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THE EFFECTIVENESS OF FAST AND THERMAL SPECTRUM FOR TRU INCINERATION IN SUBCRITICAL SYSTEM

An investigation to compare the relative effectiveness of fast neutron with thermal neutron in a subcritical system has been performed. Accelerator driven thermal and fast neutron systems are modelled on a CANDU reactor and a typical LMR with Pb-Bi coolant, respectively. TRU mixed with Thorium was selected as a fuel in both systems. The ratio of TRU to Thorium is adjusted to make the system subcriticality about 0.97 and the system output power is set to be 1000 MWth. The thermal system was found to have unacceptable beam fluctuation and power peaking variations. The characteristics of thermal neutron are believed not to allow the employment of solid fuel concept in a thermal neutron subcritical system. In addition, the sensitiveness of thermal neutron to the concentration of TRU and fission products is believed to inevitably require on-line refuelling for reducing the beam power fluctuation. From the overall comparison, a fast neutron is concluded to be much better for the operation of the subcritical system.