Estimation of Collective External Dose during Dismantling of JPDR (BWR, 90MWt)

Collective external dose in the dismantling of the Japan Power Demonstration Reactor (JPDR; BWR, 90MWt) was estimated. Radioactive inventories of components to be dismantled were first evaluated using the operation history of the JPDR. Dose equivalent rate at each working area was calculated on the basis of the obtained radioactive inventories. To evaluate man-hours relating to the JPDR dismantling in radiation environment, the dismantling activities were further categorized to be preparation, dismantling, packaging, shipping and cleaning up, and man-hours Were calculated according to occupations such as a dismantling worker, a superviser and a radiation officer. Through these studies, collective external dose was evaluated to be approximately 300 man-mSv, which is relatively small compared with that of external dose is useful in comparison with the actual value.