ML12270A055

9/6/2012 Summary of Meeting by Conference Call with STP Nuclear Operating Company; Discuss Risk-Informed GSI-191, Assessment of Debris Accumulation on Pressurized-Water Reactor (PWR) Sump Performance, Resolution Approach for South Texas, Un

ML12270A055
Person / Time
Site:	South Texas
Issue date:	10/04/2012
From:	Balwant Singal Plant Licensing Branch IV
To:	South Texas
Rankin J
References
TAC ME7735, TAC ME7736, GSI-191
Download: ML12270A055 (8)

Text

~"R REG u(

.;:,v\,; "9~

UNITED STATES

~ 0." NUCLEAR REGULATORY COMMISSION

P ~ WASHINGTON, D.C. 20555-0001

<t

~ :0

~"l October 4, 2012

~-? ...0 LICENSEE: STP Nuclear Operating Company FACILITY: South Texas Project, Units 1 and 2 SUB..IECT:

SUMMARY

OF SEPTEMBER 6,2012, 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 September 6,2012, 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 August 23,2012, is located in the Agencywide Documents Access and Management System (ADAMS) at Accession No. ML12227A590. 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, and December 1, 2011, and February 9, March 1, March 8, March 29, and June 11, 20121. The purpose of this conference call was to discuss resolution of the outstanding chemical effects phenomena identification and ranking table (PIRT) issues and STP chemical effects testing test plan and current testing status.

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

Meeting Summary The discussion was based on the following previously provided meeting materials/handouts and no additional meeting materials were provided for the purposes of this meeting. A copy of the meeting materials can be found at ADAMS Accession No. ML12234A604.

1. STP Corrosion Head Loss Experiments (CHLE) Test Plan (Working Draft), Revision 1.4, dated August 15, 2012.

2. CHLE Equipment Description and Specifications, Revision 1, dated August 16, 2012.

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, and June 11, 2012 are available in ADAMS at Accession Nos. ML111640160, ML111950094, ML112130165, ML112411419, ML112840114, ML113120129, rvlL113180196, ML113430087, rvlL120620541, rvlL120830103, ML120830086, ML121380522, and ML12187A081 , respectively.

-2

3. Determination of the Initial Pool Chemistry for the CHLE test, Revision 1, dated August 13, 2012.

4. STP Material Calculations, Revision 1, August 15, 2012.

5. Debris Bed Requirements and Preparation Procedures, Revision 3, dated August 11, 2012.

6. CHLE Tank Test Results for Blended and NEI [Nuclear Energy Institute] Fiber Beds with Aluminum Addition, Revision 2, dated August 29, 2012.

Results of Discussions Representatives of STPNOC and its contractors provided an overview of the CHLE tank test results for debris beds formed by fibers prepared by blending and debris beds formed with fibers prepared by the NEI protocol. Highlights from this discussion include the following:

• The NRC staff and the licensee discussed how the fiber preparation technique affects the ability of the vertical head loss loop debris bed to filter chemical preCipitate. Figures 1 and 2 in the document, "CHLE Tank Test Results for Blended and NEI Fiber Beds with Aluminum Addition," provide the differences in head loss response for the blended fiber and NEI protocol fiber beds, respectively. These figures showed that all three blended fiber beds experienced an increase in head loss after a precipitate formed by slow addition of aluminum nitrate to the bulk solution. In contrast, the test beds with fiber prepared using the NEI protocol maintained low head loss throughout the test, including after chemical precipitation had occurred. The amount of aluminum added to the NEI protocol fiber beds (that showed no head loss response) was a factor of 7-40 times higher than the amount that caused the beds with blended fiber to reach the maximum operating head loss for the test loop.

• While the blended beds showed a much greater sensitivity to the presence of chemical preCipitate, the blended beds also exhibited much greater variability in head loss before dissolved aluminum was added to the test. Column 1 exhibited low and stable head loss prior to addition of chemicals, Column 3 had the greatest head loss prior to chemical addition, and the Column 2 head loss was about one-third the value of Column 3. A representative from the test facility stated that these results may have been influenced by the fiber beds trapping particulate hideout from earlier shakedown tests. This explanation seemed consistent with the post-test appearance of the three fiber beds adjacent to the test screen. The lowest head loss corresponded to a yellow (fiberglass) colored bed and the highest head loss corresponding to the darkest colored bed. The NRC staff has observed other tests where particulate has migrated through a debris bed and produced a darker appearance on the screen side of the bed.

