Analysis of the transmutation behavior of transuranium elements within the heterogeneous spectrum of boiling water reactors

The high-level waste of BWR-type reactors is actually stored in interim storage facilities. The conventional BWR fuel elements show a burnup profile with strong axial variations due to the axially different neutron moderation of the coolant medium. The axially heterogeneous plutonium enrichment and the differences for the fuel type mixed-oxide, plutonium and minor actinides are presented. The modeling of the geometry and the particle transport is performed by the MCNP code, the temporal behavior of the fuel by the code ORIGEN, the coupling of the codes by VESTA. The simulations show that the fast neutron spectra in the upper range of the BWR core can be used to reach more homogeneous burnup and better transmutation rates than in conventional BWR systems. Two different methods were investigated: an axial heterogeneous plutonium enrichment and an axially heterogeneous loading with different fuel types. The results show comparable and favorable safety properties. The advantage of the method is the use of existing reactors and the transmutation of high-level waste with long half-life into short-lived waste.