ML24080A395
| ML24080A395 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 03/28/2024 |
| From: | Hipolito Gonzalez Plant Licensing Branch 1 |
| To: | Susquehanna |
| Klett A | |
| References | |
| EPID L-2023-LLR-0044 | |
| Download: ML24080A395 (1) | |
Text
March 28, 2024
SUSQUEHANNA STEAM ELECTRIC STATION, UNITS 1 AND 2 - AUTHORIZATION AND SAFETY EVALUATION FOR ALTERNATIVE REQUEST RR02 FOR FIFTH 10-YEAR INTERVAL INSERVICE TESTING PROGRAM (EPID L-2023-LLR-0044)
LICENSEE INFORMATION
Recipients Name and Address: Edward Casulli Site Vice President Susquehanna Nuclear, LLC 769 Salem Boulevard NUCSB3 Berwick, PA 18603 -0467
Licensee: Susquehanna Nuclear, LLC
Plant Name and Units: Susquehanna Steam Electric Station (Susquehanna),
Units 1 and 2
Docket Nos.: 50-387 and 50-388
APPLICATION INFORMATION
Submittal Date: August 3, 2023
Submittal Agencywide Documents Access and Management System (ADAMS)
Accession No.: ML23215A173 (Enclosure 2, Relief Request RR02) 1
Supplement Date: January 4, 2024
Supplement ADAMS Accession No.: ML24004A146
Applicable Inservice Testing (IST) Program Interval and Interval Start/End Dates:
Fifth 10-Year IST Program interval (June 1, 2024, to May 31, 2034)
Alternative Provision: The licensee requested an alternative under Title 10 of the Code of Federal Regulations (10 CFR), Section 50.55a, paragraph (z)(1).
1 Relief Request RR02, as supplemented, is referred to as Alternative Request RR02 in this safety evaluation to denote that it is a proposed alternative.
IST Requirements:
Edition 2020 of the American Society of Mechanical Engineers (ASME) Operation and Maintenance of Nuclear Power Plants, Division 1, OM Code: Section IST (ASME OM Code),2 Subsection ISTC, Inservice Testing of Valves in Water-Cooled Reactor Nuclear Power Plants, paragraph ISTC-3522, Category C Check Valves, subparagraph (a),
states, in part:
During operation at power, each check valve shall be exercised or examined in a manner that verifies obturator travel by using the methods in ISTC-5221.
Each check valve exercise test shall include open and close tests.
ASME OM Code, Subsection ISTC, paragraph ISTC-3522, subparagraph (c), states, If exercising is not practicable during operation at power and cold shutdown outages, it shall be performed during refueling outages.
ASME OM Code, Subsection ISTC, paragraph ISTC-3630, Leakage Rate for Other Than Containment Isolation Valves, states:
Category A valves with a leakage requirement not based on an Owners 10 CFR [Part] 50, Appendix J program, shall be tested to verify their seat leakages [are] within acceptable limits. Valve closure before seat leakage testing shall be by using the valve operator with no additional closing force applied.
ASME OM Code, Subsection ISTC, paragraph ISTC-3630, subparagraph (a),
Frequency, states, Tests shall be conducted at least once every 2 yr [years].
ASME OM Code, Subsection ISTC, paragraph ISTC-5120, Motor-Operated Valves
[MOVs], states, Active MOVs shall meet the requirements of Division 1, Mandatory Appendix III.
ASME OM Code, Mandatory Appendix III, Preservice and Inservice Testing of Active Electric Motor-Operated Valve Assemblies in Water-Cooled Reactor Nuclear Plants, Section III-3600, MOV Exercising Requirements, states that all MOVs within scope of Appendix III shall be tested at least once per refueling cycle with maximum of time between exercises to be not greater than 2 years.
Applicable Code Edition and Addenda: ASME OM Code, 2020 Edition, as incorporated by reference in 10 CFR 50.55a
Applicable Code Components Affected:
ASME OM Code components applicable to Alternative Request RR02 are the pressure isolation valves (PIVs) and listed in section 1 of the submittal for the residual heat removal and core
2 All references to ASME OM Code in this document are to Edition 2020 unless another edition is explicitly cited.
spray systems. The submittal identified the PIVs as motor-operated, air-operated valves, or check valves. The submittal also identified the valves as PIVs or as both PIVs and containment isolation valves (CIVs).
