NL-24-0060, Request for Relief and Alternative Requirements for Squib Valves First Test Interval (V34-IST-ALT-03)
| ML24046A230 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 02/15/2024 |
| From: | Coleman J Southern Nuclear Operating Co |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| NL-24-0060 | |
| Download: ML24046A230 (1) | |
Text
Southern Nuclear Operating Company, Inc.
3535 Colonnade Parkway Birmingham, AL 35243 Tel 205.992.7079
February 15, 2024
Docket Nos.: 52-025 NL-24-0060 52-026 10 CFR 50.55a
U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001
Southern Nuclear Operating Company Vogtle Electric Generating Plant Units 3 and 4 Request for Relief and Alternative Requirements for Squib Valves First Test Interval (V34-IST-ALT-03)
Ladies and Gentlemen:
Pursuant to 10 CFR 50.55a(f)(6), Southern Nuclear Operating Company (SNC) requests Nuclear Regulatory Commission (NRC) authorization for relie f from, and authorization to use an alternative to, the requirements of Title 10, Code of Federal Regulations (10 CFR) Section 50.55a(f) and the American Society of Mechanical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants (OM Code) testing and replacement interval requirements for the squib valves in OM Code Sections ISTC-5260(c) and ISTC-5260( e)(4). The proposed alternative would allow for no testing or replacement of the squib valve pyrotechnic charges during the first refueling outages for Vogtle Electric Generating Plant (VEGP) Unit 3 and Unit 4, with increased testing and replacement during the second refueling outage for each unit. This request was discussed with NRC Staff during the January 24, 2024, presubmittal public meeting.
The details of the 10 CFR 50.55a(f) request for relief are provided in Enclosure 1 of this letter.
Associated markups of the Inservice Testing Program Plan are provided in Enclosure 2 of this letter.
SNC requests the NRC authorize this proposed relief by August 31, 2024, which is prior to the first refueling outage for Vogtle Unit 3.
This letter contains no regulatory commitments. This letter has been reviewed and confirmed to contain no security-related information.
U.S. Nuclear Regulatory Commission NL-24-0060 Page 2 of 2
Should you have any questions, please contact Mr. Ryan Joyce at (205) 992-6468.
Respectfully submitted,
Jamie M. Coleman Director, Fleet Regulatory Affairs Southern Nuclear Operating Company
- Request for Relief and Alternative Requirements for Squib Valves First Test Interval (V34-IST-ALT-03)
- Markup of VEGP Units 3 and 4 Inservice Testing Program Plan - 1 st Interval (For Information)
cc: Regional Administrator, Region ll NRR Project Manager - Vogtle 3&4 Senior Resident Inspector - Vogtle 3&4 Document Services RTYPE: VND.LI.L00 File AR.01.02.06 Southern Nuclear Operating Company
NL-24-0060 Enclosure 1
Vogtle Electric Generating Plant (VEGP) Unit 3 and Unit 4
Request for Relief and Alternative Requirements for Squib Valves First Test Interval (V34-IST-ALT-03)
(This enclosure consists of 7 pages, including this cover page.)
NL-24-0060 Request for Relief and Alternative Requirements for Squib Valves First Test Interval (V34-IST-ALT-03)
Plant Site-Unit: Vogtle Electric Generating Plant (VEGP) - Unit 3 and Unit 4
Interval-Interval Applies to the initial inservice test (IST) interval for Unit 3 and Unit 4 Dates: beginning April 1, 2023, and ending March 30, 2033
Requested Date for Authorization is requested by August 31, 2024 Approval:
Automatic Depressurization System (ADS) Stage 4 Valves 3/4-RCS-V004A, B, C & D Containment Recirculation Sumps to Reactor Coolant System (RCS)
ASME Code Actuation Squib Valves 3/4-PXS-V118A & B Components Containment Recirculation Sumps to RCS Actuation Squib Valves Affected: 3/4-PXS-V120A & B In-Containment Refueling Water Storage Tank (IRWST) Injection Isolation Valves 3/4-PXS-V123A & B IRWST Injection Isolation Valves 3/4-PXS-V125A & B
Applicable ASME Operation and Maintenance of Nuclear Power Plants (OM)
Code Edition Code, 2012 Edition for 1st Inservice Test Interval and Addenda:
OM Code ISTC-5260(c), "Explosively Actuated Valves," states: At least 20% of the charges in explosively actuated valves shall be fired and replaced at least once every 2 years.
