<p style="text-align: justify">Small modular reactors (SMRs) are expected as a suitable candidate to fulfill energy needs in the future. In the latest&nbsp;progress, United States Nuclear Regulatory Commission (NRC) completed phase 6 review of NuScale reactor's design certification application last August. In the process of their safety review, 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 has still under discussion. It was shown that reducing the EPZ size from conventional 10 miles to the very narrow range like the site boundary would significantly reduce offsite emergency planning cost. Selection of the protective action depends on the predictions of radiological incidents. The major emergency responses to radiological incidents in the early phase are evacuation from the area and sheltering-in-place within a building. Inhalation of radionuclides in atmospheric plume and radiation exposure should be prevented as much as possible. Emergency reponses to nuclear accidents in SMR has not been established well, and the research on the atmospheric dispersion from the plant needs to be performed to determine the approptiate size of EPZs. Comparison between the dose incurred during evacuation and that with sheltering-in-place is necessary to consider the proper protective actions. This study focuses on effect of wall materials on indoor doses for sheltered population from small modular reactor severe accident. In this study, the source term came from loss of coolant accident or station blackout. Based on the atmospheric dispersion theory, the time change of air concentration and the ground deposition data was calculated with RASCAL, a software developed by 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. The cloudshine and groundshine were calculated with Monte Carlo methods, and the shielding function of each house was evaluated by comparing the indoor dose with outdoor dose. It was confirmed that the wall material gave a significant impact on the radiological dose inside a building. The result will be a basis for calculating the radiological dose for sheltered cases in case of nuclear emergency for SMR, which will be valuable to have an more effective emergency planning.</p>

Wall Materials Effects on Sheltered Indoor Doses From an SMR Hypothetical Severe Accident Release

Paper Proceedings: https://asmedigitalcollection.asme.org/ICONE/ICONE28/volume/85246

2021 28th International Conference on Nuclear Engineering (ICONE28)

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