ML25125A226
| ML25125A226 | |
| Person / Time | |
|---|---|
| Site: | Technical Specifications Task Force |
| Issue date: | 06/13/2025 |
| From: | Office of Nuclear Reactor Regulation |
| To: | Technical Specifications Task Force |
| References | |
| EPID L-2024-PMP-0003 | |
| Download: ML25125A226 (7) | |
Text
DRAFT SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION 1
TECHNICAL SPECIFICATIONS TASK FORCE TRAVELER 2
TSTF-600, REVISION 2 3
"REVISE THE REACTOR COOLANT SYSTEM (RCS) PRESSURE ISOLATION VALVE (PIV) 4 LEAKAGE TESTING FREQUENCY" 5
USING THE CONSOLIDATED LINE ITEM IMPROVEMENT PROCESS 6
(EPID: L-2024-PMP-0003) 7 8
1.0 INTRODUCTION
9 10 By [[letter::TSTF-25-03, TSTF Response to NRC Second Request for Additional Information on TSTF-600, Revision 1, Revise the Reactor Coolant System (RCS) Pressure Isolation Valve (PIV) Leakage Testing Frequency|letter dated March 24, 2025]] (Agencywide Documents Access and Management System 11 (ADAMS) Accession No. ML25083A153), the Technical Specifications Task Force (TSTF) 12 submitted Traveler TSTF-600, Revision 2, Revise the Reactor Coolant System (RCS) Pressure 13 Isolation Valve (PIV) Leakage Testing Frequency. Traveler TSTF-600 proposed changes to the 14 Standard Technical Specifications (STS) for boiling-water reactor (BWR) and pressurized-water 15 reactor (PWR) designs under the consolidated line item improvement process (CLIIP). Upon 16 approval, this traveler will be made available to nuclear power plant applicants and licensees for 17 adoption and the changes will be incorporated into future revisions of the following US Nuclear 18 Regulatory Commission (NRC) STS1:
19 20 NUREG-1430, Standard Technical Specifications, Babcock and Wilcox Plants, Volume 1, 21 Specifications, and Volume 2, Bases, Revision 5, September 2021 (ML21272A363 and 22 ML21272A370, respectively).
23 NUREG-1431, Standard Technical Specifications, Westinghouse Plants, Volume 1, 24 Specifications, and Volume 2, Bases, Revision 5, September 2021 (ML21259A155 and 25 ML21259A159, respectively).
26 NUREG-1432, Standard Technical Specifications, Combustion Engineering Plants, 27 Volume 1, Specifications, and Volume 2, Bases, Revision 5, September 2021 28 (ML21258A421 and ML21258A424, respectively).
29 NUREG-1433, Standard Technical Specifications, General Electric BWR/4 Plants, 30 Volume 1, Specifications, and Volume 2, Bases, Revision 5, September 2021 31 (ML21272A357 and ML21272A358, respectively).
32 NUREG-1434, Standard Technical Specifications, General Electric BWR/6 Plants 33 Volume 1, Specifications, and Volume 2, Bases, Revision 5, September 2021 34 (ML21271A582 and ML21271A596, respectively).
35 36 The proposed change would revise the Frequency of the Surveillance Requirement (SR) to 37 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 1
plants that have adopted TSTF-596, Revision 2, Expand the Applicability of the Surveillance 2
Frequency Control Program (SFCP), (ML24362A054), the proposal includes a variation to set 3
the Frequency in accordance with the SFCP.
4 5
1.1
System Description
6 7
RCS PIVs are two normally closed valves in series in RCS piping that separate the 8
high-pressure RCS from attached low-pressure systems, such as the Residual Heat Removal 9
System and the low-pressure Emergency Core Cooling System. The number, design, and 10 function of the RCS PIVs are plant specific. However, the main purpose of the PIVs is to prevent 11 RCS fluid from over pressurizing systems that are not rated for RCS pressure that might result 12 in an intersystem loss-of-coolant accident (ISLOCA) outside of containment. The RCS PIVs are 13 described in the plant's Updated/Final Safety Analysis Report and IST Program documentation.
