ML120830103

3/1/12 Summary of Meeting by Conference Call with STP Nuclear Operating Company to Discuss Risk-Informed GSI-191, Assessment of Debris Accumulation on Pressurized-Water Reactor (PWR) Sump Performance, Resolution Approach for South Texas, Un

ML120830103
Person / Time
Site:	South Texas
Issue date:	03/30/2012
From:	Balwant Singal Plant Licensing Branch IV
To:
Singal, Balwant, 415-3016, NRR/DORL/LPL4
References
TAC ME7735, TAC ME7736
Download: ML120830103 (5)

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• • • • 1' LICENSEE:

STP Nuclear Operating Company FACILITY:

South Texas Project, Units 1 and 2

SUMMARY

OF MARCH 1, 2012, PRE-LICENSING PUBLIC MEETING WITH STP NUCLEAR OPERATING COMPANY HELD VIA CONFERENCE CALL TO DISCUSS THE PROPOSED RISK-INFORMED APPROACH TO THE RESOLUTION OF GSI-191, "ASSESSMENT OF DEBRIS ACCUMULATION ON PWR SUMP PERFORMANCE" (TAC NOS. ME7735 AND ME7736)

On March 1, 2012, a public meeting was held via conference call 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 3, 2012, is located in the Agencywide Documents Access and Management System (ADAMS) under Accession No. ML120340043. The purpose of the meeting was to discuss the proposed risk-informed approach to the resolution of Generic Safety Issue (GSI)-191, "Assessment of Debris Accumulation on PWR [Pressurized-Water Reactor]

Sump Performance." South Texas Project (STP) is the lead plant and STPNOC plans to submit a license amendment request before the end of the year. The licensee previously provided an overview of its proposed approach during the public meetings held on June 2, July 7, July 26, August 22, October 3, November 1, November 2, December 1, 2011, and February 9, 20121.

The purpose of this conference call was to have a follow-up discussion regarding Loss-of Coolant Accident (LOCA) Initiating Event Frequencies and Uncertainties. This topic was previously discussed during public meetings held on June 2, July 7, October 3, and November 2, 2011.

A list of meeting attendees is provided in the Enclosure to this meeting summary.

Meeting Summary The licensee provided a copy of the following documents prior to the meeting:

1.

Introduction - NRC Public Meeting on Risk-Informed Resolution of GSI-191. Topic:

LOCA Frequency (ADAMS Accession No. ML120540557)

2.

Uncertainty Modeling of LOCA Frequencies and Break Size Distributions for the STP GSI-191 Resolution (Presentation) (ADAMS Accession No. ML120540570)

Summaries of the meetings held on June 2, July 7, July 26, August 22, October 3, November 1, and November 2, December 1,2011, and February 9, 2012, are available in ADAMS Accession Nos.

ML111640160, ML111950094, ML112130165, ML112411419, ML112840114, ML113120129, ML113180196, ML113430087, and ML120620541, respectively.

- 2

3.

Uncertainty Modeling of LOCA Frequencies and Break Size Distributions for the STP GSI-191 Resolution (Description) (ADAMS Accession No. ML120540604)

4.

Resolution of Outstanding Chemical Effects PIRT [Phenomena Identification and Ranking Table] Issues by Kerry Howe (ADAMS Accession No. ML120540727)

5.

Experimental Setup for Chemical Head Loss Experiment (CHLE) Test Equipment by Kerry Howe (ADAMS Accession No. ML120540816)

6.

Risk-Informed Resolution of GSI-191 at South Texas Project (Report) (ADAMS Accession No. ML120540667)

7.

STP Post-Meeting Notes for January 26-27,2012 Public Meeting at Nuclear Energy Institute Office (ADAMS Accession No. ML120540758)

During the meeting, only item 2 above, was discussed in detail by STPNOC. The rest of the documents were either provided as reference materials for the topic of discussion or in support of future discussions.

Results of Discussions The licensee presented an alternative method to develop frequency/break-size distributions for welds. The alternative method uses multi-parameter distributions to very closely match the expert elicitation's distributions from NUREG-1829, "Estimating Loss of-Coolant Accident (LOCA) Frequencies Through the Elicitation Process," April 2008, at each of the seven break sizes. The distributions are being assumed constant (at the lower break-size frequency) between the seven break sizes.

The licensee reported that the previous frequency/break-size distributions resulted in frequencies about 30 percent lower than the expert elicitation results. The licensee did not provide an estimate on how the new frequencies might change the change in risk results that have initially been provided in item (6) above.

