ML13004A401

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, Units 1 &

ML13004A401
Person / Time
Site:	South Texas
Issue date:	01/31/2013
From:	Balwant Singal Plant Licensing Branch IV
To:
Singal B
References
TAC ME7735, TAC ME7736
Download: ML13004A401 (8)

Text

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1-~ ****... ~o January 31, 2013 LICENSEE: STP Nuclear Operating Company FACILITY: South Texas Project, Units 1 and 2

SUMMARY

OF DECEMBER 10, 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 December 10, 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 November 27, 2012, is located in the Agencywide Documents Access and Management System (ADAMS) at Accession No. ML12340A135. 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 by March/April 2013. 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, and December 1, 2011, and February 9, March 1, March 8, March 29, June 11, September 6, October 10, and December 3, 20121. The purpose of this conference call was to discuss the following topics:

1. Chemical effects testing

2. Coatings

3. Texas A&M bypass test follow-up

4. Bump-up factor

5. Non-chemical head loss testing

6. NRC staff feedback to the discussion on licensing strategy during the conference call public meeting held on December 3, 2012 However, it was decided during the meeting that a separate conference call public meeting will be arranged in the future to discuss item 6 and item 6 was not discussed during the meeting.

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

Summaries of the meetings held on June 2, July 7, July 26, August 22, October 3, November 1, November 2, and December 1, 2011, and February 9, March 1, March 8, March 29, June 11, September 6, October 10, and December 3,2012, are available in ADAMS at Accession Nos. ML111640160, ML111950094, ML112130165, ML112411419, ML112840114, ML113120129, ML113180196, ML113430087, ML120620541, ML120830103, ML120830086, ML121380522, ML12187A081, ML12270A055, ML12300A297, and ML12341A170, respectively.

-2 Meeting Summary The discussion was based on the following previously provided meeting materials/handouts.

1. Alion Science and Technology Calcualtion No. ALiON-CAL-STP-8511-06, Revision 2, for STP Unqualified Coatings Debris Generation (ADAMS Accession No. ML12335A177)

2. Bench Top Screen Penetration Test (Water Type Sensitivity Analysis) by Yassin A.

Hassan of Texas A&M University (ADAMS Accession No. ML12335A184)

3. Volume 3.6 - GSI-191 License submittal Documentation for Chemical Effects at STP (Document No. CHLE-015, dated November 26, 2012) (ADAMS Accession No. ML12335A190)

Results of Discussions Unqualified Coatings

1. Although the licensee provided some insight during the call related to its treatment of unqualified coatings, the NRC staff emphasized that staffs review will ultimately depend on how the licensee implements the information from various reports and the basis for its assumptions concerning unqualified coating degradation. For example, the staff expressed concerns about the licensee's proposed treatment of unqualified epoxy coatings debris characteristics based on testing of degraded qualified epoxy.

2. The NRC staff questioned how the licensee would use the coatings evaluation that predicted failure timing, rates, and debris characteristics. The licensee stated that the evaluation would be used to predict the amount and types of coatings reaching the strainer for various break sizes and locations and to further assess plant response scenarios.

3. The NRC staff asked how the coatings that fail in upper and lower containment are treated in the analysis. The licensee stated that coatings in upper containment that fail after sprays are secured and assumed not to transport to the pool. Coatings in lower containment that fail are assumed to transport no matter when they fail. The licensee stated that transport mechanisms other than spray washdown were not considered for upper containment. The licensee also stated that no unqualified coatings within the Zone of Influence (ZOI) were assumed to fail and this assumption was bounded by the fact that the maximum amount of qualified coatings was assumed to fail which bounds the potential total amount of qualified and unqualified failed coatings within the ZOI.

4. The licensee stated that the amount of intumescent coatings is negligible (approximately 2 pounds).

-3 Chemical Effects

1. The NRC staff noted that the Chemical Head Loss Experiments (CHLE) test report was well written, clear, and provided easy to follow benchmarks to previous test results.

2. The licensee provided an update on the CHLE tests at the University of New Mexico (UNM) and stated that the tests were further evaluated and that there was statistical evidence that head loss had increased during the test and this increase in head loss may be associated with chemical effects. The observed increase in head loss was small and the post-test analysis of the results is continuing. The licensee indicated that zinc phosphate may have formed during the test.

3. The licensee stated that it was planning to conduct additional chemical effects tests including a CHLE tank test with filter beds made from blended fibers as well as bench scale tests. The details of the longer term CHLE test were not yet determined and the licensee and NRC staff agreed to discuss the timing and details of that test in a future meeting prior to the start of that test. The staff's views concerning the debris bed's role in the detection of chemical precipitates has been documented in the September 6, 2012, phone call summary (ADAMS Accession No. ML12270A055).

