ML22024A051

Breakout Questions - Trp 149.4 - LBB

ML22024A051
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Site:	Oconee
Issue date:	01/20/2022
From:	Angela Wu NRC/NRR/DNRL/NLRP
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Wu A, 301-415-2995
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Oconee Nuclear Station Units 1, 2, 3 SLRA TRP 149.4 Breakout Audit Questions

TLAA Section 4.7.4 Leak-Before-Break Analysis for Reactor Coolant System Piping

1. SLRA SLRA Page Question / Issue Why are we asking?

Section 1 4.7. 4 17 of SRP 3.6.3 Rev.1 (dated 2007) states that SRP 3.6.3 of NUREG -0800 Framatome Primary Water Stress Corrosion states that PWSCC is considered Document No. Cracking (PWSCC) is considered to be to be an active degradation 51-5000709-an active degradation mechanism in mechanism in Alloy 600/82/182 002 Alloy 600/82/182 materials in PWRs. materials in PWRs and needs to Assessment of Section 4.1 of Framatome Document be addressed.

TLAA Issues in No. 51-5000709-002 Assessment of LBB Analysis of TLAA Issues in LBB Analysis of RCS RCS Primary Primary Piping, states the RCS Piping primary piping is primarily constructed from carbon steel which has been clad with austenitic stainless steel or Alloy 82/182. Please identify how the applicant is demonstrating that PWSCC is not a potential source of pipe rupture as required in SRP 3.6.3 Rev.1.

2 4.7. 4 75 In the TLAA, it states that the fatigue flaw The TLAA states that transient growth evaluations are based on cycles are monitored for RCS transients defined by ONS UFSAR components, but there is no Table 5.2, Transient Cycles for RCS mention how the Pressurizer components Except Pressurizer Surge Surge Line is monitored.

Line. It states that these transients are monitored by the Fatigue Monitoring Program (Section B3.1, Gall - SLR X.M1) and provides an acceptable method for managing the fatigue flaw growth aspect of the LBB evaluation

for the SPEO. How is the pressurizer surge line monitored?

3 4.7.4 77 In the TLAA, it states that the subsequent data TLAA needs to close the loop on published in NUREG/CR-6177, the analysis.

Assessment of Thermal Embrittlement of Cast Stainless Steels indicate that prolonged exposure of CASS to reactor coolant operating temperature can lead to reductio of fracture toughness by thermal embrittlement.

Therefore, a Flaw Stability Analysis (FSA) using the lower-bound CASS fracture toughness curves from NUREG/CR-6177 was used to demonstrate the acceptability of LBB of CASS items for the RCS for the SPEO.

Please state the results of the FSA and if indeed it is bounding to the SPEO.

Please expand on the TLAA Evaluation for the CASS items which were screened out.

4 4.7.4 On page 77, the third paragraph of the page states Why was it determined that in that the ONS 2 and 3, the discharge and support of SLR for 80years suction nozzles of the RCP casings were of operation, the most evaluation for LBB using the heat specific recent fracture toughness fracture toughness curves per NUREG/CR-data from NUREG/CR-4513, 4513, Revision 2. It was previously stated Rev. 2 was evaluated and that the assumptions in BAW-1847 Rev. 1, determined to be limiting that the fracture toughness of the ferritic compared to the piping and ferritic weldments bounding NUREG/CR-6177 fracture the fracture toughness of CASS materials toughness data for the cannot be supported. Therefore, for the specific RCP material heats

SPEO for 60 years, an FSA was performed evaluated? What changed using the lower-bound CASS fracture to make the fracture toughness curves from NUREG/CR-6177 to toughness data more show acceptability of LBB. limiting for NUREG/CR-4513? Please provide clarification.