ML20002C373
| ML20002C373 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 12/19/1980 |
| From: | Chiramal M NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD) |
| To: | NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD) |
| References | |
| TASK-AE, TASK-E019, TASK-E19 AEOD-E019, AEOD-E19, NUDOCS 8101100184 | |
| Download: ML20002C373 (2) | |
Text
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o DEC 1 J 1930 l'E"0RA!! Dull FOR:
File FROM:
- 1atthew Chiramal Office for Analysis and Evaluation of Operational Data
SUBJECT:
DAVIS BESSE 1 - ECCS ACTUATI0!i DURIllG HOT SHUTD0utt Oil 12/5/80
Reference:
Pf;0 III-30-227, dated 12/3/30 On December 5,1980, while the licensee and vendor representatives were attempting to isolate an electrical fault in the safety features actuation system (SFAS), an inadvertent SFAS Level 1, 2, 3, and 5 actuation occurred.
During the investigation, ac power had been turned off to SFAS channel 3 cabinet. When pcwer was turned back on again (with the channel 3 trip bi-stables still in the tripped state), an indicatinq light failed to illuminate.
While removing a healthy lamp from another output slot, an electrical arc was apparently caused between the lamp and the chassis. This caused the loss of a power supply in Channel 1 SFAS cabinet. The loss of power supply caused Channel 1 trip of SFAS Level 1, 2, 3, and 5.
This, coupled with the trips existing in Channel 3, resulted in 2 of 4 channels actuation of SFAS Level 1, 2, 3, and 5 (i.e., containment isolation, RP injection, LP injection, and recirculation mode). With the system in the recirculation ccde, water drained from the BUST to the containment sump (15,000 gallons in approximately B minutes). fio water was injected into the RCS since RCS pressure was at 2150 psig. By clearing the trips and installing a new power supply in Channel 1, the licensee reset SFAS and eliminated the electrical problem.
From information obtained from the Resident Inspector, other IE and flRR personnel, and the licensee, the following is surnised:
a) The initial electrical problem was noticed by plant operators when the monitoring lamps in Channel 3 and Channel 1 started
" blinking."
b) Channel 1 and Channel 3 power supply comons are connected to-gether (the sane for Channels 2 and 4).
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c) The electrical problen with the SFAS system was a short within a power supply in Channel I which caused the 120V ac input vol-tage to be imposed on the 24V and 15vde comen of both Channels 1 and 3.
d) The secund fault caused by the arcing of a lamp caused the loss of the power supply, thus causing SFAS actuation.
IE. and NRR are reviewing this event. IE is conducting an onsite technical review of the event. IE will: (a) detemine cocpliance with IEEE 279-1971 regarding separation of Channels; (b) issue Infomation Notice / Bulletin as appropriate; and (c) detemine if any other plant has similar channel inter-correction problems.
!!RR will:
a) Provide technical assistance to IE in the review of the incident; b) Review generic aspects of automatic recirculation mode in light of such operating experience; c) Review licensee's analysis of the effect of 24V and 15vde common being conr.ected to 120 vac; and d) Conduct a review of Davis Gesse regarding use of bypasses (instead of trip) in the SFAS systen.
Based on an engineering analysis, I consider that the event follow-up effort by.'IRR and IE to be sufficient for this event.
S
!!atthew Chiranal Office for Analysis and Evaluation of Operational Data cc:
C. ;iichelson J. Heltenes H. Ornstein Distribution: /
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