ML20084S693
| ML20084S693 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 07/25/1975 |
| From: | Kalivianakis N COMMONWEALTH EDISON CO. |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20084S694 | List: |
| References | |
| AO-50-265-75-23, NJK-75-379, NUDOCS 8306170168 | |
| Download: ML20084S693 (3) | |
Text
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N Commr.
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Post Othee Box 216 Cordova,lihnois 61242 Telephone 309/654 2241 oist.: -
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July 25, 1975
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'WW' Director of Office of Nuclear Reactor Regulation U.
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Nuclear Regulatory Commission Washington, D.
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20555 Re f e ren ce :
Quad-Cities Nuclear Power Station Docket No. 50-265, DP R-3 0, Unit 2 Appendix A, Sections 1.0.A.2, 3.1,6.6.B.l.A Enclosed please find Abnormal Occurrence Report No. 50-265/75-23 for Quad-Cities Nuclear Power Station.
This occurrence was previously reported to Region 111, Directorate of Regula' tory Operations by telephone on July 18, 1975 and to you and Region 111, Directorate o f Regulatory Operations by telecopy on July 18, 1975.
This re p o r t.
is submitted to you in accordance with the requirements o f Te chnical Specification 6. 6.B.1. a.
Very truly yours, COMMONWEALTH EDISON COMP ANY QUAD-CITIES N UCLEAR POWER STATION ff4A9 N.
J.
Kalivianakis Station Superintendent NJK/KML/lp cc: Region 111, Directorate of Regulatory Operations J.
S.
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Report Number A0-50-265/75-23 Report Date:
July 25, 1975 Occurrence Date:
July 18, 1975 Facility [
Quad-Cities Nuclear Power S ta tion Cordova, Illinois 61242.
Identification o f Occurren ce :
High drywell pressure switch 2-1001-89B failed to operate.
Conditions Prior to Occurrence:
Unit 2 was in the run mode with core thermal power of 1968 MW t and electrical output of 605 MUe.
De s crip tion o f Occurrence:
While performing routine surveillance on July 18, 1975, at approximately 9:30 a.m.,
it was discovered th at pressure switch 2-1001-89B (High drywell pressure) would not operate.
Instrument maintenance personnel tes ted and found the three remaining switches operable.
The existing switch was replaced with a cew spare, but this switch failed to operate p ro pe rly also.
Further inves tigation revealed that the pressure pulsation dampener located on the inlet to the pressure swi t ch had become fouled with dirt and scale.
The dampener was cleaned and at approximately 1:00p.m. July 18, 1975 pressure switch 2-1001-89B was restored to service.
Designation o f Apparent Cause of Occurrence:
Equipment Failure The apparent cause of this occurrence is designated as equipment failure.
The pressure pulsation dampener performs its functions th rough the use of small orifices that limit the rate at which the me te re d fluid can pass.
Only a very small amount o f s cale and crud was needed to plug the orifices.
This crud, in e f fe ct, isolated the pressure switch from the rest of the system.
Analysis of Occurrence :
Pressure switch 2-1001-89B is one of four switches operating contacts in a logic sequence designed to give a high drywell pressure signal to Reactor Protection Systems.
The "one-out-of-two-twice" logic gives not only a means of testing and maintaining the circuits, but also provides redundancy in the event that one switch or contact fails.
Technical S p e ci fica tion 3.1 allowes for plant operation with a failed sensor for brief periods while maintenance is performed.
In this case, the o the r th ree p ressure switches were operable and the logic sequence would have supplied the appropriate high pressure signal; the re fo re,
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consequences or potential consequences from the H
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o o
.gport Number A0-50-265/75-23 con't standpoint o f public health and safety were minimized.
No plant personnel were injured and there was no release of radioactive material as a result of this abnormal occurrence.
Corrective Action:
The corrective action taken was to clean the dampener, and test the remaining swit ches.
Failure Data:
i No previous failures of this type have occurred; therefore, there are no safety implications based on cumulative experience related to this occurrence.
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