Abstract
Technical problems of the first Japanese criticality accident occurred at the JCO plant located at Tokai-mura, Ibaraki Prefecture were examined from the viewpoint of a nuclear chemist. The following points were discussed in detail : (1) Emission of fission neutrons from "precipitation vessel" in the conversion building where the accident occurred, (2) Total number of fission events and time variation of fission rate, (3) Health effects on the persons exposed to radiations, (4) Discharge and dispersion of volatile radioactive nuclides in the environment, (5) Contamination of the conversion building by radioactive substances. Consequences of the accident are discussed in connection to the role of nuclear energy in Japanese energy policy. It is evident that the investigation of the accident has been insufficient. Future studies are needed.