14 15 The RCS PIV Leakage Limiting Condition for Operation (LCO) limits the leakage through the 16 RCS PIVs to amounts that do not compromise safety. The RCS PIV leakage limit applies to 17 each PIV and is specified in the Technical Specifications (TS) and the American Society of 18 Mechanical Engineers (ASME) Operation and Maintenance of Nuclear Power Plants (OM 19 Code). Any leakage through both RCS PIVs on a penetration is included in identified leakage, 20 and is limited by the TS LCO on RCS Operational LEAKAGE. All RCS PIVs required to be 21 tested by the TS are also governed by the IST Program.
22 23 1.2 Proposed Changes to the Standard Technical Specifications 24 25 Traveler TSTF-600, Revision 2, proposed revising the Frequency by deleting the other options 26 (an 18-month Frequency, a Frequency based on valve actuation or flow through the valve, and 27 the SFCP), so that only In accordance with the INSERVICE TESTING PROGRAM remains 28 for:
29 30 NUREG-1430, NUREG-1431, and NUREG-1432, SR 3.4.14.1, 31 NUREG-1433, SR 3.4.5.1, and 32 NUREG-1434, SR 3.4.6.1.
33 34 Additionally, Notes 2 and 3 of SR 3.4.14.1 in NUREG-1430, NUREG-1431, and NUREG-1432 35 are deleted.
36 37 Plants that have adopted Traveler TSTF-596, Revision 2, will use a Frequency of In 38 accordance with the Surveillance Frequency Control Program. Under TSTF-596, references to 39 the IST Program were replaced with references to the SFCP. The NRC staff notes that the IST 40 Program requirements specified in the ASME OM Code as incorporated by reference in Title 10 41 of the Code of Federal Regulations, Section 50.55a (10 CFR 50.55a) apply as regulatory 42 requirements regardless of SFCP provisions. Additionally, TS Section 5.5, Surveillance 43 Frequency Control Program, references 10 CFR 50.55a(f), which is the NRC regulatory 44 requirement to establish the IST Program in accordance with the ASME OM Code as 45 incorporated by reference in 10 CFR 50.55a, for the applicable SRs, such as the RCS PIV SR.
46 47 In the proposed change, only the SR Frequency is revised. The proposed change does not add 48 or remove any RCS PIVs from the STS or ASME OM Code requirements. The proposed 49 change does not alter the method of testing or the SR acceptance criteria.
50 51 The traveler stated that the ASME OM Code requires a 2-year interval for PIV testing. The 1
traveler also notes the ability to adopt ASME OM Code Case OMN-23, Alternative 2
Requirements for Testing Pressure Isolation Valves, as accepted in NRC Regulatory 3
Guide 1.192, Operation and Maintenance Code Case Acceptability, ASME OM Code, to 4
extend this interval to a maximum of every 6 years if the history of valve performance justifies 5
such an extension without a significant reduction in PIV reliability. Licensees would have to 6
follow appropriate regulatory processes to adopt this Code Case or other potential changes to 7
the basic ASME OM Code requirements.
8 9
The traveler discussed Frequency based on valve actuation or flow through the valve. This 10 Frequency is proposed to be deleted. The traveler stated that this testing is not necessary to 11 provide protection for the low-pressure piping. The leakage rate testing interval required by the 12 ASME OM Code or its applicable Code Case adequately demonstrates operational readiness of 13 a valve from a leakage perspective. Valve position indication acceptably shows that the valve 14 has closed after operation. Therefore, leakage testing after operation of the PIVs is not 15 necessary considering the ASME OM Code and Code Case provisions for leakage testing.
16 TSTF-600 also stated that some STS PIV leakage specifications do not include the 17 condition-based Frequency. The traveler also cited an amendment issued to Duke Energy that 18 concluded the condition-based testing was not required (ML23241A987).
19 20 TSTF-600 stated that the Frequency of every 9 months prior to entering Mode 2 if the plant has 21 been if Mode 5 for 7 days or more is also unnecessary. The traveler cited the same Duke 22 Energy amendment in which the NRC determined that the IST Program testing interval was 23 adequate for providing reasonable assurance of PIV leakage capability.
