ML25247A240
| ML25247A240 | |
| Person / Time | |
|---|---|
| Site: | Technical Specifications Task Force |
| Issue date: | 09/08/2025 |
| From: | Shawn Smith NRC/NRR/DSS |
| To: | Technical Specifications Task Force |
| Shared Package | |
| ML25247A238 | List: |
| References | |
| TSTF-600, Rev. 2, EPID L-2024-PMP-0005 | |
| Download: ML25247A240 (7) | |
Text
FINAL SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION TECHNICAL SPECIFICATIONS TASK FORCE TRAVELER TSTF-600, REVISION 2 "REVISE THE REACTOR COOLANT SYSTEM (RCS) PRESSURE ISOLATION VALVE (PIV)
LEAKAGE TESTING FREQUENCY" USING THE CONSOLIDATED LINE ITEM IMPROVEMENT PROCESS (EPID: L-2024-PMP-0005)
1.0 INTRODUCTION
By letter dated March 24, 2025 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML25083A153), the Technical Specifications Task Force (TSTF) submitted Traveler TSTF-600, Revision 2, Revise the Reactor Coolant System (RCS) Pressure Isolation Valve (PIV) Leakage Testing Frequency. Traveler TSTF-600 proposed changes to the Standard Technical Specifications (STS) for boiling-water reactor (BWR) and pressurized-water reactor (PWR) designs under the consolidated line item improvement process (CLIIP). Upon approval, this traveler will be made available to nuclear power plant applicants and licensees for adoption and the changes will be incorporated into future revisions of the following US Nuclear Regulatory Commission (NRC) STS1:
NUREG-1430, Standard Technical Specifications, Babcock and Wilcox Plants, Volume 1, Specifications, and Volume 2, Bases, Revision 5, September 2021 (ML21272A363 and ML21272A370, respectively).
NUREG-1431, Standard Technical Specifications, Westinghouse Plants, Volume 1, Specifications, and Volume 2, Bases, Revision 5, September 2021 (ML21259A155 and ML21259A159, respectively).
NUREG-1432, Standard Technical Specifications, Combustion Engineering Plants, Volume 1, Specifications, and Volume 2, Bases, Revision 5, September 2021 (ML21258A421 and ML21258A424, respectively).
NUREG-1433, Standard Technical Specifications, General Electric BWR/4 Plants, Volume 1, Specifications, and Volume 2, Bases, Revision 5, September 2021 (ML21272A357 and ML21272A358, respectively).
NUREG-1434, Standard Technical Specifications, General Electric BWR/6 Plants Volume 1, Specifications, and Volume 2, Bases, Revision 5, September 2021 (ML21271A582 and ML21271A596, respectively).
The proposed change would revise the Frequency of the Surveillance Requirement (SR) to 1NUREG-1433 provides the STS for BWR/4 plant designs, but is also representative of the BWR/2, BWR/3, and, in this case, the BWR/5 plant design.
NUREG-1434 provides the STS for BWR/6 plant designs, but is also representative in some cases of the BWR/5 plant design.
perform RCS PIV leakage testing to reference only the Inservice Testing (IST) Program. For plants that have adopted TSTF-596, Revision 2, Expand the Applicability of the Surveillance Frequency Control Program (SFCP), (ML24362A054), the proposal includes a variation to set the Frequency in accordance with the SFCP.
1.1
System Description
RCS PIVs are two normally closed valves in series in RCS piping that separate the high-pressure RCS from attached low-pressure systems, such as the Residual Heat Removal System and the low-pressure Emergency Core Cooling System. The number, design, and function of the RCS PIVs are plant specific. However, the main purpose of the PIVs is to prevent RCS fluid from over pressurizing systems that are not rated for RCS pressure that might result in an intersystem loss-of-coolant accident (ISLOCA) outside of containment. The RCS PIVs are described in the plant's Updated/Final Safety Analysis Report and IST Program documentation.
