ML22024A009

Breakout Questions - Trp 3 - RPV Closure Head Studs

ML22024A009
Person / Time
Site:	Oconee
Issue date:	01/20/2022
From:	Angela Wu NRC/NRR/DNRL/NLRP
To:
Wu A, 301-415-2995
Shared Package
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References
Download: ML22024A009 (3)

Text

Oconee SLRA: Breakout Questions SLRA Section B2.1.3 Reactor Head Closure Stud Bolting TRP 3 Question Number SLRA Section SLRA Page Background / Issue (As applicable/needed)

Discussion Question /

Request 1

B2.1.3 B - 35 One of the degradation mechanisms addressed by this AMP is stress corrosion cracking (SCC) within the reactor head closure studs (Item No.

B6.20) and the threads in the reactor vessel flange (Item B6.40).

The ASME Code Section XI volumetric examinations for the reactor head closure studs (RHCSs) and the threads in the reactor vessel flange are the most effective examinations to detect SCC.

Discuss the results of the ASME Code Section XI IWB volumetric examinations for the 60 reactor closure head studs (B6.20) and the 60 threads-in-flange (B6.40) of each Oconee Nuclear Station (ONS) unit from the last required examinations.

2 B2.1.3 B - 40 Operating experience #1 (April 2011) in the SLRA for the AMP is discussed in AR 01806638. This AR discusses studs that had gouges and missing threads in lower threads and scratch across six threads near top. An engineering evaluation per guidance in Dominion Engineering Calc R-3181-003 was performed to determine acceptability of these studs for continued use.

a) Put Dominion Engineering Calc R-3181-003 in the ePortal and discuss the engineering evaluation, that determined that the damaged studs were acceptable for continued use.

b) Discuss potential causes of the damage in the studs.

3 B2.1.3 B - 36 to B - 37 Details of measured ultimate strengths of the ONS reactor closure studs from CMTR data are in SLR-ONS-AMPR-XI.M3.

a) Clarify that the 60 installed RHCSs and 12 spare RHCSs of ONS Unit 1 are made from heat 6780366, and the data shown on page 13 of SLR-ONS-AMPR-XI.M3 are the only data on this heat.

b) Similarly, clarify that the 60 installed RHCSs of ONS Unit 2 are made from heat

Oconee SLRA: Breakout Questions Question Number SLRA Section SLRA Page Background / Issue (As applicable/needed)

Discussion Question /

Request 6880366, and the data shown on page 14 of SLR-ONS-AMPR-XI.M3 are the only data on this heat.

c) Similarly, clarify that the 60 installed RHCSs and 3 spare RHCSs of ONS Unit 3 are made from heat 159628, and the data shown on page 14 of SLR-ONS-AMPR-XI.M3 are the only data on this heat.

4 B2.1.3 B - 42 to B - 43 Operating experience #3 (December 2013) in the SLRA for the AMP is discussed in PIP O-13-15069. This AR discusses and summarizes differences between EPRI performance demonstration initiative (PDI) used to volumetrically examine the ONS RHCSs and the volumetric examination methods in ASME Code,Section XI, Appendix VIII, Supplement 8.

a) Discuss whether a request for alternative through the 10 CFR 50.55a(z) process (10 CFR 50.55a(g)(5) back in 2013) was ever submitted and approved for the EPRI PDI program and if not, why not. Will an alternative request be submitted for future required volumetric examinations? Or, alternatively, clarify whether the EPRI PDI program was ever compliant with Appendix VIII Supp 8 (i.e., provide the historical context of the EPRI PDI program as it relates to the requirements of Appendix VIII; it could be that the program was compliant or it was developed to be compliant with App VIII Supp 8, then the Dec 2013 alert came out that identified a discrepancy).

Oconee SLRA: Breakout Questions Question Number SLRA Section SLRA Page Background / Issue (As applicable/needed)

Discussion Question /

Request b) The discussion of operating experience #3 states that the volumetric exams for the ONS RHCSs were reperformed. Were they reperformed with volumetric examination methods that closed the gaps identified in the Dec 2013 alert and therefore compliant with ASME Code,Section XI, Appendix VIII, Supplement 8?

c) Have the PDI examination procedures been updated to close the gaps identified in the Dec 2013 alert, and therefore, all future examinations for the ONS RHCSs will be compliant with ASME Code,Section XI, Appendix VIII, Supplement 8?