ML20244A189
| ML20244A189 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 09/11/2020 |
| From: | Kimberly Green Plant Licensing Branch II |
| To: | Tennessee Valley Authority |
| Green K | |
| References | |
| EPID L-2020-LRM-0077 | |
| Download: ML20244A189 (5) | |
Text
September 11, 2020 LICENSEE:
Tennessee Valley Authority FACILITY:
Watts Bar Nuclear Plant, Units 1 and 2
SUBJECT:
SUMMARY
OF AUGUST 27, 2020, TELECONFERENCE CALL WITH TENNESSEE VALLEY AUTHORITY REGARDING A PROPOSED CHANGE TO THE CONTAINMENT LEAKAGE RATE TESTING PROGRAM (EPID L-2020-LRM-0077)
On August 27, 2020, the U.S. Nuclear Regulatory Commission (NRC) staff conducted a Category 1 public teleconference with representatives of Tennessee Valley Authority (TVA).
The purpose of the call was to discuss TVAs planned license amendment request (LAR) to revise the containment leakage rate testing program at Watts Bar Nuclear Plant (WBN), Units 1 and 2.
The meeting notice and agenda, dated August 17, 2020, are available at Agencywide Documents Access and Management System (ADAMS) Accession No. ML20230A233. TVAs slides for the meeting are available at ADAMS Accession No. ML20239A867. A list of participants is provided as an enclosure to this summary. No regulatory decisions were made at this meeting.
TVA began its presentation by reviewing the current requirements for the WBN Containment Leakage Rate Testing Program, which is delineated in Technical Specification (TS) 5.7.2.19, Containment Leakage Rate Testing Program. The program currently requires compliance with Regulatory Guide 1.163, Performance-Based Containment Leak-Test Program, which endorses Nuclear Energy Institute (NEI) 94-01, Revision 0, Industry Guideline for Implementing Performance-Based Option of 10 CFR Part 50, Appendix J, for establishing performance based test intervals, with certain exceptions, that allow Type A test interval up to 10 years, Type B test interval up to 120 months, and Type C test interval up to 60 months. TVA is proposing to revise TS 5.7.2.19 to add the guidelines contained in NEI 94-01, Industry Guideline for Implementing Performance-Based Option of 10 CFR Part 50, Appendix J, Revision 3-A, dated July 2012, with the conditions and limitations specified in NEI 94-01, Revision 2-A, October 2008. NEI 94-01, Revision 3-A increases the maximum Type A test interval from 10 to 15 years and Type C test interval from 60 to 75 months. It also updates the technical methods reference from American National Standards Institute (ANSI)-56.8-1994, Containment System Leakage Testing Requirements, to ANSI 56.8-2002.
TVA reviewed the two conditions for use from the safety evaluation (SE) for NEI 94-01, Revision 3-A, and the six Limitations and Conditions in the SE for NEI 94-01, Revision 2-A, and described how it addressed each in the proposed LAR. The descriptions are documented in TVAs slide presentation (ADAMS Accession No. ML20239A867).
The Limitations and Conditions in the SE for NEI 94-01, Revision 2-A, mainly pertain to the probabilistic risk analysis. TVA stated that using the methodology from EPRI guidance, the increase in large early release frequency (LERF) resulting from a change in the Type A integrated leakage rate test (ILRT) interval from 3 tests-in-10 years to 1 test-in-15 years is estimated as 1.90E-07/year for both units (internal events and external events). The total LERF is estimated to be 1.61E-6/year for Unit 1 and 1.60E-6/year for Unit 2. Another Limitation and Condition states that there should only be a small increase in population dose when extending the testing frequency, which is defined as an increase in population dose of less than or equal to either 1.0 person-rem per year or 1 percent of the total population dose, whichever is less restrictive. TVA estimated the increase to the total integrated plant dose for those accident sequences influenced by Type A testing to be 0.058 person-rem/year, or 0.4 percent (both units).
