05000412/LER-2021-002, Unit 2, Automatic Reactor Trip and Automatic Actuation of the Auxiliary Feedwater System
| ML21337A224 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 12/03/2021 |
| From: | Grabnar J Energy Harbor Nuclear Corp |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| L-21-272 LER 2021-002-00 | |
| Download: ML21337A224 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(iv)(B)(1) 10 CFR 50.73(a)(2) 10 CFR 50.73(a)(2)(iv)(B)(6) |
| 4122021002R00 - NRC Website | |
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energy harbor John J. Grabnar Site Vice President December 3, 2021 L-21-272 ATTN: Document Control Desk U. S. Nuclear Regulatory Commission Washington, DC 20555-0001
SUBJECT:
Beaver Valley Power Station, Unit No. 2 Docket No. 50-412, License No. NPF-73 LER 2021-002-00 10 CFR 50.73 Beaver Valley Power Station P.O. Box 4 Shippingport, PA 15077 724-682-5234 Fax: 724-643-8069 Enclosed is Licensee Event Report (LER) 2021-002-00, "Unit 2 Automatic Reactor Trip and Automatic Actuation of the Auxiliary Feedwater System." This event is being reported in accordance with 10 CFR 50.73(a)(2)(iv)(A).
There are no regulatory commitments contained in this submittal. Any actions described in this document represent intended or planned actions and are described for information only.
If there are any questions or if additional information is required, please contact Mr. Steve Sawtschenko, Manager, Regulatory Compliance and Emergency Response, at 724-682-4284.
Sincerely, John J. Grabnar Enclosure: Beaver Valley Power Station, Unit 2 LER 2021-002-00 cc:
Mr. D. C. Lew, NRC Region I Administrator NRC Senior Resident Inspector Ms. S. Goetz, NRC Project Manager INPO Records Center (via INPO Industry Reporting and Information System)
Mr. L. Winker (BRP/DEP)
FOR INTERNAL DISTRIBUTION USE ONLY Internal Distribution of Letter L-21-272 H. E. Gilliam J. A. Hartig B. D. Kremer
Enclosure L-21-272 Beaver Valley Power Station, Unit 2 LER 2021-002-00
Abstract
Beaver Valley Power Station, Unit 2 412 3
Unit 2 Automatic Reactor Trip and Automatic Actuation of the Auxiliary Feedwater System 10 05 2021 2021 002 00 12 03 2021 1
90 Steve Sawtschenko, Manager, Regulatory Compliance and Emergency Response 724-682-4284 B
JG IMOD W120 Y
At 0632 on October 5, 2021, Beaver Valley Power Station, Unit 2 (BVPS-2) automatically tripped due to a loss of the Reactor Trip System Interlock for Power Range Neutron Flux (P-10) and associated power range trip block signals. BVPS-2 was at approximately 90% power and in an end of cycle coast down. The Auxiliary Feedwater System automatically started as designed. The apparent cause was a premature failure of a Train A Solid State Protection System (SSPS) universal logic board (ULB) due to manufacturing defects with the solder joints which may have resulted in an intermittent loss of connection.
This is reportable under 10 CFR 50.73(a)(2)(iv)(A) as an event that resulted in automatic actuation of the Reactor Protection System per 10 CFR 50.73(a)(2)(iv)(B)(1) and an automatic actuation of the Auxiliary Feedwater System per 10 CFR 50.73(a)(2)
(iv)(B)(6). Corrective actions include replacement of the ULB, vendor testing of several ULBs within the SSPS, review of the final vendor test report for additional actions, and establishment of maintenance plans for periodic testing of the SSPS ULBs at both units.
Energy Industry Identification System (EIIS) codes are identified in the text as [XX].
BACKGROUND The Solid State Protection System (SSPS) [JG] takes binary inputs (voltage/no voltage) from the process and nuclear instrument channels corresponding to conditions (normal/abnormal) of BVPS-2 parameters. The SSPS performs the decision logic for actuating a reactor trip or ESF actuation, generates the electrical output signal that will initiate the required trip or actuation, and provides the status, permissive, and annunciator output signals to the main control room of the unit.
DESCRIPTION OF EVENT
At 0632 on October 5, 2021, BVPS-2 automatically tripped with an initial annunciator indication of a Power Range Low Setpoint Neutron Flux High Reactor Trip. BVPS-2 was at approximately 90% power and in an end of cycle coast down. No equipment was inoperable at the start of the event that would have contributed to the event. The Auxiliary Feedwater System [BA] automatically started as designed. The trip was not complicated and the plant was stabilized in Mode 3.
The trip was caused by an intermittent internal failure of the SSPS, specifically the loss of the reactor trip system interlock for power range neutron flux (P-10) and associated power range trip block signals. Troubleshooting was performed and three universal logic boards (ULBs) were replaced. Following the replacement, the SSPS was returned to service and BVPS-2 was put back online on October 8, 2021. The replaced ULBs along with several additional extent of condition ULBs from within both trains of the SSPS system were sent to Westinghouse for Westinghouse Automated Board Test System (WABTS) testing. The testing identified deficiencies in some of the ULBs.
CAUSE OF EVENT
Based on review of the Sequence of Events Log, the trip was generated within the Train A SSPS due to a loss of the reactor trip system interlock for power range neutron flux (P-10) and associated power range trip block signals. The direct cause of the trip was determined to be an internal failure of the A403 SSPS ULB. The apparent cause was a premature failure of the Train A SSPS ULB due to manufacturing defects with the solder joints which may have resulted in an intermittent loss of connection.
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Beaver Valley Power Station, Unit 2 412 2021 002 00Page of 05000-
- 3. LER NUMBER YEAR SEQUENTIAL NUMBER REV NO.
ANALYSIS OF EVENT
This is reportable under 10 CFR 50.73(a)(2)(iv)(A) as an event that resulted in automatic actuation of the Reactor Protection System per 10 CFR 50.73(a)(2)(iv)(B)(1) and an automatic actuation of the Auxiliary Feedwater System per 10 CFR 50.73(a)(2)(iv)(B)(6).
The plant risk associated with the BVPS-2 reactor trip on October 5, 2021, is considered to be very low. This is based on the change in average core damage frequency derived using the conditional core damage probability and change in average large early release frequency derived using conditional large early release probability for the event.
CORRECTIVE ACTIONS
Completed Actions:
The 3 suspect SSPS ULBs were replaced and sent for WABTS testing.
An additional 15 ULBs from both trains of SSPS were replaced and sent for WABTS testing as extent of condition.
Planned Actions:
The final Westinghouse WABTS test reports will be evaluated for additional actions that may be necessary based on the reports findings.
Periodic WABTS testing maintenance plans for both units will be established at an appropriate frequency.
PREVIOUS SIMILAR EVENTS
A review of the previous three years did not identify similar events that have occurred at BVPS.
CR 2021-07409 3
3 Beaver Valley Power Station, Unit 2 412 2021 002 00