NRC Generic Letter 1982-26
| ML031080494 | |
| Person / Time | |
|---|---|
| Issue date: | 11/12/1982 |
| From: | Eisenhut D Office of Nuclear Reactor Regulation |
| To: | |
| References | |
| NUREG-0744 GL-82-026, NUDOCS 8211160047 | |
| Download: ML031080494 (2) | |
NOv 1 2 1982 TO ALL POWER REACTOR LICENSEES (EXCEPT FT. ST. VRAIN)
Gentlemen:
SUBJECT: NUREG-0744 REV. 1; (GENERIC LETTER NO. 82- 26 ) -
PRESSURE VESSEL MATERIAL FRACTURE TOUGHNESS
Appendix G to 10 CFR 50 specifies fracture toughness requirements for pressure retaining components, fabricated from ferritic materials, in the reactor coolant pressure boundary of water cooled reactors. In the event a pressure retaining component falls to meet the material toughness requirements during its service life due to neutron radiation embrittlenent, continued operation of the component is permissible provided certain requirements, specified In Section V.C of Appendix G,
are satisfied.
One of the requirements of Section V.C is that a fracture analysis of the component is to he performed to demonstrate the existence of ade- quate margin for continued operation. The proposed progran for satis- fying this requirement is to be submitted to the USNRC for review and approval at least 3 years prior to the date fracture toughness levels are predicted to no longer satisfy requirements.
Appendix H to 10 CFR 50 specifies the surveillance program which all power reactor licensees must maintain to monitor irradiation-induced fracture toughness changes. Impact data from this program are used to adjust the reference toughness curve for irradiation effects through the application of the adjusted reference temperature. The Charpy V-notch 50 ft-lb level is used to determine the temperature shift;
therefore, when the upper shelf energy falls below 50 ft-lb, the requirements of 10 CFR 50 Appendix G are no longer ret.
To provide guidance to licensees who may be required to submit a fracture analysis to Justify continued operation of a pressure vessel, the USNRC has developed an elastic-plastic fracture mechanics analytical procedure. This analytical methodology is presented in NUREG-0744, Revision 1 (Office of Management and Budget Clearance Number 3150-0011), a copy of which is enclosed with this letter.
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NRC FORM 318 (t0 80) NRCM 0240 O.FFICIA L RE C OR.D C OPY USGPO: 1981-335-960
ftU. i ALL POWER REACTOR LICENSEES -2- This document presents one methodology which is acceptable to the USNRC staff for meeting the requirement for a fracture analysis with sufficient accuracy and reliability to demonstrate adequate margins for continued operation in accordance with Section V.C.3 of Appendix G to
10 CFR 50. Licensees, however, need not employ this specific fracture analysis methodolog~y and may submit an analysis based on other tech- niques for NRC review and approval.
Available evidence reveals that the upper shelf energy of a number of power reactor pressure vessels may fall below the 50 ft-lb level before the end of their design life unless measures such as revised fuel manage- ment schemes are instituted. It is likely that several licensees nay elect to subrilt fracture analysis to support continued operation. All licensees are encouraged to review NUJREG-0744. Revision 1 and consider its application in those cases where it may be necessary to submit a fracture analysis to the NRC for review and approval.
Sincerely, original signed by Parll. Eisenhuat Darrell Gi.Eisenhut, Director Division of Licensing Office of Nuclear Reactor Regulation Enclosure:
NUREG-0744, Rev. 1IC
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NRC FORM 318 (10-80) NRCM 0240 OFFICIAL RECORD COPY USGPO: 1981-435-9w