Optimal design of HYPER target system based on the thermal and structural analysis of Pb–Bi spallation target and beam window

KAERI (Korea Atomic Energy Research Institute) has been developing an accelerator driven transmutation system called HYPER (HYbrid Power Extraction Reactor). It is designed to transmute long-lived TRU and fission products such as Tc-99 and I-129. Pb–Bi is used as the coolant and target material at the same time. HYPER is expected to need about 20 mA proton beam to sustain a 1000 MWth power level. One of the problems to be solved is to design a target system which can accept such a high current while keeping the integrity of the target system. The cylindrical beam tube and spherical window is adopted as the basic window design of HYPER. The window diameter is varied to find the maximum allowable current based on the design criteria: Pb–Bi temperature <500 °C, window temperature <600 °C, Pb–Bi velocity <2m/s and window stress <160 MPa. The LAHET code is used to simulate heat generation. CFX and ANSYS are used for the thermal-hydraulics and stress calculations, respectively. Based on our design criteria and the current HYPER system parameters, the maximum allowable current is calculated to be about 8 mA, which is smaller than the required current. Therefore, an upgrade of the target design is under progress.