Cascade Reactor Concept For Neutron Multiplication of Subcritical Core

摘要

A “cascade reactor concept” represents a kind of system with anrnaccelerator driven subcritical core consisting of two sections with differentrnneutron spectra. It can generate more neutrons than one-section fast corernwith the same subcriticality and the same neutron source strength.rnThis study deals with the effect of the cascade reactor concept by analogyrnof a coupling core and direct simulation using a Monte Carlo code. Thernproton energy is assumed to be 1.0 GeV and a Pb-Bi target is at the center ofrnthe core. The cascade reactor has two sections. The inner section is a fastrnflux core and the outer section is a thermal flux core. There is a neutronrnabsorber between two sections. As the result of direct simulation, therncascade reactor concept is confirmed to generate twice as many neutrons asrna one-section reactor with the same neutron source. It is found that thernthickness of fast core should be small to enhance the cascade effect, thernthickness of Sm absorber is optimized to be 5 cm and that cascade effectrnincreases when the subcriticality becomes small. These results are consistentrnwith the basic theory of coupling core.