ML20056B272
| ML20056B272 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 08/20/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20056B271 | List: |
| References | |
| GL-90-05, GL-90-5, TAC-M77037, NUDOCS 9008280042 | |
| Download: ML20056B272 (2) | |
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- NUCLE AR REGULATORY COMMISSION
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W SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REQUEST FOR RELIEF FROM ASME CODE REPAIR REQUIREMENTS FOR ASME CODE CLASS 3 PIPING 1
TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION DOCKET NO. 50-346 I.
BACKGROUND' Temporary Non-Code Repairs 10 CFR 50.55a(g) requires nuclear power facility piping and components to meet the app (licable requirements of Section XI of the ASME Boiler and Pressure
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Vessel Code theCode).'SectionXIoftheCodespecifiesacceptablerepair methods for flaws.that exceed Code acceptance limits in piping that is in service. A Code repair is required to restore the structural integrity of flawed Code piping, inde)endent of the operational mode of the plant when the flaw is detectcd.. T1ose repairs not in compliance with Section XI of i
the Code are non-Code repairs.
However, the required Code repair may be-impractical for a flaw detected during p(g)nt operation unless the facility la
,J is shutdown. Pursuant to 10 CFR 50.55a (6)(1), the NRC will evaluate determinations of impracticality, and may grant relief and may impose
' alternative requirements. Generic Letter 90-05, entitled " Guidance for
-l Performing Temporary Non-Code Repair of ASME Code Class 1, 2, and 3 Piping "
'I dated June 15,1990,.providesguidanceforlicenseesindevelopingevaluations-regarding relief requests for temporary non-Code repairs of Code Class 3 piping. The NRC may grant relief based on an evaluation considering the guidance in Generic Letter-90-05.
Licensee's Relief Request By letter dated July 10,'1990, theToledoEdisonCompany(thelicensee) requested relief from Code repair requirements'of certain Code Class 3 piping at Davis-Besse. A leak was detected in the Code Class 3 moderate energy service water system piping during plant operation and the licensee has determined that conformance with Code repair requirements is imprac--
tical. The licensee's basis for this determination is that it would require about-89 hours to do-a repair per the Code which is in excess of the 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> permitted for isolating systems as specified in the Limiting Condition for Operation (LCO) in Technical Specification (TS) 3.6.2.2 of the Davis-Besse TSs.
Pursuantto10CFR50.55a(g)(5)(iii),thelicenseesubmitteda relief request to-the Commission. The subject piping is 4 inches in diameter (schedule 40) and fabricated from ferritic steel. The licensee proposed a temporary non-Code repair based on a non-welded repair.
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.I II. EVALUATION OF RELIEF REQUEST Code Requirement Article IWA-4000 of Section XI of the Code specifies the Code repair procedures.
Code Relief Request Relief is requested from performing a Code repair for the flaw detected during plant operation in Code Class 3 piping.
Basis for Relief Code repair requirements are impractical unless the facility is shutdown.
Proposed Alternative The licensee proposes to utilize the guidance in Generic Letter 90-05 to-perform a temporary non-Code repair.
Staff Evaluation and Conclusions The staff has determined that Code repair requirements in this case are impractical, as defined in Generic Letter 90-05. Our basis for this deter-mination is that the time to repair the pipe in conformance with'the Code requirements would require a plant shutdown as discussed above. -Although-the staff disagrees with the licensee's argument that the guidance for. flaw evaluation in Generic Letter 90-05 is not applicable to thin wall piping, the staff finds the flawed piping-to have adequate structural integrity.
Our basis for this finding is that it is acceptable to substitute the nominal pipe thickness for the Code minimum pipe thickness in the flaw.
i evaluation, according to Section C.3.a in Enclosure 1 to Generic Letter 90-05, when the flaw is entirely contained within a region bounded by the assumed flaw length and the nominal pipe wall.
Furthermore, the licensee has committed to the guidance provided in Generic Letter 90-05 which will reasonably assure structural integrity and protect-public health and safety. Accordingly, the staff concludes that grantingc relief where Code requirements are impractical and imposing alternative requirements are authorized by law and will not endanger life oriproperty or the common defense and security and are otherwise in the public interest, given due consideration to the burden upon the licensee and facility that could result if the Code requirements were imposed on the facility. Hrsuant to10CFR50.55a(g)(6)(i)andconsistentwiththeguidanceinGenericLetter 90-05, relief is granted until the next scheduled outage exceeding 30 days, but no later than the next scheduled refueling outage. The temporary non-Code repair must then be replaced with a Code repair.
Principal. Contributor:
S. Lee Date: August 20, 1990 t
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