05000458/LER-2016-002, Regarding Automatic Reactor Scram and Division 2 Primary Containment Isolation Due to Offsite Grid Electrical Transient
| ML16084A143 | |
| Person / Time | |
|---|---|
| Site: | River Bend  |
| Issue date: | 03/07/2016 |
| From: | Vazquez S Entergy Operations |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| RBG-47661 LER 16-002-00 | |
| Download: ML16084A143 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 4582016002R00 - NRC Website | |
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- ===-Entergy RBG-47661 March 7, 2016 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555
Subject:
Licensee Event Report 50-458 I 2016-002-00 River Bend Station - Unit 1 Docket No. 50-458 License No. NPF-47 RBf 1-16-0028
Dear Sir or Madam:
Entergy Operations, Inc.
River Bend Station 5485 U.S. Highway 61 N St. Francisville, LA 70775 In accordance with 10 CFR 50. 73, enclosed is the subject Licensee Event Report.
This document contains no commitments. If you have any questions, please contact Mr. Joseph Clark at 225-381-4177.
Sincerely, Se~i::::C~
Director - Engineering Enclosure cc:
U. S. Nuclear Regulatory Commission Region IV 1600 East Lamar Blvd.
Arlington, TX 76011-4511
Licensee Event Report 50-458 I 2016-002-00 March 7, 2016 RBG-47661 Page 2 of 2 NRC Sr. Resident Inspector P. 0. Box 1050 St. Francisville, LA 70775 INPO (via ICES reporting)
Central Records Clerk Public Utility Commission of Texas 1701 N. Congress Ave.
Austin, TX 78711-3326 Department of Environmental Quality Office of Environmental Compliance Radiological Emergency Planning and Response Section Ji Young Wiley.
P.O. Box 4312 Baton Rouge, LA 70821-4312
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NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 01/31/2017 (02-2014)
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
YEAR
- 6. LER NUMBER I
SEQUENTIAL I REV NUMBER NO.
2016 002 00
- 3. PAGE 2
OF 3
On January 9, 2016, at approximately 2:37 a.m. CST, with the plant operating at 100 percent power, an automatic reactor scram occurred concurrent with the closure of all main steam isolation valves (MSIV s ). That action was the result of an electrical transient caused by *a phase-to-phase fault on a nearby 230kV transmission line. The transient caused a momentary decrease in the voltage on both reactor protection system busses, which also power the MSIV control solenoids. The Division 2 primary containment isolation logic was also actuated, causing the Division 2 valves in balance-of-plant systems.to close. Both divisions of the standby gas treatment system [BR] automatically started due to the shutdown of the normal annulus pressure control system. Both reactor recirculation [AD] pumps downshifted to slow speed.
- The initial upward swell of reactor water' level caused all three reactor feedwater pumps to trip. Reactor feedwater pump "C" was restarted approximately eight minutes after the scram.
Following the first automatic actuations of the reactor safety-relief valves (SRVs), operators controlled reactor pressure with intermittent manual opening of selected SRV s. After reactor parameters were stabilized, the MSIV s on the "D" main steam line were opened at approximately 4:29 a.m. to re-establish automatic pressure control.
The Division 1 and 2 reactor protection system (RPS) busses were on their alternate power supplies (i.e., offsite power) at the time of the event. No safety-related systems were out of service at the time. No plant parameter limits requiring the automatic actuation of any of the emergency core cooling systems or the emergency diesel generators were exceeded.
This event is being reported in accordance with 10 CFR 50.73(a)(2)(iv)(A) as the actuation of the reactor protection system [JC] and the primary containment isolation logic [JM].
INVESTIGATION and CAUSAL ANALYSIS The company's transmission department investigated the event. Although no definite source of the fault was found, it was concluded that a lightning strike likely caused the transient.. The fault occurred on a 230kV transmission line approximately three miles from the station. The fault lasted for 5.4 cycles before it was*isolated by automatic breaker action, and caused the voltage on the switchgear: 1 supplying the RPS busses to decrease to approximately 34 percent of normal. This transient was sufficient to trip the scram solenoids and the MSIV solenoids.
CORRECTIVE ACTIONS TO PREVENT RECURRENCE As of January 17, both divisions of the RPS system were running on their normal power sources (i.e., in-plant switchgear).