The NRC staff observed that it was conservative to assume that the NUREG-1829 LOCA frequencies were constant between the break sizes at a frequency equivalent to the lower break size.

Currently, STP is assuming that the frequency per susceptible location is constant for a given break size regardless of the piping system, material, loading, and environmental considerations. The NRC staff was concerned that not considering the effects of potential degradation mechanisms on the relative break susceptibility for each location is inconsistent with other weld-related, risk-informed activities that tend to incorporate the effects of specific degradation mechanisms at susceptible locations.

The licensee reported that the overview report (item 6 above) was still an accurate description of all parts of the evaluation except that the previous frequency/break-size

- 3 distributions would need to be replaced with the new distributions. This will change the estimated risk results initially reported in item 6 above.

No Public Meeting Feedback Forms were received for this meeting.

Please direct any inquiries to me at (301) 415-3016, or balwant.singal@nrc.gov.

Sincerely, I

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Balwant K. Singal, Senior Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-498 and 50-499

Enclosure:

List of Attendees cc w/encl: Distribution via Listserv

LIST OF ATTENDEES MARCH 1, 2012, MEETING WITH STP NUCLEAR OPERATING COMPANY REGARDING RISK-INFORMED APPROACH TO RESOLUTION OF GSI-191 ISSUE SOUTH TEXAS PROJECT, UNITS 1 AND 2 DOCKET NOS. 50-498 AND 50-499 NAME TITLE ORGANIZATION Rick Grantum**

Manager Risk Project STPNOC Ernie Kee**

Risk Management STPNOC Elmira Popova**

University of Texas at Austin Alexander Galenko**

University of Texas at Austin Zahra Mohaghegh**

Soteria Consultants Seyed Reihani**

Soteria Consultants Tim Sande**

Principal Engineer Arion Science and Technology David Johnson**

ABS Consulting Bruce Letellier**

Las Alamos National Laboratory William Cross*

Projects Nuclear Licensing Manager Entergy Jeffrey Weyhmiller*

Design Engineering Entergy Phillip Grissom*

Principal Engineer

~ear Company Amir Afzali Risk Informed Engineeri lear Company Bradely Tyers*

n John Butler*

Nuclear Energy Institute (NEI)

Mark Richter*

Senior Project Manager NEI Michael Snodderly Senior Reliability and Risk Engineer U.S. Nuclear Regulatory Commission (NRC)

Rob Tregoning NRC Balwant K. Singal Senior Project Manager NRC Steve Dinsmore Senior Reliability and Risk Engineer NRC Stewart Bailey Branch Chief NRC Steve Smith Reactor Systems Engineer NRC John Tsao NRC

• Participated via phone

• • Participated via phone and represented STPNOC Enclosure

-3 distributions would need to be replaced with the new distributions. This will change the estimated risk results initially reported in item 6 above.

No Public Meeting Feedback Forms were received for this meeting.

Please direct any inquiries to me at (301) 415-3016, or balwant.singal@nrc.gov.

Docket Nos. 50-498 and 50-499

Enclosure:

List of Attendees cc w/encl: Distribution via Listserv DISTRIBUTION:

PUBLIC LPLIV r/f RidsAcrsAcnw_MailCTR Resource RidsNrrDeEsgb Resource RidsNrrDorlLpl4 Resource RidsNrrDprPgcb Resource RidsNrrDraApla Resource RidsNrrDssSsib Resource RidsNrrLAJBurkhardt Resource RidsNrrPMSouthTexas Resource RidsOgcRp Resource ADAMS Accession No. ML120830103 Sincerely, IRA by James R. Hall forI Balwant K. Singal, Senior Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation RidsRgn4MailCenter Resource TWertz, NRR LChang, EDO RIV SDinsmore, NRR/DRAIAPLA BPurnell, NRR/DPRlPGCB SBailey, NRRlDSS/SSIB MSnodderly, NRR/DRAIAPLA SSmith, NRRlDSS/SSIB JTsao, NRR/DElEPNB RTregoning, RES

• Via E-mail OFFICE NRR/LPL4/PM NRR/LPL4/LA NRR/DRAIAPLA NRR/DRAIAPLA NRR/DE/EPNB NAME JBurkhardt*

MSnodderly*

BSingal SDinsmore*

JTsao*

DATE 12 3/29/12 3/21/12 3/28/12 e

1/12 NRR/DSS/SSIB/BC NRRlLPL4/BC OFFICE RESIDE NRR/LPL4/PM MMarkley BSingal (JRHall (NKalyanam for)

NAME RTregoning*

SBailey*

for 3/30/12 3/30/12 DATE 3/28/12 13/23712 OFFICIAL RECORD COpy