Calculation of the accidental gamma dose rate at the top of the low power research reactor

Abstract

Owing to the high risk through conducting the experiment of losing the core water shield, the analytical and statistical (MCNP) methods were used to estimate the gamma dose rate at the reactor top when the core water shield level decreases to the value less than the Miniature Neutron Source Reactor (MNSR) safety limit. For normal operation condition, the results showed that the core water shield attenuated the gamma dose rate by 3 × 106 times. The gamma dose rate values at the reactor top due to the core and the water impurities were 46.8, 89.9 and 52 μSv.h−1 for the statistical, analytical calculations and experimental reference value respectively. For the accidental condition (the core water shield level is 12 cm), the results showed that the maximum gamma dose rate value at the reactor top was 1.4 × 10−8 μSv.h−1. Therefore, no one should stay at the reactor top if an accident occurs. These results of dose rate can be used as reference values in order to set the radiation protection requirements in the MNSR reactor.