ML121380522

3/29/12 Summary of Conference Call Meeting 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, Units

ML121380522
Person / Time
Site:	South Texas
Issue date:	05/31/2012
From:	Balwant Singal Plant Licensing Branch IV
To:
Singal, Balwant, 415-3016, NRR/DORL/LPL4
References
TAC ME7735, TAC ME7736
Download: ML121380522 (7)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 May 31,2012 LICENSEE: STP Nuclear Operating Company FACILITY: South Texas Project, Units 1 and 2

SUMMARY

OF MARCH 29, 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 29, 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 March 15, 2012, is located in the Agencywide Documents Access and Management System (ADAMS) under Accession No. ML120740031. 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, and March 8, 20121. The purpose of this conference call was to discuss GSI-191 bypass testing and head-loss protocols and plans for the STP pilot program (follow-up discussion from the meeting on March 1, 2012) and resolution of the outstanding chemical effects phenomena identification and ranking table (PIRT) issues.

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.

1. STP Corrosion Head Loss Experiments (CHLE) Test Plan (Working Draft), Revision 1.2, dated February 29,2012 (ADAMS Accession No. ML120610074)

2. Resolution of Outstanding Chemical Effects PIRT Issues by Kerry Howe, February 9, 2012 (ADAMS Accession No. ML120540727)

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, and March 8, 2012, are available in ADAMS Accession Nos. ML111640160, ML111950094, ML112130165, ML112411419, ML112840114, ML113120129, ML113180196, ML113430087, ML120620541. ML120830103, and ML120830086, respectively.

- 2 Results of Discussions STPNOC asked if the NRC staff had additional comments on the fiber bypass and vertical loop test procedures discussed during the call on March 8,2012. The NRC staff stated that they did not have additional comments.

The NRC staff and licensee discussed item 2, "Resolution of Outstanding Chemical Effects PIRT Issues." STPNOC provided an updated copy of the document dated March 28, 2012, just before the meeting. The NRC staff clarified that the discussion during the meeting would be based on the version dated February 9, 2012, since the NRC staff was not able to review the contents of the version dated March 28, 2012. The NRC staff also reiterated its expectation that materials intended to be discussed during the meetings need to be provided in sufficient time for the staff to review and discuss internally before the meeting. For sake of efficiency, the NRC and STPNOC had agreed previously that the meeting materials will be provided at the time the meeting request is made and last-minute updates may require rescheduling of the meeting.

Highlights from discussions related to the Chemical Effects PIRT Issues document follow:

• The NRC staff had no additional comments on PIRT items 1.3, 2.3, 4.1, 4.4, 6.3, and 7.1 during the previous meeting. These items were not discussed during the meeting on March 29, 2012.

• Based on its review of the document provided, the NRC staff indicated that it had no additional comments for PIRT items 1.4, 1.5,3.2,3.3,3.4,3.8,3.9,3.10,3.11, 4.5, 5.1, and 7.2.

• For item 1.1, "RCS Coolant Chemistry Conditions at Break" and Item 1.2, "pH Variability," the NRC staff and the licensee expressed general agreement that testing should occur at representative pH values and consider pH variability. The staff indicated that it would like to know more details about pH used during the test and pH variation as a function of time, particularly since there is a range of pool pH that can occur following a loss-of-coolant accident (LOCA) and the pH is a key factor in material corrosion rates and species solubility. The licensee stated that alternate source term-related calculations predicted the sump pool pH at STP to decrease by approximately 0.15 pH units over time due to post-LOCA acid formation. The NRC staff expressed the view that the licensee should account for the expected drop in the value of pH during testing.

• For item 2.1, "Radiolytic Environment," and item 2.2, "Radiological Effects Corrosion Rate Changes," the licensee indicated that it would be adding both nitric acid and hydrochloric acid later to the test loop to simulate post-LOCA acid formation. The NRC staff expressed the view that adding both acids would be acceptable since analysis indicates both acids could form in the post-LOCA environment.

• For item 2.5, "Additional Debris Bed Chemical Reactions," the NRC staff indicated that additional discussion would be needed concerning potential radiation effects on plant debris such as non-qualified coatings and microtherm.

The licensee agreed to discuss this matter during future meetings.

- 3

• 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 3.5, "Containment Spray Transport," the NRC staff questioned whether, after the sprays are secured, the CHLE tank tests would dry the materials above the water line more than in a plant that experienced a LOCA. The NRC staff questioned whether the 30-day test wetting of coupons located above the water level in the CHLE tank would be representative of postulated plant conditions.

