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Event Notification Report for January 3, 2018


"On 12/30/17 at 0717 CST, the University of Missouri-Columbia Research Reactor (MURR) was shut down due to the loss of negative pressure in the reactor containment building. Prior to the shutdown, the reactor was operating for a period of time during the loss of negative pressure which is a deviation from MURR Technical Specifications (TS). This email is a required notification per TS 6.6.c.(1) to report to the NRC Operations Center that an Abnormal Occurrence, as defined by MURR TS 1.1, had occurred. Specifically, MURR was not in compliance with all TS Limiting Conditions for Operations (LCOs). MURR was not in compliance with TS's 3.4.b and 3.4.a.(6). 

"TS 3.4.b. states, 'Reactor containment integrity shall be maintained at all times except when: (1) The reactor is secured...' TS. 3.4.a.(6) states, 'For reactor containment integrity to exist, the following conditions shall be satisfied:...(6) The reactor containment building is at a negative pressure of at least 0.25 inches of water with respect to the surrounding areas: and...' 

"While on Routine Patrol on the morning of 12/30/17, an operator noted that the differential pressure gauge between the reactor containment building and the MURR laboratory building was reading zero (0.0) inches of water vacuum. The operator on Routine Patrol radioed the Lead Senior Reactor Operator in the Control Room, and the reactor was shut down. The cause of the loss of negative pressure was the closing of a backup ventilation exhaust door from the reactor containment building. With the backup ventilation exhaust door closed, the ventilation system was only supplying air to the reactor containment building, not allowing a balanced air recirculation to maintain a negative pressure. 

"The backup ventilation exhaust door actuator was found to be inoperable. The backup ventilation exhaust door operation was repaired by melting ice that had formed in the air supply lines to the door's operating air cylinder. Condensation that had formed in the air lines was removed, and heat trace and insulation were installed around all the backup door air supply lines. The compliance procedure for verifying backup ventilation doors' operability was conducted satisfactorily as post-maintenance testing. Permission from the Interim Facility Director was obtained prior to the reactor returning to operation later on 12/30/17. A detailed event report will follow within 14 days as required by MURR TS 6.6.c.(3)."


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