ML19347A778
| ML19347A778 | |
| Person / Time | |
|---|---|
| Issue date: | 09/10/1980 |
| From: | Snaider R Office of Nuclear Reactor Regulation |
| To: | Kniel K Office of Nuclear Reactor Regulation |
| References | |
| REF-GTECI-A-12, REF-GTECI-EQ, TASK-A-12, TASK-OR GL-80-74, NUDOCS 8009300214 | |
| Download: ML19347A778 (21) | |
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Generic Task No. A-12 MEMORANDuti FOR:
K. Kniel, Chief Generic Issues Branch Division of Safety Technology FROM:
R. P. Snaider, Task Manager Unresolved Safety Issue A-12, " Potential for Low Fracture Toughness on Component Supports" SUPNARY OF MEETING TO DISCUSS INDUSTRY'S ALTERNATIVE
SUBJECT:
PROGRAM FOP, RESOLUTION OF THE A-12 PROGRAM On Wednesday, August 27, 1980, a meeting was held between NRC staff A list of personnel and representatives of the nuclear industry.
attendees is included as Attachment 1.
(
The purpose of the meeting was to resolve the differences that existed between NRC and industry approaches to the resolution of the component The NRC's position had first been support fracture toughness problem.
issued in NUREG-0S77 in November 1979, but the implementation guidance contained therein had been substantially modified by letters dated May 19, 1980 and May 20, 1980, to licensees and applicants, respectively.
The major change of the letters, and the cause for industry concern, was the elimination of a frav m-mechanics based evaluation of support materials and its replacement by stringent and prescriptive Charpy V-notch and Nil-Ouctility Transition Temperature criteria and a failure-In addition, the industry objected to the stringent consequence analysis.
criteria included in the May 19th and 20th letters for high s!-ength structural and bolting materials.
The reason for changing the implementation guidance was that the materials properties, such as toughness, and the selection of an initial flaw size, would vary widely and would require that the staff resolve the The NRC does parameters of interest with each licensee or applicant.
The staff not have the staff resources to support such an effort.
was also concerned about the anticipated impact on utility staffs to complete an acceptable fracture mechanics analysis.
8009300214
y_.__
. SEP 101980 K. Kniel The NRC staff clarified two other problem areas that had been raised by the industry in response to the NRC documents. First, the industry need not at this time address lamellar tearing. The staff considers it to be l
primarily a fabrication problem of second-order importance and believes that research is necessary to answer the remaining question of residual strength of a torn joint. The Electric Power Research Institute (EPRI) has been asked to fund and manage such research. An EPRI representative made a brief presentation on the subject and stated that EPRI is presently investigating lamellar tearing research.
The second topic which the staff believes the industry need not concern itself with at the present time is radiation effects on reactor vessel support materials. This sutject is under investigation by the NRC and has been recommended as a potential unresolved safety issue.
EPRI has proposed programs to respond to the NRC concerns while still allowing licensees and applicants to utilize fracture-mechanics based analyses. An EPRI repcesentative and EPRI consultants made presentations
- 1) acceptance of regarding the proposed alternative approaches for:
low toughness support structures (This study has already been contracted) and 2) assessment of stress corrosion cracking of high strength materials (Contractdiscussionsareunderway). The slides used in these presentations are included as attachments 2 and 3.
The NRC staff opened discussion of both its own program and the EPRI proposals. After receiving coments, the staff held a caucus to discuss the alternative approaches. The result was the presentation of the following criteria to the industry representatives:
Prior to the end of December 1980, licensees and applicants (1) must comit to completing the following items (2) through (5) if a fracture mechanics approach is desired.
Items (6) and (7) apply to the staff's acceptance criteria for different aspects of the proposed alternathe program.
(2) The NRC staff will require materials toughness data for the fracture mechanics approach. Significant testing may be required because the staff wants confirmation of the correlation between CVN and Kre data. The staff will require data from several KrIass of material listed in the Sandia Laboratoriesic-like" t or "K for each c report (Appendix C to NUREG-0577). Also, weld material or heat-affected-zone material must be included if limiting.
K. Kniel calculations for specific (3) The staff will insist upon KIc geometries, since flat plate calculations may not be applicable.
