ML13308B499
| ML13308B499 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 05/14/1976 |
| From: | Fogarty D SOUTHERN CALIFORNIA EDISON CO. |
| To: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| References | |
| NUDOCS 8103060570 | |
| Download: ML13308B499 (6) | |
Text
Regulatory Diet 1U thern California Edison Company P. 0. BOX 800 2244 WALNUT GROVE AVENUE DA FOGAR Y ROSEMEAD, CALIFORNIA 91770 TELEPHONE 213-572-2796 May 14, 1976 U. S. Nuclear Regulatory Commission Region V Office of Inspection and Enforcet Walnut Creek Plaza, Suite 202 1990 North California Boulevard V
Walnut Creek, California 94596 OR Attention:
R. H. Engelken, Director Docket No. 50-206 San Onofre Unit 1
Reference:
Letter dated May 4, 1976 from SCE to NRC concerning cracking in cask rectangular coupling lifting device
Dear Sir:
As cited in the referenced letter, cracks were discovered in the spent fuel cask rectangular coupling lifting device on May 3, 1976 and the device was determined to be unsuitable for further service.
The cracks occurred in the welds and parent-metal adjacent to the welds (heat affected zone) as shown in Figure 1 (attached).
Slag pockets were found in the welds after surface grinding.
The defects were due to the use of improper weld procedures and failure to comply with original material specifications during initial fabrication. This determination is based on a preliminary evaluation by the Company's Metalurgical Laboratory and a review of original design criteria. A detailed metalurgical analysis of the defective lifting device is in progress and will be available at the Station for inspection.
As shown in Figure 1, cracks were discovered in all welds holding Block A to sides 1 and 2 except the bottom welds which exhibited.some apparent lack of fusion. However, the bottom welds were of sufficient integrity to provide the structural strength needed to keep Block A positioned between sides 1 and 2. There was no need for any of the welds to provide great tensile strength as a recessed lip (see Figure.II) in both sides 1 and 2 carried the tensile load.
Therefore, there was no immediate possibility of the rectangular coupling device experiencing complete structural failure leading to a cask drop accident.
-2 A new lifting device has been manufactured and is now being used for spent fuel shipments.
It was fabricated in accordance with the original design requirements using appropriate weld and fabrication procedures. A Licensee Event Report to cover this occurrence is attached. A drawing of the new replacement lifting device is also included, incorporating appropriate descriptive information.
The new device is made of ASTM-A-283-70A Grade D carbon steel. The stress analysis for the rectangular lifting device was re-evaluated and the results were acceptable. An ultrasonic inspection was satisfactorily performed on the component metal parts of the lifting device before and after machining, heat treatment and welding. The Inspection Standard was ASME Boiler and Pressure Vessel Code Section II, Subsection SA-435. A magnetic particle inspection was performed on all welds of the lifting device per ASME Boiler and Pressure Vessel Code Sections III and VIII and the device was load tested satisfactorily to 130,000 pounds.
Based on the above information, the new rectangular coupling lifting device is qualified for spent fuel cask lifting service.
As outlined in the referenced letter, the difficulties with the rectangular coupling device were discovered during the course of a continuing six month interval lifting device inspection program. This device was the last component to be inspected and all other members of the lifting rigging had been satisfactorily checked.
In an effort to increase our surveillance over this equip ment and eliminate future difficulties associated with individual lifting components, nondestructive testing of all accessible cask lifting device members will be performed once again before spent fuel shipments are terminated for the next refueling outage, scheduled to begin August 1, 1976.
Sincerely, Attachments cc:
Director, Office of Inspection and Enforcement Director, Office of Management Information and Program Control
guaor DocketEI A.
TOP VIEW 211 2"
CRACKS IN WELD
.10"1 CRACKS IN HEAT JCI AFFECTED ZONE H 1/2" 1 1/2' B.