• For item 3.6, "Initial Debris Dissolution," the NRC staff stated that the initial debris dissolution is a critical part of the experiments. Previous NRC staff comments related to the use of extra coupons in lieu of testing at the highest projected post LOCA temperatures are contained in the summary of the phone call on March 8, 2012. Since the temperature can influence other reaction processes in addition to leaching rates, the NRC staff is interested to know how (e.g., bench tests) the licensee will confirm that the extra coupon approach will produce representative amounts of dissolved materials.

• 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-LOCA fluid by vinyl covers. STPNOC does 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.

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

during its review of licensees' responses to NRC Generic Letter 2004-02, 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 an eXisting source term of biological material in containment.

• For Item 3.13, "Reactor Core: Fuel Deposition Spalling" the licensee stated that the PWROG developed a generic method to evaluate deposit formation (LOCADM) would be used at STP. In addition, the precipitation of materials with retrograde solubility will be addressed in bench scale testing based on plant-specific parameters. The NRC staff stated that the proposed approach is acceptable.

• 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 expressed the view that it would be worthwhile to visually inspect the heat exchanger for evidence of precipitates after each 30-day test.

- 4

• For item 4.3, "Reactor Core: Precipitation," the NRC staff and 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 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 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.

• For item 6.4, "Coating Dissolution and Leaching," the NRC staff expressed the view that licensee should evaluate whether non-qualified coating degradation could impact plant-specific chemical effects. The NRC staff and licensee agreed to re-visit this issue during a future meeting.

• Item 7.3, "Reactor Core: Fuel Deposition and Precipitation," item 7.4, "Reactor Core: Diminished Heat Transfer," item 7.5, "Reactor Core: Blocking of Flow Passages," and item 7.6, "Reactor Core: Particulate Settling," are issues related to reactor core such as debris blockage, and heat transfer and are beyond the scope of the CHLE experiments. The licensee agreed to address these items using a combination of pressurized-water reactor owners group (PWROG) developed methods (e.g., LOCADM to evaluate fuel rod deposition) and plant specific testing/analysis.

• The licensee asked if the NRC staff had any major concerns or questions regarding the overall test approach. The licensee indicated that it was in the process of procuring materials for the test and any additional NRC staff input will be valuable. The NRC staff did not identify any major concerns to the overall approach for the chemical tests. The NRC staff suggested that more interaction may be needed after the test setup details became available to the NRC staff.

• The NRC staff acknowledged that the licensee's plans to conduct a series of tests to force precipitation has merit, since they would provide some indication of the conditions that would result in chemical precipitate formation. The licensee stated that the forced precipitation tests would include calcium sources to evaluate the potential formation of calcium phosphate precipitate.

• The NRC staff noted that standard practices (e.g., American Society for Testing and Materials (ASTM) G1, "Standard Practice for Preparing, Cleaning, and Evaluating Corrosion Test Specimens") are available for preparing, cleaning, and evaluating corrosion test specimens. These practices are designed to remove corrosion products without significant removal of base metal to allow accurate determination of mass loss.

• The NRC staff noted that the description provided in Section 2.2, "Bench-Scale Laboratory Tests," of Appendix B to the "STP Corrosion Head Loss Experiments (CHLE) Test Plan" document was incomplete. The staff plans to review this

- 5 section and provide comments once the licensee provides a more complete description.

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~ ',-,- I~t ~'a9-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 MARCH 29, 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 Wes Schulz** - STPNOC Jamie Paul** Licensing Engineer STPNOC Rodolfo Vagetto*'" - Texas A&M University Zahra Mohaghegh** - Soteria Consultants Craig Sellers - CDS Tim Sande*'" Principal Engineer Alion Science and Technology David Johnson** - ABS Consulting Kerry Howe*'" - University of New Mexico Janet Leavitt** - University of New Mexico Alex Galenko - University of Texas Gil Zigler* Senior Scientist/Engineer Alion Science and Technology William Closser Assistant Vice President/Divisional Alion Science and Technology Manager Phillip Grissom*"'* - Southern Nuclear Company Michael Snodderly Senior Reliability and Risk Engineer U.S. Nuclear Regulatory Commission (NRC)

Mark Blumberg Senior Reliability and Risk Analyst NRC Donnie Harrison Branch Chief NRC Lynnea Wilkins Project Manager NRC Paul Klein Senior Materials Engineer NRC Stewart Bailey Branch Chief NRC Steve Smith Reactor Systems Engineer NRC Ervin Geiger Senior Engineer NRC

• Represented STPNOC

• • Participated via phone and represented STPNOC

• • • Participated via phone Enclosure

ML121380522 *Via E-mail OFF I NRRlLPL4/LA NRR/DRAlAPLAlBC NAME JBurkhardt* DHarrison 5/18/12 N/A NRR/DE/ESGB C NRR/LPL4/BC NRRlLPL4/PM NAME GKulesa SBailey* MMarkley BSingal DATE 5/24/12 5/24/12 5/31/12 5/31/12