The NRC staff stated that additional discussion is needed on the fiber preparation method to be used for the upcoming 30-day CHLE tests.

- 3

• The licensee indicated that the current test in the CHLE facility involves debris beds made with fiber prepared with the NEI protocol and an aluminum source consisting of aluminum scaffolding that was previously installed at STP.

• Based on the results to date, the NRC staff has no confidence that CHLE loop beds comprised of fiber prepared with the NEI protocol can detect chemical precipitates. The staff's understanding of the purpose of these tests is to detect whether precipitates will form. Therefore, the staffs position is that a debris bed that is sensitive to precipitates should be used for this phase of testing.

• Several test parameters were evaluated to determine if they might provide secondary confirmation of precipitate formation. Turbidity increased in direct proportion to increased aluminum addition to the test loop and may offer a secondary indicator of precipitate formation. Total suspended solids (TSS) is a less reliable indicator for detecting precipitates since small precipitates may pass through the filter used for the TSS measurement. Turbidity offers an additional advantage by providing immediate results.

• Tests with fiber prepared with the NEI method and chemical precipitates made with the WCAP-16530-Np2 protocol (Le., formed prior to the test and added to the test loop) produced a rapid increase in head loss after an amount corresponding to 40 ppm aluminum was added to the test loop. The licensee performed additional evaluations to compare precipitates since the same quantity of aluminum added in-situ and with similar debris beds did not produce a head loss response. The head loss results difference between the two precipitates was primarily attributed to a smaller particle size for the in-situ generated precipitate. It was also noted that the zeta potential of the WCAP-16530-NP prepared precipitate was dependent on whether it was prepared in tap water, deionized water, or borated, buffered water. This could affect the relative attraction between precipitate and fibers.

• Some of the tests may have been influenced by the turnover time between the tank and the head loss columns. For example, it is uncertain if some of the tests where WCAP-16530-NP precipitate was added would have exhibited a head loss response with less precipitate if more time had elapsed before more precipitate was added to the tank.

The NRC staff and the licensee briefly discussed some remaining Chemical Effects PIRT issues. Highlights from this discussion include the following:

• For item 2.5, "Additional Debris Bed Chemical Reactions," the NRC staff indicated that there is not a sufficient basis to address the potential radiation effects on plant debris such as non-qualified coatings. Due to time constraints, 2 Westinghouse Electric Company, LLC, WCAP-16530-NP, Revision 0, "Evaluation of Post-Accident Chemical Effects in Containment Sump Fluids to Support GSI-191" dated February 2006 (ADAMS Accession No. ML060890509).

-4 the NRC staff and the licensee agreed to discuss this matter during a future meeting.

• For item 3.1, "Crud Release," the NRC staff stated that additional discussion would be needed to determine if simulated crud should be included as a particulate source in some of the chemical tests. The licensee agreed to discuss this matter during future meetings.

• For item 3.7, "Submerged Source Terms: Lead Shielding," the licensee indicated that lead blankets in STP containments are either in barrels that would protect the blanket from a break zone of influence or are sealed from post-Ioss-of coolant accident (LOCA) fluid by vinyl covers. In previous meetings, STPNOC did not plan to include lead in the 30-day CHLE tests; however, the NRC staff expressed the view that the licensee should include lead in the bench tests.

During this phone call, the staff indicated that STP should either provide justification that shows lead will not contribute to post-LOCA chemical effects or perform a screening test. STPNOC stated that bench testing has not been completed.

• For item 3.12, "Submerged Source Terms: Biological Growth in Debris Beds,"

during its review of licensees' responses to NRC Generic Letter 2004-02, "Potential Impact of Debris Blockage on Emergency Recirculation during Design Basis Accidents at Pressurized-Water Reactors," dated September 13, 2004 (ADAMS Accession No. ML042360586), the NRC staff noted that at least one plant indicated the presence of biological material in a wet sump in containment.

The NRC staff, therefore, expects the licensee to verify that it does not have a significant existing source term of biological material in containment.

• For item 4.2, "Heat Exchanger: Solid Species Formation," the licensee stated that the CHLE test would include a heat exchanger loop to simUlate the temperature drop that occurs as emergency core cooling system (ECCS) flow passes through a heat exchanger prior to entering the reactor vessel. The NRC staff stated that the heat exchanger loop would address this question and expressed the view that it would be worthwhile to visually inspect the heat exchanger for evidence of precipitates after each 30-day test.

