Calculation of neutron dose in the JCO criticality accident in Tokaimura with MCNPX

Recognizing the accident and estimating absorbed doses at the incident time, is one of the requirements for radiation safety. The aim of this paper is designing a model for assessment of nuclear criticality effectiveness in non-reactor units and evaluation of the effect of variation of distances on dose rate and neutron energy spectrum. In this study neutron dose-rate was simulated between 0.5m to 45m from accident location by using MCNPX monte carlo code. The neutron energy spectrum was estimated in the tank and over the detectors at 20m, 25m and 30m. Experimental results of JCO accident in Japan and simulation results were compared with our results for validation. Statistical analyses showed that there is no significant difference between results. Therefore, by using this model we can design for control room and placement of monitoring equipment. Maximum allowable time for workers at the 50m from accident location obtained approximately 3 hours with implementation of essential hypothesis, according to the annual dose limit of occupational exposure.