ML031560317

Davis- Besse, Lessons Learned Task Force Recommendations, Stress Corrosion Cracking

ML031560317
Person / Time
Site:	Davis Besse
Issue date:	06/04/2003
From:	Moroney B Office of Nuclear Reactor Regulation
To:
Moroney B, NRR/DLPM, 415-3974
References
Download: ML031560317 (5)

Text

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180%(5 5(&200(1'$7,21 3.1.1(1) The NRC should assemble foreign and domestic information concerning Alloy 600 (and other nickel based alloys) nozzle cracking and boric acid corrosion from technical studies, previous related generic communications, industry guidance, and operational events. Following an analysis of nickel based alloy nozzle susceptibility to stress corrosion cracking (SCC),

including other susceptible components, and boric acid corrosion of carbon steel, the NRC should propose a course of action and an implementation schedule to address the results.

3.2.2(1) The NRC should inspect the adequacy of PWR plant boric acid corrosion control programs, including their implementation effectiveness, to determine their acceptability for the identification of boric acid leakage, and their acceptability to ensure that adequate evaluations are performed for identified boric acid leaks.

3.3.2(1) The NRC should develop inspection guidance for the periodic inspection of PWR plant boric acid corrosion control programs.

3.3.4(3) The NRC should strengthen its inspection guidance or revise existing guidance, such as IP 71111.08, to ensure that VHP nozzles and the RPV head area are periodically reviewed by the NRC during licensee ISI activities. Such NRC inspections could be accomplished by direct observation, remote video observation, or by the review of videotapes.

General guidance pertaining to boric acid corrosion observations should be included in IP 7111.08 3.3.4(8) The NRC should encourage ASME Code requirement changes for bare metal inspections of nickel based alloy nozzles for which the code does not require the removal of insulation for inspections. The NRC should also encourage ASME Code requirement changes for the conduct of non-visual NDE inspections of VHP nozzles. Alternatively, the NRC should revise 10 CFR 50.55a to address these areas.

Medium Priority NUMBER RECOMMENDATION 3.1.4(1) The NRC should determine if it is appropriate to continue using the existing SCC models as predictors of VHP nozzle PWSCC susceptibility given the apparent large uncertainties associated with the models. The NRC should determine whether additional analysis and testing are needed to reduce uncertainties in these models relative to their continued application in regulatory decision making.

Low Priority NUMBER RECOMMENDATION 3.3.7(6) Determine whether ISI summary reports should be submitted to the NRC, and revise the ASME submission requirement and staff guidance regarding disposition of the reports, as appropriate.