The different power outputs and power densities are evaluated in order to estimate the effect of that parameter to the breeding capability. The significant effect of MFR and power density for required enrichment and conversion ratio are when the MFR is low and the breeding capability of the reactor increases with increasing power output.
The feasibility of Sn-126 transmutation using spallation reaction in ADS was evaluated in viewpoints of proton utilization, neutron production, support ratio, effective half-life, equilibrium toxicity, and radioactivity. Parametric studies on spallation target and proton beam sizes were also performed for effective transmutation. It was found that the spallation target gives better transmutation properties than other transmutation systems.
In a once-through refueling pebble bed core, fresh pebbles with large k-inf in the upper part of the core leads to an excessively high axial power peaking factor. An attempt has been done to minimize axial power peaking through controling axial k-inf distribution by adding burnable poison into the fuel pebbles.
For realistic analysis of very high temperature reactors, there is strong desire to explicitly model the double heterogeneity of the fuel and stochastic geometry in the core. Sub-fine lattice stochastic (Sub-FLS) modeling recently developed is described. It gives more random distribution of particle fuels, which results in more accurate criticality calculation with acceptable efficiency. Furthermore, packing fraction variability concept is newly proposed and successfully imbedded into the Sub-FLS model to reflect the manufacturing quality. We compare the model with the truly random Metropolis model derived from the Metropolis algorithm.