(4) Residual stresses must be addressed in the fracture mechanics analysas.
(5) The staff will need to enmi7e the criteria used to define initial flaw size to be usec in the fracture mechanics analysis.
If ultrasonic testing (OT) is to be used to define the initial flaw size, the staff will "equire a demonstration, by mockup or model, that UT can find a flaw of specified minimum size.
(6) The staff will not accept a probability argument alone as a means of proving acceptability of high strength materials against stress carrosion cracking.
j (7) For materials of greater than 180 ksi yield strength, the staff will evaluate the EPRI - proposed fracture mechanics analysis method for applicability.
The staff made two r.dditional points of clarification regarding the analyses to be performed. The first was that LOCA and SSE loads were not to be combinef in this analysis. The subject of load combination is an ongoing NRC gencric task. The second was that the loads to be applied to the supports are those accident loads of the Final Safety Analysis Report (oritsequivalentdocument).
In response to a question regarding assumptions of the analysis, the staff stated that the plant is assumed to be at full power operation when SSE loads are applied. Analysis at shutdown conditions is not required.
Because of the divergence of viewpoints between the NRC staff and industry, licensees and applicants have not started implementation. Because a decision on using the NRC program or the EPRI proposed alternative will not be made until the end of 1980, a one-year extension of the implementation deadline, until December 31, 1982, is justified. The arguments of NUREG-0577 regarding continued operation and licensing are still valid in this regard. Additional comments regarding aspects of the program other than the fracture mechanics analysis are under investigation and will be resolved by December 31, 1980.
R. P. Snaider Task Manager A-12 Generic Issues Branch Attachments: As stated cc: R. Snaider N. Anderson All Attendees
ATTACHMENT 1 NAME AFFILIATION R. P. Snaider NRR/ DST /GIB R. E. Nickell EPRI Consultant M. Kupinski Northeast Utilities J. M. Small BECHTEL P. B. Desai BECHTEL S. Rothstein Con Edison A. W. Zeuthen Long Island Lighting L. E. Titland Baltimore Gas and Electric D. A. Mauney Carolina Power and Light J. A. Gorman Dominion Engineering J. M. McAvoy VEPC0 M. B. Shelton VEPC0 E. J. Bracken Combusion Engineering D. J. Ayres Combustion Engineering B. J. Elliot NRR/MTEB M. N. Bressler TVA - Chmn, ASME BAPVC WG on Comp Supoorts E. A. Merrick TVA - EN DES, Nuclear Engineering Branch M. F. Stuchfield BECHTEL J. Burns Washington Public Power Supply System A. L. Lowe, Jr.
B&W - NPGD R. W. Ganthner B&W - NPGD J. F. Copeland General Electric Company H. T. Watanabe General Elecric Company R. M. Gamble NRC C. Z. Serpan, Jr.
NRC/RES P. N. Randall NRC/SD T. C. Stilwell Franklin Institute Research Center R. E. Johnson NRC/ DST R. A. Kaminsky Florida Power and light Company D. E. Smith NRC/NRR/DE/MTEB J. R. Fair NRC/NRR/ DOL C. D. Sellers NRC/NRR/DE/!iTEB J. O. Schiffaers NRC/NRR/DE/MTEB J. M. Grant NRC/NRR/DE/MTEB Gary Pitzi TVA I. Sprung Stone & Webster D. L. Rehn Duke Power Company N. R. Anderson NRC/NRR/GIB Anthony V. Sorrentino Power Authority of the State of New York Joseph Vattamattam Florida Power Corporation Sergio Verduci Westinghouse i
E. I. Landerman Westinghouse D. G. Maire Westinghouse T. Satyan-Sharma AEP Service Corporation D. L. Dill Wisconsin Elecric Power Company Robert H. Zong Philadelphia Electric Company G. R. Egan APTECH Engineering Services R. C. Cipolla APTECH Engineering Services T. U.'Marston EPRI, Palo Alto, CA 94303 J. Strosnider NRC/RES
ATTACHPENT 2 ALTERNATE APPROACH FOR THE ACCEPTANCE 0F LOW TOUGHNESS SUPPORT STRUCTURES 1
RP 1757-2 i
3Y t
i R. C. CIPOLLA i
G. R. EGAN APTECH ENGINEERING SERVICES l
795 SAN ANTON!o ROAD t
PALO ALTO, CA 94303 I.
