Neutronic Study on a New Concept of Accelerator Driven Subcritical System in China

Accelerator driven subcritical system (ADS) has been considered as an advanced nuclear waste transmutation facility with inherent safety feature. Nowadays, Institute of Modern Physics, Chinese Academy of Science (IMPCAS) has made a plan to research and develop ADS, which project was formally approved by the National Development and Reform Commission at the end of 2015. In order to pursue high transmutation rate of Minor Actinide (MA), a new concept design of the lead-bismuth cooled ADS is proposed in present work, in which a gravity-driven dense granular flow spallation target has been designed to substitute the traditional solid or liquid heavy metal spallation target. Sensitive parameters of the spallation target have been investigated, such as the radius and axial position of the spallation target, the size of heavy metal grains, the granular filling rate, the spallation neutron yield, and the distribution of neutron source. Furthermore, an optimized design of sub-critical reactor has been proposed with three zone loading pattern as a consequence of eliminating the power peak factor, which thermal power is 10MW with the operation cycle 600 EFPD. Finally, some important physical parameters in the coupling depletion system have been studied, including the effective multiplication factor k-eff, subcritical multiplication factor k-s, the change of beam current, time-dependent void and Doppler effect, fraction of effective delayed neutron, and the transmutation supporting ratio.