EVALUATION OF SHELTER-IN-PLACE FROM A SMR HYPOTHETICAL ACCIDENT RELEASE

Small modular reactors (SMRs) are expected as a suitable candidate to fulfill energy needs in the future. The regulation of the emergency planning zone (EPZ) has been a controversial issue. The possibility of smaller EPZs because of their small core size and passive safety functions is still under discussion. The major emergency responses to radiological incidents in the early phase are evacuation from the area and shelter-in-place within a building. Comparison between the dose incurred during evacuation and that with shelter-in-place is necessary to consider the proper protective actions. The effect of shelter-in-place from small modular reactor hypothetical accident was studied. The source term came from a long-term station blackout (LTSBO) and loss of cooling accident (LOCA), and the time change of air concentration and the ground deposition data through the atmospheric spread around the plant was calculated with Radiological Assessment System for Consequence Analysis (RASCAL), a software developed by United States Nuclear Regulatory Commission (NRC) to provide dose projection around the plant. Then general one-story and two-story houses were set up, and 6 wall materials were selected for calculating indoor doses. Cloudshine and groundshine were calculated with Monte Carlo methods. In addition, the conservation of mass, air flow model was established to evaluate the inhalation for sheltered cases. The shielding function of each house for each pathway was evaluated by comparing the indoor dose with outdoor dose. The projected dose for sheltered cases was much smaller than that for unsheltered cases. Even though the projected dose will not completely perish, it was quite effective to reduce radiation exposure and can be superior to evacuation. The result will be a basis for calculating the radiological dose for sheltered cases in case of nuclear emergency for SMRs, which will be valuable to have a more effective emergency planning.