BETHESDA, MD
' 1 AUGUST 27, 1980 i
4
ALTERNATE APPROACH FOR THE ACCEPTANCE OF LOW TOUGHNESS SUPPORT STRUCTURES RP 1757-2 INTRODUCTION:
NRC PROPOSED PROCEDURES e
FRACTURE CONTROL PHILOSOPHY BASED ON NDT APPROACH WHERE LOWEST SERVICE TEMPERATURE EXCEEDS NDT BY ADEQUATE MARGINS e
ASSUMES STRUCTURE IS SUBJECTED TO DYNAMIC LOADING e
PROVIDES CRACK ARREST ASSURANCE WHEN NOMINAL STRESSES ARE YIELD ORDER e
NDT PHILOSOPHY WAS DEVELOPED ON MATERIALS WITH HIGH LEVELS OF INHERENT TOUGHNESS (SUCH AS SUBMARINE HULLS AND REACTOR PRESSURE VESSELS)
ALTERNATE APPROACH e
FRACTURE CONTROL PLAN BASED ON PREVENTING FRACTURE INITIATION e
STRUCTURAL STEELS OF TYPE USED IN SUPPORTS HAVE OPERATED SUCCESSFULLY IN THE PAST (BRIDGES, STEEL FRAME BUILDINGS, TOWERS) e CRITICAL COMBINATION OF STRESS, FLAW SIZE AND FRACTURE TOUGHNESS MUST BE AVOIDED
ALTERNATE APPROACH FOR THE ACCEPTANCE OF LOW TOUGHNESS SUPPORT STRUCTURES RP 1757-2 OBJECTIVES:
(1)
TO REVIEW CURRENTLY PROPOSED NRC PROCEDURES FOR ACCEPTANCE AND EVALUATION OF LOW TOUGHNESS SUPPORT MATERIALS, (2)
TO RECOMMEND PROCEDllRES BASED ON FRACTURE MECHANICS (PREVENTING FRACTURE INITIATION) AND TO COMPARE BOTH METHODS, AND (3)
TO DEVELOP THE ANALYTICAL PROCEDURES AND STANDARDS WHEN EVALUATION IS REQUIRED.
0
ALTERNATE APPROACH FOR THE ACCEPTANCE OF LOW TOUGHNESS SUPPORT STRUCTURES RP 1757-2 WORKSCOPE:
TASK 1 - REVIEW NRC PROPOSAL PROCEDURES e
NUREG-0577 AND NRC LETTER DATED 5/19/80 e
REVIEW DATA BASE AND JUSTIFICATION FOR CVN ENERGY REQUIREMENTS e
ESTABLISH IMPACT ON EXISTING SUPPORT DESIGNS e
COMPARE NRC TOUGHNESS REQUIREMENTS WITH NF-2311 0F CODE TASK 2 - COLLECT AND REVIEW OF MATERIAL PROPERTIES AND FABRICATION DATA e
ESTABLISH TYPICAL SUPPORT MATERI ALS AND GEOMETRIES (EXPAND UPON NUREG-0577) e ESTIMATE MEAN AND LOWER BOUND PROPERTIES e
FABRICATION PRACTICE (MACHINING, WELDING ETC)
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FLAW DISTRIBUTION DATA e
e SELECT " TYPICAL" CASES (SAY 4 EXAMPLES) FOR EVALUATION UNDER IASK 4
TASK 3 - REVIEW NORMAL OPERATING AND POSTULATED ACCIDENT CONDITIONS e
STRUCTURE DESIGN AND DEGREE OF REDUNDANCY e
QUANTIFY LOADS, STRESSES AND SERVICE TEMPERATURES FROM DESIGN REPORT TASK 4 - DEVELOP EVALUATION PROCEDURE e
PROCEDURE FOR DETERMINING CRITICAL FLAW SIZE e
ACCEPTANCE CRITERIA ON FLAW SIZE e
EXECUTE PROCEDURE ON TYPICAL CASES e
