CBRN event in India on Mon 30th May 2011

Kakrapar Atomic Power Station (KAPS) is a twin unit station with 220 MWe Pressurized Heavy Water Reactors. Refueling of these reactors is done when the reactor is on-power. The spent fuel bundles discharged from the reactor are transferred to Spent Fuel Storage Bay (SFSB) through the Spent Fuel Transfer Duct (SFTD). The radiation field in the SFTD area goes high during transfer of spent fuel bundles through SFTD.

On May 30, 2011, Unit-2 of KAPS was operating at 98% FP. For carrying out painting job, SFTD shielding blocks were removed. Radiological work permit was issued for the painting job after taking clearance from engineer-in-charge of refueling operations. This permit was issued to carry out painting work between 09.15 hrs and 13.00 hrs in the SFTD area. Control room staff was instructed not to transfer any spent fuel during this period. However, at around 12.00 hrs, refueling operator in the control room inadvertently discharged a pair of spent fuel bundles to SFSB through SFTD after refueling. Four workers who were carrying out the job got exposed to radiation and received 90.72 mSv, 66.81 mSv & 58.70 mSv, and 23.23 mSv radiation dose. The radiation doses to the workers were higher than the prescribed annual regulatory limit stipulated by Atomic Energy Regulatory Board (AERB).