ML19331B900

Ro:On 800724,decay Heat Flow Interrupted Twice.Caused by Inadvertently Shorted Decay Heat Isolation Valve DH12 Fuse Clip to Ground & by Tripped Output Bistable BA413 During Facility Change Request Work

ML19331B900
Person / Time
Site:	Davis Besse
Issue date:	07/26/1980
From:	TOLEDO EDISON CO.
To:
Shared Package
ML19331B901	List: ML19331B900 ML19331B903
References
NUDOCS 8008130504
Download: ML19331B900 (1)

Text

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4 July 26, 1980 TELECOPY Q Beceived Verified Receipt: h /no Date-7'MY 0"#8

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Initials TO: U. S. Nuclear Regulatory Commission Office of Inspection and Enforcement Region III Attention: Tom Tambling

SUBJECT:

Two occurrences of interruption in decay heat flow Davis-Besse Unit 1 Mode 5 Power (MWT) = 0, Load (Gross MWE) = 0 At 0955 hours0.0111 days <br />0.265 hours <br />0.00158 weeks <br />3.633775e-4 months <br /> on July 24, 1980, a construction electrician inadvertently shorted a fuse clip te ground on the close control circuit of the decay heat isolation valve DH12 while pulling cable per Facility Change Request 77-391. The decay heat isola-tion' valve traveled to the closed position, isolating the suction of the operating decay heat pump. The, decay heat pump was shutdown as soon as the decay heat flow degraded (a decay heat flow watch was in effect). Since the indication of DH12 position was lost and the reactor coolant system water level was being maintained at a low elevation for maintenance purposes (approximately 572' 4"), the decay heat system was carefully vented prior to restarting the decay heat pump at 1045 hours0.0121 days <br />0.29 hours <br />0.00173 weeks <br />3.976225e-4 months <br />. The control room monitored the incore temperatures during the interruption of decay heat flow with a maximum incore temperature reading of 111 F.

At 2232 hours0.0258 days <br />0.62 hours <br />0.00369 weeks <br />8.49276e-4 months <br /> on July 24, 1980, while testing Safety Features Actuation System Channel 4 after completion of Facility Change Request 79-439A, output bistable BA413 was tripped which caused decay heat isolation valve DHil to travel closed.

The operator was not aware of the fact the slide link and jumper had been removed previously by instrument and control personnel. The decay' heat pump was shutdown as soon as the decay heat flow degraded (a decay heat flow watch was still in effect). Operations personnel realized what had caused the closure of DHil and re-opened the valve. The decay heat pump was returned to service a,t 2234 hours0.0259 days <br />0.621 hours <br />0.00369 weeks <br />8.50037e-4 months <br />.

Each of these occurrences placed the unit in violation of Technical Specification 3.4.1 which requires at least one decay heat pump be in operation while the unit is

'in Mode 5. _This incident is being reported in accordance with Technical Specifica-tion 6.9.1.8. Luis Reyes, Davis-Besse Unit 1 Resident Inspector, has been notified of both occurrences.

There was no danger to the health and safety of the public or station personnel.

The water temperatures in the core only slightly increased due to the low decay heat being generated. Core water temperatures were maintained over 100 F subcooled.

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