resolution, great depth of field imaging technique. It shows topographical, structural and some elemental information at magnifications of 10X to 300,000X. SEM Applications include:
- 1. Materials Evaluation:
Grain size distribution Surface roughness and pwosity Particle sizing Materials homogeneity Intermetallic distribution Characterization of elemental diffusion
- 2. Failure Analysis:
Contamination location Examination for mechanical damage Electrostatic discharge determination Microcrack detection
- 3. Quality Control Screening:
Comparison of good to bad samples Material thickness determination Dimension verification MIL-standard screening Principle of Operation: A finely focused electron beam is scanned across the surface of the sample generating secondary electrons, backscattered electrons and x-ray signals. These signals are collected by specific detectors and displayed on a viewing cathode ray tube. The raster on the cathode ray tube corresponds to the raster on the sample, while the brightness on the cathode ray tube corresponds to the amount of signal generated at each point on the sample. D-92 4 Arrow Drive,Wobum,Massachuseus 01801 A Telephone:(617)938-0300 A Fax:(617) 935-5087
Secondary Electron Imaging (SEI) shows the topography of surface features as small as 6 nm. The production of the SE1 signal is primarily dependent on surface roughness. High Resolution Secondary Electron Imaging (HRSEI) shows the topography of features as small as 3 nm. HRSEI can also image films and stains as thin as a few atomic monolayers. An HRSEI equipped SEM can evaluate electron beam sensitive and charging sensitive materials at magnifications up to 300,000X, often without the need for sample coating and without sample damage. Cryogenic Secondary Electron Imaging (CSEt) shows the size, structure, and shape of wet materials such as hydrated polymers, slurries, oils, biological materials and food products. an SEM equipped with a cryo-preparation system will allow all SEM imaging and analysis capabilities without the need for drying the sample or extensive extraction procedures. Backscattered Electron Imaging (BEI) shows the lateral distribution of elements or compounds within the top micron of the sample. An SEM equipped with a high resolution Robinson type detector (RBEI) can analyze features as small as 10 nm and composition variations of as little as 0.2 percent. The production of the RBEI signal is primarily dependent on surface composition. The Robinson Backscattered Electron Signal is sorted by intensity to produce images which show the distribution of elements and compounds within the top 0.5 microns of the sample's surface. Electron Beam Induced Current (EBIC) Imaging shows the location of sub-surface opens or shorts in microelectronic devices. It is a useful failure analysis diagnostic tool. Voltage Contrast (VC) Imaging shows presence of applied bias on the surface of a circuit or device. It identifies opens or shorts as well as voltage drops across a circuit. Electron Channeling Patterns (ECP) show localized crystallinity in a 3 micron area. It can analyze the crystalline structure of a material on a microscale and locate defects within structures. I Data Output: I The SEM images are viewed on a TV screen and photographed from a high resolution (2000 lines per inch) cathode ray tube with positive or positive / negative Polaroid film. S Sample Constraints: The sample can be up to 15 cm x 10 cm x 7.5 cm in size. The sample must be compatible with a 104 torr vacuum; i.e., non-volatile and not susceptible to electron beam induced damage. i l D-93 l l 1
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- I 1
ENERGY DISPERSIVE X-RAY SPECTROSCOPY (EDS) Energy Dispersive X-Ray Spectroscopy (EDS) is an analytical technique that qualitatively and quantitatively identifies the elemental composition of mcterials analyzed in an SEM. EDS analyzes the top two microns of the sample with a spatial resolution of one micron. Beryllium windowed EDS detects all elements with atomic numbers greater than oxygen at concentrations greater than 0.1%. " Windowless" EDS detectors can also detect carbon, nitrogen and oxygen at concentrations greater than 1.0%. EDS displays the distribution of elements as either dot maps or line profiles with a spatial resolution of one micron. EDS Applications Include:
- 1. Materials Evaluation Contaminant location and identification Alloy and intermetallic identification Material composition verification Discrimination between electroless and electroplated nickel Elemental diffusion profiles Multiple spot analysis of areas from 1 micron to 10 centimeters
- 2. Failure Analysis Contaminant identification Identification and quantification of unknown materials ,
Stringer location ) Cosmetic stain identification 1
- 3. Quality Control Screening !
