Nuclear Event – Potential uncontrolled radiation release: Watts Bar Nuclear Plant Unit 1

North America – USA | State of Tennessee, Rhea County, Spring City, Watts Bar Nuclear Plant
Location: 35°36’10.0″N 84°47’22.0″W
Present Operational Age: ~30 years
Event: POT UNCNTRL RAD REL – ACCIDENT MITIGATION

Nuclear Event in USA on Thursday, 17 March, 2016 at 01:15 [EDT].

LOSS OF EMERGENCY AND AUXILIARY GAS TREATMENT SYSTEMS

“On March 17, 2016, at 0115 [EDT], Watts Bar Unit 1 (WBN1) entered Technical Specification Limiting Condition of Operation (TS LCO) 3.0.3 due to the inoperability of both trains of the Emergency Gas Treatment System (EGTS). TS LCO 3.7.12 Condition B was also entered at this time due to the inoperability of both trains of the Auxiliary Gas Treatment System (ABGTS). The train B EGTS and train B ABGTS had been removed from service for scheduled maintenance, when at 0115, the train A Auxiliary Air Compressor became inoperable. On March 17, 2016, at 0133, the train A Auxiliary Air Compressor was declared OPERABLE, and TS LCO 3.0.3 and 3.7.12 Condition B were exited.

“The auxiliary air system supports the EGTS by providing a safety grade air supply. When train A auxiliary air became inoperable, the supported train A EGTS and ABGTS became inoperable, creating a condition where both trains of EGTS and ABGTS were unavailable. In the event of an accident, the EGTS establishes a negative pressure in the annulus between the shield building and the steel containment vessel and the ABGTS establishes a negative pressure in the Auxiliary Building Secondary Containment Enclosure (ABSCE). Filters in these system mitigate the release of radioactive contaminants to the environment.

“WBN1 remained in Mode 1 at 100% power and no safety functions were required during the event.

“This event is reportable under 10 CFR 50.72(b)(3)(v)(C) and (D) as a condition that could have prevented the fulfillment of a safety function.

“The NRC Resident Inspector has been notified.”

Source: NRC  Event Number: 51795