The RCS PIV Leakage Limiting Condition for Operation (LCO) limits the leakage through the RCS PIVs to amounts that do not compromise safety. The RCS PIV leakage limit applies to each PIV and is specified in the Technical Specifications (TS) and the American Society of Mechanical Engineers (ASME) Operation and Maintenance of Nuclear Power Plants (OM Code). Any leakage through both RCS PIVs on a penetration is included in identified leakage, and is limited by the TS LCO on RCS Operational LEAKAGE. All RCS PIVs required to be tested by the TS are also governed by the IST Program.
1.2 Proposed Changes to the Standard Technical Specifications Traveler TSTF-600, Revision 2, proposed revising the Frequency by deleting the other options (an 18-month Frequency, a Frequency based on valve actuation or flow through the valve, and the SFCP), so that only In accordance with the INSERVICE TESTING PROGRAM remains for:
NUREG-1430, NUREG-1431, and NUREG-1432, SR 3.4.14.1, NUREG-1433, SR 3.4.5.1, and NUREG-1434, SR 3.4.6.1.
Additionally, Notes 2 and 3 of SR 3.4.14.1 in NUREG-1430, NUREG-1431, and NUREG-1432 are deleted.
Plants that have adopted Traveler TSTF-596, Revision 2, will use a Frequency of In accordance with the Surveillance Frequency Control Program. Under TSTF-596, references to the IST Program were replaced with references to the SFCP. The NRC staff notes that the IST Program requirements specified in the ASME OM Code as incorporated by reference in Title 10 of the Code of Federal Regulations, Section 50.55a (10 CFR 50.55a) apply as regulatory requirements regardless of SFCP provisions. Additionally, TS Section 5.5, Surveillance Frequency Control Program, references 10 CFR 50.55a(f), which is the NRC regulatory requirement to establish the IST Program in accordance with the ASME OM Code as incorporated by reference in 10 CFR 50.55a, for the applicable SRs, such as the RCS PIV SR.
In the proposed change, only the SR Frequency is revised. The proposed change does not add or remove any RCS PIVs from the STS or ASME OM Code requirements. The proposed change does not alter the method of testing or the SR acceptance criteria.
The traveler stated that the ASME OM Code requires a 2-year interval for PIV testing. The traveler also notes the ability to adopt ASME OM Code Case OMN-23, Alternative Requirements for Testing Pressure Isolation Valves, as accepted in NRC Regulatory Guide 1.192, Operation and Maintenance Code Case Acceptability, ASME OM Code, to extend this interval to a maximum of every 6 years if the history of valve performance justifies such an extension without a significant reduction in PIV reliability. Licensees would have to follow appropriate regulatory processes to adopt this Code Case or other potential changes to the basic ASME OM Code requirements.
The traveler discussed Frequency based on valve actuation or flow through the valve. This Frequency is proposed to be deleted. The traveler stated that this testing is not necessary to provide protection for the low-pressure piping. The leakage rate testing interval required by the ASME OM Code or its applicable Code Case adequately demonstrates operational readiness of a valve from a leakage perspective. Valve position indication acceptably shows that the valve has closed after operation. Therefore, leakage testing after operation of the PIVs is not necessary considering the ASME OM Code and Code Case provisions for leakage testing.
TSTF-600 also stated that some STS PIV leakage specifications do not include the condition-based Frequency. The traveler also cited an amendment issued to Duke Energy that concluded the condition-based testing was not required (ML23241A987).
TSTF-600 stated that the Frequency of every 9 months prior to entering Mode 2 if the plant has been if Mode 5 for 7 days or more is also unnecessary. The traveler cited the same Duke Energy amendment in which the NRC determined that the IST Program testing interval was adequate for providing reasonable assurance of PIV leakage capability.