Material verification Alloy identification i Certifying platings to specification
]
l D-94 4 Arrow Drive, Woburn, Massachuseus 01801 A Telephone:(617)938-0300 A Fax:(617) 935-5087 i _- ---______-__________--________________-_-____-___L
I Principle Of Operation: When the electron beam of the SEM is scanned across the sample, it generates x-rays from the atoms in the top two microns. The energy of each x-ray is characteristic of the atom from which it escaped.. The EDS system collects the x-rays, sorts them by energy and displays the number of x-rays versus their energy. This qualitative EDS spectrum can be either photographed or plotted. This data can then be further analyzed to produce either an area elemental analysis (displayed as a dot map) or a linear elemental analysis (displayed as a line scan) showing the distribution of a particular element within the top two microns of the surface of the sample. The EDS data can be compared to either known standard materials or computer-generated theoretical standards to produce either a full " quantitative" or a " semi-quantitative" analysis. Data Output: EDS dot maps and line scans may be smoothed, background corrected and overlaid to show the distributions of several elements together. EDS systems also produce color dot maps which show each element's distribution in a different color. These systems also compute concentration line profiles displaying exact composition in steps as small as 1 micron across the sample. Qualitative EDS data is typically presented as color photographs or as full-page spectral plots while quantitative EDS data is typically presented as tables. Sample Constraints: The sample can be up to 15 cm x 10 cm x 75 cm in size. The sample must be compatible with a 104 torr vacuum, i.e., non-volatile and not susceptible to electron beam induced damage. i D-95
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- FOURIER TRANSFORM INFRARED SPECTROSCOPY (FTIR)
Fourier Transform Infrared Spectroscopy (FTIR) is an analytical technique which determines the chemical composition and bonding of organic, polymeric and many inorganic materials. FTIR can be used to analyze various types of materials in thin film, solid, powder or liquid form. Conventional FTIR analyzes an area 11+ millimeters in diameter, while Micro-FTIR analyzes areas from 10 to 250 micrometers in diameter, The wave number range available is 400 to 4000 cms (wavelength from 2.5 to 25 microns) at up to 0.5 cm ' resolution. FTIR Applications Include:
- 1. Materials Evaluation Identification of most solid or liquid organics Identification of many crystalline and amorphous solid inorganics Identification of polymers Depth profiling from 0.3 to 4 microns Surface mapping of concentration and/or composition Quantitative analysis of the composition of organics
- 2. Failure Analysis Identification of contaminants on microelectronic packages and devices Identification of organic stains Identification of contaminants in process fluids Inspecting for component chemical degradation or decomposition
- 3. Quality Control Screening Comparison of good to bad samples l Verification of solvent cleanliness Analysis of evolved gases Verification of parts cleanliness Analysis of surface chemistry modification D-96 4 Arrow Drive,Woburn, Massachusetts 01801 A Telephone:(617)938-0300 A Fax:(617) 935-5087
Principle Of Operation: A beam of infrared light generated by a small furnace in the FTIR spectrometer is focused on a sample using special optics. The sample absorbs the light at very specific wavelengths depending on the atomic composition, structure and thickness of tbe sample. The reflected or transmitted IR light is measured at the detector to construct (by fourier transform) the IR spectrum of the substance or mixture. Each substance gives a unique IR spectrum with the exception of optical isomers and polymers which vary only slightly in molecular weight. The vibrations of atoms in each functional group of a substance have characteristic IR absorption frequencies which permit substance identification. User-provided reference samples aid in positive substance identification. Data Output: An FTIR spectrum is a plot of IR light absorbance by the sample as function of wavelength. FTIR data can be presented as plotted spectra, as multi-spectral display with unknowns and controls, or as unknowns plotted with Sadtler Library Reference Spectra. Micro-FTIR Sample Constraints: A microscope attachment to the FTIR operates at 360X magnification and permits collecting spectra of small samples, down to 10 microns in diameter in either reflectance or transmittance modes. Adjustable circular and re :tangular apertures pennit sample masking to optimize spectra collection. The Micro-FTIR can accommodate just about any size sample because a small piece of the material ofinterest can be removed and placed in the spectrometer. less than one drop of liquid or one grain of solid is required for analysis. The only significant constraint for Micro-FTIR is that the sampling head has to be placed within 5 millimeters perpendicular to the face ofinterest and that the area ofinterest must be at least 10 microns in diameter. ATR-FTIR Sample Constraints: Attenuated Total Reflectance (ATR) FTIR is used to obtain IR spectra of surfaces and to perform depth profiling. Surface characterization in the range of 0.3 to 4 microns is easily performed on flat samples 10 mm by 10 mm. 1 D-97 l l l
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- EVALUATION Analytical Answers, Inc. is constantly striving to provide its customers with the finest quality service within the required time frame.
To assist us in meeting these goals, we would appreciate your answering the following questions and returning the summary in the enclosed, stamped, self-addressed envelope. Yes No
- 1. Has the analysis been completed to your satisfaction?
- 2. Would you like further clarification of any of the results?
- 3. Is the report, if required, as definitive, factual and conclusive as you requested?