TVA also discussed the estimation of conditional containment failure probability (CCFP) required by Limitation and Condition 2.c, which states that a small increase in CCFP should be defined as a value marginally greater than that accepted in a previous one-time 15-year ILRT extension requests. This would require that the increase in CCFP be less than or equal to 1.5 percentage points. TVA estimated the increase in CCFP from the 3 tests-in-10 years interval to 1 test-in-15 years interval to be 0.908 percent, thus meeting Limitation and Condition 2.c.
In addition to extending the containment leakage rate test interval, TVA is also proposing to use a bounding value of 15.0 pounds per square inch gauge (psig) for Pa, in place of the calculated Pa value as defined in 10 CFR Part 50, Appendix J, Option B,Section II Definitions and ANSI/ANS 56.8, Section 2 Definitions. Pa is the calculated peak containment internal pressure related to the design basis loss-of-coolant accident. The current calculated Pa value is 9.36 psig for both Unit 1 and Unit 2. TVA stated that the purpose for requesting a bounding value for Pa is to minimize the impact on related documents when the calculated Pa is changed. Use of a bounding value for Pa of 15.0 psig in lieu of the calculated value for Pa of 9.36 psig results in an increase in the allowable leak rate (La), going from 199.67 standard cubic feet per hour (scfh) at 9.36 psig to 246.48 scfh at 15.0 psig. TVA explained that the increase in La due to use of a bounding Pa of 15.0 psig has been included as part of WBN accident analysis (i.e., dose rates) since startup and commercial operation of each unit. Therefore, TVA considers this deviation a technicality that does not have any adverse effects.
TVA also explained that use of a bounding value for Pa of 15.0 psig in lieu of the calculated value for Pa of 9.36 psig results in an increase in the maximum allowable test pressure (1.1 Pa) for those components where a higher differential pressure results in increased sealing. The maximum allowable test pressure increases from 10.30 psig to 16.50 psig. TVAs contractor performed a detailed evaluation of increased maximum allowable test pressure (1.1 Pa). The purpose of the detailed evaluation was to determine whether an increase in seat leakage is expected when the differential pressure (local leakage rate test (LLRT) test pressure) is reduced from 16.5 psig to 9.0 psig. TVA stated that the maximum LLRT test pressure of 16.5 psig (1.1 times the historical Pa value of 15.0 psig) is the current and historical maximum LLRT test pressure allowed by WBN specific LLRT procedures. The detailed evaluation determined that an increase in leakage is not expected when the LLRT test pressure is reduced from 16.5 psig to a bounding lower limit of 9.0 psig.
TVA plans to submit the LAR to the NRC in September 2020.
No comments or public meeting feedback were received.
Please direct any inquiries to me at 301-415-1627, or Kimberly.Green@nrc.gov.
/RA/
Kimberly J. Green, Senior Project Manager Plant Licensing Branch II-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-390 and 50-391
Enclosure:
List of Participants cc: Listserv
Enclosure LIST OF PARTICIPANTS AUGUST 27, 2020, PUBLIC TELECONFERENCE CALL TENNESSEE VALLEY AUTHORITY REGARDING PLANNED LICENSE AMENDMENT REQUEST WATTS BAR NUCLEAR PLANT, UNITS 1 AND 2 Name Organization Kim Green U.S. Nuclear Regulatory Commission (NRC)
Tom Stephen NRC Brian Wittick NRC Weijun Wang NRC Steve Smith NRC Bob Pettis NRC Bhagwat Jain NRC Zachary Gran NRC Nan Chien NRC Andy Taylor Tennessee Valley Authority (TVA)
Russ Wells TVA Mark Gowin TVA Jose Ortiz TVA Gerry Kindred TVA Dean Baker TVA Gordon Williams TVA Charlie Driskell TVA Shane Norton TVA Kyle Loomis TVA Stuart Rymer TVA Neal Estep Kalsi Engineering
- via e-mail OFFICE NRR/DORL/LPL2-2/PM* NRR/DORL/LPL2-2/LA* NRR/DORL/LPL2-2/BC* NRR/DORL/LPL2-2/PM*
NAME KGreen BAbeywickrama UShoop KGreen DATE 09/08/2020 09/03/2020 09/11/2020 09/11/2020