Brief Description of the Proposed Alternative:
In its submittal, the licensee stated that the subject 34 PIVs are presently leak tested on a refueling outage frequency as required by the ASME OM Code, as incorporated by reference in 10 CFR 50.55a. The licensee proposed an alternative to perform PIV leak rate testing of the subject PIVs at intervals ranging from every refueling outage to every third refueling outage. The specific interval for each valve would be a function of its performance and would be established in a manner consistent with the CIV process under 10 CFR Part 50, Appendix J, Option B, Performance-Based Requirements. The licensee would establish controls, such that if any valve fails the PIV test, the test interval would be reduced, consistent with 10 CFR Part 50, Appendix J, Option B requirements until good performance is re-established. The test intervals for the valves with a PIV-only function would be determined in a similar manner as is performed for CIV testing under 10 CFR Part 50, Appendix J, Option B. The test interval could be extended upon completion of two consecutive periodic PIV tests with results within prescribed acceptance criteria. Any PIV test failure would require a return to the initial interval until good performance can again be established. The licensees basis for this alternative is that it continues to provide assurance of the PIVs operational readiness and provides an acceptable level of safety and quality.
As described in Alternative Request RR02, several valves in section 1 of the submittal have a dual function as a PIV and a CIV, which is denoted as Both under the CIV, PIV, Both column in the submittal. The valves identified as both PIVs and CIVs are subject to PIV seat leakage testing under the OM Code and CIV local leak rate testing under 10 CFR Part 50, Appendix J, Option B. Alternative Request RR02 would not affect the Appendix J testing intervals because CIVs are already using performance -based intervals required under Option B. The licensee stated that it is requesting permission to extend intervals for PIV seat leakage testing comparable to 10 CFR Part 50, Appendix J, Option B.
The documents located at the ADAMS Accession Nos. identified above have additional details about the licensees request.
STAFF EVALUATION
In Alternative Request RR02, the licensee proposed an alternative to the requirements in ASME OM Code, Subsection ISTC, paragraph ISTC -3630(a), as incorporated by reference in 10 CFR 50.55a, for 34 PIVs (17 PIVs for each unit) for the fifth 10 -year interval IST program.
Specifically, the licensee proposed to functionally test and verify the leakage rate of the PIVs using a 10 CFR Part 50, Appendix J, Option B, performance -based schedule. Per the proposed alternative, the PIVs demonstrating good performance for two consecutive cycles may have their test interval extended to up to each third refueling outage (72 months) in lieu of testing every refueling outage or 2 -year interval specified in paragraph ISTC -3630(a). Any PIV leakage test failure would require the leakage testing for the valve to return to the initial interval of every refueling outage or 2 years until good performance can again be reestablished, as described in licensees supplement.
In Alternative Request RR02, the licensee stated that the reason for proposing the alternative was to satisfy the as low as reasonably achievable radiation dose principles. The licensee stated that recent historical data indicate that PIV testing alone incurs a total dose of approximately 500 millirem each refueling outage. The licensee determined that the proposed alternative would provide a savings of approximately 1.0 rem over a 4.5 -year period, which encompasses two refueling outages.
The PIVs are defined as two valves in series within the reactor coolant pressure boundary that separate the high-pressure reactor coolant system from an attached lower pressure system.
The failure of a PIV could result in an overpressurization event that could lead to a system rupture and possible release of fission products to the environment. This type of failure event was analyzed in NUREG/CR-5928, ISLOCA [Inter System Loss-of-Coolant Accident] Research Program (ML072430731). The purpose of NUREG/CR-5928 was to quantify the risk associated with an ISLOCA event. NUREG/CR-5928 analyzed boiling-water reactor (BWR) and pressurized-water reactor designs. The conclusion of the analysis was that an ISLOCA is not a risk concern for BWR designs, such as Susquehanna, Units 1 and 2.
