ML15103A002

Summary of 4/8/15 Meeting with STP Nuclear Operating Company to Discuss Revised Pilot Submittal and Request for Exemptions for a Risk-Informed Approach to Resolve Generic Safety Issue (GSI)-191 at South Texas, Units 1 and 2

ML15103A002
Person / Time
Site:	South Texas
Issue date:	05/13/2015
From:	Lisa Regner Plant Licensing Branch IV
To:	Koehl D South Texas
Regner L
References
TAC MF2400, TAC MF2401, TAC MF2402, TAC MF2403, TAC MF2404, TAC MF2405, TAC MF2406, TAC MF2407, TAC MF2408, TAC MF2409
Download: ML15103A002 (5)

Text

LICENSEE:

FACILITY:

SUBJECT:

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 May 13, 2015 STP Nuclear Operating Company South Texas Project, Units 1 and 2

SUMMARY

OF APRIL 8, 2015, PUBLIC MEETING WITH STP NUCLEAR OPERATING COMPANY TO DISCUSS THE LICENSE AMENDMENT AND EXEMPTION REQUESTS TO USE A RISK-INFORMED APPROACH TO THE RESOLUTION OF GENERIC SAFETY ISSUE 191, "ASSESSMENT OF DEBRIS ACCUMULATION ON PWR SUMP PERFORMANCE" (TAC NOS. MF2400, MF2401,MF2402,MF2403,MF2404,MF2405,MF2406,MF2407,MF2408,AND MF2409)

On April 8, 2015, a public meeting was held between the U.S. Nuclear Regulatory Commission (NRC) and representatives of STP Nuclear Operating Company (STPNOC, the licensee), at NRC Headquarters, Rockville, Maryland. The meeting notice and agenda, dated February 13, 2015, are located in the Agencywide Documents Access and Management System (ADAMS) at Accession No. ML15091A578. The licensee's handouts from the meeting are available in ADAMS at Accession Nos. ML15098A605 and ML15098A606. A list of meeting attendees is provided in the Enclosure to this meeting summary.

By letter dated June 19, 2013 (ADAMS Accession No. ML131750250), as supplemented by letters dated October 3, October 31, November 13, November 21, and December 23, 2013 (two letters); and January 9, February 13, February 27, March 17, March 18, May 15 (two letters),

May 22, June 25, and July 15, 2014; and March 10, and March 25, 2015 (ADAMS Accession Nos. ML13295A222, ML13323A673, ML13323A128, ML13338A165, ML14015A312, ML14015A311, ML14029A533, ML14052A053, ML14072A076, ML14086A383, ML14087A126, ML14149A353, ML14149A354, ML14149A434, ML14178A481, ML14202A045, ML15072A092, and ML15091A440, respectively), STPNOC submitted exemption requests accompanied by a license amendment request (LAR) for a risk-informed approach to resolve Generic Safety Issue (GSl)-191, "Assessment of Debris Accumulation on PWR [Pressurized-Water Reactor] Sump Performance," at South Texas Project, Units 1 and 2 (STP).

The purpose of this public teleconference call was to discuss the licensee's proposed structure of the methodology change submittal which the licensee plans to provide to the NRC staff in June 2015. The June 2015 supplement is expected to provide information on the new Risk over Deterministic methodology, and modify the license amendment and exemption requests.

Also, the NRC staff provided initial feedback on the licensee's request for additional information (RAI) Round 2 responses dated March 25, 2015.

Meeting Summary The NRC staff discussed the "Max Debris Loading Strainer Head Loss psi [pounds per square inch] vs. Temperature F [degrees Fahrenheit]" graph provided by STPNOC (ADAMS Accession No. ML15098A605). This was used as an aid in clarifying the licensee's response to the NRC's Mechanical and Civil Engineering Branch (EMCB) question 2 from the March 25, 2015, STPNOC response. The staff stated that the graph clarifies STPNOC's response, but needs to be submitted formally as a supplement to the question. STPNOC stated it would include this clarification to EMCB question 2 in the June supplement (the June supplement was discussed in the February 4, 2015, public meeting summary, which is available in ADAMS at Accession No. ML15084A003).