Notes 2 and 3 are proposed for removal from the PWR SR 3.4.14.1. Note 2 states that the SR is not required to be performed on the RCS PIVs located in the decay heat removal or shutdown cooling flow path when the system is functioning in that Mode of operation. Note 3 states that RCS PIVs actuated during the performance of SR 3.4.14.1 are not required to be tested more than once if a repetitive testing loop cannot be avoided. These Notes provide duplicate exceptions to performance of the SR to those already contained in TS 3.4.14. Also, with the change to eliminate condition-based testing and require testing per the IST Program, these Notes are no longer needed.
1.3 Proposed Changes to the STS Bases The proposed change would modify the SR Bases to reflect the changes to the SR Frequency.
In addition, a typographical error in the SR Bases, which refers to 10 CFR 50.55a(g) instead of 10 CFR 50.55a(f), is being corrected. The STS Bases are updated to reflect the current safety basis of the requirements. References to outdated studies, such as WASH-1400 (1975) and NUREG-0677 (1980), are being removed.
1.4 Reason for Proposed Change The change is proposed to align the TS requirements for PIV leakage testing with ASME OM Code requirements where possible. The change is based on updated knowledge both of PIV leakage behavior and risks associated with ISLOCAs. The change will make it possible for licensees to decrease the number of leakage tests performed on the PIVs, making plant operation more efficient.
2.0 REGULATORY EVALUATION
As described in the Commissions Final Policy Statement on Technical Specifications Improvements for Nuclear Power Reactors (58 FR 39132, dated July 22, 1993), [t]he new STS should include greater emphasis on human factors principles in order to add clarity and understanding to the text of the STS, and provide improvements to the Bases Section of the Technical Specifications which provides the purpose for each requirement in the specification.
The improved vendor specific STS were developed and issued by the NRC in September 1992.
The Commissions Final Policy Statement states that each LCO, Action, and Surveillance Requirement (SR) should have supporting Bases, and [t]he Bases should, at a minimum, address [certain] questions and cite references to appropriate licensing documentation (e.g.,
FSAR or Topical Report) to support the Bases.
The NRC regulations in 10 CFR 50.36(b) requires:
Each license authorizing operation of a utilization facility will include technical specifications. The technical specifications will be derived from the analyses and evaluation included in the safety analysis report, and amendments thereto, submitted pursuant to [10 CFR] 50.34 [Contents of applications; technical information]. The Commission may include such additional technical specifications as the Commission finds appropriate.
10 CFR 50.36(c) states that TS will include items in several categories, which include Paragraph (3), Surveillance requirements. It defines SRs as requirements relating to test, calibration, or inspection to assure that the necessary quality of systems and components is maintained, that facility operation will be within safety limits, and that the LCOs will be met.
The NRC staffs guidance for the review of TS is provided in NUREG-0800, Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants: LWR [light-water reactor] Edition (SRP), Chapter 16.0, Technical Specifications, Revision 3, dated March 2010 (ML100351425). As described therein, as part of the regulatory standardization effort, the NRC staff has prepared STS for each of the LWR nuclear designs.
The NRC regulations in 10 CFR 50.55a(f)(4), Inservice testing standards requirement for operating plants, state, in part, that [t]hroughout the service life of a boiling or pressurized water-cooled nuclear power facility, pumps and valves that are within the scope of the ASME OM Code must meet the inservice test requirements (except design and access provisions) set forth in the ASME OM Code and addenda that become effective subsequent to editions and addenda specified in [10 CFR 50.55a(f)(2) and (3)] and that are incorporated by reference in
[10 CFR 50.55a(a)(1)(iv)], to the extent practical within the limitations of design, geometry, and materials of construction of the components.
Section 50.55a(f)(5)(ii), IST program update: Conflicting IST Code requirements with technical specifications, states, in part, that [i]f a revised inservice test program for a facility conflicts with the technical specifications for the facility, the licensee must apply to the Commission for amendment of the technical specifications to conform the technical specifications to the revised program.
