Summary of the JCO criticality accident in Tokai-mura and a dose assessment

東海村でのJCO臨界事故と線量評価の概要

田中 俊一

Tanaka, Shunichi

1999年9月30日、JCO東海事業所の転換棟で臨界事故が発生し、約19時間にわたって臨界反応が持続した。この間の核分裂数は、約2.5x10と推測された。この事故によって3人のJCO従業員が重篤な被曝を受け、この内2名は致命的な被曝を受けた。住民234人、従業員169人、緊急作業者260人の被曝線量は、最大で48mSvであった。

A criticality accident occured on September 30,1999, in a conversion facity at the JCO tokai site. The accident continued for about 19 hours before the criticality could be stopped, during which time neutrons and gamma-rays were emitted continuously due to fission reactions. The total number of fission reactions was 2.5x10. The accident gave radiation dose to 3 employees and fatal dose to 2 of them. The individual dose was estimated for 234 resident, 169 JCO employees and 260 emergency personnel, of which the maximum dose was 48 mSv.