ML19256C612
| ML19256C612 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 05/25/1979 |
| From: | Bryan S, Nolan F NRC OFFICE OF INSPECTION & ENFORCEMENT (IE) |
| To: | |
| References | |
| PNO-79-124, NUDOCS 7910100609 | |
| Download: ML19256C612 (2) | |
Text
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PRELIMINARY NOTIFICATION May 25, 1979 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE--PNO-79-124 This preliminary notification constitutes EARLY notice of an event of POSSIBLE safety or public interest significance.
The information presented is as initially received witnout verification or evaluation and is basically all that is known by IE staff on this date.
Facility:
Commonwealth Edison Company Zion Unit 1 (DN50-295)
Zion, Illinois
Subject:
INADVERTENT MSIV CLOSURE AND SAFETY INJECTION At 1:45 p.m., on May 23, 1979, while operating at full power, Unit 1 experienced a Main Steam Isolation Valve (MSIV) isolation, a reactor scram, and a safety injection.
An immediate check of major plant and operating parameters verified that the above events were not due to actual plant conditions.
The NRC Resident Inspector was present in the control room and also verified that the event was due to spurious signals.
The safety injection signal was reset after injection through the boron injection tank for a total of three minutes.
During this event the pressurizer pressure and level, and the steam generator levels remained within acceptable limits.
No system pressure or temperature limits were exceeded, and no radiation releases occurred.
At the time of the event, a monthly surveillance test of the safeguards logic of train "A" was in progress.
The cause of this event is attributed to human error.
It was determined that an operator inadvertently skipped one page of the checklist in the performance of the test.
This error introduced a steam line break signal into the train "A" logic which resulted in an MSIV isolation, and a reactor scram.
MSIV's "A", "C",
and "D", closed but MSIV "B" remained open.
This resulted in a 100 pound differential pressure betweeen two steam lines and initiated a safety injection signal from safeguards train "B".
The feedwater isolation signal tripped both main feedwater pumps as designed, but the "B" feedwater regulation valve remained open.
All three auxiliary feedwater pumps started automatically, as designed, however, the steam supply valve to the turbine driven auxiliary feed pump tripped closed, apparently from an overspeed signal.
All four steam generator water levels were maintained within acceptable limits during this event.
The MSIV closure resulted in the lifting of several atmospheric relief valves on the steam generators.
One atmospheric relief valve on the "A" steam generator did not fully reseat upon closure.
.,n, 100 CONTINUED I49I PRELIMINARY NOTIFICATION 7910100607
Continued PNO-79-124 Page 2 May 25, 1979 The licensee visually examined the main steam and main feedwater lines to verify that no leaks existed (routine for each safety injection).
The licensee will correct the cause of the "B" MSIV failure to close, the cause of the "B" feedwater regulation valve failure to close, and the leaking atmospheric relief valve on the "A" steam generator prior to start-up.
The licensee will also re-run the monthly safeguards logic test on both trains "A" and "B" prior to startup.~ The NRC Resident Inspector will verify the above.
The licensee also intends to correct the cause of the steam driven auxiliary feed pump trip prior to startup, but is not committed to do so since the Technical Specifications permit a restart with any two auxiliary feed pumps operable.
Both of the motor driven auxiliary feed pumps performed as designed during this event.
The NRC Resident Inspector has verified that corrective action has been completed and operability verified on the following:
The "B" MSIV, the "B" feedwater regulation valve; and the atmospneric relief valve on the "A" steam generator.
The licensee also re-ran periodic surveillance tests PT-10A and B for the safeguard's logic.
The State of Illinois has been notified.
Region III has issued a press release on this event.
Region III (Chicago) was informed of this event by the Resident Inspector at 2:20 p.m., on fiay 23, 1979.
This PN reflects updated information as of 11:00 a.m., on May 24, 1979.
Contact:
F. Nolan, IE x28019; S. E. Bryan IE x28019 Distribution:
Transmitted H St o'. e Chairman Hendrie Commissioner Bradford S. J. Chilk, SECY Commissioner Kennedy Commissioner Ahearne C. C. Kammerer, CA Commissioner Gilinsky ACRS (For Distribution)
IE J. G. Davis,F ff.
Transmitted:
MNBB I'5a P. Blda 4. 0 0 Region g L. V. Gossick, ED0 H. R. Denton, NRR H. L. Ornstein, EDO R. C. DeYoung, NRR J. J. Fouchard, PA R. J. Mattson, NRR N. M. Haller, MPA V. Stello, NRR (MAIL)
R. G. Ryan, OSP R. S. Boyd, NRR J. J. Cummings, OIA H. K. Shapar, ELD SS Bldg 8'.53 R. Minogue, SD W. J. Dircks, HMSS S. Levine, RES PRE *.IMINARY NOTIFICATION 1447 WO