05000461/LER-2002-003, Re Manufacturing Process Deficiency in Main Power Transformer Sudden Pressure Relay Causes False Actuation of Relay Resulting in Generator & Turbine Trip & Reactor Scram
| ML022480344 | |
| Person / Time | |
|---|---|
| Site: | Clinton  |
| Issue date: | 08/28/2002 |
| From: | Pacilio M AmerGen Energy Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| U-603579 LER-02-003-00 | |
| Download: ML022480344 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| 4612002003R00 - NRC Website | |
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An Exelon/British Energy Company Clinton Power Station R R 3 Box 228 Clinton, IL 61727-9351 10 CFR 50.73 U-603579 August 28, 2002 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001 Clinton Power Station Facility Operating License No. NPF-62 NRC Docket No. 50-461
Subject:
Licensee Event Report No. 2002-003-00 Enclosed is Licensee Event Report (LER) No. 2002-003-00: Manufacturing Process Deficiency in Main Power Transformer Sudden Pressure Relay Causes False Actuation of Relay Resulting in Generator and Turbine Trip and Reactor Scram. This report is being submitted in accordance with the requirements of 10CFR50.73' ectfu l M. J. Pacilio Vice President Clinton Power Station RSF/bIf Enclosures cc:
Regional Administrator-NRC Region Ill NRC Senior Resident Inspector - Clinton Power Station Office of Nuclear Facility Safety - Illinois Department of Nuclear Safety D
bC,
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Abstract
On July 4 the sudden pressure alarm for the 'B' Main Power Transformer (MPT) actuated in the Main Control Room and at the same time the reactor automatically scrammed from 95 percent reactor power. The sudden pressure alarm was initiated by a malfunction of the sudden pressure relay (SPR).
The SPR initiated a Generator trip and lockout.
The Generator trip caused a Main Turbine trip and Turbine Control Valve fast closure, resulting in the reactor scram.
The SPR trip also initiated the 'B' MPT deluge system, and the fire pumps automatically started as expected.
Operators entered Emergency Operating Procedures due to an expected low reactor water level transient.
The root cause for the reactor scram was a latent defect in the bimetal of the SPR control orifice that likely occurred during the manufacturing process and resulted in a false actuation of the SPR.
Corrective action for this event includes replacing the deficient 'B' MPT relay, testing the MPT SPRs for proper operation, and implementing a design change to modify the SPR trip logic.
NRC FORM 366 (7-2001)
(If more space is required, use additional copies of (if more space is required, use additional copies of (if more space is required, use additional copies of NRC Form 366A) (17)
The plant responded normally to the reactor scram.
The response and behavior of the plant during this event were compared to the Generator Load Rejection transient discussed in Chapter 15 of the Updated Safety Analysis Report and the General Electric Transient Safety Analysis Report and were determined to be within those analyses.
This event posed no challenges to fission product barriers.
All systems responded as required for an event without bypass valve failure.
No safety system functional failures occurred during this event.
CORRECTIVE ACTION
The faulty sudden pressure relay in the 'B' MPT was replaced with the relay from the spare MPT ('D' MPT).
The sudden pressure relays for the 'A' and 'C' MPTs and the replacement 'B' MPT relay were tested and verified to operate properly.
A design change will be implemented to remove the station's vulnerability to single failure of the Sudden Pressure Relay that results in plant shutdown.
design change will modify the sudden pressure relay protection scheme from a out-of-one trip logic to a fault tolerant trip logic in all 4 MPTs.
a The one-
PREVIOUS OCCURRENCES
LER Number Title LER 89-028 Water Intrusion Into Main Power Transformer Sudden Pressure Sensor Relay Causes Corrosion and Results in Relay Failure, Turbine Generator Trip and a Reactor Scram Clinton Power Station experienced a previous sudden pressure relay false actuation resulting in a reactor scram in June 1989 when the 'C' MPT Qualitrol sudden pressure relay malfunctioned; however, that malfunction was caused by internal corrosion resulting from water intrusion into the relay.
Deterioration of the sudden pressure relay from the water intrusion caused the relay to operate erratically.
COMPONENT FAILURE DATA
Manufacturer Nomenclature Manufacturer Model Number Serial Number Qualitrol Corporation Rapid pressure rise relay 900-021-61 58179