05000388/LER-2019-002, Valid Actuation of the Primary Containment Isolation System Due to a Trip of Reactor Protection System Bus 2B
| ML19234A257 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 08/22/2019 |
| From: | Cimorelli K Susquehanna, Talen Energy |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| PLA-7807 LER 2019-002-00 | |
| Download: ML19234A257 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(iv)(B), System Actuation 10 CFR 50.73(a)(2)(iv)(B)(2) |
| 3882019002R00 - NRC Website | |
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Kevin Cimorelli Site Vice President Attn: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 Susquehanna Nuclear, LLC 769 Salem Boulevard Berwick, PA 18603 Tel. 570.542.3795 Fax 570.542.1504 Kevin.Cimorelli@TalenEnergy.com SUSQUEHANNA STEAM ELECTRIC STATION LICENSEE EVENT REPORT 50-388/2019-002-00 UNIT 2 LICENSE NO. NPF-22 PLA-7807 TALEN~
ENERGY 10 CFR 50.73 AUG 2 2 2019 Docket No. 50-388 Attached is Licensee Event Report (LER) 50-388/2019-002-00. This LER is reporting a condition in which there was a loss of the Unit 2 B Reactor Protection System Bus, which resulted in a valid actuation of the Primary Containment Isolation System. This condition was determined to be reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A) as a valid actuation of a system identified in 10 CFR 50.73(a)(2)(iv)(B). There were no actual consequences to the health and safety of the public as a result of this event.
This letter contains no new or revised regulatory commitments.
Attachment: LER 50-388/2019-002-00 Copy:
NRC Region I Ms. L. H. Micewski, NRC Sr. Resident Inspector Ms. T. E. Hood, NRC Project Manager Mr. M. Shields, PA DEP/BRP
NRC FORM 366 (04-2018)
NRC FORM 366 (04-2018)
U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
LICENSEE EVENT REPORT (LER)
(See Page 2 for required number of digits/characters for each block)
(See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/)
- 1. Facility Name Susquehanna Steam Electric Station Unit 2
- 2. Docket Number 05000388
- 3. Page 1 OF 3
- 4. Title Valid Actuation of the Primary Containment Isolation System due to a Trip of Reactor Protection System Bus 2B
- 5. Event Date
- 6. LER Number
- 7. Report Date
- 8. Other Facilities Involved Month Day Year Year Sequential Number Rev No.
Month Day Year Facility Name Docket Number 05000 06 27 2019 2019 002 00 08 22 2019 Facility Name Docket Number 05000
- 9. Operating Mode 1
)
No Abstract (Limit to 1400 spaces, i.e., approximately 14 single-spaced typewritten lines)
On June 27, 2019, at 0937 a half scram signal was received on Unit 2, Division 2 of the Reactor Protection System (RPS). The half scram signal resulted in a trip of the 2B RPS instrument bus, a trip of the 2A Residual Heat Removal Service Water (RHRSW) Pump, a loss of the 2A and 2B Containment Radiation Monitors (CRMs), and Primary Containment Isolation System (PCIS) actuations. The loss of both CRMs resulted in entering Condition B of Technical Specifications (TS) Limiting Condition for Operation (LCO) 3.4.6, RCS Leakage Detection Instrumentation. The PCIS actuation resulted in isolation of containment isolation valves in multiple systems and was determined to be reportable in accordance with 10 CFR 50.72(b)(3)(iv)(A) for the valid isolation signal. The 2B RPS instrument bus was transferred to its alternate power supply and the 2A and 2B CRMs were restored. The 2B RPS instrument bus was realigned to its normal source on July 2, 2019. The condition was also determined to be reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A) for the valid PCIS signal.
The event was determined to be caused by an age-related failure of a control relay on the normal power supply to the 2B RPS instrument bus. Corrective actions included replacing the failed relay.
There were no actual safety consequences associated with the condition.
CONDITIONS PRIOR TO EVENT
Unit 1 - Mode 1, approximately 100 percent Rated Thermal Power Unit 2 - Mode 1, approximately 100 percent Rated Thermal Power There were no structures, systems, or components that were inoperable at the start of the event that contributed to the event.
EVENT DESCRIPTION
On June 27, 2019, at approximately 0937, a half scram signal was received on Susquehanna Steam Electric Station (SSES) Unit 2, Division 2 of the RPS [EIIS Code: JC]. Concurrently, operators were performing SO-216-A03, Quarterly Residual Heat Removal Service Water (RHRSW) System Flow Verification Division I, The half scram signal resulted in a trip of the 2B RPS instrument bus, a trip of the 2A RHRSW Pump [EIIS System / Component Code: BO/P], a loss of the 2A and 2B CRMs [EIIS System / Component Code: IL / MON], and PCIS [EIIS Code: JM] actuations. The loss of both CRMs resulted in entering Condition B of SSES TS LCO 3.4.6, RCS Leakage Detection Instrumentation. The 2B RPS instrument bus was transferred to its alternate power supply at 0941 and the 2A and 2B CRMs were restored at 0956 and 0959, respectively; Condition B of LCO 3.4.6 was exited at 1000; all TS Completion Times were met.
Upon tripping the 2B RPS instrument bus, SSES personnel performed troubleshooting on the normal power supply to the bus. It was determined that Control Relay 2Y201BC72BK1B [Component Code: RLY]
(hereafter referred to as the K1B relay) failed. The K1B relay was replaced and SSES personnel restored the 2B RPS instrument bus to its normal source on July 2, 2019.
The PCIS actuations resulted in isolations of multiple systems as designed. As a result, this condition was determined to be reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A) as an event that resulted in automatic actuation of a system as identified in 10 CFR 50.73(a)(2)(iv)(B)(2).
CAUSE OF EVENT
The direct cause of the event was determined to be an age-related failure of the K1B relay.
ANALYSIS/SAFETY SIGNIFICANCE
Failure of the K1B relay caused a loss of power to one of two power distribution systems of the B RPS. The RPS is one out of two taken twice logic. The loss of power resulted in a valid isolation signal on the B logic division. This response is consistent with the safety analysis. Since the plant response was as designed, all accident functions would have been met. Therefore, there was no loss of safety function. Accordingly, this event will not be counted as a safety system functional failure in the Reactor Oversight Process Performance Indicators.
Page 3 of 3 (04-2018)
U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET (See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/)
- 3. LER NUMBER Susquehanna Steam Electric Station Unit 2 05000-388 YEAR SEQUENTIAL NUMBER REV NO.
2019 002 00 There were no actual consequences to the health and safety of the public as a result of this event.
CORRECTIVE ACTIONS
Corrective actions included replacement of the K1B relay.
COMPONENT FAILURE INFORMATION
Component Identification - 2Y201BC72BK1B Component Name - B RPS Normal Power Contactor Component Manufacturer - GE Relay Type - GE Type CR305 Relay Manufacturer Part Number - 117C2491P002
PREVIOUS OCCURRENCES
LER 50-388(387)/2000-005-01, ESF Actuations Due to RPS EPA Breaker Trip, dated March 25, 2003 LER 50-388/2000-003-00, Inadvertent ESF Actuation Caused by Loss of RPS Power Supply, dated August 2, 2000