ML19326E242
| ML19326E242 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 07/22/1980 |
| From: | Ullrich W PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | |
| References | |
| FOIA-81-159 NUDOCS 8007280649 | |
| Download: ML19326E242 (2) | |
Text
I THIS DOCUMENT CONTAINS POORQUALTYPAGES PHILADELPHIA ELECTRIC COMPANY Peach Botton Atomic Power Station Delts, Femasylvania 17314 July 22, 1980 Mr. Boyce H.
Grier Office of Inspection and Enforcement Region 1 United States Nuclear Regulatory Commission C31 Park Avenue King of Prussia, PA 19406
SUBJECT:
REPORTABLE OCCURRENCE - PROMPT NOTIFICATION
-~ C5hfit"mi1'i W.
T.
UI.l~ric.h's :coseersation with Myr-Cowgil.1 on
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Tuly 21, 1980.
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Reference:
Docket No. 50-277/278 Peach Botton Units 2 and 3 Technical Specification
Reference:
- 6. 9. 2. a (s)
Report No. 2-80-12/IP Occurrence Date:
July 21, 1980 Identification of Occurrence:
Inoperability of scram backup valves in air supply ts control rod drive scram valves.
Conditions Prior to Occurrence:
Unit 2 shut down for refueling.
Unit 3 operating at full power.
Apparent Cause of Occurrence:
Cesign error.
solenoid installed in three way backup air scram coleasid valve has a 250 volt DC rating.
The circuitry supplies this component with 125 volt DC.
1 Analysis of Occurrence:
Testing of Unit 2 during therefueling outage identified failure of the backup scram air valves to qperate.
Investigation identified the casse of inoperability as seated above.
The condition is commee to both Units 2 and 3.
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During normal operation, the scram valves on each hydraulic controi ocdule for each control rod are maintained in the closed position by an air supply which maintains pressure on the valve diaphragm.
When scram is initiated via the RPS logic, two AC solenoid valves I
in the supply piping to the scram valves ou each hydraulic control codule are de-energized which vent the air from the diaphragm and permit the scrsa valve to open thereby initiating red insertion.
As designed, the backup air scram valves should be energized via the RPS logic when scram is initiated.
Energising of these solenoid valves removes the air supply from the entire scram valve pilot air header and exhausts the air in this header to the atmosphere.
In the unlikely event that the air pilot valves on a hydraulic control cadule failed to properly port when de-energized, venting of the entire scram valve pilot air header would result in venting the diaphragm of the affected hydraulic control module and permit a delay of that particular control rod.,
Inoperability of the backup scram valves uould result in the pil.ot air header not being depressurized and requiring manual insertion-of the affected rod. -
It appears that this defect may have existed in the ori f.nal 2
installation.
During the operating history at Peach Botcom, all rods have scrammed each time a scram was initiated.
Corrective Action:
Immediate corrective action was taken to provide manual venting i
of the scram pilot air header following a scram.
An individual dedicated to this function was stationed in the area and given a procedure which closes a manual air supply valve and opeaa two or three vent valves on the scram vent pilot air heeder.
This canus1 operation can be performed within 30 seconds following scram.
General Electric Company and Electrical Engineering have been informed on this design defect.
Steps are being taken to provide cq initial and permanent design change to correct this problem.
Previous Occurrence:
None.
Very truly yours, W. T. Ullrich Semtion Superintendent WT5r31h c.
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