A preliminary shielding design of 150 MWe liquid metal reactor

A preliminary shielding design of the KALIMER (Korea Advanced Liquid Metal Reactor) was established by two-dimensional discrete ordinate radiation transport analyses. The shielding design has tentatively adopted to use two limits on the fast neutron fluence and the DPA (Displacement Per Atom) simultaneously as a base for the exposure limit for neutron damages to reactor structures. In addition, activities in the PSDRS air effluent and the IHX secondary sodium were also examined. The DORT two-dimensional transport code was used to evaluate the KALIMER shielding design. The reactor system was represented by four axial zones, each of which was modeled in the R-Z geometry. The KAFAX-F22 library was used in the analyses, which was generated from the JEF-2.2 of OECD/NEA for LMR applications by KAERI (Korea Atomic Energy Research Institute), and consists of 80 neutron and 24 gamma energy groups. The performance of the shielding design is compared against the shielding design criteria. The results indicate that the support barrel, upper grid plate, and other reactor structures meet both the maximum neutron fluence and DPA limits established in the shielding design criteria. Activities of the air effluent in the PSDRS were also evaluated and are shown to satisfy the effluent concentration limits in 10 CFR Part 20. It is found that maximum DPAs show larger margins than the case when the neutron fluence limit is used as a design criterion. Therefore, the use of DPA as a shielding design criterion allows for a more flexibility in the LMR shielding design. (author)