At 0712 [MDT] on 6/30/16 a routine GSTR [Geological Survey
TRIGA Reactor] startup and ascent to 900 kW was initiated after successful completion of the daily prestart checks and an excess reactivity check. At 0715 [MDT], as power was passing through [approximately] 200 kW, it was clear to the operator that one of the three power instruments (the NP1000) was not functioning since it was still reading 0% when it should have been reading [approximately] 20%. The reactor was then shutdown, Reactor Supervisor notified, and troubleshooting commenced. Shortly after this, the NP1000 signal cable was found to have the coaxial cable pulled out of one of the connectors in the signal path. Repair, troubleshooting, and testing were performed to resolve the problem. At 0804 [MDT] the reactor was started up and all power instrumentation operated correctly and the daily power operation was performed without further problems.
The NP1000 is a required safety instrument for operation of the reactor, so malfunction of the instrument is a violation of the facility's Technical Specifications.
Specifically, specification E.7 states: 'The type and minimum number of safety systems which shall be operable for reactor operation are shown in Table I.' Table I requires the NP1000 to provide a high power scram at 110% power, but the cable problem would have prevented the high power scram from occurring in that instrument.
The licensee will notify the NRC Project Manager.