- 4. Would you utilize our analytical services again, and __
would you refer us to other companies? Please feel free to elaborate below on any of the above points, or to add your own suggestions. Thank you for your assistance, and we look fonvard to performing additional analysis for you in the very near future. Client Comments: D-98 4 Arrow Drive,Wobum, Massachusetts 01801 A Telephone:(617)938-0300 A Fax:(617) 935-5087
l Appendix E Commonwealth of Massachusetts inspection Report Dated March 5,1998
$\_
sww The Commonwealth of Massachusetts
@g Executive Office of Health and Human Services Department of Public Health Radiation Control Program 305 South Street, Jamaica Plain, MA 02130 j ^"' EN o CE M CCI (617) 727-6214 (617) 727-2098 - Fax WILLIAM D. O' LEARY Secneu ny DAVID H. MULUGAN COMANS$10NeR March 5, 1998 Amersham Corporation Mr. William McDaniel Facility Manager 40 North Avenue Burlington, Massachusetts 01803
Dear Mr. McDaniel:
On January 22-23, 1998, Agostino Savastano, Salifu Dakubu, and Richard Fairfull of The Massachusetts Department of Public Health, Radiation Control Program, and Larry Camper, Douglas Broaddus, Deborah Piskura, and John Pelchat of the Nuclear Regulatory Commission (NRC) conducted a quality assurance inspection at the above address. Also, an in office review of your "Part 21 Evaluation Report: Projector Drive Cables dated February 6, 1998" was performed from February 16 to 20, 1998. The purpose of the inspection was to determine whether activities authorized by the Amersham Quality Assurance program were conducted safely and in accordance with Agency requirements. At the conclusion of the on-site portion of the inspection, an interim exit briefing was conducted with members of your staff. A final telephonic exit briefing was conducted by Agostino Savastano of this office with Kate Roughan on February 25, 1998. The enclosed Inspection Report documents this inspection. The inspection consisted of selective examinations of procedures and representative records, interviews with personnel, and observation of activities in progress. Based on the results of this inspection, two items of non conformance were identified. If you have questions concerning this inspection, Agostino Savastano will be pleased to discuss them with you. Sincerely, Robert M. Hallisey, Director Radiation Control Program E-1 NUREG - 1631
MASSACHUSETTS DEPARTMENT OF PUBLIC HEALTH RADIATION CONTROL PROGRAM INSPECTION REPORT Report No: License No 12-8361 Licensee: Amersham corneration M North Avanna nurlineten. Mannachunatta 01803 Facility: Amersham corneratien M North Avenue Burlinaten. Mamanchusette Inspection Duration: January 22-23, 1998 Inspected by: OSandser Agosti Savasta MkM Dated Signed R er Richa(d Fairf ' Dated Signed Radiation Con t @rol Officer Approved by: 3[ TP Salite Dakubu Dated Signed Tnanection augmuy: Special announced inspection conducted January 22, and 23, 1998 (Inspection Report No.12-8361-01). Areas inanected: programmatic evaluation of the licensee's Quality Assurance / Quality Control (QA/QC) program as it relates to the manufacturing and servicing of radiography camera controls utilizing teleflex source drive cable. Rasults: In the areas inspected, there were two non conformances identified. The Sealed Source and Device Registry Sheet No. NR-628-D-124-S, dated September 30, 1992, does not uniquely identify the Quality Assurance (QA) Program under which the device is manufactured. This is an item of non comformance. i NUREG - 1631 E-2
A decision was made to remove a sleeve used in the male connector attached to the control cable. Certificate of Registration Sheet No. NR-628-D-124-S dated Septe.mber 30, 1992 does not reflect the change to remove the sleeve. The current male connector is being manufactured without the sleeve. The sheet needs to be amended to reflect this change (Section 5.C). This is an item of non comformance In the licensee's report of the investigation of cable breaks, the licensee undertook a retrospective review of the Return Material Authorization (RMA) database to determine if previous similar control cable. breaks have occurred and to characterize them in a similar manner as the current ones. A full examination of the RMA database should be performed. (Section 4) E.3 NUREG - 1631
DETAILS l
- 1. Persons Contacted
- William McDaniel Operations Director
- Khaja N. Afeef Manager, Regulatory Affairs / Quality Assurance
- Kathleen Roughan Regulatory Affairs Manager
- Lori Podolak Radiation Safety Officer
- Greg Field. Engineering Manger Richard Evans Production Manager David Ward Technician Thomas Shea Quality Control Technician Mary Starble Purchasing Manager Jack Haney Production Control Coordinator Alan Cain Production Planner
- 2. Organization And ScoDe si Licensed Activities Amersham Corporation located in Burlington, Massachusetts manufactures radiography cameras, controls, and Ir-192 and Co-60 source assemblies. In addition to the manufacturing operations Amersham also repairs, maintains, and services radiographic equipment.
- 3. Backcround The Amersham Model 660 is a portable, hand carried, gamma radiography projector system. The system consist of three parts:
e the croiect2r featuring a DU shield, connection ports for the controls and source guide tubes, and a lock assembly for securing the source (typically Ir-192) in the shielded position; e a control unit, consisting of a teleflex drive cable and crank system, for moving the source out of and into the projector; and e up to three 7 foot cuide tubes connected to the projector exit port, used to guide the source to the focal point for radiographic exposures As stated above the Model 660 utilizes a teleflex dJ:ive cable for movf.ng the source out of and into the projector. This "off-the-l NUREG - 1631 E-4 J
shelf" component is received in bulk and cut to size by the licensee. At one end a spring is wound onto the cable to prevent it from unwinding off the crank when exposing (cranking out) the source. A male connector, used for connecting the source assembly, is swaged on the opposite end. Teleflex drive cable has been used in the Model 660 since the device was initially approved for licensing by the U.S. Nuclear Regulatory Commission (U.S. NRC) on April 1, 1970. The cable consists of single 0.138 inch in diameter center core, comprised of 19 wire strands. A single 0.047 inch in diameter wire is wrapped around the core wire at a pitch angle of 0.1 inches off set by 14.5 degrees. A drawing of the cable can be found in Appendix X. Teleflex cable is also used in radiography projectors manufactured by INC, a California licensee, and SPEC a Louisiana licensee. During the period from November 24, 1997 through December 9, 1997 three source disconnect events involving the Amersham Model 660 radiography camera were reported to the Massachusetts Radiation Control Program (MRCP) . Each disconnect was caused by failure of the teleflex cable. Of the three failures reported, two are known to have occurred approximately 1/8"-1/4" from the male connector. In addition to these failures, similar failures were discovered after an Agency /U.S. NRC review of licensee records and the U.S. NRC Nuclear Medicine Event Database (NMED). As a result of the occurrence of these source disconnect events, a ] special announced inspection was conducted at Amersham Corporation's facility in Burlington MA to perform a programmatic l evaluation of the licensee's QA/QC program as it relates to the manufacturing and servicing of radiography camera controls utilizing teleflex cable.
