Experience at the radiation monitoring in criticality accident of JCO

This report describes the time series of author's experience at his Research Center. On September 30, he noticed the abnormality on the alarm of Funaishikawa monitoring station which showed an transient elevation at 10:38 of 2 min-dose rate to 0.4 μGy/h in both NaI detector and ionization chamber. He at 11:27 by phone from the atomic safety department of the prefecture office, actually knew the criticality accident of 10:35 at JCO and asked all personnel to be in the Center. Thereafter, the activities were: request for measuring radioactivity of soil and air; measuring radioactivity of city water source; faxing of dose rate data of monitoring stations to counter-planning headquarters; and arrangements of monitoring with national headquarters at Tokai JAERI. Continuous monitoring and consultation were done as well. The author pointed out, in conclusion, the importance of rapid detection of accidents, of legal national inspection of atomic facilities, of education of atomic energy and radiation for prefecture personnel and people, and of common recognition of official information. (K.H.)