24 25 Notes 2 and 3 are proposed for removal from the PWR SR 3.4.14.1. Note 2 states that the SR is 26 not required to be performed on the RCS PIVs located in the decay heat removal or shutdown 27 cooling flow path when the system is functioning in that Mode of operation. Note 3 states that 28 RCS PIVs actuated during the performance of SR 3.4.14.1 are not required to be tested more 29 than once if a repetitive testing loop cannot be avoided. These Notes provide duplicate 30 exceptions to performance of the SR to those already contained in TS 3.4.14. Also, with the 31 change to eliminate condition-based testing and require testing per the IST Program, these 32 Notes are no longer needed.
33 34 1.3 Proposed Changes to the STS Bases 35 36 The proposed change would modify the SR Bases to reflect the changes to the SR Frequency.
37 In addition, a typographical error in the SR Bases, which refers to 10 CFR 50.55a(g) instead of 38 10 CFR 50.55a(f), is being corrected. The STS Bases are updated to reflect the current safety 39 basis of the requirements. References to outdated studies, such as WASH-1400 (1975) and 40 NUREG-0677 (1980), are being removed.
41 42 1.4 Reason for Proposed Change 43 44 The change is proposed to align the TS requirements for PIV leakage testing with ASME OM 45 Code requirements where possible. The change is based on updated knowledge both of PIV 46 leakage behavior and risks associated with ISLOCAs. The change will make it possible for 47 licensees to decrease the number of leakage tests performed on the PIVs, making plant 48 operation more efficient.
49 50
2.0 REGULATORY EVALUATION
1 2
As described in the Commissions Final Policy Statement on Technical Specifications 3
Improvements for Nuclear Power Reactors (58 FR 39132, dated July 22, 1993), [t]he new STS 4
should include greater emphasis on human factors principles in order to add clarity and 5
understanding to the text of the STS, and provide improvements to the Bases Section of the 6
Technical Specifications which provides the purpose for each requirement in the specification.
7 The improved vendor specific STS were developed and issued by the NRC in September 1992.
8 9
The Commissions Final Policy Statement states that each LCO, Action, and Surveillance 10 Requirement (SR) should have supporting Bases, and [t]he Bases should, at a minimum, 11 address [certain] questions and cite references to appropriate licensing documentation (e.g.,
12 FSAR or Topical Report) to support the Bases.
13 14 The NRC regulations in 10 CFR 50.36(b) requires:
15 16 Each license authorizing operation of a utilization facility will include technical 17 specifications. The technical specifications will be derived from the analyses and 18 evaluation included in the safety analysis report, and amendments thereto, submitted 19 pursuant to [10 CFR] 50.34 [Contents of applications; technical information]. The 20 Commission may include such additional technical specifications as the Commission 21 finds appropriate.
22 23 10 CFR 50.36(c) states that TS will include items in several categories, which include 24 Paragraph (3), Surveillance requirements. It defines SRs as requirements relating to test, 25 calibration, or inspection to assure that the necessary quality of systems and components is 26 maintained, that facility operation will be within safety limits, and that the LCOs will be met.
27 28 The NRC staffs guidance for the review of TS is provided in NUREG-0800, Standard Review 29 Plan for the Review of Safety Analysis Reports for Nuclear Power Plants: LWR [light-water 30 reactor] Edition (SRP), Chapter 16.0, Technical Specifications, Revision 3, dated March 2010 31 (ML100351425). As described therein, as part of the regulatory standardization effort, the NRC 32 staff has prepared STS for each of the LWR nuclear designs.
33 34 The NRC regulations in 10 CFR 50.55a(f)(4), Inservice testing standards requirement for 35 operating plants, state, in part, that [t]hroughout the service life of a boiling or pressurized 36 water-cooled nuclear power facility, pumps and valves that are within the scope of the ASME 37 OM Code must meet the inservice test requirements (except design and access provisions) set 38 forth in the ASME OM Code and addenda that become effective subsequent to editions and 39 addenda specified in [10 CFR 50.55a(f)(2) and (3)] and that are incorporated by reference in 40
[10 CFR 50.55a(a)(1)(iv)], to the extent practical within the limitations of design, geometry, and 41 materials of construction of the components.