- 4. Failure Analysis Reoorts The licensee performed an analysis for the drive cable breaks that have occurred. The report is entitled "Part 21 Evaluation Report:
" Projector Drive Cables, dated February 6, 1998." An in office review of the licensee's report was performed from February 16 to 20.
The inspectors agreed with the findings as they appear in the Conclusions section of the report. However, the inspectors noted that the licensees review of previous R!Ss back to 1991, listed in Table 1 of the report did not include certain RMAs discovered during the QA inspection. Specifically, RMA 544 was discovered during the QA inspection and not included in Table 1 of the licensee's report. Additionally RMA 600 evaluation report indicated that there were other failures that have occurred that E-5 NUREO - 1631
would support the licensee's conclusion for scenario A of the report.. Comment: The RMA database review should be repeated to determine if other failures have occurred that would support your conclusion for scenario A in your submitted report.
- 5. . Scone af.OA/OC Evaluation Areas inspected during this program evaluation are described in detail below. Each description includes a. listing of Standard Operating Procedures'(SOPS) and Work Instructions (WIs) applicable j to that program area. The scope of the programmatic evaluation covered the following drive cable manufacturing operations:
- design of components, e purchasing of components,
*- receipt of components, e incoming QC. inspection of components, e stockpiling of drive cable components, e
drive cable assembly, e stockpiling of drive cable assemblies, e customer problems / complaints relating to drive cables, and Part 21 evaluation / procedures. A. Quality Assurance Organization The ' licensee supplied the team with a current organizational chart. .The chart ~ indicates that the Regulatory Affairs /QA Director ' position is in upper management, without responsibility for production. Discussions with the Regulatory /QA Director indicated that he was actively involved in the direction and management of -the QA/QC program. B.. Quality Assurance Program SOP-Q001 " Quality Assurance Program" documents and describes the license's QA program. The licensee's QA program conforms to 10 CFR l ,71 requirements for type B transportation packages. The QA /QC program is extensive and well documented. In general the licensee control's quality through the use of engineering drawings, Standard NUREG - l631 E-6
Operating Procedures (SOPS), Work Instructions (WIs), Quality Control (QC) inspections, and a material control system. One important aspect of the program is indoctrination and training of personnel performing quality related activities. Comment: This Quality Assurance (QA) Program is not uniquely identified on Sealed Source and Device Registration Sheet No. NR-628-D-124-S dated September 30, 1992. The sheet needs to be amended to include this information. Based on direct observations and a review of applicable SOPS, the QA program was found to be adequate for the control design, fabrication, inspection, testing, maintenance, repair, modification, and distribution of drive cables used in control units. C. Design Control (SOP-E001, New Product Design and Design Modification Procedure; SOP-E003, General Drawing Definition and Control) , The licensee has implemented measures that ensure design activities are carried out in a planned, controlled, and orderly manner. A procedure has been established to translate the applicable regulatory requirements and design bases into specifications, drawings, written procedures, and instructions. Quality standards are specified in the design documents, and deviations and changes from these quality standards are documented and controlled. Designs are reviewed to assure that design characteristics can be controlled, inspected and tested and that inspection and test criteria are identified. Designs are verified by design reviews, alternate calculations, or qualification testing. Designs are also reviewed by individuals other than the designer. Any design or specification changes are subject to the same design controls as the original design. Finally, appropriate controls are used to assure the preparation and control of drawings conform with standard engineering practices. Comment: A decision was made to remove a sleeve used in the male connector. The change was annotated on the drawing with an engineering change order number and the date of the update. This sheet No. NR-628-D-124-S dated September 30, 1992 does not reflect the change to remove the sleeve. The current male connector is being manufactured without the sleeve. The sheet needs to be amended to reflect this change. Based on direct observations and a review of applicable drive cable ' drawings, the licensee's QA program was found to be adequate to control the design of drive cable components and assemblies. E-7 NUREG - 1631
D. Drive Cable Component Procurement Control (SOP-M001, , Purchasing Policies and Responsibilities) The licensee has established procedures that clearly delineate the sequence of actions to be accomplished in the preparation, review, approval, and control of procurement documents. The documents contain or zeference the material and component identification requirements, drawings, specifications, codes and industrial standards, test and inspection requirements, and special process instructions as needed. Changes and revisions to procurement documents are subject to the same review and approval as the original document. An interview was conducted with the purchasing manager to review purchasing procedures. The drive cable component procurement process was tracked from initial order to component stocking. This review indicated that the licensee is implementing the procedures discussed above. Based on an interview with the purchasing manager, direct observations, and a review of applicable SOPS and WIs procedures used to procure drive cable components were found to be adequate to control quality. E. Assembly Work Instructions, Procedures, and Drawings (SOP-000??, Measuring and Test Equipment; SOP-S012, Periodic Maintenance / Calibration Program; WI-AS-08, Control Assembly; WI-AS-14, Drive Cable Assembly; WI-E04, Tools and Fixtures) Manufacturing activities (swaging, cutting, etc.) that affect quality have been documented in Wis. These WIs are to ensure that manufacturing is accomplished in accordance with instructions, procedures, and drawings. The inspection team observed the male connector to drive cable swaging process. A technician placed a male connector on the cable and positioned the assembly in the swage die. He then closed the die with a pneumatic press. The dies were observed to be in calibration. Based on direct observations and a review of applicable SOPS and WIs, the licensee was found to have sufficient control of the assembly process to ensure drive cable assemblies conform to specifications. F. Document Control The licensee has established procedures for the review, approval, and issuance of documents and changes, prior to release, to assure they are adequate and the quality requirements are stated. NUREG - 1631 E-8
.The format of the SOPS and WIs indicate that the document control l system is in use. However, a direct inspection of this program l
. area was not conducted.