Applicable OM Code ISTC-5260(e)(4), states: For the valves selected in the test Code sample for subparagraph ISTC-5260(c), the sampling must select at Requirements: least one explosively actuated valve from each redundant safety train every 2 yr. Each sampled pyrotechnic charge shall be tested in the valve or a qualified test fixture to confirm the capability of the charge to provide the necessary motive force to operate the valve to perform its intended function without damage to the valve body or connected piping.
Currently, all known charges used in explosively actuated (squib) valves in post-2000 Generation III+ nuclear power facilities are sole Reason for sourced from a single company. The manufacturer of these charges Request: (Collins Aerospace) has recently informed the industry that they will no longer be supporting replacement orders of the charges for the nuclear industry. Owners of nuclear facilities that utilize this type of charges do
Page 2 of 7 NL-24-0060 Request for Relief and Alternative Requirements for Squib Valves First Test Interval (V34-IST-ALT-03)
not maintain a large inventory of spare charges as they are used infrequently and have a short shelf life and a service life of 8 years. In addition, they are hazardous and require special handling and storage requirements. As a result, Vogtle Units 3 & 4 elected not to keep extra charges in inventory, but decided instead to order additional charges as needed as the time to replace some of them for testing purposes came near. Vogtle will therefore not have spare charges available to replace those that are removed from valves currently in service to be test fired to meet OM Code requirements for Inservice Testing (IST) during the first refueling outage of each unit unless a manufacturer that can manufacture and supply charges to Vogtle prior to the first refueling outage for each unit is identified.
The Southern Nuclear Operating Company (SNC) Supply Chain has made efforts to identify a replacement vendor authorized by the appropriate authorities to manufacture explosive material, qualify the material for use in squib valve charges, and produce replacement charges. A supplier was recently identified to manufacture and supply charges in the near term, however, due to the length of manufacturing time, the charges will not be available for use during the first refueling outages for Vogtle Units 3 & 4. SNC has made every effort to ensure the necessary charges will be available for the second refueling outages and beyond to complete the required testing.
Proposed Alternative:
VEGP proposes to modify the requirement to test and replace at least 20% of the pyrotechnic charges used in explosively actuated valves at least once every two years for the first refueling outage for Units 3 & 4 by requesting an allowance to skip the first refueling outage occurrence of testing and increase the number of test and replacements that would occur at the second occurrence. This would result in zero tests and replacements taking place during the first two years of the First IST Interval for Units 3 & 4, which would include the first refueling outage for each unit but plans to test and replace 100% of the squib valve Proposed explosive charges within the second 2 years of the First IST Interval.
Alternative and Following the second two-year period, testing and replacement of the Basis for Use: charges would resume at a normal rate of approximately 50% within each two-year period as originally required per ASME OM Code subparagraph ISTC-5260(c) and ISTC-5260(e)(4).
Thus, testing in accordance with the proposed alternative would include:
Type Tag 3R1 3R2 3R3 3R4 Install 14" RCS-PL-V004A 0 1 1 10-2022 14" RCS-PL-V004B 0 1 1 10-2022 14" RCS-PL-V004C 1 1 10-2022 14" RCS-PL-V004D 1 1 10-2022
Page 3 of 7 NL-24-0060 Request for Relief and Alternative Requirements for Squib Valves First Test Interval (V34-IST-ALT-03)
8" HP PXS-PL-V123A 1 1 11-2022 8" HP PXS-PL-V123B 0 1 1 10-2022 8" HP PXS-PL-V125A 0 1 1 10-2022 8" HP PXS-PL-V125B 1 1 5-2021 8" HP PXS-PL-V120A 1 1 1-2023 8" HP PXS-PL-V120B 0 1 1 10-2022 8" LP PXS-PL-V118A 0 1 1 11-2022 8" LP PXS-PL-V118B 1 1 10-2022 Count per Outage 0 12 6 6 --
Row Sum of Sum of Sum of Sum of Labels 3R1 3R2 3R3 3R4 Schedule F2024 S2026 F2027 S2029 14" 0 4 2 2 8" HP 0 6 3 3 8" LP 0 2 1 1 Total 0 12 6 6
Type Tag 4R1 4R2 4R3 4R4 Install 14" RCS-PL-V004A 0 1 1 5-2021 14" RCS-PL-V004B 0 1 1 11-2023 14" RCS-PL-V004C 1 1 11-2023 14" RCS-PL-V004D 1 1 5-2021 8" HP PXS-PL-V123A 1 1 9-2023 8" HP PXS-PL-V123B 0 1 1 9-2023 8" HP PXS-PL-V125A 0 1 1 5-2021 8" HP PXS-PL-V125B 1 1 5-2021 8" HP PXS-PL-V120A 1 1 5-2021 8" HP PXS-PL-V120B 0 1 1 5-2021 8" LP PXS-PL-V118A 0 1 1 5-2021 8" LP PXS-PL-V118B 1 1 5-2021 Count per Outage 0 12 6 6 --
Row Sum of Sum of Sum of Sum of Labels 4R1 4R2 4R3 4R4 Schedule F2025 S2027 F2028 S2030 14" 0 4 2 2 8" HP 0 6 3 3 8" LP 0 2 1 1 Total 0 12 6 6
Page 4 of 7 NL-24-0060 Request for Relief and Alternative Requirements for Squib Valves First Test Interval (V34-IST-ALT-03)
SNC would also replace the charges not tested during the first refueling outage during an unplanned outage should the unplanned outage occur following receipt of acceptable replacement changes and prior to the second refueling outage and if there is sufficient time for planning and completing the replacement such that it would not extend the unplanned outage. The replaced charges would then be tested as required.