42 43 Section 50.55a(f)(5)(ii), IST program update: Conflicting IST Code requirements with technical 44 specifications, states, in part, that [i]f a revised inservice test program for a facility conflicts with 45 the technical specifications for the facility, the licensee must apply to the Commission for 46 amendment of the technical specifications to conform the technical specifications to the revised 47 program.
48 49
3.0 TECHNICAL EVALUATION
1 2
The NRC staff reviewed Traveler TSTF-600, which proposed changes to NUREGs1430, -1431, 3
-1432, -1433, and -1434. The regulatory framework the NRC staff used to determine the 4
acceptability of the proposed changes consists of the requirements and guidance listed in 5
Section 2.0 of this safety evaluation. The NRC staff reviewed the proposed changes to the STS 6
to determine whether they meet the standards for TS in 10 CFR 50.36(c)(3) and conform to the 7
Final Policy Statement on Technical Specifications Improvements for Nuclear Power Reactors.
8 9
10 3.1 Evaluation of the Proposed TS Changes 11 12 The NRC staff reviewed the proposed changes to the PIV Leakage STS and concluded that the 13 leakage testing frequency required by the IST Program is adequate to assure operational 14 readiness, with respect to leakage, of the PIVs.
15 16 3.1.1 Evaluation of Revised Frequency 17 18 The existing frequencies, based on time between tests and other operational conditions, in the 19 PIV Leakage STS were determined to be unnecessary to demonstrate that the PIVs will 20 continue to reliably perform their design functions. These frequencies were imposed based on 21 risk studies that indicated that the testing was needed to assure low plant risk. Operating 22 experience with PIV operation, maintenance, and testing has demonstrated that the more 23 frequent time-based frequencies and condition-based frequencies do not contribute significantly 24 to valve reliability. TSTF-600 also included information based on a survey of licensees that 25 indicates that the risk of ISLOCA is no longer considered to be a significant contributor to core 26 melt or large early release, and that the more frequent testing is not necessary to maintain the 27 risk at an acceptable level. The model application in the traveler includes a requirement for each 28 licensee adopting TSTF-600 to confirm that ISLOCA is not a significant contributor to plant risk 29 and that even with the elimination of the event driven and 9-month frequencies, plant risk 30 remains acceptable. The NRC staff found that this adequately ensures that plant risk is not 31 adversely affected by the change.
32 33 Frequencies established based on the SFCP are required to refer to applicable codes and 34 standards. Since the ASME OM Code requires the testing to be completed every 24 months, or 35 in accordance with an NRC-accepted ASME OM Code Case, unless a licensee is granted relief 36 or authorized for an alternative via the appropriate regulatory process, the maximum interval is 37 limited to 24 months, or the NRC-accepted Code Case interval. The NRC review of any relief 38 request or proposed alternative would verify its acceptability for the plant requesting the relief or 39 alternative to the ASME OM Code requirement. The SFCP allows surveillance frequencies to be 40 adjusted using risk insights. The SFCP implementation document, NEI 04-10, Revision 1, 41 Risk -Informed Method for Control of Surveillance Frequencies, (ML071360456) requires that 42 licensees review applicable codes and standards, including the ASME OM Code, to ensure that 43 any deviations are reviewed and documented. Since the ASME OM Code as incorporated by 44 reference in 10 CFR 50.55a is a regulatory requirement, any changes to surveillance frequency, 45 including those permitted under the SFCP, are required to meet the applicable regulatory 46 requirements in the ASME OM Code, NRC-accepted ASME OM Code Cases, or 47 NRC-authorized relief or alternative requests proposed by the licensee. Therefore, the 48 elimination of the SFCP as a frequency for the PIV leakage testing is acceptable because the 49 NRC regulatory requirements in the ASME OM Code as incorporated by reference in 10 CFR 50 50.55a, or NRC -accepted Code Cases, continue to apply to nuclear power plants regardless of 51 SFCP provisions. In addition, as discussed above, TSTF-596 replaced the IST Program as a 1
frequency with the SFCP2 although the IST Program requirements specified in the ASME OM 2
Code as incorporated by reference in 10 CFR 50.55a apply as regulatory requirements 3
regardless of SFCP provisions. The implementation of TSTF-596 has adequate controls to 4
ensure that licensees are aware that the ASME OM Code, as incorporated by reference in 5
10 CFR 50.55a, includes required tests and that the ASME OM Code frequencies must be met 6
when the SFCP is used to revise the TS frequencies.