The U.S. Nuclear Regulatory Commission (NRC) regulations in 10 CFR Part 50, Appendix J, Option B, allow the establishment of a performance -based leakage test program. Guidance for implementation of acceptable leakage rate test methods, procedures, and analyses for 10 CFR Part 50, Appendix J, Option B, is provided in Regulatory Guide (RG) 1.163, Revision 1, Performance-Based Containment Leak-Test Program (ML23073A154). RG 1.163, Revision 1, endorses Nuclear Energy Institute (NEI) 94 -01, Revision 3-A, Industry Guideline for Implementing Performance-Based Option of 10 CFR 50, Appendix J (ML12221A202), with the limitation that Type C component CIV test intervals may be extended to 75 months with a permissible extension for nonroutine emergent conditions of 9 months (84 months total).
RG 1.163, Revision 1, states that licensees planning to use the RG should follow the limitations and conditions identified in the NRC safety evaluation appended to NEI 94 -01, Revision 3-A. By letters dated June 8, 2012 (ML121030286), and December 6, 2012 (ML12226A546), the NRC staff found the guidance in NEI 94 -01, Revision 3-A, to be acceptable with two conditions on the use of NEI 94-01, Revision 3. Per NRCs letter dated June 8, 2012, those conditions state:
- 1. NEI TR [topical report] 94-01, Revision 3, is requesting that the allowable extended interval for Type C LLRTs [local leakage-rate tests] be increased to 75 months, with a permissible extension (for non-routine emergent conditions) of nine months (84 months total). The staff is allowing the extended interval for Type C LLRTs to be increased to 75 months with the requirement that a licensees post-outage report include the margin between the Type B and Type C leakage rate summation and its regulatory limit. In addition, a corrective action plan shall be developed to restore the margin to an acceptable level. The staff is also allowing the non-routine emergent extension out to 84-months [sic] as applied to Type C valves at a site, with some exceptions that are detailed in NEI 94-01, Revision 3. At no time shall an extension be allowed for Type C valves that are restricted categorically (e.g., BWR MSIVs [main steam isolation valves]), and those valves with a history of leakage, or any valves held to either a less than maximum interval or to the base refueling cycle interval. Only nonroutine emergent conditions allow an extension to 84 months....
- 2. The basis for acceptability of extending the ILRT [integrated leak rate testing]
interval out to once per 15 years was the enhanced and robust primary containment inspection program and the local leakage rate testing of penetrations. Most of the primary containment leakage experienced has been attributed to penetration leakage[,] and penetrations are thought to be the most likely location of containment leakage at any time. The containment leakage condition monitoring regime involves a portion of the penetrations being tested each refueling outage, [with] nearly all LLRTs [sic] being performed during plant outages. For the purposes of assessing and monitoring or trending overall containment leakage potential, the as-found minimum pathway leakage rates for the just tested penetrations are summed with the as-left minimum pathway leakage rates for penetrations tested during the previous 1 or 2 or even 3 refueling outages. Type C tests involve valves which, in the aggregate, will show increasing leakage potential due to normal wear and tear, some predictable and some not so predictable. Routine and appropriate maintenance may extend this increasing leakage potential.
Allowing for longer intervals between LLRTs means that more leakage rate test results from farther back in time are summed with fewer just tested penetrations and that total used to assess the current containment leakage potential. This leads to the possibility that the LLRT totals calculated understate the actual leakage potential of the penetrations. Given the required margin included with the performance criterion and the considerable extra margin most plants consistently show with their testing, any understatement of the LLRT total using a 5-year test interval is thought to be conservatively accounted for. Extending the LLRT intervals beyond 5 years to a 75-month interval should be similarly conservative provided an estimate is made of the potential understatement and its acceptability determined as part of the trending specified in NEI 94-01, Revision 3, Section 12.1.
When routinely scheduling any LLRT valve interval beyond 60-months [sic]
and up to 75-months [sic], the primary containment leakage rate testing program trending or monitoring must include an estimate of the amount of understatement in the Type B & [and] C total, and must be included in a licensees post-outage report. The report must include the reasoning and determination of the acceptability of the extension, demonstrating that the LLRT totals calculated represent the actual leakage potential of the penetrations....