COMPARE ANALYSIS OUTCOME WITH NRC PROCEDURE RESULTS IASK 5 - FINAL REPORT 9
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ALTERNATE APPROACll FOR THE ACCEPTANCE 0F LOW TOUGHNESS SUPPORT STRUCTURES RP 1757-2 METHOD OF APPROACH:
TOUGHNESS ACCEPTANCE STANDARDS e
CONFORM WITH EVALUATION PROCEDURES e
CONSISTANT WITH CODE REQUIREMENTS EVALUATION PROCEDURE e
FRACTURE-INITIATION ilASED FOR CALCULATING CRITICAL FLAW SIZE e
SUB-CRITICAL CRACK EXTENSION e
ACCEPTANCE CRITERIA ON INITIAL FLAW SIZE i
CORRECTIVE ACTIONS e
REPLACEMENT OF MATERIAL e
REPAIR OPTION TO ADD REDUNDANCY e
INSERVICE INSPECTION e
CONSEQUENCE ANALYSIS e
ANCILLARY HEAtlNG
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TABLE 1 REQUIRED VALUE5* OF CHARPY ENERGY AT 0
75 F, AS A FUNCTION OF THICKNESS A40 YIELD STRENGTH Energy, (t. Ib. for Base Materials of SpecifieJ flinirnri Yield Strength Nominal Thickriess 40 ksi Over 40 Gver 55 Over 75 Inches or Belew to 55 ksi to 75 Lsi to 105 ksi (AC)
(LG) 5/8 in. or less Oyer 5/8in,to1in.
20 [35) 20
(~10) 25
(~25) 30
(~IS)
Over 1 in. to 1 1/2 in.
20 /1d 25 (25')
30 (24) 35 (v20)
Over 1 1/2 in, to 2 in.
25[S8) 30 (W) 35 (27) 40
(-2 0 Over 2 in. to 2 1/2 in.
30 [43) 35 (3D 40 (3I) 45 (25)
Over 2 1/2 in. (for use with certain tests of 45
/4h 50 (19) 55 (F)
[65) welds) 40 The tabulated values are the ninimun required energy for the average of 3 specimens. The recuired energy for the lowest 1 of 3 is 5 ft. 10 b a lc*e the value shown. Retests per Paragraph NC-2350 of the A5:'E Core are per.itted.
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-w 3BM 1 REQUIRED VALUE5* OF CHARPY Et4ERGY AT 0
75 F, AS A FUNCTION OF THICKNESS AND YIELO STRENGTH Energy, (t. Ib. for Gase Materials of Specifiej Minir tsm Yield Strength ficminal Thickriess 40 ksi 0ser 40 Over 55 Over 75 inches or Below to 55 ksi to 75 ksi to 105 ksi 5/8 in. cr less 00er5/8in.to1in.
20 (35) 20
(~20) 25
(~20')
30
(~IS)
Over 1 in, to 1 1/2 in.
20 [15) 25 (25) 30 (24) 35 (v2A Over 1 1/2 in, to 2 in.
25[58) 30 (24) 35 (27) 40
(-21)
Over 2 in, to 2 1/2 in.
30 [#)
35 (39) 40 (30 45 (25)
Over 2 1/2 in. (for use with certain tests of 45 (4h 50 (19) 55 (F)
[66) welds) 40 The tabulated values art the minimum required energy for the avera;0 of 3 e (t. Ib. talow the specimens. The re uired energy for the lowest 1 of 1 is i
value shown. Retests per Paragraph NC-2350 of the I5:'E Care ara permitted.