7 8
Leakage through the PIVs is required to be included as TS operational leakage and tracked.
9 This requirement provides defense-in-depth to the SR leakage requirements and helps to 10 assure that PIV leakage does not become excessive between leakage tests. The model 11 application in the traveler requires licensees to confirm that they do not have other licensing 12 basis requirements that would require more frequent leakage testing of the PIVs.
13 14 3.1.2 Evaluation of Deletion of Notes 2 and 3 15 16 Upon approval of TSTF-600, Notes 2 and 3 SR 3.4.14.1 in NUREG-1430, NUREG-1431, and 17 NUREG-1432 will no longer be needed. With the IST Program (and the SFCP) and elimination 18 of the time and condition-based frequencies, the SR will be completed as required by the IST 19 Program, and exceptions based on the system configuration, as allowed in Note 2, are no 20 longer needed. In addition, Note 3 allows the licensee to not perform repetitive testing that 21 would result from stroking RCS PIVs during performance of SR 3.4.14.1, then requiring an 22 added test because the valve was stroked. This exception will no longer be necessary because 23 the condition-based frequencies are deleted. Therefore, the NRC staff concluded that these 24 Notes are no longer needed upon approval of TSTF-600.
25 26 3.1.3 Summary 27 28 The NRC staff concluded that the traveler contains sufficient justification for the proposed 29 change. In addition, the TSTF-600 provides sufficient detail to ensure that plant-specific 30 requests for changes to the SR Frequency for PIV testing will be appropriately evaluated.
31 10 CFR 50.36(c)(3) requirements for SRs will continue to be met with the changes to the 32 required Frequency and the proposed deletion of the SR Notes. Therefore, the NRC staff 33 concluded that changing from the current surveillance frequencies to a surveillance Frequency 34 that is in accordance with the IST Program is acceptable.
35 36 3.2 Evaluation of Proposed STS Bases Changes 37 38 This traveler will become part of the next major revision of the NRCs STS Bases NUREG 39 documents. As such, the NRC staff assessed the proposed Bases changes included in 40 TSTF-600 to determine if they addressed the items in the Commissions Final Policy Statement 41 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.
described in Section 2.0 above. For the reasons below, the NRC staff found that the proposed 1
STS Bases changes sufficiently meet the Final Policy Statement.
2 3
The Final Policy Statement states that Bases should provide the justification for the TS, i.e.,
4 discuss which Policy Statement criterion requires it to be in the TS. This standard continues to 5
be met because the proposed STS Bases changes are consistent with the proposed change.
6 Additionally, the Bases for PIV leakage state that RCS PIV leakage satisfies Criterion 2 of 7
10 CFR 50.36(c)(2)(ii). Therefore, this statement in the STS Bases is unchanged and remains 8
valid.
9 10
4.0 CONCLUSION
11 12 The NRC staff reviewed Traveler TSTF-600, Revision 2, which proposed changes to the STS in 13 NUREGs-1430, -1431, -1432, -1433, and -1434. The NRC staff determined that the proposed 14 changes to the STS continue to meet the Commissions Final Policy Statement on Technical 15 Specifications Improvements for Nuclear Power Reactors, and the NRC regulatory requirements 16 in 10 CFR 50.36. Additionally, the NRC staff reviewed the changes to the STS and found them 17 to be technically clear and consistent with customary terminology and format in accordance with 18 SRP Chapter 16.0. The NRC staff reviewed the proposed changes to the SR Frequencies 19 affected by the proposal and concludes that 10 CFR 50.36(c)(3) will continue to be met, and the 20 changes continue to provide reasonable assurance of adequate protection of the health and 21 safety of the public. Therefore, the NRC staff concludes that the proposed STS changes are 22 acceptable.
23 24 Principal Contributors: S. Smith, NRR/DSS 25 N. Hansing, NRR/DEX 26 T. Scarbrough, NRR/DEX 27 28 Date: June 13, 2025 29