BOTTOM VIEW 2"1 APPARENT LACK OF FUSION IN A PORTION OF THE WELD 10" C. SIDE VIEW 7 1/2")
SIDE 2 BLOCK A SIDE 1CRACKS IN WELD CRACKS IN HEAT AFFECTED ZONE FIGURE I CRACKS IN WELDS OF THE ORIGINAL RECTANGULAR COUPLING DEVICE
HOLE FOR U810flator Docket E CONNECTING PIN 3 15/16" V
5 1/ 8"'
46" 37" 7 1/2" WELD (TYPIC 1/2" LEGS 5"
SIDE 2 SIDE 1 4"
2" BLOCK A HOLE FOR EXTENSION SHAFT FIGURE II DETAIL OF THE NEW RECTANGULAR COUPLING DE.V ICE
May 14, 1976 aMa MAY 20 '1976i->
.-S. NilCLEAR ItEGUL01 COMMISSION U. S. uclear Re ulator Commission Region V Office of Irispection arid Eriforcement Walnut Creek Plaza,.Suite 202 1990 North Californ iaEBdulevard 3,
Walnut Creek, California 94596" Attention, R. H. Engelken, Director Docket No. 50 206 San -Onrrofr Unit I.
Reference:
Letter dated May 4, 1976 from SCE to NRC.
concerning crackin.in cask. rectanqu1 t co6upling I iftiing deviceg
Dear Sir:
As cited in the referenced letter, cracks wee discovered
.in the spent. fuel cask -re'ctangularcoupling.1ifting devi e on May 3, 1976 *and the device was determined t0 be unsuitable for further service.
The cracks occurred in the weld s and parent metal adjacent to the, welds (heat affected, zone) as shown in Figuire 1. attached).
Slag pockets were found in the welds after surface grinding.
.The defects were due to the use of improper weld procedures and failure to comply w-ith original material specifications during initial-fabriaition.
This determinatioh is based on a preliminary evaluation by the Company's. Metalurgical Laboratory 'ard a' eview of original design criteria.. A detailed metalurgical analysis of the defective lifting device is in progress and will: be available at the Station for inspect ion..
As. shownin Figure 1, cracks were.discovered in all welds holding Block A to side 1 and 2 except the bottom welds which exhibited some apparent lack of fusion..
However',
the bottom walds were of: sufficient iritecrity to provide the 'structura1
-strencth needed to keep Block A positioned between sides 1 and 2.
There was no need for any 4of the: welds to provide great tensile strength as a recessed lip (see Figue II) in both sides 1 and 2 carried, t he tensile load.
Therefore, there was no immediate possibilit of the rectangular coupling device experiencing complete structural failure leading to acask drop accident.
t103\\
5
-2 Arnew liftpng devic has been npfactured a is row being used for spent fuel-shipnernts.
Itwas fabricated in-accordance with the original design -requirenents usingappropriate'weld and fabr fcation procedues.
Licensee Event Report_ to cover this occurrence i'6 attached A dawing of the new. rep acepient "lifting device is also included, ico porati a
rop iate desc'v information.
The new device is made of ASTM-A-28370A Gr de rbon eel.
~
sess aialysisfor the reciaiguat liftihg vice was re-evd~ated and the' results were adceptable An:ultrasonic inspection xssatisfactoriiy perf6rmd ori the compoent metal parts of the li ftic gdvicehbeforeand'.afte'r machifning, 'h-at treatment and we dig' The Inspectiont Standard was ASE Boiler
,and Pressur e el.
Code Setion JI, S u.bsection S 35 magnetic particlejinspectior was performed o all welds of the iftinc device per ASMEBoiler -and Pressur ess1 Code Sections
- I and VI lad'tie dv ce was load tested satisfactor ly to 13, 00 p p
i Based' oh the above informat ion, th new rectangular coupling Lif tinc devic i
qualifiedfor spent ful cask lift ing service outlined in the referencedle:tter, the difficulties wi the recfangular coupling device w e discovefredduing the cours of a continuing six Ifonth, irtervi-lftting device inspedtin program.
This device as the last componet to be inspeOted and all other members. of the iftig riggig ad benn saqtisfac o ily checked."
In an effaort to -increase.Our, survillince. ove t his equi ment and eliminate fulture difficut'ies. associated with individual lifting.components,, nonde.struuctive testiig of all ace ssible cask ifting -device members ewi
. prfoned once a ain before spent fuel shipments are terminated.for 'the next refueling outage, schedUl1ed tb egin August 1, 1976.
oRIGIAL I1E 4('D Oc ogrty' 1
Attachments cc:
Director, Office of Inspet ion and Enforcement Director, Office of Management In formation and Program Cont rol