ML18074A142
| ML18074A142 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 03/15/2018 |
| From: | NRC |
| To: | NRC/NRO/DNRL/LB4 |
| References | |
| Download: ML18074A142 (6) | |
Text
1 Vogtle PEmails From:
Patel, Chandu Sent:
Thursday, March 15, 2018 11:17 AM To:
Vogtle PEmails Cc:
Patel, Chandu
Subject:
Summary of Audit conducted for LAR 17-027, for Vogtle 3 and 4, RCS Vacuum Fill and ITAAC for Containment Flood up Attachments:
LAR 17-027 Audit Summary.docx Attached is a summary of audit conducted in January 2018 for Vogtle Units 3 and 4 License Amendment Request 17-027 related to Reactor Coolant System Vacuum Fill and ITAAC for Containment Flood-up.
Chandu Patel, Senior Project Manager U.S. NRC, Office of New Reactors NRC/NRO/DNRL/LB4, Washington, DC 20555-0001 301.415.3025 MS T6C20M
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237 Mail Envelope Properties (BN7PR09MB25620B170D390DB91FC14D8082D00)
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Summary of Audit conducted for LAR 17-027, for Vogtle 3 and 4, RCS Vacuum Fill and ITAAC for Containment Flood up Sent Date:
3/15/2018 11:17:12 AM Received Date:
3/15/2018 11:17:15 AM From:
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Audit Summary for Vogtle Electric Generating Plant Units 3 and 4 License Amendment Request 17-027 Reactor Coolant System Vacuum Fill and ITAAC for Containment Floodup A. Background By letter dated September 27, 2017 Southern Nuclear Operating Company (SNC) submitted license amendment request (LAR)-17-027 requesting changes to technical specifications to allow reactor coolant system (RCS) vacuum fill operations in cold shutdown conditions (Reference 1). As described in LAR-17-027, the proposed change is supported by safety analyses. The purpose of this audit was to gain a better understanding of the analyses supporting LAR-17-027.
B. Regulatory Audit Bases This regulatory audit was based on the following:
COL, Appendix C (and Plant -Specific Tier 1) Section 3.3 UFSAR, Section 6.3.2.2.3 COL, Appendix A, Technical Specifications, Specification 3.4.12 C. Logistics The audit was conducted from NRC Headquarters via the Westinghouse electric reading room.
Date: January 22-31, 2018 Location:
NRC Headquarters Two White Flint North 11545 Rockville Pike Rockville, MD 20852-2738 D. Audit Team Members Donald Palmrose, Senior Reactor Systems Engineer Timothy Drzewiecki, Reactor Systems Engineer Chandu Patel, Senior Project Manager
E. Licensee and Industry Staff Participants SNC Wesley Sparkman Amy Chamberlain Westinghouse Camille Zozula F. Documents Audited APP-PXS-M3C-034, Rev. 4, Containment Flood-up Level, January 8, 2016.
APP-SSAR-GEF-088, Revision 0, Small Break LOCA (SBLOCA), Loss of Normal Residual Heat Removal System (RNS) Cooling, and Long Term Core Cooling Mass and Energy Release Assessments of Outstanding Design Debt, September 1, 2016.
G. Description of Audit Activities and Summary of Observations NRC staff examined calculation APP-PXS-M3C-034, Rev. 4, Containment Flood-up Level.
During this examination NRC staff noted the purpose of the calculation, important inputs into the analysis, and the main results. In particular, NRC staff noted:
The purpose of the calculation is to determine the initial containment flood levels following actuation of the automatic depressurization system (ADS).
The calculation evaluated 12 cases and varied multiple parameters, including break location, leak rate, and containment volumes.
The minimum containment flood-up level is 2.34 meters above nominal (7.68 ft above nominal), where nominal is 100 m or 100 ft depending on units. The minimum flood-up level occurs for a leak originating in the passive core cooling system (PXS) B room of the containment, with a leak rate of 0.00151 m3/s (24.0 gallons per minute), and the containment volumes set to minimize the containment level.
The minimum containment flood level corresponds to:
o A minimum flood-up volume in the normal and PXS B volumes of 1,956.3 m3 (69,086 ft3) o A best estimate flood-up volume in the normal and PXS B volumes of 1,997.1 m3 (70,525 ft3.)
o A maximum flood-up volume in the normal and PXS B volumes of 2,037.8 m3 (71,964 ft3).