G. Control of Purchased Material, Equipment and Services (SOP-0015, Incoming Inspection; SOP-0032, Measuring and Test Equipment; SOP-QOl8, Determination of Sample Size; SOP-Q019 Mechanical Inspection) The licensee has implemented a system of evaluating suppliers and conducting receiving inspections to control the quality of purchased material, parts, and components. The suppler evaluation is based on one or more of the following: receiving inspection; a review of previous records and performance of suppliers who have provided similar articles of the type being produced; periodic special verification and testing against certificates; and a vendor approval program of the suppliers QA program to determine their capability to supply a product which meets design, manufacturing, and. quality requirements. The licensee controls materials purchased or manufactured in-house with a two form system. One form is the Inspection Instruction and Record (IIR), used for material control; the other is the Route Card, used to control the flow of parts or assemblies between manufacturing areas (i.e. production area, QC area, etc.). When drive cable components are received in the receiving department an IIR is generated to document the QC checks and results performed on the component. The QC checks performed on teleflex cable are outlined in Section J.
~
Based on direct observations and a review of applicable SOPS and WIs, the IRR and route card system were found to be adequate to ensure that drive cable assemblies meet specifications, applicable standards, and pertinent regulations. I H._ Identification and Control of Drive Cable Materials, Parts and Components (SOP-QO25, Route Card) The licensee has established procedures to identify and control materials, parts, and components including partially fabricated sub-assemblies. The purpose of the procedures is to assure that identification is maintained with or on the item, or on records traceable to the item, to preclude use of nonconforming or
. defective items.
The IIR is used to identify and control materials, parts, and components received from suppliers or manufactured in house. The inspectors observed the use of IIR's to identify drive cable components and record results of quality control inspections. E-9 NUREG -4631
Based on direct observations and a review of applicable SOPS the licensee's materials, parts and components identification and control system was found to be adequate for ensuring that nonconforming materials are not used in manufacturing operations. I. Control of Special Processes No special processes (such as welding, heat treatment, nondestructive testing and chemical cleaning) are used in the drive cable assembly manufacturing process. J. Licensee Inspection (SOP Q-15 Incoming Inspection, SOP Q-025 Route Card) The . licensee conducts an inspection program which verifies conformance of quality affecting activities with requirements. The inspectors observed the following processes performed on incoming teleflex cable. A Quality Control Technician was observed removing one lot of teleflex cable from the storage area. The technician was observed measuring the outside diameter using a properly calibrated micrometer. The technician then measured the pitch diameter using a calibrated optical comparitor. During quality control testing all data and results were well documented on an IIR. After being inspected and tested for acceptance, the cable was labeled with a QC Acceptance Tag, QC label, and Controlled Material Tag. A copy of the an IIR for incoming teleflex cable can be found in Appendix X. Based on direct observations and a review of applicable SOPS and WIs, the licensee's procedures were found to be adequate to verify conformance with applicable drawing. K. Test Control (WI-AS-014, Drive Cable Assembly) The licensee has instituted a QC acceptance and in-process testing program to demonstrate that items or components meet design specifications. The Quality Control Department performs a 125 pound pull test for 25 seconds on all drive cable assemblies. The inspectors observed a demonstration of the 125 pound pull test on a sample drive cable and male connector. Based on direct observations and a review of applicable WIs the licensee's QC checks were found to be adequate to verify that drive cable assemblies conform to specified design standards. L. Control of Measuring and Test Equipment (SOP-QO12, Periodic Maintenance / Calibration Program) NUREG ; 1631 E-10
The licensee uses a database to ensure that measuring and test equipment is calibrated at the appropriate interval and properly maintained. All equipment observed in use was found to be in calibration. 1 Based on direct observations of equipment in use and a review of ! applicable SOPS the licensee appears to have an adequate calibration program. M. Handling, Storage, and Shipping Control The licensee controls the handling and storage of drive cable components and assemblies with the IIR/ route card system. An inspection of the shipping program area was not conducted. Based on direct observations and a review of applicable SOPS, the licensee appears to have adequate procedures for controlling the handling and stockpiling of drive cable components and assemblies. N. Inspection, Tests, and Operating Statue (SOP Q-1s Incoming Inspection, SOP Q-025 Route Card) The licensee uses the IIR/ route card system to document quality control inspections, and to control drive cable components and assemblies. This system prevents the inadvertent use of non-conforming drive cable componuits or assemblies. Based on direct observations of the use of the IIR and applicable SOPS, the licensee was found to have adequate QC procedures to ensure the quality of drive cable components and assemblies. O. Non-Conforming Materials, Parts, or Components (SOP-Q-005, Control of Non-Conforming Material) The licensee has implemented procedures for the identification, documentation, segregation, review, disposition, and notification to affected organizations of nonconforming materials. Defects observed during quality control inspections of drive cable components and assemblies are documented on the IIR. Documented defects . are reviewed by the licensee's Materials Review Board I (MRB). The Board decides if the material should be used as is, l repaired, reworked, returned to supplier, or scrapped. i Direct observations of how nonconforming material is handled were not made. l Comment: The licensee receives from customers used equipment for I servicing and applys these same QA standards to repair operations. The-licensee has no control over the radiographic exposure device, E-Il NUREG - 1631 A
1 and associated equipment used with it, once it is delivered to the licensed customer. . When services . or materials are provided by third part vendors, they are not subject to these QA standards.