3.0 TECHNICAL EVALUATION
The NRC staff reviewed Traveler TSTF-600, which proposed changes to NUREGs1430, -1431,
-1432, -1433, and -1434. The regulatory framework the NRC staff used to determine the acceptability of the proposed changes consists of the requirements and guidance listed in Section 2.0 of this safety evaluation. The NRC staff reviewed the proposed changes to the STS to determine whether they meet the standards for TS in 10 CFR 50.36(c)(3) and conform to the Final Policy Statement on Technical Specifications Improvements for Nuclear Power Reactors.
3.1 Evaluation of the Proposed TS Changes The NRC staff reviewed the proposed changes to the PIV Leakage STS and concluded that the leakage testing frequency required by the IST Program is adequate to assure operational readiness, with respect to leakage, of the PIVs.
3.1.1 Evaluation of Revised Frequency The existing frequencies, based on time between tests and other operational conditions, in the PIV Leakage STS were determined to be unnecessary to demonstrate that the PIVs will continue to reliably perform their design functions. These frequencies were imposed based on risk studies that indicated that the testing was needed to assure low plant risk. Operating experience with PIV operation, maintenance, and testing has demonstrated that the more frequent time-based frequencies and condition-based frequencies do not contribute significantly to valve reliability. TSTF-600 also included information based on a survey of licensees that indicates that the risk of ISLOCA is no longer considered to be a significant contributor to core melt or large early release, and that the more frequent testing is not necessary to maintain the risk at an acceptable level. The model application in the traveler includes a requirement for each licensee adopting TSTF-600 to confirm that ISLOCA is not a significant contributor to plant risk and that even with the elimination of the event driven and 9-month frequencies, plant risk remains acceptable. The NRC staff found that this adequately ensures that plant risk is not adversely affected by the change.
Frequencies established based on the SFCP are required to refer to applicable codes and standards. Since the ASME OM Code requires the testing to be completed every 24 months, or in accordance with an NRC-accepted ASME OM Code Case, unless a licensee is granted relief or authorized for an alternative via the appropriate regulatory process, the maximum interval is limited to 24 months, or the NRC-accepted Code Case interval. The NRC review of any relief request or proposed alternative would verify its acceptability for the plant requesting the relief or alternative to the ASME OM Code requirement. The SFCP allows surveillance frequencies to be adjusted using risk insights. The SFCP implementation document, NEI 04-10, Revision 1, Risk -Informed Method for Control of Surveillance Frequencies, (ML071360456) requires that licensees review applicable codes and standards, including the ASME OM Code, to ensure that any deviations are reviewed and documented. Since the ASME OM Code as incorporated by reference in 10 CFR 50.55a is a regulatory requirement, any changes to surveillance frequency, including those permitted under the SFCP, are required to meet the applicable regulatory requirements in the ASME OM Code, NRC-accepted ASME OM Code Cases, or NRC-authorized relief or alternative requests proposed by the licensee. Therefore, the elimination of the SFCP as a frequency for the PIV leakage testing is acceptable because the NRC regulatory requirements in the ASME OM Code as incorporated by reference in 10 CFR 50.55a, or NRC -accepted Code Cases, continue to apply to nuclear power plants regardless of SFCP provisions. In addition, as discussed above, TSTF-596 replaced the IST Program as a frequency with the SFCP2 although the IST Program requirements specified in the ASME OM Code as incorporated by reference in 10 CFR 50.55a apply as regulatory requirements regardless of SFCP provisions. The implementation of TSTF-596 has adequate controls to ensure that licensees are aware that the ASME OM Code, as incorporated by reference in 10 CFR 50.55a, includes required tests and that the ASME OM Code frequencies must be met when the SFCP is used to revise the TS frequencies.
Leakage through the PIVs is required to be included as TS operational leakage and tracked.
This requirement provides defense-in-depth to the SR leakage requirements and helps to assure that PIV leakage does not become excessive between leakage tests. The model application in the traveler requires licensees to confirm that they do not have other licensing basis requirements that would require more frequent leakage testing of the PIVs.
