05200025/LER-2022-002-01, Automatic Depressurization System Stage 4 Flow Paths Inoperable During Mode 6 with Upper Internals in Place Due to Inadequate Work Processes
| ML23034A235 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 02/03/2023 |
| From: | Martino P Southern Nuclear Operating Co |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| ND-23-0001 LER 22-002-01 | |
| Download: ML23034A235 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(v), Loss of Safety Function |
| 0252022002R01 - NRC Website | |
text
3/4e, Southern Nuclear Docket No.:
52-025 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Patrick Martino Site Vice President, Vogtle Unit 3 7825 River Road Waynesboro, Georgia 30830 706 848 6602 tel ND-23-0001 10 CFR 50. 73(a)(2)(i)(B) 10 CFR 50. 73(a)(2)(v)(D) 10 CFR 50.73(a)(2)(vii)(D)
Southern Nuclear Operating Company Vogtle Electric Generating Plant (VEGP) - Unit 3 Licensee Event Report 2022-002-01 Automatic Depressurization System Stage 4 Flow Paths Inoperable During Mode 6 with Upper Internals in Place Due to Inadequate Work Processes Ladies and Gentlemen:
In accordance with the requirements of 10 CFR 50.73(a)(2)(i)(B), 10 CFR 50.73(a)(2)(v)(D), and 10 CFR 50.73(a)(2)(vii)(D), Southern Nuclear Operating Company is submitting the enclosed revised Licensee Event Report for VEGP Unit 3.
This revision adds reporting criterion under 10 CFR 50.73(a)(2)(vii)(D).
This letter contains no regulatory commitments. If you have questions regarding the enclosed information, please contact Will Garrett at (706) 848-7154.
Respectfully submitted, Patrick A. Martino Site Vice President, Unit 3 PAM/NBC/sfr
Enclosure:
Revised Unit 3 Licensee Event Report 2022-002-01 February 3, 2023
~ Southern Nuclear cc:
Regional Administrator, Region II VPO Project Manager Senior Resident Inspector - Vogtle 3 & 4 Patrick Martino Site Vice President, Vogtle Unit 3 Director, Environmental Protection Division - State of Georgia 7825 River Road Waynesboro, Georgia 30830 706 848 6602 tel
Vogtle Electric Generating Plant - Unit 3 Licensee Event Report 2022-002-01 Automatic Depressurization System Stage 4 Flow Paths Inoperable During Mode 6 with Upper Internals in Place Due to Inadequate Work Processes Enclosure Revised Unit 3 Licensee Event Report 2022-002-01
Abstract
On October 23, 2022, at 0405 EDT with Vogtle Electric Generating Plant (VEGP) Unit 3 in Mode 6 at O percent power, the Automatic Depressurization System (ADS) Stage 4 Squib Valve Component Interface Modules (CIMs) were discovered in "local" control while preparing to return ADS Stage 4 Division A to service, which rendered the associated ADS Stage 4 flow paths inoperable. The operators responded timely by placing all ADS Stage 4 Squib Valve CIMs in "remote" to restore operability to the ADS Stage 4 flow paths. The root cause of the event was inadequate work processes. The corrective actions completed for this event include revision of the mode change checklist procedure GOP-301 and reinforcement of configuration management with maintenance work planners. This event is reportable under 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by Technical Specifications, 10 CFR 50.73(a)(2)(v)(D) as a condition that could have prevented the fulfillment of the safety function, and 10 CFR 50. 73(a)(2)(vii)(D) as an event where a single cause or condition caused at least two independent trains or channels to become inoperable in a single system designed to mitigate the consequences of an accident. VEGP Units 1, 2, and 4 were unaffected by this event.
EVENT DESCRIPTION
I
- 2. DOCKET NUMBER
- 3. LER NUMBER I YEAR SEQUENTIAL REV 00025 NUMBER NO.
12022 -I 002 1-0 On October 23, 2022, at 0405 EDT with Vogtle Electric Generating Plant (VEGP) Unit 3 in Mode 6 at O percent power, the Automatic Depressurization System (ADS) Stage 4 Squib Valve [EIIS: AB/ V] Component Interface Modules (CIMs) [EIIS:
JE / IMOD] were discovered in "local" control, which rendered the associated ADS Stage 4 flow paths inoperable. Based on the Cl Ms being in "local," the ADS Stage 4 valves were inoperable when the unit entered the mode of applicability for Technical Specifications (TS) Limiting Condition for Operation (LCO) 3.4.13. The applicability of TS LCO 3.4.13 is Mode 6 with upper internals in place, which occurred on October 22, 2022, at 1430 hours0.0166 days <br />0.397 hours <br />0.00236 weeks <br />5.44115e-4 months <br />. Therefore, the placement of the upper internals resulted in the unit being in a condition prohibited by the TS, because TS 3.4.13 requires three flow paths in ADS Stage 4 to be operable in Mode 6 with the upper internals in place. The CIMs had been previously placed in "local" control for installation of the ADS Stage 4 squib valve actuator cartridges. The ADS Stage 4 Cl Ms being in "local" control was discovered while preparing to return ADS Stage 4 Division A to service on October 23, 2022. The Cl Ms being in "local" control would have prevented the automatic open function for these valves. This resulted in a condition where no Stage 4 ADS flow paths were operable during plant conditions that required at least three operable flow paths (i.e., Mode 6 with Upper Internals in place in accordance with TS 3.4.13). The operators responded timely by placing the CIMs in "remote" for ADS Stage 4 Divisions A and Cat 0432 EDT, and the CIMs for Divisions Band D were placed in "remote" at 0447 EDT, which restored operability to the required ADS Stage 4 flow paths and established compliance with the TS LCO 3.4.13. This event is reportable under 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by Technical Specifications, 10 CFR 50.73(a)(2)(v)(D) as a Safety System Functional Failure (SSFF), and 10 CFR 50.73(a)(2)(vii)(D) as an event where a single cause or condition caused at least two independent trains or channels to become inoperable in a single system designed to mitigate the consequences of an accident.
EVENT ANALYSIS
The root cause of this event was determined to be inadequate work processes. Procedures did not include a step to check CIM configuration prior to mode changes and procedural guidance was not in place to identify CIM status as part of TS compliance verification. Additionally, maintenance work control documents did not address restoration of the Cl Ms.
REPORTABILITY AND SAFETY ASSESSMENT
There were no safety consequences due to this event because during the time that the ADS Stage 4 flow paths were inoperable, there was no irradiated fuel in the core and no decay heat present. No radiological release occurred due to this event. Under alternate conditions, such as the presence of decay heat, manual actuation of ADS Stage 4 via the Diverse Actuation System (DAS) could have been utilized to open the valves. This event is reportable under 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by Technical Specifications, 10 CFR 50.73(a)(2)(v)(D) as a condition that could have prevented the fulfillment of the safety function, due to the condition of having no ADS Stage 4 flow paths operable during the TS mode of applicability, and 10 CFR 50. 73(a)(2)(vii)(D) as an event where a single cause or condition caused at least two independent trains or channels to become inoperable in a single system designed to mitigate the consequences of an accident.
CORRECTIVE ACTIONS COMPLETED
- The mode change checklist procedure GOP-301 was revised to check CIM configuration prior to entry into applicable modes.
- Reinforced with Planning and Procedure writers the importance and process for ensuring configuration control is restored to normal position.
PREVIOUS SIMILAR EVENTS
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