ML20212M116
| ML20212M116 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 07/30/2020 |
| From: | NRC |
| To: | NRC/NRR/DNRL |
| References | |
| Download: ML20212M116 (4) | |
Text
From:
Schiller, Alina Sent:
Thursday, July 30, 2020 5:04 PM To:
Vogtle PEmails
Subject:
Discussion points for 8/6/20 call with SNC on LAR 20-005, Vacuum Relief Valve TS Changes For discussion at the August 8th public meeting.
- a. Identify the dominant risk scenarios affected by the proposed change.
- b. For the dominant risk scenarios identified in item (a), discuss risk management actions that will be used to manage the risk from the scenarios or provide justification that such actions are unnecessary. Such actions can include existing or enhanced procedures (e.g., checking that the unaffected CIVs are in their proper position prior to performance of corrective maintenance or repair on the affected CIV(s)).
- c. Based on the plant-specific thermal-hydraulic analyses, identify the accidents that result in the earliest Containment Radioactivity High and/or Containment Isolation signal. For the identified accidents, if the unaffected CIV(s) fail to remain closed while the affected CIV(s) are in maintenance or repair, discuss the cues, available time, and procedures for operators to take action to isolate the containment.
- d. Discuss whether the performance of the vacuum relief isolation valves and vacuum relief check valves will be monitored by the maintenance rule; or discuss how existing or planned performance monitoring strategies will ensure that the conclusions drawn from the risk insights remain valid.
- e. Describe potential impacts to defense-in-depth aspects of the plants design and operation and the adequacy of safety margins following the proposed change.
- f.
Provide the basis for screening the impact of other external hazards and low power and shutdown on the proposed change.
- g. Discuss if and how key assumptions and sources of uncertainty in the inputs for the risk insights impact the responses to the above items. If key assumptions and sources of uncertainty impact the responses, explain how they will be dispositioned for the proposed change.
- h. In LAR 20-005, the licensee proposes to change current SR 3.6.9.2 (proposed SR 3.6.9.3) as follows:
As shown above, the proposed license amendment would change the expression vacuum relief flow path to vacuum relief valve. The proposed SR 3.6.9.3 retains wording to verify each vacuum relief is operable in accordance with the Inservice Testing Program [emphasis added].
The VEGP Units 3 and 4 Inservice Testing Program Plan describes the inservice testing (IST) activities for pumps, valves, and snubbers within the scope of the ASME OM Code (2012 Edition) as incorporated by
reference in 10 CFR 50.55a. Paragraph ISTC-5230, Vacuum Breaker Valves, in the ASME OM Code, Subsection ISTC, specifies that vacuum breakers shall meet the IST requirements of paragraph ISTC-5220 and Mandatory Appendix I. Paragraph ISTC-5220, Check Valves, in the ASME OM Code, Subsection ISTC, specifies the IST requirements for check valves. Mandatory Appendix I, Inservice Testing of Pressure Relief Devices in Light-Water Reactor Nuclear Power Plants, of the ASME OM Code includes the IST requirements for safety and relief valves, including vacuum relief valves. Given that the vacuum relief flow path in VEGP Units 3 and 4 is comprised of two check valves and two isolation valves (motor-operated valves), the NRC staff is concerned that only referring to vacuum relief valve in accordance with the Inservice Testing Program might not provide assurance that these dual function (safety function to open and close) check valves and isolation valves are demonstrated to be operable as intended by the Technical Specifications.
Hearing Identifier:
Vogtle_COL_Docs_Public Email Number:
582 Mail Envelope Properties (BL0PR0901MB2994F0A2229AEA17AF66AE9096710)
Subject:
Discussion points for 8/6/20 call with SNC on LAR 20-005, Vacuum Relief Valve TS Changes Sent Date:
7/30/2020 5:03:51 PM Received Date:
7/30/2020 5:03:54 PM From:
Schiller, Alina Created By:
Alina.Schiller@nrc.gov Recipients:
"Vogtle PEmails" <Vogtle.PEmails@nrc.gov>
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