ML20082P016

Ro:On 910830 Analog scram-capable Safety Channel of Dow Triga Research Reactor Found to Be Not Operating During power-up Operation of Reactor.Caused by Broken Connection in high-voltage Cable for Neutron Detector.Broken Cable Fixed

ML20082P016
Person / Time
Site:	U.S. Geological Survey
Issue date:	09/03/1991
From:	Kocher C INTERIOR, DEPT. OF, GEOLOGICAL SURVEY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9109100154
Download: ML20082P016 (2)

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, o ,_ 2 1602 Building 3 September 1991 US Nuclear Regulatory Commission A'I*IN: Document Control Desk Washington DC 20555 DOW TRIGA RESEARCil REACTOR . DOCKET 50-274 EVENT The analog scram capable safety channel of the Dow TRIGA Research Reack>r was found to be not operating during a power up operation of the reactor at 1132 on 30 August 1991. This is a violation of the Technical Specifications, w hich require There shall be a minimum of one scrarn-capable analog safety channel (operating when the reactor is operating); and There shallle a minimum of two scram-capable safety channels operating w hen the reactor is .

operating.

During this event one independent scram-capable safety channel (digital) was operating. The reactor was under control and operating within spctified limits at all times.

The reactor was shut down and secured as soon as the taalfunction was noticed.

ANALOG S AFETY CilANNEl, The analog safety channel is one of two scram-capable safety channels which are used to control vid protect the operation of the reactor. The analog channel uses an uncompensated ion chamter outside the l reflector, and is intended to monitor the top two decmics of operating range. %c single range exten 1s to 100% of full power (full power is 300 kilowatts) and the present scram setting is 90% (270 kilowatts).

. The display legins to respond at the low end at a few percent of full range (atout 5 kilowatts). His channel is tot equipped with a source-level interlock.

CAUSE The loss of the safety channel information was caused by a broken connection in the high voltage cable for the neutron detector his cable shares an unprotected run at poolside under the grids that cover the -

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RESIONSE The troken cable was repaired. 'Ihe neutron detector was evaluated at source level, through rnovernent of the neutron source, without opera ing the reactor. Other cables and connectors in the same area associated with .e safety channels were checked for physical sturdiness and continuity; all were found to be satisfactory The scram capability of the analog ciennel was confirmed and the reactor was operated at a power level sulliciently high to show that calitrations of the two scrarn capable channels agreed. The reactor was returned to service.

RECURRENCE The cables at poolside have been confined to a smaller area, to allow access to the poolside without disturbance of the cables. A covering device has teen ordered which will further protect the cables from stress or movement which could damage them.

All tractor operators have been informed of tids event. The operators and the Reactor Operations Committee (ROC) will review this event at the Septemler (necting of the ROC and will consider changes of equipment and surveillance procedures which could help prevent similar occurrences.

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C. W. Kocher Reactor Supervisor i

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