The Lead-Bismuth Eutectic(LBE) spallation target has been considered as one of the two alternatives for the spallation target for China Initiative Accelerator-Driven System.This paper reports the preliminary study on physical feasibility of a U-type LBE target with window.The simulation results based on Monte Carlo transport code MCNPX indicate that the spallation neutron yield is about 2.5 per proton.The maximum spallation neutron flux is observed at about 3 cm below the lowest part of the window.When the LBE target is coupled with the reactor,the reactor neutrons from the fission reaction increased the neutron field significantly.The energy deposition of highenergy protons is the main heat source;the spallation neutrons and reactor neutrons contribute only a small fraction.The maximum energy deposition in the LBE is about 590 W/cm^3 and that in the target window is about319 W/cm^3.To estimate the lifetime of the target window,we have calculated the radiation damages.The maximum displacement production rate in the target window is about10 dpa/FPY.The hydrogen and helium production rates generated during normal operation were also evaluated.By analyzing the residual nucleus in the target during the steady operation,we estimated the accumulated quantities of the extreme radioactivity toxicant ^(210)Po in the LBE target loop.The results would be helpful for the evaluation of the target behavior and will be beneficial to the optimization of the target design work of the experimental facilities.
The fuel assembly is key structure in China Initiative Accelerator Driven System,and the axial fitting clearance(AFC) for the fuel assembly design is an essential subject of study.In this paper,different methods are used to calculate critical stress in cylindrical shells.Because the thermal expansion of fuel assembly outer tube is larger than that of the cladding of fuel rod,enough space should be reserved between the upper end plug and upper seat slot.The collapse critical compressive stress of the cladding is obtained numerically through ANSYS simulation calculation.The AFC range between the fuel rod cladding and the end seat due to the displacement of thermal expansion is given by the theoretical formulas and ANSYS buckling analysis.These provide a reference for the AFC design of the reactor fuel assembly.
