Impact of plant incidents on worker radiation exposure for the SEAFP design

Fusion power reactors represent a significant source of energy supply with the potential for little adverse safety and environmental impact. Occupational radiation exposure, however, has been recognized as a potential area of concern, due to the significant quantities of activated products generated in a D-T fusion reactor and the need for frequent replacement of reactor components. This study was undertaken to provide a preliminary estimate of the potential impact of plant incidents on the annual station dose of two fusion reactor designs—SEAFP Model 1 (helium-cooled) and Model 2 (water-cooled). The assessment comprised an evaluation of the impact that plant incidents have on the annual station dose of fission reactor plants, and an assessment of the potential dose contribution of some incidents in a fusion reactor plant. The evaluation of water-cooled reactor data indicates that worker overexposures (>20 mSv) from plant incidents are rare and that significant overexposures (>50 mSv) are even less frequent—of the order of one in 600 reactor-years of operation. Furthermore, the number of workers exposed due to unplanned events is of the order of 0.2% of monitored workers. The evaluation of helium-cooled reactor data indicates better performance—no exposures above 20 mSv have been recorded. The assessment results for SEAFP Models 1 and 2 are consistent with the fission reactor results, however, only one category of incidents has been considered to date.