~
P. Corrective Action The license's QA program contains measures to ensure that causes of adverse quality are promptly identified and evaluated to. determine the need for corrective action. Direct observations of this program area were not made. Q. Quality Assurance Records The licensee's QC processes generate records to provide documentary evidence of the quality and safety of items and the activities affecting quality and safety.
'As~ stated above, the inspectors observed the results of QC checks being documented on an IRR for a spool of teleflex cable.
Direct observations of the filing system used in this program area were not made. R. Audits The licensee has implemented audit procedures. Audit results are documented and reviewed by responsible management for action. Deficient areas are re-audited on a timely basis to verify implementation of corrective actions. QA program audits are performed at least annually based on the safety significance of the activity being audited. The teleflex cable manufacturer is audited by the licensee every three years. Direct observations of internal licensee audits were not made.
- 6. Customer comolaints (SOP-0-030, Product Complaint Handling -
Returned Material Authorization) The licensee has established a product complaint procedure for handling customer complaints and returned material. This procedure applies to all product complaints received, concerning manufactured materials and equipment but does not apply to service complaints. Equipment received for evaluation that is not manufactured by the licensee is_ evaluated at 'the discretion of Regulatory Affairs / Quality Assurance. Equipment received for evaluation that is distributed, but not manufactured by the licensee will be evaluated in accordance with the supplier's procedures and agreed NUREG - 1631 E-12 ___-_______-_a
upon by the Regulatory Affairs / Quality Assurance Manager. Evaluations are tracked through the use of a Return Materials Authorization (RMA) number. Inspectors interviewed the engineering manager on the procedure used to handle customer complaints. Typically the customer phones the licensee with the product complaint. After a telephone interview with the customer a RMA number is assigned and the material is shipped to licensee's facilities in Baton Rouge, Louisiana or Burlington. RMA numbers and complaint evaluation status are tracked with a spreadsheet program. This RMA log is evaluated monthly for completeness and timeliness of evaluation against Part 21 requirements (see below). The inspector's review of the RMA log revealed that while the log is adequate for tracking of product returns and evaluations, it does not readily allow for identification and trending of similar problems. Another potential weakness of the RMA system is that problems identified by licensee personnel during routine maintenance are not identified or tracked.
- 7. Part 21 Review Process (SOP-Q002 Part 21 Procedure)
The licensee has a procedure in place to evaluate and report defects and items of noncompliance which may result in a substantial safety hazard. The procedure assigns responsibilities for actions required to assure the proper implementation of the requirements of 10 CFR Part 21, and establishes the methods of .' Nntifying, evaluating, and reporting defects that could ; potentially result in a substantial safety hazard. I Engineering and Regulatory perform a preliminary evaluation for 10 CFR Part 21 applicability upon discovery of a an event that could potentially be the result of a defect or item of noncompliance in a critical component in either safety class category A or B. If Engineering and Regulatory determine that there is no substantial safety hazard this is documented with the reasons for the , conclusion. The licensee maintains a Part 21 Review Board consisting of the Regulatory Affairs Manager, Radiation Safety Officer, the Engineering Manager, the Operations Manager, and the Regulatory Affairs / Quality Assurance Manager. A meeting of the Part 21 Review , Board is convened within 5 days if any of the following conditions are met as a result of the Engineering and Regulatory preliminary evaluation as stated above: e It is determined that the event is a potential Part 21 and requires a more detailed evaluation, before a conclusion can be made. E-13 NUREG - 1631
e It is determined that the event may be Part 21 reportable e If consensus can not be reached between Engineering and Regulatory. The Part 21 Review' Board performs an evaluation of the potential defect, then .a final determination must be by consensus vote of the Review Board. If it is determined by the Review Board that a substantial safety hazard could result, notification to the NRC is required within 2' business days of the determination. A.-written notification to the NRC,is made within 30 days of.the
. determination that'a substantial safety hazard exists.
- 8. Exit Conference The. inspectors met with the individuals specified in Section 1 of this report at the conclusion of the inspection. The inspectors discussed the purpose, scope and findings of the inspection.
1 NUREG - 1631 - E-14
l l l i t i Appendix F Drive Cable Cleaning Procedure l l t t I l l l j l I i
l j APPENDIX F l Drive Cable Cleaning Procedure
- 1. Disassemble the controls and remove the drive cable from the conduit.
- 2. Visually inspect and reject the cable for damage such as unwinding, nicks which would cause a stmss point or excessive rust which would cause embrittlement. Check for embrittlement / flexibility and stress points by curling at any point suspected into a 3 foot diameter coil. Anywhere along the length of the cable should pass this test without bending or kinking.
- 3. Report rejected cables to the Maintenance or Shop Supervisor (or equivalent).
- 4. Cables which are acceptable will be coiled and placed into the cleaning tub.
- 5. Pour degreaser into the cleaning tub. Fill the tub enough to cover the drive cable plus % inch.
- 6. Let the cable soak in the degreaser for approximately I hour, shaking the cable vigorously every 15 minutes to dislodge dirt and work the degreaser into the cable.