Basis for Use:
Post-2000 plants that use pyrotechnically actuated valves all use similar valve designs. In these designs, a chemical charge is ignited within the valves actuator and the rapid expansion of the chemical reaction increases pressure within the actuator ultimately leading to failure of a retention pin causing, and allowing, the actuator to shear a cap within the valve body. The process depends upon the reliability of the chemical charge. Testing of these chemical charges found that, while chemical charges may degrade over time, they would not degrade to the point of unviability within the inservice life of the charge. Periodic testing of the charges only confirms that no other degradation mechanisms are in play, which could not be simulated and tested during equipment qualification. However, the alternative testing schedule would result in testing of all squib valves within approximately 6 yrs of installation (May 2021 to spring 2027), i.e., within the manufacturers recommendations for the service life of the explosive charges.
During the Preservice Testing (PST) period at Vogtle Units 3 & 4, SNC had submitted VEGP 3&4-PST-Alt-01, Alternative Requirements for Preservice Testing of Explosively Actuated Valves, as a proposed alternative to the PST requirements of the above listed explosively actuated valves in lieu of the requirements in paragraph ISTC-3100(d)(2) of the 2012 Edition of the ASME OM Code for performing PST activities on Category D explosively actuated valves.
This proposed alternative requested that SNC be permitted to Select a sample of pyrotechnic charges, following fabrication for testing; this may include charges used for qualification of the batch. The sample shall include a quantity of charges equal to at least 20% of the number of charges of each size installed in the plant and shall include at least one from each manufacturer batch. It was also proposed that Each selected charge shall be tested in a qualified test fixture to confirm the capability of each sampled charge to provide the necessary motive force to operate the valve to perform its intended function without damage to the valve body or connected piping. The proposed alternative also included a table that outlined the number of charges that would be tested, which resulted in a much larger percentage of charges (approximately 40%) than would have been tested under ISTC-3100(d)(2) requirements.
In the NRC Safety Evaluation response to the request for alternative requirements, the NRC noted that With respect to the provision in paragraph ISTC-3100(d)(2) of the OM Code for pyrotechnic charge sampling, SNCs alternative identified three batches of pyrotechnic
Page 5 of 7 NL-24-0060 Request for Relief and Alternative Requirements for Squib Valves First Test Interval (V34-IST-ALT-03)
charges: one batch for each of the three sizes of the pyrotechnic charges specified as the 14-inch squib valve, 8-inch squib valve - high energy, and 8-inch squib valve - low energy. SNC states that the number of charges to be tested from each of the three batches will exceed the number that would be required based on provisions paragraph ISTC-3100(d)(2) of the OM Code for 20 percent sampling and redundant safety trains. In particular, SNC will test half of the pyrotechnic charges in Batch A (14-inch squib valves), almost half of the pyrotechnic charges in Batch B (8-inch squib valves - high energy),
and more than half of the pyrotechnic charges in Batch C (8-inch squib valves - low energy). The NRC Staff also noted that In comparison to paragraph ISTC-3100(d)(2) of the OM Code provisions, SNC will perform significant percentage test sampling (equal to or greater than 40 percent) of the total charges in the specific batch for each squib valve charge size. Based on the significant percentage of sample testing of the pyrotechnic charges, the staff considers SNCs proposed alternative to provide an acceptable level of sample testing of the pyrotechnic charges for squib valves in the ADS and PXS safety trains.
The testing that was proposed by SNC to be performed in lieu of PST in accordance with the 2012 Edition of the ASME OM Code was later performed by UTC Aerospace Systems - Interiors (UPCO) during the period of March 9 - 16, 2021. The charges had initially been manufactured between September of 2020 and February of 2021. All completed testing of the charges in March 2021 yielded satisfactory results (one charge did not fire during the testing due to a loose wire on a firing initiator). The results of the testing activities are documented and available on site.