• For item 4.3, "Reactor Core: Precipitation," the NRC staff and the licensee discussed whether some high-temperature autoclave tests would be needed to address precipitates that may form due to retrograde solubility. The NRC staff stated that the licensee should evaluate for materials that could exhibit retrograde solubility.

• For item 6.1, "Break Proximity to Organic Sources," and item 6.2, "Organic Agglomeration," the NRC staff and the licensee agreed to have additional discussions concerning the potential role of organic materials. The licensee stated that it is evaluating various options to address the issue and a literature review is ongoing.

-5

• For item 6.4, "Coating Dissolution and Leaching," the NRC staff noted that STP has a significant quantity of unqualified enamel and alkyd coatings. The staff requested that STP perform an analysis to determine the amount and type of chemicals that may be leached from these coatings, and evaluate the impact that those chemicals may have on the post-LOCA sump chemistry, including any impact on precipitate formation.

Lastly, the STPNOC and the NRC staff discussed some additional items that the NRC staff had raised during earlier calls and left as issues that would be revisited after additional test plans and analysis were performed. Due to time constraints, the NRC staff was not able to discuss all items during the call.

• The NRC staff asked the licensee about its plans for including zinc in the upcoming tank tests. The staff reiterated that zinc should be considered in the STP chemical effects evaluation since there appears to be a significant amount of zinc in the plant and the water analysis results from the Integrated Chemical Effects Test (Test 2) suggest some zinc-based precipitate may have formed.

• CHLE tank coupons above the water line. The NRC staff reiterated that the materials located within the spray zone of the CHLE tank should experience a representative amount of moisture compared to plant materials. The licensee stated that dry conditions after sprays are terminated may be representative of the plant conditions. NRC staff indicated it will be pursuing additional information internally to support further discussion.

• The NRC staff asked the licensee to clarify whether the CHLE tank flow rates would provide for a representative flow for the submerged materials relative to materials in a post-LOCA sump pool. Representative flow past the coupons is important both from a transport perspective and for the leaching rate of materials.

The licensee indicated that a computational fluid dynamics analysis of the CHLE tank was provided in the most recent material sent to the NRC staff.

STPNOC noted that the next long-term tank test would possibly start in October 2012 and indicated that it would keep the NRC staff informed of the schedule.

- 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,

~_\~~\~~

Barwant 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 SEPTEMBER 6,2012, 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 I

Steve Blossom** - STPNOC

! Ernie Kee** Risk Management STPNOC i I Wes Schulz** - STPNOC i Jamie Paul** Licensing Engineer STPNOC Coley Chappel** - STPNOC

• Rodolfo Vagetto** - Texas A&M University Zahra Mohaghegh** - Soteria Consultants Bruce Letellier*** - Los Alamos National Laboratory Tim Sande** I Principal Engineer Alion Science and Technology David Johnson** - ABS Consulting Kerry Howe** - University of New Mexico

• Janet Leavitt** - University of New Mexico Jeremy Tejada*** - University of Texas Saya Lee*** - Texas A&M University

• Joshua Wargo*** - Constellation Energy Nuclear Group Craig Sellers*** - Calvert Cliffs Nuclear Power Plant Mark Richter*** Senior Project Manager Nuclear Energy Institute Gilbert Zigler** Senior Scientist Enercon Services William Cross*** Nuclear Licensing Manager NEXTERA Energy Stan Wisla*** - NEXTERA Energy Jonathan Evans*** - SNC I Michael Snodderly Senior Reliability and Risk Engineer U.S. Nuclear Regulatory Commission (NRC)

Bruce Heida Reactor Systems Engineer NRC Matt Yoder Senior Chemical Engineer NRC Steve Smith Reactor Systems Engineer NRC I Paul Klein Senior Materials Engineer NRC Stewart Bailey Branch Chief NRC i Gloria Kulesa Branch Chief NRC Lauren Gibson Project Manager NRC

• • Participated via phone and represented STPNOC *** PartiCipated via phone Enclosure

ML12270A055 *Via E-mail dated Se tember 24, 2012 NRR/LPL4/PM NRR/LPL4/PM NRR/LPL4/LA NRR/DE/ESGB/BC JRankin BSingal JBurkhardt GKulesa*

1011/12 10/2/12 1011/12 9124/12 NRR/DSS/SSIB/BC NRR/LPL4/BC NRR/LPL4/PM SBailey MMarkley (FLyon for) BSingal 9/26/12 10/3/12 10/4/12