- 7. Run a stiff bristle brush over the cable to dislodge any loose particles.
- 8. Dip the cable back into the degreaser and agitate it vigorously for one minute.
- 9. Lay the cable out on a flat surface and dry it thoroughly with compressed air.
- 10. Coil the cable and place it into the galvanized lube tub.
I1. Pour enough Houghto-Quench G into the tub to completely cover the drive cable.
- 12. Soak the cable in the lubricant for at least % hour.
- 13. Remove the coil of cable and suspend it above the tub for at least 4 hours, to drain the excess lubricant. Excess lubricant may also be spun out of the cable by use of a centrifuge for 3 minutes. Blow excess oil from the cable using compressed air, not exceeding 25 psi. Wipe l cable with a dry, clean, lint free cloth.
- 14. Lubricate the cable with Dow Corning DC-33 Silicone Grease (light consistency). The t
grease is to be applied by hand and should fill approximately 1/3 of the space between each ! spiral (helix) wrap. Remove excess grease by running the drive cable through a clean hand held rag. f i Note: The inside of the conduit may require cleaning prior to reassembly. Conduits need cleaning if there is a noticeable buildup of debris in the windings of the drive cable or if the F-1 NUREG - 163i L-_____-_________
APPENDIX F control was difficult to operate prior to disassembly. If the conduit does need cleaning proceed as follows:
- 1. Internal conduit cleaning
. Pour suitable cleaning solvent into the conduit and let it soak for 5 minutes. . Run a drive cable (other than the one just cleaned) through the conduit to remove any obstructions and loose articles. . Blow out the conduit with compressed air. . If a lot of debris blows out of the conduit, flush and blow out the conduit again.
- 2. Continue the procedure of reinstalling the relubricated drive cable back into the conduit.
NUREG - 163I p.2
1 I 1 1 I i r I i f Appendix G , L Glossary 1 i I l f i e 1 1 l l l i i __
l l
- j. APPENDIX G l
Glossary l The description of the terms in this glossary does not provide definitions or legal interpretation of
- these terms. The description of the terms is intended for use in this report.
ALARA (Acronym for "as low as reasonably achievable") making every effort to maintain ! exposures to radiation as far below the NRC dose limits as is practical and consistent with the purpose for which the licensed activity is undertaken. Associat'ed equipment Equipment that is used in conjunction with a radiographic exposure device to make radiographic exposures that drive, guide, or come in contact with the source, (e.g., guide tube, control tube, control (drive) cable, removable source stop, "J" tube, and
' collimator when it is used as an exposure head.
l Becquerel (Bq) One disintegration per second. [ Byproduct material Any radioactive material (except special nuclear material) yielded in or l ' made radioactive by exposure to the radiation incident to the process of producing or using special nuclear material. Control (drive) cable Cable that is connected to the source assembly and used to drive the
- source to'and from the exposure location.
i Control drive mechanism Device that enables the source assembly to be moved to and from the exposure device. 1 Control tube Protective sheath for guiding the control cable. The control tube connects the l control drive mechanism' to the radiographic exposure device. Corrosion Destructive attack on metals which may be chemical or electrochemical in nature. L Curie (Cl) Unit of activity equal to 3.7 E+10 disintegrations per second. Fatigue Gradual deterioration of a material which is subjected to repeated loads. Female connector Connector that is attached to the source assembly used for connection to the male drive cable connector. This connector typically contains a slot for which die ball and shaft of the male connector are inserted. Go/no go gauge Tool supplied by Amersham for checking the critical areas of their model 550 connector. G1 NUREG - 1631
APPENDIX G Guide tube Hollow tube in which the radiography source travels when it is cranked out ofits shielded position in the camera. l In<lustrial radiography Examination of the structure of materials by nondestructive methods, using penetrating radiation to make radiographic images. Male connector Connector that is attached to the drive cable used for connection to the female source assembly connector. This connector typically is of the ball and shaft type. Metallurgical analysis The systematic study of metals and their metallurgical and physical properties. Metric prefixes Prefixes used with metric units to express numbers in a convenient form. milli (u) = 1 X 104 mega (M) = 1 X 10' micro (m) = 1 X 10-' giga (G) = 1 X 10' nano (n) = IX 104 tera (T) = 1 X 10i2 Nondestructive Testing (NDT) Testing or examination of an object without destroying the object to ensure it is free of flaws. Industrial radiography is an example of nondestructive testing. Quench Cooling accelerated by immersion in agitated water or oil. Quality Assurance (QA) Planned and systematic actions necessary to provide confidence that a firm or product will perform to established specifications. Quality Control (QC) Activities, including inspection and testing, whose purpose is to provide a means to measure the characteristics of a firm or product to the required specifications. Radiation Safety Officer Individual identified on the NRC license responsible for implementing the radiation safety program. The RSO ensures that radiation safety activities are being performed according to approved procedures and regulatory requirements in the licensee's daily operations. Rem Special unit of any of the quantities expressed as dose equivalent. The dose equivalent in rems is equal to the absorbed dose in rads multiplied by the quality factor (1 rem = 0.01 sievert). Roentgen Unit of radiation exposure in air. A roentgen is equal to 1000 milliroentgen (mR). Sealed source Any byproduct material that is encased in a capsule designed to prevent leakage or escape of the byproduct material. NUREG - 1631 G-2
APPENDIX G Shielded position Location within the radiographic exposure device or source changer where i the source is secured and restricted from movement. l Sievert SI unit of any of the quantities expressed as dose equivalent. The dose equivalent in sieverts is equal to the absorbed dose in grays multiplied by the quality factor (1 Sv = 100 rem). t l l Source changer Device designed and used for replacement of sealed sources in radiographic exposure devices, including those also used for transporting and storage of sealed sources. l S-tube Tube through which the sealed source travels when inside a radiographic exposure device. Swage Process involving squeezing. j l Total effective dose equivalent (TEDE) The sum of the deep-dose equivalent (for external exposures) and the committed effective dose equivalent (for internal exposures). Previously referred to as "whole body" exposure. l L I ? G-3 NUREG - 1631 L
i ; i 1 l l 1 [ l I , l l l l l l l I l i l-i l l Appendix H , I 1 1 References l l t 1
i l APPENDIX H References
' American National Standard N43.9-1991, " for Gamma Radiography - Specifications for Design and Testing of Apparatus," American National Standards Institute,1992.
