Preliminary Structural Safety Analysis Of Lead-Bismuth Cooled Window Target For ADS During Beam Variation Transients

Spallation target coupling the sub-critical reactor and the proton accelerator is the crucial part of ADS system, on which most of the beam energy is deposited as heat. The spallation target is of curial importance to the safety analysis of ADS. The variation of target temperature during transient conditions would produce thermal stress, posing a big threat to the integrity of the target. In this paper, thermal-hydraulic behavior as well as thermal stress response of a spallation target is investigated under steady and several typical conditions, using the commercial software CFX and ANAYS Workbench.Before we carried out the computation, grid sensitivity has been performed and the proper computational modes have been chosen. The results of the steady analysis showed that flow stagnation near the center of the window can be clearly seen. The corresponding temperature on the window surface can be expected in the same point. Based on which results, we also studied the effects of window’s thickness, burn-up as well as the window’s material. The results of the analysis presented that the temperature of the hot point on the target would increase in accordance with the thickness of window. Besides, the thermal hydraulic analysis of the target material showed that316L performed as better as T91during steady-state.As we have put, the rapid change of proton beam would pose a threat to the integrity of the target. In this paper, five typical transients such as start-up transient, beam trip, Beam intensity jump, beam trip, beam focus and beam shift were studied. The results showed us that:in the case of power jump and power ramp, no damage was observed and the maximum value of thermal tress that cause by rapid changing beam power is18.3MPa. The transient behavior of the temperature on the target window during beam trip conditions illustrated the importance of the thermal tress load of the window material. Further fatigue analysis showed that the acceptable failure frequency of the spallation target is1×106per year. Other transient analysis of three major accidental scenarios, namely beam focusing, Beam intensity jump and beam shift, indicated that beam focusing gives the most serious safety concern. In this case, window failure would be predicted. It is suggested that beam focusing accident should be avoid in practical engineering practices of ADS.