4. The NRC staff questioned why the medium break loss-of-coolant accident (MBLOCA) had a greater quantity of dissolved species compared to the large break loss-of-coolant accident (LBLOCA) test. The results seem anomalous because the LBLOCA test was run at a higher temperature and had more materials, including four to five times more fiber. The licensee stated that the reason was unknown but one theory being investigated was that some of the LBLOCA materials may have inhibited the leaching from the fiberglass. The NRC staff requested further clarification for the unexpected results including whether these results are repeatable.

5. The NRC staff expressed the desire to visit UNM to observe testing and discuss the results of chemical effects evaluation. The NRC staff suggested that such a visit would include:

a. Observing a CHLE test with blended fiber beds.

b. Reviewing test results to the date of the visit.

c. Discussing how the entire chemical effects evaluation is progressing. The NRC staff views that the CHLE test results as discrete points in a range of potential post loss-of-coolant accident (LOCA) conditions. The staff also questioned how the bench tests are supporting CHLE test decisions and establishing the range of potential outcomes for different post-LOCA conditions.

6. The NRC staff agreed to provide the licensee with an updated list related to expert panel phenomenon identification ranking table (PIRT) open items that still need to be resolved by the licensee.

-4 Bump Up Factor The licensee provided information on how it plans to implement a bump-up factor (BUF) to account for chemically induced head loss that may add to the head loss across a debris bed formed of fibrous and particulate debris. The licensee stated that it plans to change the methodology that it uses for implementing the BUF, but was unclear as to the specifics of the methodology or timing of the changes. The licensee stated that the final methodology will not be ready for inclusion in the proposed forthcoming submittal because it will not be fully developed at the time of the submittal. The description of the preliminary methodology indicated that the calculation of the BUF would be somewhat complex and will be dependent upon the bed morphology, potential chemicals in solution, and temperature of the sump fluid. The licensee stated that some of the methodology will likely be based on engineering judgment which may be difficult for the NRC staff to evaluate. Because the methodology has not been finalized and it is unclear to the staff what the final methodology will be, the staff was not able to provide any feedback regarding the methodology. Based on the discussions of the BUF methodology, the staff expressed concerns that a significant test program may be required to define the range of BUFs that may be applied to the large variations in post-LOCA conditions that may occur at STP.

Vertical Loop Head Loss Testing The licensee stated that it had performed vertical loop head loss tests using the Nuclear Energy Institute (NEI) methodology and various types of particulate debris. The tests were intended to show that the NUREG/CR-6224 correlation is appropriate for estimation of head loss for the range of conditions that may occur in the STP post-LOCA environment. The licensee stated that the type of particulate included in the test had a significant effect on the resulting head loss.

Particulate types that appear to be smooth such as silicon carbide results in lower head loss while rougher particulate like epoxy and iron oxide result in higher head loss, more in line with the correlation. The licensee is attempting to define what constitutes a realistic particulate for STP. The licensee concluded that the NUREG/CR-6224 correlation bounds the head loss that may occur at STP over the range of debris loads that has been tested to date. The licensee plans to use the NUREG/CR-6224 correlation in its risk-based evaluation, but will make some corrections to the correlation to account for AdviSOry Committee on Reactor Safety (ACRS) comments on the relationship (ADAMS Accession No. ML121520429). The licensee had stated previously that it would perform validation testing of the vertical loop test by using a prototypical strainer module in a tank test. However, during the call the licensee stated that the validation testing was no longer being considered. The licensee also stated that a simple relationship between head loss and temperature based on viscosity was not observed during the testing.

The NRC staff requested to review the test results.

Bypass Sensitivity Testing at Texas A&M University The NRC staff reviewed the bypass testing sensitivity report provided by the licensee (ADAMS Accession No. ML12335A177). The staff expressed the view that the testing appears to have been run adequately. The staff requested to see the data from the test and showed interest in viewing additional photographs or videos of the testing during its trip to the test facility. The following issues were discussed during the call.

- 5

1. The NRC staff asked the licensee to explain the basis for test termination. The licensee stated that the test termination was based solely on time (125 minutes), and that it was intended to build a debris bed of at least 1f2 inch prior to termination. The 1f2 inch bed was attained in all tests.

2. The NRC staff raised several issues regarding the drying and weighing of the filter. The NRC staff expressed the concern that the methodology used (drying the filter, then allowing it to reach equilibrium with the humidity in the environment) was overly complex and added the potential for error to the results. The NRC staffs major concern was that the filters and debris were allowed to reach equilibrium before the weights were recorded. The NRC staff further stated that it will be interested in viewing test data to verify that equilibrium was reached.

