The Dependence of the Risk of Research Reactors from Their Operating Schedule–A Case Study

The dependence of the radiological consequences of the “Demokritos” research reactor on the operating schedule of the reactor is assessed in this paper. The 5 MW reactor is located within the limits of Athens city, a large population center with over 3 million inhabitants. The consequences examined would be due to the occurrence of a postulated accident, a 20% core melt loss of coolant accident, that is also considered as the design basis accident of the reactor. Three operating schedules are taken into account: (a) a continuous operation schedule; (b) a 16 hr/day, 5 days/week schedule; and (c) the present 8 hr/day, 5 days/week operating schedule. The assessment of the source term emerges from a conservative estimation of fission product releases to the reactor operating floor, and further under the conservative assumptions of no filter mitigation, and a ground release to the environment. The results of the analysis indicate that there is a direct relation between consequences and duration of operation, the former becoming appreciable as the continuous operation limit is approached. In all cases examined, the thyroid dose and the latent thyroid health effects would be the limiting consequences.