05000366/LER-1994-001, :on 940201,coil of Relay 2A71-K57 Failed Causing Relay to Move to Deenergized State & Unplanned ESF Actuation.Blown Fuse & Coil Replaced & Valves Affected Reopened & Sys Placed Back in Svc
| ML20063L352 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 02/22/1994 |
| From: | Beckahm J, Tipps S GEORGIA POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| HL-4511, LER-94-001, LER-94-1, NUDOCS 9403040262 | |
| Download: ML20063L352 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv), System Actuation |
| 3661994001R00 - NRC Website | |
text
l Georgia Power Cornpany
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40 inverness Contor Parkway i
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Post Offee Box 1295 a
- Birrningham, Alabama 35201 Telephone 205 877 7279 i
m J. T. Beckham, Jr.
Georgia Power Vice Presidont Nuclear Hatch Project tv a.s'>cm e,y trc vuem I
February 22, 1994 Docket No. 50-366 Ill-45 I I l
I U.S. Nuclear Regulatory Commission ATTN: Document Control Desk i
Washington, D.C. 20555 l
l Edwin 1. Ilatch Nuclear Plant - Unit 2 l
Licensee Event Report j
Failed Relay Coil Results in Unplanned Actuations of Engineered Safety Features Gentlemen:
In accordance with the requirements of 10CFR50.73(a)(2)(iv), Georgia Power Company is submitting the enclosed Licensee Event Report (LER) concerning a failed relay coil which resulted in unplanned actuations of several engineered safety features. This event l
occurred at Plant Hatch - Unit '
Sincerely, j
1
. T. Beckham, Jr.
JKBicr Enclosure: LER 50-366/1994-001 cc:
Georgia Power Corwtag Mr. H. L. Sumner, General Manager - Nuclear Plant NORMS U.S. Nuclear Regulatory Commission. Washington. DL..
Mr. K. Jabbour, Licensing Project Manager - Hatch U S. Nuclear Regulatory Commission. Region 11 Mr. S. D. Ebneter, Regional Administrator Mr. L. D. Wert, Senior Resident Inspector - Hatch
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NOC PORo 366 U.S NUCLEAR GEOULATORY COMMISSION APPROYED CMD NO.31504104
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DOCKET NUMBER (2) 11 OWM l
Edwin 1. Hatch Nuclear Plant - Unit 2 0l5l0l0l0l3l6l6l1 OF 4
l TITLE (4)
Failed Relav Cclil Results in Unolanned Ac uations of Enuingered Safety Feauges EVEN T DATE (5)
LER NUldBER (6)
REPORT DATE (7)
OTHER 7 ACILITIES INVOLVED (8)
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On 2/1/94 at 2025 EST, Unit 2 was in the Run mode at a power level of 1705 CMWT (70 percent of rated thermal power). At that time, the coil of relay 2A71-K57 failed, causing the relay to move to its deenergized state. In addition, when the coil failed, the fuse which supplies its power,2A71B-l F22, also blew. These events initiated several actuations of Engineered Safety Features, including l
closure of the outboard small-bore Group 1 Primary Containment Isolation System (PCIS) valves and closure of various outboard Group 2 PCIS valves. Licensed plant operations personnel l
inspected panels in the Main Control Room and discovered the failed relay coil. By 2116 EST, a l
lead had been lifled from the failed relay, and the blown fuse had been replaced. Subsequently, affected valves were reopened and their associated systems were placed back in service with the exception of the small-bore Group 1 PCIS valves mentioned above. By 2/3/94, the relay coil was replaced and the Group 1 PCIS valves were placed back in their normal system lineups.
The cause of this event was a failed coil in relay 2A71-K57.
Corrective actions for this event include replacing the blown fuse and failed relay coil and returning affected systems and valves to their normal lineups. These actions are complete.
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NRC Form 366 (542)
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OF FICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503 F.tcluiY NAME (1)
DOCKEi NUMBER (2)
LER NUMBER (6)
PAoE (3)
VEAR SEQUE.NTIAL REVi$ N Edwin L Hatch Nuclear Plant - Unit 2 0 l5 l0 l0 l0 l3 l6 l6 9 l4 0 l0 l1
- - 0l0 l2 OF l4 1LKT @ mare space sa requaed. nose addotuonal Copes d IVHC Form 366A)(1 f)
PLANT AND SYSTEh1 IDENTIFICATION General Electric - Boiling Water Reactor Energy Industry Identification System codes appear in the text as (Ells Code XX).
