ML24025A137
| ML24025A137 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 01/31/2024 |
| From: | John Lamb NRC/NRR/DORL/LPL2-1 |
| To: | Southern Nuclear Operating Co |
| Shared Package | |
| ML24022A109 | List: |
| References | |
| EPID L-2023-LRM-0109 | |
| Download: ML24025A137 (10) | |
Text
January 31, 2024
LICENSEE: Southern Nuclear Operating Company, Inc.
FACILITY: Vogtle Electric Generating Plant, Units 3 and 4
SUBJECT:
SUMMARY
OF JANUARY 24, 2024, OBSERVATION PRE-SUBMITTAL MEETING HELD WITH SOUTHERN NUCLEAR OPERATING COMPANY, INC.,
REGARDING A PROPOSED ALTERNATIVE REQUEST REGARDING EXPLOSIVELY ACTUATED VALVES FOR VOGTLE ELECTRIC GENERATING PLANT, UNITS 3 AND 4 (EPID NO. L-2023-LRM-0190)
On January 24, 2024, an Observation meeting was held between the U.S. Nuclear Regulatory Commission (NRC) and representatives of Southern Nuclear Operating Company, Inc. (SNC, the licensee). The purpose of the meeting was for SNC to describe its plan to submit an alternative request under Title 10 of the Code of Federal Regulations (10 CFR),
Section 50.55a(z) regarding explosively actuated valves for Vogtle Electric Generating Plant (Vogtle), Units 3 and 4.
SNC is proposing to submit an alternative request to American Society of Mechanical Engineers (ASME) Operation and Maintenance of Nuclear Power Plants, 2012 Edition, Division 1, OM Code: Section IST (OM Code), Subsection ISTC, paragraph ISTC-5260, Explosively Actuated Valves. ASME OM Code, Subsection ISTC, paragraph ISTC-5260, requires a sample of at least 20 percent of the charges in explosively actuated valves to be test fired and replaced once every 2 years. In a Safety Evaluation dated March 26, 2019 (ML19071A237), the NRC staff authorized Alternative Request PST-ALT-01 for Vogtle, Units 3 and 4, related to sample testing of explosively actuated valves during the Preservice Testing Program at Vogtle, Units 3 and 4.
On December 15, 2023 (ML23349A074), the meeting was noticed on the NRC public webpage.
A list of attendees is provided in Enclosure 1.
has background information.
The NRC staff opened the meeting with introductor y remarks and a roll call of the attendees.
MEETING
The SNC representative presented the slides contained in ML24022A119.
SNC stated:
VEGP [Vogtle Electric Generating Plant, Units 3 and 4] 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 [Inservice Test] 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).
SNC said, 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.
SNC stated:
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.
ASME OM Code, Subsection ISTC, paragraph ISTC-5260(a) states:
A record of the service life of each charge in each valve shall be maintained. This record shall include the date of manufacture, batch number, installation date, and the date when service life expires based on manufacturers recommendations. In no case shall the service life exceed 10 yr.
The NRC staff asked about the manufacturer of the charges at Vogtle, Units 3 and 4. SNC will provide that information in the alternative request. The NRC staff asked about the explosively actuated valves at Edwin I. Hatch Nuclear Power Plant, Units 1 and 2. SNC reported that those charges were provided by a different manufacturer that could not make charges for the valves at Vogtle, Units 3 and 4. The NRC staff asked whether the current manufacturer for the valves at Vogtle, Units 3 and 4 is no longer supplying charges to the nuclear industry or to all industries.
SNC stated that the manufacturer is no longer supplying charges for the type of valves used at Vogtle, Units 3 and 4.
SNC stated:
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.
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.
The NRC staff asked how long it will take to obtain a new qualified vendor for the charges in the explosively actuated valves at Vogtle, Units 3 and 4. SNC said that it would take one and a half years at best. The NRC staff asked what would be SNCs contingency plan if a vendor is not qualified in time for the second refueling outage. SNC stated that it would require another licensing action.
The NRC staff asked about the percentage of pyrote chnic charges tested for the explosively actuated valves and whether it is based on per unit. SNC stated that sample testing is per unit basis and per valve size. The NRC staff asked if SNC has prepared a table of the charges to be tested in the second refueling outage per unit, such as provided for Alternative Request PST-ALT-01. SNC did not have a table in the presentation but would consider including one in the submittal.
The NRC staff asked about the service life for the charge in each valve.
SNC stated:
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.
The NRC staff asked about the record of service life in accordance with ISTC-5260(a) whether any explosively actuated valve at Vogtle, Units 3 and 4, has an end of service life of 2030 or earlier.
The NRC staff stated that ISTC-5260(e) is also applicable to post-2000 plants, such as Vogtle, Units 3 and 4.
SNC plans to submit the alternative request in the first quarter of calendar year 2024, requesting completion by August 31, 2024.
The NRC staff made no regulatory decisions during the meeting. Once received, the NRC staff will perform a thorough review of the proposed alternative request. The NRC staff will make any regulatory decisions in writing in a timely manner. Public Meeting Feedback forms were available, but no comments were received.