The minimum flood-up level and associated maximum flood-up volume from this analysis are recommend to be used as the basis for ITAAC Table 3.3-6, Item 2.h.
NRC staff examined calculation APP-SSAR-GEF-088, Revision 0, Small Break LOCA (SBLOCA), Loss of Normal Residual Heat Removal System (RNS) Cooling, and Long Term Core Cooling Mass and Energy Release Assessments of Outstanding Design Debt. This examination was limited to Attachment D, Shutdown Loss-of-RNS Debt Assessment Evaluation. During this examination NRC staff noted the purpose of the evaluation, important inputs into the analysis, and the main results. In particular, NRC staff noted:
The evaluation analyzes the loss of the normal residual heat removal system (RNS).
Analyses were performed using the thermal-hydraulic code NOTRUMP.
The analysis assumed reduced ADS valve operability in accordance with a proposed update to Technical Specifications (TS). This availability is provided in the table below.
provided TS 3.4.12 TS 3.4.13 RCS Configuration Flow Paths Operable RCS Configuration Flow Paths Operable ADS 1-3 ADS 4 ADS 1-3 ADS 4 Current RCS intact 9 ADS flow paths RCS open 8 ADS Flow Paths 6
2 Expected Update RCS intact Reactor Subcritical
<28 hours 5
4 RCS open Reactor Subcritical
<28 hours 5
4 RCS intact Reactor Subcritical 28 hour3.240741e-4 days <br />0.00778 hours <br />4.62963e-5 weeks <br />1.0654e-5 months <br /> 3
3 RCS open Reactor Subcritical 28 hour3.240741e-4 days <br />0.00778 hours <br />4.62963e-5 weeks <br />1.0654e-5 months <br /> 3
3 Analyses are performed for the following scenarios:
o MODE 4 and MODE 5, RCS intact, subcritical Less than 28 hours3.240741e-4 days <br />0.00778 hours <br />4.62963e-5 weeks <br />1.0654e-5 months <br />, automatic S-signal.
o MODE 4 and MODE 5, RCS intact, subcritical Less than 28 hours3.240741e-4 days <br />0.00778 hours <br />4.62963e-5 weeks <br />1.0654e-5 months <br />, manual S-Signal.
o MODE 4 and MODE 5, RCS intact, subcritical Greater than 28 hours3.240741e-4 days <br />0.00778 hours <br />4.62963e-5 weeks <br />1.0654e-5 months <br />, automatic S-signal o MODE 5, subcritical Greater than 28 hours3.240741e-4 days <br />0.00778 hours <br />4.62963e-5 weeks <br />1.0654e-5 months <br />, Vacuum Refill Configuration, automatic ADS actuation An analysis was not performed for MODE 5, RCS open, and subcritical less than 28 because this scenario is bounded by previous analysis that assumed fewer ADS valves were available.
An analysis was not performed for MODE 5, RCS open, and subcritical greater than 28 hours3.240741e-4 days <br />0.00778 hours <br />4.62963e-5 weeks <br />1.0654e-5 months <br /> because this scenario is bounded by the vacuum refill analysis due to an earlier depressurization.
The analysis supporting the RCS vacuum refill configuration credits operator action to actuate ADS based on low hot leg level.
The analyses for the scenarios with the reactor subcritical for greater than 28 hours3.240741e-4 days <br />0.00778 hours <br />4.62963e-5 weeks <br />1.0654e-5 months <br />, were performed at 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
The result of all the analyses showed that the core region remains covered with a two-phase mixture while considering the reduced equipment available to mitigate a loss of RNS cooling in shutdown MODE 4 and MODE 5.
H. Requests for Additional Information Resulting from Audit This audit did not result in the issuance of any Requests for Additional Information.
I.
References
- 1. Vogtle Electric Generating Plant, Units 3 and 4 - Request for License Amendment and Exemption Regarding Technical Specifications for Reactor Coolant System Vacuum Fill and Inspections, Tests, Analyses, and Acceptance Criteria for Containment Floodup (LAR-17-027), September 25, 2017 (ADAMS Accession Number ML17268A188).