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ATTACHMENT 3 I
t ALTERNATE APPROACH FOR THE STRESS CORROSION CRACXING ASSESSMENT t
OF HIGH STRENGTH ftATERIAL I
I 1
4 i
BY i
G. R. EGAN R. H. RICHMAN R. C. CIPOLLA t
4 BETHESDA, MD AuousT 27, 1930
t ALTERNATE APPROACH FOR THE STRESS CORROSION CRACKING ASSESSMENT OF HIGH STRENGTH MATERIAL BACKGROUND:
e ISOLATED EXAMPLES OF SCC IN BOLTING AND SUPPORT COMPONENTS HAVE OCCURRED e
PRELOAD STRESS IN BOLTING IS SUFFICIENT TO CAUSE CRACKING e
PRESERVICE FAILURES HAVE OCCURRED e
GENERALLY THE MATERIALS HAVE BEEN OUTSIDE THE SPECIFICATION ON BOTH MAXIMUM TENSILE STRENGTH AND HARDNESS e
A CORROSIVE ATMOSPHERE IN THE FORM OF HUMID AIR HAS BEEN PRESENT
ALTERNATE APPROACH FOR THE STRESS CORROSION CRACKING ASSESSMENT OF HIGH STRENGTH MATERIAL NRC PROPOSED PROCEDURES:
i ANALYSIS TO DEMONSTRATE APPLIED K LEVELS e
KISCC ARE BELOW THRESHOLD e
ASSUMPTION OF 1/10 T FLAW IS MADE WHICH IS VERY RESTRICTIVE AND SOMEWHAT ARBITRARY e
BREAKDOWN OF KISCC AS A FUNCTION OF YIELD STRENGTH FOR MATERIALS INTO LOW ALLOY AND MARAGING CATEGORIES ALTERNATE APPROACH:
e ESlABLISH A DATA BASE ON SCC FAILURES e
D2VELOP PROCEDURE TO SCREEN MATERIALS BASED ON FIELD EXPERIENCE e
USE FRACTURE MECHANICS TO PERFORM THRESHOLD ANALYSIS (KISCC) FOR REALISTIC FLAW SIZE WITH APPROPRIATE MARGINS OF SAFETY w
ALTERNATE APPROACH FOR THE STRESS CORROSION CRACKING ASSESSMENT OF HIGH STRENGTH MATERIAL OBJECTIVES:
(1)
TO REVIEW CURRENTLY PROPOSED NRC PROCEDURES FOR THE ACCEPTANCE AND EVALUATION OF SCC SUSCEPTIBILITY IN HIGH STRENGTH MATERIALS (2)
TO RECOMMEND PROCEDURES FOR MATERIAL ACCEPTANCE AND EVALUATION (3)
TO DEVELOP RATIONAL ANALYTICAL EVALUATION PROCEDURES 4
i o
i ALTERNATE APPROACH FOR THE STRESS CORROSION CRACKING ASSESSMENT OF HIGH STRENGTH MATERIAL STRATEGY:
SIX STEPS ARE REQUIRED TO DEVELOP A SCC ASSESSMENT 3
PROCEDURE -
(1)
REVIEW MATERIALS APPLICATIONS IN NUCLEAR SYSTEMS (MATERIAL INVENTORY)
(2)
REVIEW EXISTING SCC EXPERIENCE IN A) OPERATING PLANTS AND B) PLANTS UNDER CONSTRUCTION (3)
DEVELOP STRESS CORROSION CRACKING RESISTANCE DATA BASE (4)
INITIATE AND DEVELOP A SCREENING TEST BASED ON MEASURED PROPERTIES (SUCH AS HARDNESS AND/0R TENSILE STRENGTH, TYPE OF THREAD ETC)
(5)
DEVELOP AN ANALYSIS PROCEDURE USING FRACTURE MECHANICS PRINCIPLES TO ENSURE THAT MATERIALS OPERATE BELOW A THRESHOLD STRESS INTENSITY FACTOR LEVEL FOR SCC (6)
DEVELOP A STRATEGY FOR ASSURING SHORT-TERM LOADING CAPABILITY
.=
ALTERNATE APPROACH FOR THE STRESS CORROSION CRACKING ASSESSMENT OF HIGH STRENGTH MATERIAL WORK SCOPE:
TASK 1 - REVIEW NRC PROPOSED PROCEDURES TASK 2 - DEVELOP SCC DATA BASE TASK 3 - REVIEW SCC FIELD EXPERIENCE TASK 4 - REVIEW NORMAL OPERATING AND POSTULATED ACCIDENT LOADING CONDITIONS TASK 5 - DEVELOP EVALUATION PROCEDURES TASK 6 - FINAL REPORT l
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