ML20046C740
| ML20046C740 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 08/06/1993 |
| From: | Simpkin T COMMONWEALTH EDISON CO. |
| To: | Murley T NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM), Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 9308120033 | |
| Download: ML20046C740 (2) | |
Text
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Commonwoolth Edison 1400 Opus Place e
C' Downers Grove. Illinois 60515 August 6, 1993 Dr. Thomas E. Murley, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C.
20555 Attention: Document Control Desk
Subject:
Zion Station Unit 2 Eagle 21 Process Protection System Periodic System Performance. Report NRC Docket No. 50-304
References:
(a)
April 10, 1992 letter from S.F. Stimac to T.E. Murley
Dear Dr. Murley:
Commonwealth Edison Company committed via reference (a) to provide NRC periodic performance reports related to the Zion Unit 2 Eagle 21 Process Protection System.
Pursuant to this commitment, please find enclosed one copy 4 he subject report for the interval of..
March 30, 1993 through July 28, 1993.
As described in reference (a), additional performance reports will-be submitted periodical.ly throughout the first Unit 2 operating cycle with Eagle 21.
Please direct any questions you may have to this office.
Respectfully, h
Qp%.
T.W. Simpkin Nuclear Licensing Administrator TWS/gp Enclosure cc:
Regional Administrator - RIII C.Y.
Shiraki, Project Manager - NRR i
J.D.
Smith, Senior Resident Inspector - Zion Office of Nuclear Facility Safety - IDNS k;\\nl elt.1-nrcz..ptil
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ZION STAT 10N UNIT 2 o
EAGLE 21 PERFORMANCE REPORT (OPERATIONAL PERFORMANCE)
On June 21. 1993. spurious " Trouble" and " Channel Set Failure" alarms were received from Protection Set III. The alarms came in again on June 25. 1993.
In both occurrences, the duration of the alarms ciere too short to utilize the Man Machine Interface (MMI) to determine the error code associated with the alarms.
Action Taken: To aid in determining the error code associated with the alarms.
Westinghouse is manufacturing an extra set of specially designed EPROM's. They are identical to the ones presently being used in Protection Set III of Unit 1 to trouble shoot a spurious alarm problem there. The new EPROM's have had their software slightly modified when compared against the existing EPROM's in the Test Sequence Processor (TSP) board in Protection Set Ill. The difference resides in a write command that will output the error code associated with any alarm to an output port regardless of the duration of the alarm.
Once the EPROM's are received they will be installed in racks 11 and 12 of Protection Set Ill to determine the root cause of the spurious alarms.
Root Cause:
An update will be provided in the next Eagle 21 System Performance Report.
(OPERATIONAL PERFORMANCE)
On July 1.1993 the Containment Pressure Hi Hi Bistable for train B (BS-CS22B2) in Protection Set IV tripped. A subsequent alarm was received on July 13, 1993.
In botn cases the pressure transmitter 2PT-CS22 showed no indication of an elevated reading. Also, train A and B will energize on an increasing pressure signal from 2PT-CS22. but in this event only train B tripped.
Action Taken-The Operations Department declared the channel inoperable and tripped BS-CS22A1 and BS-CS22A2. BS-CS22B1 and BS-CS22B2 were placed in the bypass mode of operation to facilitate operability testing of the channel. The Instrument Maintenance department proceeded to procedurally perform a channel check on the portion of the Eagle Partial Trip (EPT) board that contains BS-CS22B1 and BS-CS22B2, Both channels passed the channel check test. Based on this, the Operations department declared the channels operable. All bistables for the loop were returned to there normal operational positions. A chart recorder was then strategically placed on various test points in the loop to aid in determining a root cause. The recorder remained in placed for several weeks. but did not reveal sufficient information to aid in the determination a root.cause.
Based on the information collected about the event, the most probable cause is that the EPT beard spuriously actuated caus1ng BS-CS22B2 to trip. As a result of this. the EPT board has been replaced.
Root Cause:
The EPT board has been shipped back to Westinghouse for failure analysis. An update will be given in the next report after the failure analysis is completed by Westinghouse.
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