ML24022A119

Slides - SNC Slides - Pre-Submittal Meeting on January 24, 2024 - Vogtle 3 & 4 Explosively Actuated Valves Relief Request

ML24022A119
Person / Time
Site:	Vogtle
Issue date:	01/24/2024
From:	Georgia Power Co, Southern Nuclear Company
To:	Office of Nuclear Reactor Regulation
Lamb J, NRR/DORL/LPL2-1
Shared Package
ML24022A109	List: ML24022A119 ML24025A137
References
EPID L-2023-LRM-0109
Download: ML24022A119 (1)

Text

1

2 V34 IST-ALT-03 Interval-Interval Dates:

• Applies to the V34 initial inservice test (IST) interval beginning April 1, 2023, and ending March 30, 2033 Duration of Proposed Alternative:

• Initial reactor criticality through the end of the second refueling outage (RFO2) for each unit Applicable Code Requirements:

• 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.

3 V34 IST-ALT-03 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 and 40% tests and replacements occurring within the second 2 years of the First IST Interval. Following the second two-year period, testing and replacement of the charges would resume at a normal rate of 20% within each two-year period as originally required per ASME OM Code subparagraph ISTC-5260(c).

4 V34 IST-ALT-03 ASME Code Components Affected

• RCS-V004A, B, C & D - Automatic Depressurization System (ADS) Stage 4 Valves

• PXS-V118A & B - Containment Recirculation Sumps to Reactor Coolant System (RCS) Actuation Squib Valves

• PXS-V120A & B - Containment Recirculation Sumps to RCS Actuation Squib Valves

• PXS-V123A & B - In-Containment Refueling Water Storage Tank (IRWST) Injection Isolation Valves

• PXS-V125A & B - IRWST Injection Isolation Valves

5 V34 IST-ALT-03

Reason for Request

• Known charges used in explosively actuated (squib) valves in post-2000 Generation III+ nuclear power facilities are sole sourced from a single company.

• The manufacturer of these charges 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 not maintain a large inventory of spare charges as they are used infrequently and have a shelf life of 10 years. In addition, they are hazardous and require special handling and storage requirements.

• Vogtle Units 3 & 4 elected not to keep extra charges in inventory, but decided instead just to order additional charges as needed as the time to replace some of them for testing purposes came near.

6 V34 IST-ALT-03 Reason for Request (continued)

• 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.

• To date, an entity has not been located to provide replacements.

Mitigation Efforts

• SNC is attempting 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.

7 V34 IST-ALT-03 Mitigation Efforts (continued)

• A prospective new supplier was recently identified outside of the nuclear industry and the industry is hopeful that this prospective vendor will agree to obtain the necessary approvals and certifications to be able to service nuclear power facilities.

• Time that will be required for such a supplier to develop a quality assurance program compliant with the requirements of 10 CFR Part 50 Appendix B, 10 CFR Part 21, and NQA-1, pass the required auditing, qualify the chemical compounds, perform equivalency testing, and fabricate the production replacement charges.

• It is highly improbable that replacement charges will be available when needed to replace charges to be tested at the next refueling outage of Vogtle Units 3 & 4.

8 V34 IST-ALT-03 Basis for Relief and Use of Alternative

• The pyrotechnically actuated valves use a chemical charge 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 relies upon the potency and chemical stability of the chemical charge.

• Equipment qualification testing of these chemical charges environmentally and radiationally aged the charges and found that, while chemical charges would degrade over time, they would not degrade to the point of unviability within the design 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.

9 V34 IST-ALT-03 Basis for Relief and Use of Alternative (continued)

• Preservice Testing (PST) per PST-ALT-01, Alternative Requirements for Preservice Testing of Explosively Actuated Valves, (in lieu of ISTC 3100(d)(2))

• 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.

• 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.

10 V34 IST-ALT-03 Basis for Relief and Use of Alternative (continued)

• The PST 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).

• The NRC Safety Evaluation noted that the number of charges to be tested from each of the three batches will exceed the number that would be required.

• 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).

11 V34 IST-ALT-03 Basis for Relief and Use of Alternative (continued)

• The preservice testing during March 2021, on charges initially manufactured between September 2020 and February 2021, yielded satisfactory results. The results of the testing activities are documented and available on site.

• Thus, there is reasonable assurance that the installed charges would actuate as required if called upon to do so by the circuitry of the valves.

12 V34 IST-ALT-03 Proposed Changes to V34 Inservice Testing Program Plan - First Interval

• Section 6.0, Valve Notes, is revised to include new Note 12 to read:

• 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 at least 40% of the total number of pyrotechnic charges during the second refueling outage of each unit.

• Section 6.0 is also revised to include a reference to new Note 12 in Note 2.

13 V34 IST-ALT-03 Proposed Changes to V34 Inservice Testing Program Plan - First Interval

• Sections 7.0, VEGP-3 Valve Tables, and 8.0, VEGP-4 Valve Tables, are revised to include Note 12 in the Plan Notes column for valves PXS-V118A/B, PXS-V120A/B, PXS-V123A/B, PXS-V125A/B and RCS-V004A/B/C/D.

• Section 3.1, Alternatives, is 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.

14 V34 IST-ALT-03 Requested Date for Approval:

• Authorization is requested by August 31, 2024

• Allows for implementation prior to the first refueling outage for Vogtle Unit 3.

15 V34 IST-ALT-03 QUESTIONS?