ML20079M215
| ML20079M215 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 01/04/1984 |
| From: | Kemper J PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | Murley T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| SDR-108, NUDOCS 8401270215 | |
| Download: ML20079M215 (3) | |
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4 PHILADELPHIA ELECTRIC COMPANY 2301 M ARKET STREET P.O. BOX 8699 PHILADELPHIA, PA.19101 JOHN 5. KEMPER
.... =.: = :...
JAN 4 1984 Mr. Thomas E. Murley, Director United States Nuclear Regulatory Commission Office of Inspection and. Enforcement, Region I 631 Park Avenue King of Prussia, PA 19406
SUBJECT:
Significant Deficiency Report Final Report on 480 volt Solid State Trip Devices Limarick Generating Station, Units 1 and 2 NRC Construction Permits Nos. CPPR-106 & 107
REFERENCES:
Telecon of December 5, 1983 P.
K. Pavlides (PECO) to M. Conner (USNRC)
FILE: QUAL 2-10-2 (SDR #108)
Dear Mr. Murley:
In compliance with 10CFR50.55 (e), enclosed is the final report on j
the subject deficiency.
Sincerely, IM Copy to: Director of Inspection and Enforcement United States Nuclear Regulatory Commission Washington, DC 20555 S. K. Chaudhary, Resident NRC Inspector (Limerick)
J. Wiggins, Resident NRC Inspector (Limerick)
DCD:nel-p nel-p1228831215 Enclosure 8401270215 840104 PDR ADOCK 05000352 4
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l December 30, 1983 Limerick Generating Station Units 1 and 2 Significant Deficiency Report #108 Defective Silicon - Controlled Rectifiers (SCR't) in 480 Volt solid State Trip Devices Final Report 1.0 Introduction This is a final report regarding a significant deficiency involving silicon -controlled rectifiers (SCR's) in the solid state trip devices which are used in the 480 Volt Class IE unit substations supplied to Limerick Generating Station by Brown Boveri Electric Inc.
(BBE).
The USNRC was previously notified of this deficiency in a telecon between P.
K.
Pavlides of Philadelphia Electric Company and M. Conner of USNRC Region I on December 5, 1983.
2.0 Description of Problem Brown Boveri Electric Inc. supplied the Class IE and non-Class IE 480 volt circuit breakers which are used at Limerick in the BBE unit substations.
These circuit breakers are I-T-E types K-600S and K-1600S.
Only the K-600S are used in Class IE applications at Limerick.
All of these circuit breakers are supplied with solid state trip devices.
During preoperational testing of the solid state trip devices, it was determined that the SCR's in several of the solid state trip devices were allowing excessive current passthrough with no control voltage applied to the gate.
Seven (7) SCR's have been found to be defective out of sixty-six (66) tested thus far.
3.0 Analysis of Deficiency The subject SCR's are used in the solid state trip circuitry as switching devices which actuate the magnetic latch release to trip the circuit breaker upon detection of current magnitudes in excess of the set point.
Should the leakage current through the SCR become excessive, spurious tripping of the circuit breaker could result.
The defective SCR's showed no outward signs of the defect in that their appearance was normal.
The defect can only be detected by measuring the leakage current through the SCR.
4.0 Safety Implication Spurious tripping of Class IE 480 volt circuit breakers would cause loss of power to Class IE motor control centers and motors. Due to the random nature of this failure, it is considered to be extremely unlikely that multiple failures resulting in the loss of more than one redundant load group would occur simultaneously.
C, 5.0 Corrective Action The SCR's. in all Class IE and non Class IE solid state trip devices are being tested for excessive leakage current.
All solid state trip -devices with SCR's found to be defective will be returned to the manufacturer for repairs.
All Unit 1 trip devices will be tested and replaced as neces -
prior to Unit 1 fuel load.
All Unit 2 trip devices will be tested and replaced as necessary prior to Unit 2 fuel load.
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