In response to the NRC staff's questions, the licensee acknowledged that the text associated with Table 4 in the RAI response incorrectly stated that all risk results were calculated by STPNOC from Regulatory Guide (RG) 1.174, Revision 2, "An Approach for Using Probabilistic Risk Assessment in Risk-Informed Decisions on Plant Specific Changes to the Licensing Basis,"

May 2011 (ADAMS Accession No. ML100910006), acceptance guidelines for core damage frequency (CDF) and large, early release frequency (LERF) (i.e., Region 111 of RG 1.17 4 ),

except when the 95th percentile LOCA frequencies from NUREG-1829, "Estimating Loss-of-Coolant Accident (LOCA) Frequencies Through the Elicitation Process," April 2008 (ADAMS Accession No. ML082250436), were used. Region Ill in RG 1.174 indicates "very small" changes in risk. The NRC staff agreed that this was incorrect and should be corrected to state that the 95th percentile and mean values for arithmetic mean LOCA frequencies from NUREG-1829 produced risk results in excess of RG 1.17 4, Region 111. STPNOC staff agreed to make this correction.

NRC staff stressed that the June supplement should provide a strong basis for using the risk-informed methodology by discussing the principles in RG 1.17 4 including defense-in-depth and safety margins with respect to the analyzed design characteristics.

STPNOC and the NRC staff discussed the progress made concerning the calculation techniques used by the licensee to analyze the number of welds expected to generate debris loads in excess of deterministic thresholds. The staff received additional information on March 10, 2015, that has allowed staff to better understand STPNOC's CASA Grande results (CASA Grande is the software providing the integrated probabilistic risk analysis framework).

The STPNOC staff offered to provide draft sections to the NRC staff for review as they become available to discuss during upcoming public meetings. The next scheduled public meeting is April 22, 2015, at 3:00 p.m. eastern time (meeting notice and agenda available in ADAMS at Accession No. ML15091A578).

STPNOC and the NRC staff discussed some of the logistics of the proposed CASA Grande audit. The licensee offered to hold the audit in Albuquerque, New Mexico, during the week of May 11, 2015. NRC staff will verify that the proposed week is acceptable to the staff, will provide an expected duration, and discussion topics by April 11.

Action Items STPNOC staff will include a supplemental response to the strainer structural question, EMCB question 2 from the licensee's response dated March 25, 2015.

NRC staff will confirm a proposed audit dates and timeframe, and provide draft audit discussion topics to STPNOC staff by Friday, April 10, 2015.

No Public Meeting Feedback Forms were received for this meeting.

Please direct any inquiries to me at 301-415-1906, or lisa.regner@nrc.gov.

Docket Nos. 50-498 and 50-499

Enclosure:

List of Attendees cc w/encl: Distribution via Listserv Sincerely,

~er*~

fc-<

Lisa M. Regner, Senior Project Manager Plant Licensing Branch IV-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation

LIST OF ATTENDEES APRIL 8. 2015. CONFERENCE CALL WITH STP NUCLEAR OPERATING COMPANY REGARDING RISK-INFORMED APPROACH TO RESOLUTION OF GSl-191 NAME Lisa Regner John Stang Victor Cusumano Caroline Tilton Ashley Guzzetta Tim Lupold CJ Fong Mike Murray Steve Blossom Drew Richards Ernie Kee Wayne Harrison Wes Schulz Mark Wales Linda Dyer Bruce Letellier Ron Holloway Jeremy Tejada Tim Sande SOUTH TEXAS PROJECT. UNITS 1 AND 2 DOCKET NOS. 50-498 AND 50-499 ORGANIZATION U.S. Nuclear Regulatory Commission (NRC)

NRC NRC NRC NRC NRC NRC STP Nuclear Operating Company (STPNOC)

STPNOC STPNOC STPNOC STPNOC STPNOC STPNOC STPNOC Al ion Wolf Creek Nuclear Generating Corporation University of Texas at Austin Enercon Enclosure

ML15103A002 OFFICE NRR/DORL/LPL4-1/PM NRR/DORL/LPL4-1 /LA NRR/DSS/SSIB/BC NAME LRegner JBurkhardt VCusumano DATE 4/22/15 4/20/15 4/24/15 OFFICE NRR/DRA/APLA/BC NRR/DE/EMCB/BC NRR/DORL/LPL4-1 /BC NAME HHamzehee TLupold MMarkley (LRegner for)

DATE 4/22/15 4/22/15 5/13/15