l i American National Standard N432, " Radiological Safety for the Design and Construction of
, Apparatus for Gamma Radiography," National Bureau of Standards Handbook 136, U.S.
Government Printing Office, Washington, D.C.,1981. American National Standard N432, " Radiological Safety for the Design and Construction of - Apparatus for Gamma Radiography," National Bureau of Standards Handbook 136, U.S. n Government Printing Office, Washington, D.C.,1981. Amersham Corporation, Burlington Massachusetts, " Gamma Radiography Radiation Safety L Handbook," undated.
. Amersham Corporation, Burlington Massachusetts, "Model 660 Operational Manual," March 1991.
l Eugene A. Avallone and Theodore Baumeister III, Marks' Standard Handbook for Mechanical Engineers. McGraw-Hill, Inc.,1987. l
. Intemational Organization for Standardization ISO 3999 " Apparatus for Gamma Radiography-Specification," Intemational Organization for Standardization, Switzerland,1977.
l l Joseph E. Shigley and Lany D. Mitchell, Mechanical Fnoineerino Desien. McGraw-Hill, Inc., L 1983. B. Shicien and M.S. Terilak, The Health Physics and Radiological Health Handbook. Nucleon l Lecturn Associates,Inc.,1984. l Lawrence H. Van Vlack, Elements of Material = Science and Enoineerino Addison-Wesley
' Publishing Company,Inc.,1985.
E H-1 NUREG - 1631
NRC FORM 33s u.s. NUCLEAR REGULATORY cOMMisslON 1. REPORT NUMBER 1102* um N en 32oi 32o2 l CELIOGRAPHIC DATA SHEET (see warnmeons e fne reame>
- 2. TITLE AND SUBTITLE NUREG-1631 Source Disconnects Resulting From Radiography Drive Cable Failures
- 3. DATE REPORT PuBUSHED i Final Report wouTN YEAR ;
l t June 1998 l 4. FIN OR GRANT NUMBER l ! 6. TYPE OF REPORT
- 5. AUTHOR (S)
L.W. Camper, D.A. Broaddus, J.M. Pelchat, D.A. Piskura Fid j
- 7. PERIOD COVERED (trciumw celes)
- s. PERFORMING ORGANil.ATION . NAME AND ADDRESS (# NRC. prowde Dwoon, occo or Rega. u S. Nuc#sar Reputatory c1 , and madas adeoss. a contractor, prowde name end memng edsess)
Office of Nuclear Material Safety and Safeguards Division of Industrial and Medical Nuclear Safety U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 l 9. SPONSORINo ORGANIZATION NAME AND ADDRESS (aNRC, type "Same as abovoi aconirsefor, prowds NRC Dwson, omce or Regen. u S. Nuc# ear Reputetory comrmsson, and madng edsess) Same as above
- 10. SUPPLEMENTARY NOTES
- 11. ABSTRACT (200 worcs ormes)
( From November through December 1997, the NRC received three reports of drive cable failures associated with the Amersham Model 660B radiography system. All three failuree occurred immediately behind the male connector and appeared l to be generic in nature. Although dnve cable failures have occurred periodically within the industrial radiography industry, it
- was uncommon to experience so many apparently identical failures within such a brief period of time. The events were
! reviewed by the NRC to determine if the failures met the criteria in NRC Management Directive 8.3, "NRC Incident l Investigation Program," for initiating an inspection as either an Augmented inspection Team (AIT) or a incident investigation Team (IIT). It was decided that the reported failures did not satisfy all of the criteria for initiating these categories of inspections, but the apparent generic nature of the events, the potential for serious exposure to radiographer, and the possibility that the issue went beyond NRC jurisdiction thus affecting Agreement States warranted NRC's attention. As a result, a Special Team inspection was initiated on December 22,1997. The Team, led by a Senior Executive Service (SES) executive, included members with a broad knowledge in health physics, mechanical engineering, and industrial radiography operations. The inspection involved interaction with three Agreement States including close coordination of inspection activities conducted within their jurisdiction. This report describes the investigation of the initially reported drive cable failures, other failures identified during the inspection, the methodology used in the inspection, and presents the Team's findings, conclusions, and recommendations.
l l 13 AvAiLAB UTV $1 ATEMENT
- 12. KEY WORDS/DESCRIPToRS (ust words or phreses that m# assst researchers m mesang me reporr) unlimited drive cable is. SECURITY CLASSIFICATION materials '
licensees (yn,, p,,,,
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