The Nuclear Regulation Authority said Feb. 5 it instructed Tokyo Electric Power Co. to reduce radiation exposure among workers who are removing spent and unspent fuel from a reactor building at the Fukushima No. 1 nuclear plant.
The NRA issued the instructions after it started studying radiation levels around the work site on the fifth floor of the No. 4 reactor building in December. NRA officials said they found high levels of radiation emitted from cobalt-60 that was apparently mixed with shavings produced when workers cut into reactor components inside the storage pool there.
TEPCO in November began moving nuclear fuel from the storage pool to a shared-use pool elsewhere on the plant’s compound. The workers normally wear protective gear and full face masks to guard themselves against high radiation levels.
The NRA found that the use of lead plates on the floor with hoisting equipment above the storage pool reduced the radiation levels to about one-third.
The NRA cited that and other survey results for calling for increased protective measures as part of the work process. The agency said it will do follow-up studies on worker doses.