ML18136A498

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COL Docs - Vogtle 3 and 4 Audit Summary Vegp LAR 17-021
ML18136A498
Person / Time
Site: Vogtle  Southern Nuclear icon.png
Issue date: 05/16/2018
From:
NRC
To:
NRC/NRO/DNRL/LB4
References
Download: ML18136A498 (6)
v • d • e


Text

Vogtle PEmails From: Hearn, Peter Sent: Wednesday, May 16, 2018 8:30 AM To: Vogtle PEmails; ADAMS IM

Subject:

Vogtle 3 and 4 Audit Summary VEGP LAR 17-021 Attachments: Vogtle 3 and 4 Audit Summary VEGP LAR 17-021_AFD.docx Please place in ADAMS and the Public File.

Pete 1

Hearing Identifier: Vogtle_COL_Docs_Public Email Number: 276 Mail Envelope Properties (MW2PR0901MB2428CC86F9F6B5527C0094D5FD920)

Subject:

Vogtle 3 and 4 Audit Summary VEGP LAR 17-021 Sent Date: 5/16/2018 8:29:49 AM Received Date: 5/16/2018 8:29:52 AM From: Hearn, Peter Created By: Peter.Hearn@nrc.gov Recipients:

"Vogtle PEmails" <Vogtle.PEmails@nrc.gov>

Tracking Status: None "ADAMS IM" <ADAMSSupport.Email@nrc.gov>

Tracking Status: None Post Office: MW2PR0901MB2428.namprd09.prod.outlook.com Files Size Date & Time MESSAGE 61 5/16/2018 8:29:52 AM Vogtle 3 and 4 Audit Summary VEGP LAR 17-021_AFD.docx 39114 Options Priority: Standard Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:

Recipients Received:

UNITED STATES NUCLEAR REGULATORY COMMISSION AUDIT

SUMMARY

FOR THE REGULATORY AUDIT OF SOUTHERN NUCLEAR OPERATING COMPANY VOGTLE ELECTRIC GENERATING PLANT UNITS 3 AND 4 REQUEST FOR LICENSE AMENDMENT AND EXEMPTION:

CHANGES TO CONTAINMENT COOLING AND SPENT FUEL POOL MAKEUP STRATEGIES (LAR-17-021)

DOCKET NO.52-025 52-026 LICENSEE: SOUTHERN NUCLEAR OPERATING COMPANY LICENSEE CONTACT: Ryan Henderson DURATION: February 12, 2018 to March 14, 2018 LOCATIONS: VEGP-designated electronic reading room I. BACKGROUND Southern Nuclear Operating Company submitted by a letter dated July 14, 2017, to the U.S.

Nuclear Regulatory Commission (NRC) a request for license amendment and exemption Changes to Containment Cooling and Spent Fuel Pool Makeup Strategies (LAR-17-021).

The licensee is proposing to enable the PCCWST to be available to support SFP cooling as required in TS 3.7.9 earlier in a refueling outage and, consequently, enhance refueling outage efficiency.

In order to justify these changes the licensee has revised the containment cooling thermal analysis and the spent fuel pool (SFP) heatup and boiloff analysis.

To facilitate the NRC staffs evaluation of information supporting the LAR-017-021, and to complete its safety review of the proposed license changes, the NRC staff performed an audit to evaluate the revised thermal calculations as stated in the staffs regulatory audit plan, dated January 17, 2018 (NRC Agencywide Documents Access and Management System (ADAMS)

Accession No. ML18010B038).

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II. REGULATORY AUDIT BASIS This regulatory audit is based on the following regulations:

  • 10 CFR 50, Appendix A, General Design Criterion (GDC) 38, Containment heat removal, which requires that a system to remove heat from the reactor containment shall be provided. The system safety function shall be to reduce rapidly, consistent with the functioning of other associated systems, the containment pressure and temperature following any loss-of-coolant accident and maintain them at acceptably low levels.
  • GDC 61 Fuel storage and handling and radioactivity control, which requires that the fuel storage and handling, radioactive waste, and other systems which may contain radioactivity shall be designed to assure adequate safety under normal and postulated accident conditions. These systems shall be designed with a residual heat removal capability having reliability and testability that reflects the importance to safety of decay heat and other residual heat removal, and to prevent significant reduction in fuel storage coolant inventory under accident conditions.

The staff used the guidance provided in NUREG-0800, Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants: LWR Edition, Section 6.2.2, Containment Heat Removal Systems and Section 9.1.3, Spent Fuel Pool Cooling and Cleanup System, for this audit.

