On September 30, 1999, a criticality accident occurred at the Tokai nuclear fuel plant (JCO Co. Ltd., a 100% subsidiary of Sumitomo Metal Mining Co. Ltd.) in Japan. . . . The chain reaction caused heavy releases of gamma and neutron radiation. Three workers were exposed to doses of up to 17 Sv (Sieverts), causing severe radiation sickness. The worker exposed to the higest dose died on December 21, 1999. The worker exposed to the second highest dose of 6 - 10 Sv died on April 27, 2000. 68 other persons were irradiated at lower levels. Among them were the workers who stopped the chain reaction: they were exposed to doses of up to 119.79 mSv, exceeding the 100 mSv limit for emergency situations. The annual dose limit for workers is 50 mSv (while ICRP currently recommends 20 mSv). As of October 7, 1999, radiation levels remained high inside the plant building, preventing inspection of the damage inside the plant.