Wylfa (United Kingdom)

Map of Wylfa

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2 * 590 Magnox GCR; grid connection in 1971

Facilities in Wylfa

plantreactor typconstruction startoperation startshut down

the lower portion of a refueling grab used to access a fuel chute had become detached during refueling operation. The section fell 1,2 m and was subsequently located on top of the fuel channel. The reactor was tripped when the grab section was found to be missing. During the resulting depressurization 140 GBq of S-35 were released (more than twice the weekly limit). Although sufficient carbon dioxide coolant flow occured through gaps between the graphite bricks to prevent fuel melting. The incident could have been more severe had the grab fallen onto a higher rated channel, where cooling might not have been adequate. The maximum consequences in this case would correspond to INES level 4.