III. AUDIT MEMBERS AUDIT TEAM: Raul Hernandez (NRO, Audit Lead)

Hanry Wagage, NRO Peter Hearn, NRO, Project Manager IV. DOCUMENTS AUDITED The documents audited are listed below:

  • APP-SFS-M3C-012 AP1000 Spent Fuel Pool Heatup, Boiloff, and Emergency Makeup on Loss of Cooling, Revision 4.
  • APP-SFS-M3C-012 AP1000 Spent Fuel Pool Heatup, Boiloff, and Emergency Makeup on Loss of Cooling, Revision 6.
  • DCP_DCP_008777, Determination of the Impact of DCP 4441 on the AP1000 WGOTHIC Air Only Cooling Analysis of Record to Support LAR-107, June 16, 2017
  • APP-SSAR-GSC-193, Revision 2, Scaling Calculation for Time To Steady State PCS Film Coverage for the AP1000 Containment Pressure and Temperature Response Analysis, June 2011 2
  • APP-SSAR-GSC-749, Revision 0, AP1000 Dry PCS Heat Removal Capability, July 2010 V. DESCRIPTION OF AUDIT ACTIVITIES AND

SUMMARY

OF OBSERVATIONS NRC staff examined APP-SFS-M3C-012 Revision 4 and APP-SFS-M3C-012 Revision 6.

During this examination NRC staff noted:

  • the licensee has not changed the thermal analyses methodology used in APP-SFS-M3C-012 Revision 4;
  • all the volumes of the credited safety-related makeup water sources have been modified to account for construction tolerances on the wall dimensions;
  • the initial pool water temperature (APP-SFS-M3C-012 Revision 6) has been raised for all cases evaluated in APP-SFS-M3C-012 Revision 4;
  • APP-SFS-M3C-012 Revision 6 assumes limited leakage from the gate between the SFP and the CLP;
  • the most limiting event saturation time decreased from 2.33 hours3.819444e-4 days <br />0.00917 hours <br />5.456349e-5 weeks <br />1.25565e-5 months <br /> to 2.0 hours0 days <br />0 hours <br />0 weeks <br />0 months <br />;
  • the calculated minimum time to take operator action has decreased to 18.4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />; and
  • changes in pool heatload resulted in changes in makeup water requirements from the PCCAWST.

The staffs examination of the APP-SFS-M3C-012 Revision 6 did not identify any issue or generated any RAI.

The applicant has prepared DCP_DCP_008777 to support LAR 17-021 and APP-SSAR-GSC-193 and APP-SSAR-GSC-749 provide the current licensing basis. As stated in DCP_DCP_008777, the applicant first performed a re-run of the design basis containment peak pressure analysis for air-only PCS cooling (i.e., for over 7 days with an initial core decay heat of 6 MWt) with updated WGOTHIC code, which corrected the identified code errors. This resulted in lowering the containment peak pressure from design basis peak pressure which is below the containment design pressure. The applicant then used the updated WGOTHIC code to run a case with an initial core decay heat of 7 MWt and air-only PCS cooling for the first 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> following a loss of normal shutdown cooling. This involved increasing the initial core decay heat from 6 MWt in the current design basis analysis to 7 MWt and reducing the analysis time from 7 days to 3 days to determine the peak pressure before PCS water is applied, which turns the transient around. The applicant did not model the 50 gpm cooling water supplied via PCCAWST for the remainder of the 7-day period. The results showed that the containment peak pressure in 3 days remained well below the containment design pressure.

During the audit the staff reviewed the current licensing basis analysis for air-only PCS cooling provided in APP-SSAR-GSC-749. Figure 5-1 of this report provides containment pressure transients for air-only PCS cooling for four cases with different initial decay heat levels that were run for over 7 days. The staff interpolated these results to estimate the containment pressure at 3 days for an air-only PCS cooling with initial decay heat of 7 MWt. The interpolated value of containment pressure at 3 days was well below the containment design pressure of 59 psig and was comparable to the applicants revised analysis results provided in DCP_DCP_008777. The staff expects that, with initiation of 50 gpm PCS water cooling starting at 3 days, the 3

containment pressure would start dropping and, thus, the containment pressure predicted at 3 days will remain the peak containment pressure for 7 days period following a loss of normal shutdown cooling.

After auditing DCP_DCP_008777, APP-SSAR-GSC-193, and APP-SSAR-GSC-749 the staff did not identify any issues or a need to request the applicant for additional information.

VI. EXIT BRIEFING The NRC staff conducted an audit closeout meeting on March 14, 2018. At the exit briefing the NRC staff reiterated the purpose of the audit and discussed their activities. The NRC staff stated that it had not identified areas where additional information is needed.

VII. References

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