The meeting adjourned at 11:38 am Eastern Standard Time.
Please direct any inquiries to me at John.Lamb@nrc.gov or 301-415-3100.
/RA/
John G. Lamb, Senior Project Manager Plant Licensing Branch, II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation
Docket Nos.52-025 and 52-026
Enclosures:
- 1. List of Attendees
- 2. Background Information
cc w/encls: Distribution via Listserv LIST OF ATTENDEES
JANUARY 24, 2024, PRE-SUBMITTAL MEETING WITH SOUTHERN NUCLEAR COMPANY
REGARDING A PROPOSED RELIEF REQUEST
VOGTLE ELECTRIC GENERATING PLANT, UNITS 3 AND 4
ATTENDEE REPRESENTING
John G. Lamb U.S. Nuclear Regulatory Commission (NRC)
Mike Markley NRC Gordon Curran NRC Thomas Scarbrough NRC Mike Fitzgerald NRC Kerri Kavanagh NRC Cliff Roundtree NRC George Khouri NRC Brian Wittick NRC Jamie Heisserer NRC Gurjendra Bedi NRC
Keith Dorsey Southern Nuclear Operating Company (SNC)
Ken Lowery SNC Ryan Joyce SNC Eddie Grant SNC Steve Norman SNC William Garrett SNC Kyle Caver SNC Brian Coker SNC Chris Gasser SNC Betsy A. Moenkedick SNC
Enclosure 1 BACKGROUND INFORMATION
JANUARY 24, 2024, PRE-SUBMITTAL MEETING WITH SOUTHERN NUCLEAR COMPANY
REGARDING A PROPOSED ALTERNATIVE REQUEST
VOGTLE ELECTRIC GENERATING PLANT, UNITS 3 AND 4
By letter dated March 26, 2019 (ML19071A237), the NRC granted an alternative, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(z)(1), to the requirements of the American Society of Mechanical Engineers (ASME) Operation and Maintenance of Nuclear Power Plants, Division 1, OM Code: Section IST (OM Code) associated with preservice testing (PST) of pyrotechnic-actuated (squib) valves at the Vogtle, Units 3 and 4. In particular, the NRC granted the SNC request to implement a proposed alternative to specific provisions of the ASME OM Code as incorporated by reference in 10 CFR 50.55a in request PST-Alt-01 on the basis that the alternative provides an acceptable level of quality and safety pursuant to subparagraph (1), Acceptable level of quality and safety, in paragraph (z), Alternatives to codes and standards requirements, of 10 CFR 50.55a. The NRC granted the alternative PST requirements to SNC for the squib valves as follows: (a) select a sample of pyrotechnic charges, following fabrication for testing; this may include charges used for qualification of the batch; (b) the sample shall include a quantity of charges equal to at least 20 percent of the number of charges of each size installed in the plant and shall include at least one from each manufacturer batch as described in its table provided with the alternative request; and (c) 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 NRC letter and safety evaluation dated March 26, 2019 (ML19071A237) states:
The 14-inch squib valves in the Automatic Depressurization System (ADS) in VEGP [Vogtle Electric Generating Plant] Units 3 and 4 perform safety-related functions to open as part of the phased depressurization of the reactor coolant system [RCS] in AP1000 reactors to allow the gravity-driven Passive Core Cooling System (PXS) to provide cooling of the reactor core. The 8-inch PXS squib valves in VEGP Units 3 and 4 perform safety-related functions to open (1) to allow cooling water to be supplied to the reactor core from the in-containment refueling water storage tank; and (2) to allow recirculation of water from the containment sump to the reactor vessel for long-term core cooling.
These safety-related squib valves are included in the PST and IST program at VEGP Units 3 and 4.
The squib valve is a completely static electromechanical assembly. Prior to activation, there are no moving parts. No powered components are needed to hold a stem seat or globe in place by torque, solenoid coils, or friction. The explosive actuator is a simple, passive device that is triggered by an applied voltage. Explosively actuated valves have shear caps and are actuated by an explosive charge fired by an electrical signal.
Enclosure 2
VALVE NUMBER VALVE NAME RCS-V004A Automatic Depressurization System (ADS) Stage 4 Valves RCS-V004B ADS Stage 4 Valves RCS-V004C ADS Stage 4 Valves RCS-V004D ADS Stage 4 Valves PXS-V118A Containment Recirculation Sump s to Reactor Coolant System (RCS)
Actuation Squib Valves PXS-V118B Containment Recirculation Sumps to RCS Actuation Squib Valves PXS-V120A Containment Recirculation Sumps to RCS Actuation Squib Valves PXS-V120B Containment Recirculation Sumps to RCS Actuation Squib Valves PXS-V123A In-Containment Refueling Water Storage Tank (IRWST) Injection Isolation Valves PXS-V123B IRWST Injection Isolation Valves PXS-V125A IRWST Injection Isolation Valves PXS-V125B IRWST Injection Isolation Valves
The UFSAR Section 5.4.6, Automatic Depressurization System Valves (ML23165A215), states:
The automatic depressurization system (ADS) valves are part of the reactor coolant system and interface with the passive core cooling system (PXS). Twenty valves are divided into four depressurization stages. These stages connect to the reactor coolant system at three different locations. The automatic depressurization system first, second, and third stage valves are included as part of the pressurizer safety and relief valve (PSARV) module and are connected to nozzles on top of the pressurizer. The fourth stage valves connect to the hot leg of each reactor coolant loop. The reactor coolant system P&ID [Piping and Instrumentation Diagram], Figure 5.1-5, shows the arrangement of the valves.