DESCRIPTION OF EVENT
On 2/1/94 at 2025 EST, Unit 2 was in the Run mode at a power level of 1705 ChtWT (70 percent of rated thermal power) At that time, the coil of relay 2A71-K57 failed, causing the relay to spring return to its decaergized position. In addition, when the coil failed, the fuse which supplies its power,2A71B-F22, also blew. The failure of the relay to its deenergize d position caused automatic closure of the small-bore outboard Group 1 Primary Containment Isolation System (PCIS, Ells Code Jhi) valves 2B21-F019 and 2831-F020. The blown fuse deenergized several relays which caused isolation of various Group 2 PCIS valves including several primary containment vent valves, the drywell equipment drain sump isolation valves, and other valves which tripped the Fission i
Product hionitoring System (FPhi, Ells Code IJ) and the containment atmosphere hydrogen and oxygen analyzers (11/0 Analyzers, Ells Code IK). Licensed plant operations personnel inspected 2 2 panels in the hiain Control Room and discovered the failed relay coil. By 2116 EST, the failed relay j
was electrically isolated by lifling a wire to the coil, and the blown fuse was replaced. Subsequently, valves affected by the blown fuse were reopened and their associated systems were placed back in service. However, since the small-bore Group 1 PCIS valves mentioned above are controlled by the failed relay, they were left closed at that time. By 2/3/94, the failed relay coil was replaced, returning the relay to service, and the small-bore Group 1 PCIS valves were then placed back in their normal system lineups.
CAUSE OF EVENT
This event was caused by failure of the ccil in relay 2A71-K57, which caused two small bore Group i PCIS valves to close. When the coil failed, it caused fuse 2A71B-F22 to blow, which resulted in further actuations of Group 2 PCIS valves.
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DOCKET NUMBER {2)
LER NUMBER (6)
PAGE (3)
YEAR
$EQU NTIAL RE Li N Edwin I Hatch Nuclear Plant - Unit 2 0 l 5 l0 l0 l01316 l6 9 l4 0 l011 0l0 l3 oF l4 tur g,-..-,
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a a emo 36ew n REPORTABILITY ANALYSIS AND SAFETY ASSESSMENT This event is reportable per 10 CFR 50.73.(a)(2)(iv) because unplanned actuations of Engineered Safety Features occurred. Specifically, Group 1 and Group 2 PCIS valves automatically closed in response to a failed relay coil and a blown fuse.
The PCIS is designed to automatically close certain Primary Containment isolation Valves (PCIVs) to provide protection against accidents involving the release of radioactive material from the fuel or nuclear process barriers. Group 1 systems communicate directly with the reactor coolant system and isolate when process conditions such as low-low-low reactor water level indicate the presence of leakage from the reactor pressure boundary. Group 2 systems are generally those systems whose lines do not communicate directly with the reactor coolant system, but penetrate the Primary I
Containment and communicate with the free space inside it. Even thougit Group 1 and Group 2 PCIS valves generally have their own isolation logic, their logic systems occasionally share a power supply. This was the case with the logic alTected by this event. The relay which failed is located in a section oflogic which controls both Group 1 and Group 2 PCIS salves. The particular relay which failed controls two Group 1 valves, but the fuse supplying power to the relay also supplies power to several other relays which control Group 2 PCIS valves.
l In this event, the coil failed in relay 2A71-K57 causing the relay armature to spnng return to its deenergized position. When the contacts changed states, the Group 1 valves controlled by the relay moved to their isolated positions per design. The failed relay coil also blew fuse 2A71B-F22. The blown fuse caused several other relays to deenergize, sending isolation signals to various Group 2 PCIS valves. All afrected valves responded as designed given the signals introduced by the failed relay and blown fuse. The design of the logic in which this relay was located is " fail-safe;" that is, a loss of power or control signal causes the afTected components to assume their emergency positions.
l This is exactly what happened in this event. Therefore, if a design basis accident had occurred concurrently with the failure of this relay, all afTected systems would already have been in their safe condition.
Based on this analysis, it is concluded that this event did not result in any adverse effect on nuclear safety. This analysis is applicable to all power levels.
NAC 70RM 366A U S. NVCLEAR REGULATORY COMMISSION APPROVED OMB NO 31504104 JS,92)
EXPlRES: S/31195 ESr MATED DURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION COLLECTION REQUEST $00 HR$
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OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503 F ACILiiY NAME (1)
DOCKET NUMBER {2)
LER NUMBER (5)
PAGE (3)
VEAR
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CORRECTIVE ACTIONS
The blown fuse 2A71B-F22 was replaced and all Group 2 PCIS valves and associated systems were restored to normal service. This action has been completed.
l l
The coil of relay 2A7!457 was replaced with a new coil, functionally tested, and the Group 1 PCIS l
valves affected by it were restored to their normal system lineups.
Georgia Power Company is continuing to investigate the cause of the failed relay coil and will confer with tne manufacturer of the relay as necessary l
ADDITIONAL INFORMATION
l 1.
Other Systems Afli cted: No systems vmc affected by this event other than those already l
mentioned in this report.
2.
Failed Equipment Information:
Master Parts List Number: 2A71-K '
Ells System Code: JE Type: Relay Ells Component Code: RLY Manufacturer: General Electric Computy
- - Root Cause Code: X Model Number: CR120A06022AA Reportable to NPRDS: Yes Manufacturer Code: G080 3.
Previous Similar Events
Events reported in the past two years in which General Electric type CRI 20,viays failed are described LERs 50-321/1992-004, dated 02/26/92, and 50-366/19V028, dated 01/11/93. Corrective actions for these event included replacing failed relays and functionally testing af fected circuits or systems. These actions would not have prevented this event because the relays and circuits were difTerent from those affected by this event.
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