NEUTRONIC STUDY ON CONCEPTUAL LITHIUM FLUORIDE SALT COOLED FUSION DRIVEN SYSTEM FOR ACTINIDE TRANSMUTATION

摘要

The subcritical fission system could be used to transmute actinide elements from spent fuel into thermal power. Since the subcritical system needs an external neutron source, the D-T Fusion reactor was introduced as a fast neutron source to drive the chain reaction. Fusion driven system based on Spherical tokamak with a 1.7 m major radius has been designed. The breeding blanket has been modified to accommodate space for a 4.8 m length oxide fuel rod. Oxide fuel rods were immersed inside the lithium fluoride salt blanket, which acts as a coolant and liquid tritium breeder. The fully liquid blanket design was taken to reduce structure complexity and maximize tritium breeding volume. The neutronic study has been performed to calculate the neutron multiplication factor, actinide burnup in 400 days cycle and theoretical Tritium Breeding Ratio using MCNPX code. The design goal of fusion driven system with a fully liquid blanket is to reach k_(eff) value from 0.8 to 0.9 by burning sufficient actinide while breeding Tritium in Fluoride salt coolant. Various lithium fluoride coolant and reflector options have been simulated with the designed geometry. FLiNaBe salt liquid blanket was used as a reference since it could reach a k_(eff) value of 0.942 and able to transmute the actinide element in oxide fuel.