Opening of the automatic depressurization system valves is required for the passive core cooling system to functi on as required to provide emergency core cooling following postulated accident conditions. Operation of the passive core cooling system, including setpoints for the opening of the automatic depressurization system valves is discussed in Section 6.3.
The UFSAR Section 6.3, Passive Core Cooling System (ML23165A215), states:
The primary function of the passive core cooling system is to provide emergency core cooling following postulated design basis events. To accomplish this primary function, the passive core cooling system is designed to perform the following functions:
Emergency core decay heat removal
Provide core decay heat removal during transients, accidents or whenever the normal heat removal paths are lost. This heat removal function is available at reactor coolant system conditions including shutdowns. During refueling operations, when the IRWST [In-containment Refueling Water Storage Tank] is drained into the refueling cavity, other
passive means of core decay heat removal are utilized. Subsection 6.3.3.4.4 provides a description of how this is accomplished.
Reactor coolant system emergency makeup and boration
Provide reactor coolant system makeup and boration during transients or accidents when the normal reactor coolant system makeup supply from the chemical and volume control system is unavailable or is insufficient.
Safety injection
Provide safety injection to the reactor coolant system to provide adequate core cooling for the complete range of loss of coolant accidents, up to and including the double-ended rupture of the largest primary loop reactor coolant system piping.
Containment pH control
Provide for chemical addition to the containment during post-accident conditions to establish floodup chemistry conditions that support radionuclide retention with high radioactivity in containment and to prevent corrosion of containment equipment during long-term floodup conditions.
The UFSAR Section 19F.4.3, Core Cooling and Containment Integrity (ML23165A215),
states:
If necessary, core cooling can be maintained by actuating the passive safety injection portion of the Passive Core Cooling System (PXS) and Reactor Coolant System (RCS) as described in Section 6.3. The portions of the PXS and RCS required for safety injection are located inside containment and are key design features. Their location protects them from damage due to an aircraft impact because the containment vessel remains intact and has no structural damage.
The following valves are key design features and need to actuate for passive safety injection and recirculation for long-term core cooling:
ADS Stage 4 squib valves, RCS-V004A/B/C/D (3 of 4)
In-containment refueling water storage tank (IRWST) injection line squib valves, PXS-V123A/B and PXS-V125A/B (1 of 4)
Recirculation line squib valves, PXS-V118A/B and PXS-V120A/B (1 of 4)
The Updated Final Safety Analysis Report (UFSAR) Section 5.4.8.3, Design Evaluation (ML23165A215), states:
Qualification testing of each power operated valve which includes motor-operated, air operated, hydraulic operated, solenoid operated and explosive actuated valves demonstrates the capability of the operator to operate over the full range of expected plant operating conditions. Qualification testing also
demonstrates the closing, opening, and seating capability of the valve against the maximum pressure differential and flow within a specified time over the entire operating range. Requirements for qualification testing of power-operated active valves are based on ASME QME-1 (Reference 8). The testing programs in Section 3.10 demonstrate the capability of the valves to operate, as required, during anticipated and postulated plant conditions.
The UFSAR Section 13.6, Security (ML23165A215), states:
The explosive cartridge assembly used in the squib valves (see Subsection 6.3.2.2.8.9) has been determined by the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) to be exempt (Reference 5 - [ WCAP-17938 (P-A/NP-A),
Revision 3, June 2018 ] from the requirements of 27 CFR 555 as special explosive devices pursuant to 27 CFR 555.32 for possession and use for their intended purpose in the AP1000 nuclear reactor passive safety system.
However, the explosive materials used in their manufacture are subject to the provisions of 27 CFR, Part 555. Thus, any alterations to the explosive cartridge assembly will render this exemption void and any explosive materials removed from the explosive cartridge assembly are subject to the regulations of 27 CFR 555.
ML24022A109 (Package)
ML23349A074 (Meeting Notice)
ML24025A137 (Meeting Summary)
ML24022A119 (Slides)
OFFICE DORL/LPL2-1/PM DORL/LPL2-1/LA DEX/EMIB/BC DORL/LPL2-1/BC DORL/LPL2-1/PM NAME JLamb KGoldstein SBailey MMarkley JLamb DATE 01/24/2024 01/26/2024 01/25/2024 01/31/2024 01/31/2024