3. The NRC staff expressed concern that debris may have been washed out of the filter during draining or lost during handling. The licensee explained that the loop draining process was designed to ensure that water did not flow back through the filter so that it was unlikely that debris would be washed out of the filter. The licensee also stated that extreme care was taken to prevent the loss of fiber during handling.

4. The NRC staff expressed concern that the photos in the report did not appear to match their descriptions. The staff questioned whether fiber may have been lost between preparation and addition to the test tank. The licensee explained that the photos were included as an illustration to show how the fiber was prepared inside the container, but that actual preparation was performed completely in the container and that the bucket was rinsed to ensure that all fiber was flushed into the tank.

5. The NRC staff asked if photo 10e (in Revision 1.2 of the report) included the entire fibrous debris amount. The licensee confirmed that it did include the entire amount. The NRC staff questioned whether the concentration of the debris in the tank was excessive, and how this may have affected the bypass measurements.

6. The licensee asked if the NRC staff has accepted the fact that bypass amount is not affected by the water chemistry. The NRC staff expressed its view that based on the test results, the tap water used in the STP tests appeared to have behaved similarly to buffered borated water. The NRC staff acknowledged that based on the results of other testing, there may be a significant difference in the behavior of various types of tap water. Therefore, the staff had not reached a generic conclusion that tap water and buffered borated water behave similarly. The NRC staff stated that further sensitivity studies are needed for reach a conclusion.

7. The NRC staff stated that the staff will review the bypass testing sensitivity report and will forward a list of additional questions/concerns separately.

-6 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, b~*~l¥.

Balwant K. Sing ai, 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 DECEMBER 10, 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 Mike Murray** Licensing Manager STP Nuclear Operating Company (STPNOC)

Rick Grantom** Manager Risk Project STPNOC Ernie Kee** Risk Management - Technical STPNOC

• • Engineering Licensing Consult STPNOC Jamie Paul** licensing Supervisor STPNOC Zahra Mohaghegh** Principal Research Scientist Soteria Seyed Reheni** Research Scientist ~ria

• Rodolfo Vaghetto** Graduate Researci rtar as A&M University David Morton** Professor Mechanical Engineering University of Texas Austin Glover Associate Engineer Alion Science and Technology

• Kerry Howe** Professor Civil EI . I University of New Mexico I Janet Leavitt** Research Engineering University of New Mexico Tim Sande** Principal Engineer Alion Science and Technology Gil Zigler** Senior Scientist/Engineer Alion Science and Technology Ron Holloway Project Manager Wolf Creek Nuclear Operating Corporation David Johnson** VP Quantitative Risk Analysis ABS Consulting John Butler Senior Director Nuclear Energy Institute (NEI)

Craig Sellers*** Senior Project Manager Enercon Services, Inc.

Philip Grissom*** Principal Engineer Southern Nuclear Company Kip Walker*** Mechanical Engineering Lead Enercon Services, Inc.

Mark Richter*** Senior Project Manager NEI Matt Yoder*** Senior Chemical Engineer U.S. Nuclear Regulatory Commission (NRC)

Steve Smith Reactor Systems Engineer NRC Paul Klein Senior Materials Engineer NRC Stewart Bailey Branch Chief NRC

• Gloria Kulesa Branch Chief NRC Balwant K. Singal Senior Project Manager NRC Emma Wong Chemical Engineer NRC Greg Makar Materials Engineer NRC

• • Partcipated via phone and represented STPNOC

• • • Participated via phone Enclosure

-6 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, IRA!

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 DISTRIBUTION:

PUBLIC RidsNrrDssSsib Resource SSmith, NRR/DSS/SSIB LPLIV rlf RidsNrrLAJBurkhardt Resource PKlein, NRR/DE/ESGB RidsAcrsAcnw_MaiICTR Resource RidsNrrPMSouthTexas Resource MYoder, NRR/DE/ESGB RidsNrrDeEsgb Resource RidsOgcRp Resource EWong, NRR/DE/ESGB RidsNrrDorlLpl4 Resource RidsRgn4MailCenter Resource GMakar, NRO/DE/CIB RidsNrrDprPgcb Resource CSantos, EDO RIV RidsNrrDeEsgb Resource TWertz, NRR ADAMS Accession No.: ML13004A401 *via e-mail IiI' NRRlDORULPL4/PM NRRlDORULPL4/LA NRRlDElESGB/BC ME BSingal JBurkhardt* GKulesa*

1/10/13 1/9113 1/17113

• OFFICE NRRlDSS/SSIB/BC NRR/DORULPL4/BC NRR/DORULPL4/PM NAME SBailey MMarkley BSingal DATE 1/15/13 1/31113 1/31/13 OFFICIAL RECORD COpy