Preliminary analysis of radiation characteristic at upper section of Accelerator Driven Subcritical System

•A detail 3-D neutronic model of 10 MW ADS coupled 250 MeV proton accelerator was built.•Both beam losses and leakage of particles through beam duct were considerated.•The main contributors for upper radiation were beam duct leakage and secondary radiation induced by beam losses.•The impact of beam losses on total dose was greater than that on total neutrons flux.

Accelerator Driven Subcritical System (ADS) has attracted attention in many countries due to its high transmutation ability and inherent safety. The introduction of accelerator makes the radiation outside the reactor of the ADS, especially above the reactor cover, much more serious, due to particles leakage through beam duct and secondary radiation induced by beam losses. In this paper, the characteristic of the radiation fields at the upper section of the reactor of an ADS was analyzed. The radiation caused by penetration from reactor cover, the leakage of fission/spallation particles from beam duct and secondary particles induced from beam losses were compared. Results indicated that the leakage from beam duct and secondary radiation induced by beam losses were the main contributors and the dose rate induced by the proton beam losses should not be neglected. These results could be applied in guiding the shielding design for an ADS.