The licensee is currently leak testing the 34 PIVs within the scope of Alternative Request RR02 every refueling outage or 2 years. The licensee has demonstrated that these PIVs have a history of good performance from consecutive refueling outages in 2003 through 2022, as shown in Attachment RR02 -1, Leak History of SSES [Susquehanna Steam Electric Station],
Units 1 and 2 PIVs, of enclosure 2 to the submittal. The licensee indicated in its submittal that the proposed alternative would reduce radiation dose to workers. The NRC staff finds that extending the leakage test interval based on goo d performance is a logical progression for a performance-based approach.
As described in its supplement, the licensee proposed implementation of performance-based testing intervals for PIV seat leakage testing that would be comparable to the performance-based Option B in 10 CFR Part 50, Appendix J, for local leak rate testing. The
licensee stated that the justification for extending the interval for PIV seat leakage testing would be based on two prior consecutive surveillance tests not exceeding the acceptance criteria, which would show a history of good performance to support an extension of the test interval. If a PIV exceeds the acceptance criteria, then the licensee stated that it would return the PIV to the standard interval until good performance is established again. The licensee stated that it would schedule and perform valve testing such that the valves would be tested throughout the interval (e.g., staggered through the interval based on divisional outages). The NRC staff finds that this sample testing provides support for the extension of the PIV seat leakage testing intervals where good PIV performance is demonstrated.
The licensee indicated that exercise tests of the motor -operated PIVs are performed on a 2 -year frequency in accordance with ASME OM Code, Mandatory Appendix III and that the motor-operated PIV testing is not performed online to prevent the possibility of an inadvertent ISLOCA condition. The alternative request does not propose any changes to diagnostic testing under ASME OM Code, Mandatory Appendix III, to demonstrate design -basis capability of the motor-operated PIVs on a performance -based interval in accordance with the requirements of Mandatory Appendix III.
In its supplement, the licensee confirmed that check valve 251130 at Susquehanna, Unit 2, will be leak tested during the cycle 22 refueling outage in spring 2025 in accordance with the previously authorized alternative described in NRCs safety evaluation dated September 19, 2023 (ML23257A122). The licensee stated that this action is being tracked in its corrective action program.
Based on the information described above for the 34 PIVs within the scope of Alternative Request RR02, the NRC staff finds the following:
(1) These PIVs have demonstrated good historical performance.
(2) No current concerns with the performance of these PIVs have been identified.
(3) Periodic maintenance activities are not modified by this request.
(4) The alternative request allows a performance -based approach for leak testing of these 34 PIVs such that PIVs that have demonstrated good performance for two consecutive cycles may have their test interval extended up to 75 months, with a permissible extension (for non -routine emergent conditions) of 9 months (84 months total).
(5) The proposed alternative specifies that any PIV leakage test failure would require the component to be returned to the initial ASME OM Code interval until good performance can again be established.
Based on its review, the NRC staff finds that the licensees submittal, as supplemented, supports the proposed performance -based leakage testing interval in Alternative Request RR02 for the subject PIVs and that the proposed alternative meets the requirements of 10 CFR 50.55a(z)(1) by providing an acceptable level of quality and safety.
CONCLUSION
As described above, the NRC staff has determined that Alternative Request RR02 provides an acceptable level of quality and safety for the proposed performance-based leakage testing interval for the 34 PIVs listed in section 1 of the submittal.
The NRC staff concludes that the licensee has adequately addressed all the regulatory requirements set forth in 10 CFR 50.55a(z)(1).
The NRC staff authorizes the use of Alternative Request RR02 for the Fifth 10-Year IST Program interval, which is scheduled to begin on June 1, 2024, and scheduled to end on May 31, 2034.
All other ASME OM Code requirements as incorporated by reference in 10 CFR 50.55a for which relief or an alternative was not specifically requested, and granted or authorized (as appropriate), in the subject request remain applicable.
Principal Contributor: Gurjendra S. Bedi, NRR
Hipolito Gonzalez, Chief Plant Licensing Branch 1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation
cc: Listserv
ML24080A395 OFFICE NRR/DORL/LPL1/PM NRR/DORL/LPL1/LA NRR/DEX/EMIB/BC NAME AKlett KZeleznock SBailey (TScarbrough for)
DATE 03/20/2024 03/21/2024 03/06/2024 OFFICE NRR/DORL/LPL1/BC NAME HGonzalez DATE 03/28/2024