Basic Theory of CANDLE Burn-up

摘要

A new reactor burn-up strategy CANDLE was proposed, where shapes of neutron flux, nuclide densities and power density distributions remain constant but move to an axial direction. Here important points are that the solid fuel is fixed at each position and that any movable burn-up reactivity control mechanisms such as control rods are not required. The governing equation of CANDLE bum-up in the equilibrium condition is a nonlinear equation derived by combining both neutron transport and nuclide transmutation equations. In the present paper the author tries to modify it to a simple equation by introducing some artificial assumptions, and to solve it. From derived equations several characteristics of CANDLE burn-up are found. Natural uranium or depleted uranium as an initial fuel realizes shorter reactor core than conventional enriched fuels. However, obtaining critical system using such an initial fuel is very difficult. Some other characteristics of CANDLE burn-up are also discussed.