Due to the amount of testing that was performed on charges from the same batches that are currently installed in the explosively actuated valves at Vogtle Units 3 & 4, and the successful results of those tests, there is reasonable assurance that the installed charges would actuate as required if called upon to do so by the circuitry of the valves.
SNC is therefore requesting that the OM Code requirement to test 20%
of the installed charges for the explosively actuated valves at Vogtle Units 3 & 4 within 2 years as specified in ISTC-5260(c) and ISTC-5260(e)(4) be waived until the second refueling outage for each unit. During the second refueling outage for each unit, SNC proposes to test and replace 100% of the charges in the explosively actuated valves and would then continue testing on the schedule prescribed by ISTC-5260(c) and ISTC-5260(e)(4) of the 2012 Edition of the OM Code, until the end of the First IST Interval. This would provide SNC sufficient time to identify a new supplier for the charges and purchase, receive and stock enough charges to build a sufficient inventory for charges that have to be replaced due to scheduled testing or unexpected failure. In addition, the other IST requirements for explosively actuated valves will be performed at the Code required intervals.
Page 6 of 7 NL-24-0060 Request for Relief and Alternative Requirements for Squib Valves First Test Interval (V34-IST-ALT-03)
Duration of Initial reactor criticality through the end of the second refueling outage Proposed (RFO2) for each unit Alternative:
Operating Experience searches were performed on the INPO website and in the NRC ADAMS database using terms such as squib and explosively actuated, instances of charges failed to fire during testing Precedent: were noted, mostly in the 1970s, 1980s and 1990s, the number of test firing failures has dropped dramatically over the past decade and there was no reporting of situations involving the inability to obtain spare charges for explosively actuated valves.
- 2. Letter ND-18-1401 from Brian H. Whitley of Southern Nuclear Operating Company to U.S. Nuclear Regulatory Commission dated November 29, 2018, and titled Vogtle Electric Generating Plants Units 3 and 4 Request for Alternative: Alternative Requirements for Preservice Testing of Explosively Actuated Valves (VEGP 3&4-PST-Alt-01 [ML18333A356]
- 3. Letter from Peter C. Hearn of the United States Nuclear Regulatory Commission to Brian H. Whitley of Southern Nuclear Operating Company dated March 26, 2019, and titled Vogtle Electric Generating Plant Units 3 and 4 - Request for Alternative:
References:
Alternative Requirements for Preservice Testing of Explosively Activated Valves (VEGP 3 & 4-PST-Alt-01) (EPID NO. L-2018-LLA-0498)
- 4. United States Nuclear Regulatory Commission Safety Evaluation by the Office of New Reactors Related to Request for Alternative Requirements for Preservice Testing of Explosively Actuated Valves (VEGP 3&4-PST-ALT-01) [ML19071A237]
- 5. Vogtle Units 3 and 4 Inservice Testing Program Plan
[ML22102A114]
- 6. Vogtle Units 3 and 4 Updated Final Safety Analysis Report Subsection 6.3.2.2.8.9, Explosively Opening (Squib) Valves
[ML23165A215]
Status: Awaiting NRC authorization
Page 7 of 7 Southern Nuclear Operating Company
NL-24-0060 Enclosure 2
Vogtle Electric Generating Plant (VEGP) Unit 3 and Unit 4
Markup of VEGP Units 3 and 4 Inservice Testing Program Plan - 1 st Interval (For Information)
(This enclosure consists of 5 pages, including this cover page.)
NL-24-0060 Markup of Vogtle Units 3 and 4 Inservice Testing Program Plan - 1 st Interval (For Information)
Section 3.1, Alternatives, will be revised to include a discussion of the alternative schedule and the Alternative will be included following Section 3.2, Code Cases, along with other approved alternatives.
Section 6. Revise Valve Note 2 and add new Note 12.
- 1. For all active
- 2. Squib valve charges, a minimum of 20% are tested every outage (2y), with a minimum of one from each safety train. Circuit testing to verify proper electrical parameters (voltage, current) to actuate squib charge to be performed on valves selected for squib testing. Also see Note 12.
- 11. For
- 12. Squib valve charge tests that would normally be required for the first refueling outage are deferred until the second refueling outage. For valves PXS-V118A/B, PXS-V120A/B, PXS-V123A/B, PXS-V125A/B and RCS-V004A/B/C/D, there will be no tests or replacements of pyrotechnic charges performed during the first refueling outage of Unit 3 or Unit 4. Vogtle Units 3 & 4 will test and replace 100% of the total number of pyrotechnic charges during the second refueling outage of each unit.
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