CFD Study of the Active Part of the HYPER LBE Spallation Target System

In an accelerator driven system (ADS), a high-energy proton beam impinges on a heavy metal target to produce spallation neutrons that are multiplied in a subcritical blanket. Therefore, the spallation target is one of the most important units of an ADS. A beam power of 15-25 MW is required for an operation of the HYPER system. But, the design of a 20 MW spallation target is very challenging because more than 60% of a beam power is deposited as heat in a small volume of a target system. LBE is preferred as the target material due to its high neutron production rate, effective heat removal, low melting point and vapor pressure, low neutron absorption and good radiation damage properties. In addition, it can be used simultaneously as a reactor coolant. Single hemi-spherical beam window is considered for the HYPER target. The beam window is a thin physical barrier to separate the vacuum space from the LBE. It is exposed to high thermal and irradiation loads, which affect its life time. The integrity of the beam window is crucial for a safe operation of the HYPER, for preventing the penetration of the radioactive spallation products into the accelerator island. Therefore, a sufficient cooling capability of the beam window is one of the key issues of the target design. In the previous study, a series of parametric thermal and mechanical studies were made for the optimization of the HYPER target. The optimized target has a 0.2 cm thick beam window with a diameter of 35 cm. Also, a 30 cm wide proton beam with a uniform beam distribution should be adopted for the spallation target of the HYPER. A dual injection tube is adopted to economize the LBE flow in the primary system. This paper presents the numerical studies on the optimized spallation target system. Several advanced turbulence models with different grid structures are investigated by using a commercial computational fluid dynamics (CFD) code CFX 5.7.1