ML22138A395
| ML22138A395 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 05/24/2022 |
| From: | Southern Nuclear Operating Co |
| To: | Office of Nuclear Reactor Regulation |
| Lamb J, NRR/DORL/LPL2-2 | |
| References | |
| Download: ML22138A395 (15) | |
Text
May 24, 2022 SNC Pre-Submittal Meeting for Proposed Alternative to Adopt 10 CFR 50 Appendix J, Option B Frequency for Vogtle Unit 1 and 2 Refueling Water Storage Tank (RWST) Check Valves
2 Meeting Purpose and Agenda
- The purpose for this meeting is to discuss a proposed alternative to Adopt 10 CFR 50 Appendix J, Option B Frequency for Vogtle Unit 1 and 2 RWST Check Valves
- This meeting will cover the following topics:
- Background
- Proposed Alternative
- Basis
- Precedent
- Schedule
=
Background===
4 Background
- ISTC-3630 requires testing to verify seat leakage within acceptable limits for Category A valves, other than containment isolation valves.
- ISCT-3630(a) requires this testing at least once every two years
- Vogtle has 4 valves per unit that are leakage tested with water in response to IN 91-56, Potential Radioactive Leakage to Tank Vented to Atmosphere
- Required to close or remain closed during recirculation phase of a LOCA to
- Prevent backflow into RWST
- Limit potential for release of radioactivity from inside containment to atmosphere
5 Background (continued)
- Applicable valves are non-Type C tested valves that are leakage tested with water Table 1. ASME Code Components Affected Valve Number Class Category Description 1/2-1204U6090 2
A/C Safety Injection Pump A & B Suction Check Valve from RWST (Unit 1 and 2) 1/2-1205U6001 2
A/C Residual Heat Removal Pump A Suction Check Valve from RWST (Unit 1 and 2) 1/2-1205U6002 2
A/C Residual Heat Removal Pump B Suction Check Valve from RWST (Unit 1 and 2) 1/2-1208U6189 2
A/C Centrifugal Charging Pump A & B Suction Check Valve from RWST (Unit 1 and 2)
Proposed Alternative
7 Proposed Alternative
- SNC proposes to Adopt 10 CFR 50, Appendix J, Option B frequency for the RWST Check Valves as opposed to the current ASME OM Code requirement
- Specific valve testing interval would be a function of its performance, established consistent with containment isolation valve process
- Valves demonstrating acceptable performance for two consecutive cycles would have test intervals extended to every third refueling outage (not to exceed 60 months)
- If leakage results exceed maximum allowed leakage limits for any valve in Table 1 (Slide 5), all valves for that unit listed in Table 1 would return to the initial test frequency of every refueling outage
Basis
9 Basis for Request
- NUREG-1493 and App. J, Option B test frequencies apply to valves whose function is also isolation of the extended containment boundary while on sump recirculation during a LOCA
- NUREG-1493 provides historical representative industry leakage rate data (1987 to 1993)
- NUREG-1493 concludes that extending testing intervals are acceptable and compares well to the guidance of the NRCs safety goals
- Vogtle Uses the Water Bucket Test Methodology for leakage testing of these valves
- Excellent Performance, as shown on the next slide
10 Basis for Request
- Continued testing will ensure equivalent level of safety for duration of alternative
- If any valve fails, all check valves listed in Table 1 for that unit will revert to testing every 18 months, until performance is established/acceptable (for 2 cycles/tests)
Valve Number Maximum Allowed Leakage Limit (gpm)
Fall 2018 (1R21)
(gpm)
Spring 2020 (1R22)
(gpm)
Fall 2021 (1R23)
(gpm) 11204U6090 1.0 0.0 0.0 0.0 11205U6001 1.0 0.0 0.0 0.0 11205U6002 1.0 0.0 0.0 0.0 11208U6189 1.0 0.0 0.0 0.0 Valve Number Maximum Allowed Leakage Limit (gpm)
Spring 2019 (2R20)
(gpm)
Fall 2020 (2R21)
(gpm)
Spring 2022 (2R22)
(gpm) 21204U6090 1.0 0.0 0.0 0.0 21205U6001 1.0 0.0 0.0 0.0 21205U6002 1.0 0.0 0.0 0.0 21208U6189 1.0 0.0 0.0 0.0 Table 2. Measured Leakage Results for RWST Back-Leakage Valves for Unit 1 and Unit 2
Precedent
12 Precedent
- Beaver Valley Power Station, Units 1 and 2, Safety Evaluation Report in Support of Request Associated with the Fifth (Unit 1) and Fourth (Unit 2) 10-Year IST Program
[VRR4], dated July 16, 2020 (ML20153A014)
- Millstone Power Station, Unit 2, Safety Evaluation Report in Support of Request Associated with the Fifth 10-Year IST Program [V-01], dated November 13, 2018 (ML18290A602)
- Millstone Power Station, Unit 2, Safety Evaluation Report in Support of Request Associated with the Fourth 10-Year IST Program [V-001], dated October 24, 2008 (ML082470622)
- Millstone Power Station, Unit 2, Safety Evaluation Report in Support of Request Associated with the Third 10-Year IST Program [V-6], dated February 24, 2003 (ML030550672)
Schedule
14 Schedule
- Submit Alternative - June 2022
- Request approval - February 2023 (to support Vogtle Unit 1 Spring 2023 outage)
Questions?