Research on Nuclear Heat Deposition Behavior in the Spallation Target of an Accelerator Driven Subcritical System

The power density distribution behavior of the ADS spallation target, which is a key factor in the thermal-hydraulic and mechanical design of the high-power ADS target, was investigated under different proton incident energy. A Chinese ADS conceptual design of spallation target was proposed in this paper. The deposition heat in the spallation target was calculated by MCNPX code. From the results, it was found that the Bragg peak phenomenon weakens as the proton source incident energy increases. Large Bragg peak was observed for proton incident energy below 500MeV, however for the proton source energy above 900MeV, Bragg peak phenomena was not obvious. Analysis on the nuclear reactions behavior and ionization process induced by source proton in the target was carried out to address this issue. Meanwhile, the results show that the proton leakage rate from the target, which is an important factor in proton radiation shielding, greatly depends on the proton range (penetration depth) under different incident energy. In order to stop or keep the protons in the target, the minimum axial length (in the incoming particles direction) of the target at a given proton source incident energy should be determined according to the corresponding proton range. The results of this paper will be useful to guide the design of spallation target of a reference ADS.