PREVIOUS OCCURRENCE*EVALUATION No reactor scrams resulting from grid transients have occurred at River Bend Station in the last three years.
SAFETY SIGNFICANCE LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET U.S. NUCLEAR REGULATORY COMMISSION
- 2. DOCKET
- 6. LER NUMBER
- 3. PAGE 3
OF YEAR I SEQUENTIAL I REV NUMBER NO.
05000 458 3
2016 002 00 The response of the plant was bounded by the corresponding section of the Updated Safety Analysis Report. No safety-related systems were out of service at the time of the event. No plant parameter limits requiring the automatic actuation of any of the emergency core cooling systems or the emergency diesel generators were exceeded. This event, thus, was of minimal significance to the health and safety of the public.
/
(NOTE: Energy Industry Identification System component function identifier and system name of each component or system referred to in the LER are annotated as (**XX**) and [XX], respectively.)
REPORIBD CONDITION
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
YEAR
- 6. LER NUMBER I
SEQUENTIAL I REV NUMBER NO.
2016 002 00
- 3. PAGE 2
OF 3
On January 9, 2016, at approximately 2:37 a.m. CST, with the plant operating at 100 percent power, an automatic reactor scram occurred concurrent with the closure of all main steam isolation valves (MSIV s ). That action was the result of an electrical transient caused by *a phase-to-phase fault on a nearby 230kV transmission line. The transient caused a momentary decrease in the voltage on both reactor protection system busses, which also power the MSIV control solenoids. The Division 2 primary containment isolation logic was also actuated, causing the Division 2 valves in balance-of-plant systems.to close. Both divisions of the standby gas treatment system [BR] automatically started due to the shutdown of the normal annulus pressure control system. Both reactor recirculation [AD] pumps downshifted to slow speed.
- The initial upward swell of reactor water' level caused all three reactor feedwater pumps to trip. Reactor feedwater pump "C" was restarted approximately eight minutes after the scram.
Following the first automatic actuations of the reactor safety-relief valves (SRVs), operators controlled reactor pressure with intermittent manual opening of selected SRV s. After reactor parameters were stabilized, the MSIV s on the "D" main steam line were opened at approximately 4:29 a.m. to re-establish automatic pressure control.
The Division 1 and 2 reactor protection system (RPS) busses were on their alternate power supplies (i.e., offsite power) at the time of the event. No safety-related systems were out of service at the time. No plant parameter limits requiring the automatic actuation of any of the emergency core cooling systems or the emergency diesel generators were exceeded.
This event is being reported in accordance with 10 CFR 50.73(a)(2)(iv)(A) as the actuation of the reactor protection system [JC] and the primary containment isolation logic [JM].
INVESTIGATION and CAUSAL ANALYSIS The company's transmission department investigated the event. Although no definite source of the fault was found, it was concluded that a lightning strike likely caused the transient.. The fault occurred on a 230kV transmission line approximately three miles from the station. The fault lasted for 5.4 cycles before it was*isolated by automatic breaker action, and caused the voltage on the switchgear: 1 supplying the RPS busses to decrease to approximately 34 percent of normal. This transient was sufficient to trip the scram solenoids and the MSIV solenoids.
CORRECTIVE ACTIONS TO PREVENT RECURRENCE As of January 17, both divisions of the RPS system were running on their normal power sources (i.e., in-plant switchgear).
PREVIOUS OCCURRENCE*EVALUATION No reactor scrams resulting from grid transients have occurred at River Bend Station in the last three years.
SAFETY SIGNFICANCE LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET U.S. NUCLEAR REGULATORY COMMISSION
- 2. DOCKET
- 6. LER NUMBER
- 3. PAGE 3
OF YEAR I SEQUENTIAL I REV NUMBER NO.
05000 458 3
2016 002 00 The response of the plant was bounded by the corresponding section of the Updated Safety Analysis Report. No safety-related systems were out of service at the time of the event. No plant parameter limits requiring the automatic actuation of any of the emergency core cooling systems or the emergency diesel generators were exceeded. This event, thus, was of minimal significance to the health and safety of the public.
/
(NOTE: Energy Industry Identification System component function identifier and system name of each component or system referred to in the LER are annotated as (**XX**) and [XX], respectively.) c