Assessment of the radiation field from withdrawal of the internal components in a system integrated reactor

SMART (System-integrated Modular Advanced Reactor) is a small and medium size integrated reactor with 330 MW_th power which has been developed in Korea. In the SMART, some of the components such as steam generator, flow mixing header assembly and flow skirt are installed inside the reactor vessel and near the core, which lead to their activation. The components will be withdrawn for maintenance, inspection, replacement or decommissioning, which causes radiation fields from them. In order to evaluate their activities and radiation fields, a computer-based simulation was performed using the MCNPX code. We calculated the dose rates by distance from the surface of the components to 5 m away and the variation of dose rates over time. Dose rates near the withdrawn components are extremely high and the dose rate is still extremely high after sufficient cooling time. Thus, approach to these components must be prohibited and all of works relevant with the withdrawn components must be performed by remote control system. (author)