05000458/LER-2022-004, High Pressure Core Spray Inoperable Due to Transformer Failure
| ML22321A306 | |
| Person / Time | |
|---|---|
| Site: | River Bend  |
| Issue date: | 11/17/2022 |
| From: | Karenina Scott Entergy Nuclear Operations |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| RBG-48203 LER 2022-04-00 | |
| Download: ML22321A306 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v), Loss of Safety Function |
| 4582022004R00 - NRC Website | |
text
- ) entergy RBG-48203 Kent Scott Site Vice President 225-381-437 4 10 CFR 50.73 November 17, 2022 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001
Subject:
Licensee Event Report 50-458 / 2022-04-00, High Pressure Core Spray Inoperable due to Transformer Failure River Bend Station - Unit 1 NRC Docket Nos. 50-458 Renewed Facility Operating License No. NPF-47 In accordance with 10 CFR 50.73, enclosed is the subject Licensee Event Report.
This document contains no commitments.
Should you have any questions, please contact Mr. Tim Schenk, Regulatory Assurance Manager, at 225-381-4177.
RespectfullY, KCS/dmw
Enclosure:
cc:
Licensee Event Report 50-458 / 2022-04-00, High Pressure Core Spray Inoperable due to Transformer Failure NRC Region IV Regional Administrator - Region IV NRC Senior Resident Inspector-River Bend Station NRC Project Manager - River Bend Station Entergy Nuclear Operations, Inc., River Bend Station, 5485 U.S. Highway 61, St. Francisville, LA 70775
Enclosure RBG-48203 Licensee Event Report 50-458 / 2022-04-00, High Pressure Core Spray Inoperable due to Transformer Failure Entergy Nuclear Operations, Inc., River Bend Station, 5485 U.S. Highway 61, St. Francisville, LA 70775
Abstract
At 0132 CDT on September 19, 2022, River Bend Station (RBS) was operating at 100% power when the High Pressure Core Spray System (HPCS) was declared inoperable due to a transformer fault that occurred during Division Ill Standby Diesel Generator monthly surveillance testing. RBS entered Technical Specification 3.8.9, Condition E and declared HPCS and Standby Service Water System Pump 2C (SWP-P2C) inoperable. Reactor Core Isolation Cooling (RCIC) was verified operable. HPCS is a single train system at RBS, therefore an 8-hour report was submitted in accordance with 10 CFR 50.72(b)(3)(v)(D) as an event or condition that could have prevented the fulfilment of a safety function (EN 56116). This event is also being reported in accordance with 10 CFR 50.73(a)(2)(v)(D) as an event or condition that could have prevented the fulfilment of a safety function.
The condition was corrected by replacing the transformer on September 30, 2022. HPCS and SWP-P2C were restored to operable at 0921 CDT on September 30, 2022.
EVENT DESCRIPTION
At 0132 CDT on September 19, 2022, River Bend Station (RBS) was operating at 100% power. There were no other inoperable structures, systems, or components (SSCs) that contributed to this event. The Division Ill Diesel Generator [DG] was started per STP-309-0203, DIVISION Ill DIESEL GENERATOR OPERABILITY TEST. Approximately 5 seconds later the Main Control Room received multiple alarms on Division 3 components. The field operator performed a visual inspection of the Division Ill switchgear and discovered that the E22-S003, HPCS TRANSFORMER [XFMR] was damaged. The Division Ill Diesel Generator was secured and placed in maintenance mode.
The transformer failure caused a loss of power to E22-S002, Division Ill 480 VAC switchgear [SWGR]. E22-S002, Division Ill 480 VAC switchgear supplies power to HPCS motor operated valves that are required to align flow to the reactor pressure vessel following system initiation. RBS entered Technical Specification (TS) 3.8.9, Condition E and immediately declared the High Pressure Core Spray System (HPCS) [BG] and Standby Service Water System Pump 2C (SWP-P2C) [P] inoperable. This also placed RBS in a 14-day TS LCO shutdown action statement due to the inoperability of HPCS. Reactor Core Isolation Cooling (RCIC) [BN] was verified operable.
Visual inspection revealed that the transformer most likely suffered a phase-to-phase fault caused by spare conductors landing on top of the transformer core. On June 21, 2022, Preventive Work Order 53003640 was performed on the transformer. No signs of degradation were noted, and all acceptance criteria were met satisfactory. The work order task has steps to remove all transformer panels and detailed inspection criteria.
However, due to the design of the cabinet, the cabinet cover is not removable during the inspection. This prevented observation of the spare cables. Following the completion of the preventive work and prior to the transformer fault, STP-309-0203, DIVISION Ill DIESEL GENERATOR OPERABILITY TEST was successfully completed on July 25, 2022, and again on August 22, 2022.
Prior to this event HPCS and the Division 3 Transformer power source were operable. At time of discovery, the HPCS lost its initiation capability because the E22-S002, Division Ill 480 VAC switchgear would not have been powered from the Division Ill Standby Diesel Generator on any HPCS initiation signal. HPCS was inoperable and incapable of performing its design function during this event. RBS is reporting the event in accordance with 10 CFR 50.73(a)(2)(v)(D) as an event or condition that could have prevented the fulfilment of a safety function.
SAFETY ASSESMENT The RBS UFSAR states that in the event of a HPCS system failure such that HPCS cannot maintain reactor water level, the Automatic Depressurization System (ADS), which is independent of any other Emergency Core Cooling System (ECCS), reduces the reactor pressure so that flow from Low Pressure Coolant Injection (LPCI) [BO] and Low Pressure Core Spray (LPCS) [BM] systems enters the reactor vessel in time to cool the core and limit fuel cladding temperature.
Additionally, high pressure makeup was available from RCIC. Two of three divisions of ECCS are required for the RBS loss of coolant accident analysis. While HPCS was out of service, Division 1 ECCS and Division 2 ECCS systems and ADS were operable and would have met the ECCS performance criteria of 1 0CFR50.46. The out of service time was maintained within the limits of RBS Technical Specifications.
There were no actual Nuclear or Radiological safety consequences due to this event. This event was of minimal significance to the health and safety of the public.
NRC FOAM 366A (08-2020)
Page 2 of 3 (08-2020)
U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 08/31/2023 r~_4 *\\
\\~/j LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET (See NUREG-1022, R.3 for instruction and guidance for completing this fonn https://www.nrc.gov/reading-nn/doc-collections/nuregs/staff/sr1022/@
- 3. LEA NUMBER YEAR River Bend Station, Unit 1 05000-458 2022
EVENT CAUSE
SEQUENTIAL NUMBER 004 REV NO.
00 Visual inspection revealed that the transformer most likely suffered a phase-to-phase fault caused by spare conductors landing on top of the transformer core. The spare conductors were not properly secured, taped, and coiled during construction.
CORRECTIVE ACTIONS
Complete:
Replacement transformer was installed with a Temporary Modification Engineering Change and all wiring was verified to be properly secured.
Planned actions tracked in the Corrective Action Program:
- 1.
Perform an Extent of Condition to identify any spaces or compartments in the other existing installed dry type transformers that could not be accessed while performing preventive maintenance.
- 2. Accept the Temporary Modification that installed the replacement transformer as a permanent installation.
- 3. Purchase a new transformer for use as a spare.
- 4. Perform a Failure Analysis to confirm the cause of the transformer fault.
PREVIOUS SIMILAR EVENTS
None NOTE:
Energy Industry Identification System and Component Function Identification codes are identified in the text of this.report following the first mention of the system or component as [XX]. Page 3 of 3