3.1.2 Evaluation of Deletion of Notes 2 and 3 Upon approval of TSTF-600, Notes 2 and 3 SR 3.4.14.1 in NUREG-1430, NUREG-1431, and NUREG-1432 will no longer be needed. With the IST Program (and the SFCP) and elimination of the time and condition-based frequencies, the SR will be completed as required by the IST Program, and exceptions based on the system configuration, as allowed in Note 2, are no longer needed. In addition, Note 3 allows the licensee to not perform repetitive testing that would result from stroking RCS PIVs during performance of SR 3.4.14.1, then requiring an added test because the valve was stroked. This exception will no longer be necessary because the condition-based frequencies are deleted. Therefore, the NRC staff concluded that these Notes are no longer needed upon approval of TSTF-600.
3.1.3 Summary The NRC staff concluded that the traveler contains sufficient justification for the proposed change. In addition, the TSTF-600 provides sufficient detail to ensure that plant-specific requests for changes to the SR Frequency for PIV testing will be appropriately evaluated.
10 CFR 50.36(c)(3) requirements for SRs will continue to be met with the changes to the required Frequency and the proposed deletion of the SR Notes. Therefore, the NRC staff concluded that changing from the current surveillance frequencies to a surveillance Frequency that is in accordance with the IST Program is acceptable.
3.2 Evaluation of Proposed STS Bases Changes This traveler will become part of the next major revision of the NRCs STS Bases NUREG documents. As such, the NRC staff assessed the proposed Bases changes included in TSTF-600 to determine if they addressed the items in the Commissions Final Policy Statement described in Section 2.0 above. For the reasons below, the NRC staff found that the proposed STS Bases changes sufficiently meet the Final Policy Statement.
2 The implementation of TS and IST Program requirements has evolved as regulations have been updated, and the industry and NRC staff have worked to make the implementation of the different, but potentially overlapping, requirements more efficient and easier to understand. The STS contained the IST Program as a TS program in Section 5.5. TSTF-545 removed the IST Program from STS Section 5.5 and added a definition of IST Program in TS Section 1.1. TSTF-596 deleted the IST Program definition and incorporated the IST Program requirements directly into the SFCP TS program in STS Section 5.5. The TSTF-600 traveler includes a variation that allows it to be adopted regardless of whether the plant-specific TS have adopted TSTF-545 or TSTF-596.
The Final Policy Statement states that Bases should provide the justification for the TS, i.e.,
discuss which Policy Statement criterion requires it to be in the TS. This standard continues to be met because the proposed STS Bases changes are consistent with the proposed change.
Additionally, the Bases for PIV leakage state that RCS PIV leakage satisfies Criterion 2 of 10 CFR 50.36(c)(2)(ii). Therefore, this statement in the STS Bases is unchanged and remains valid.
4.0 CONCLUSION
The NRC staff reviewed Traveler TSTF-600, Revision 2, which proposed changes to the STS in NUREGs-1430, -1431, -1432, -1433, and -1434. The NRC staff determined that the proposed changes to the STS continue to meet the Commissions Final Policy Statement on Technical Specifications Improvements for Nuclear Power Reactors, and the NRC regulatory requirements in 10 CFR 50.36. Additionally, the NRC staff reviewed the changes to the STS and found them to be technically clear and consistent with customary terminology and format in accordance with SRP Chapter 16.0. The NRC staff reviewed the proposed changes to the SR Frequencies affected by the proposal and concludes that 10 CFR 50.36(c)(3) will continue to be met, and the changes continue to provide reasonable assurance of adequate protection of the health and safety of the public. Therefore, the NRC staff concludes that the proposed STS changes are acceptable.
Principal Contributors: S. Smith, NRR/DSS N. Hansing, NRR/DEX T. Scarbrough, NRR/DEX Date: September 8, 2025