Physics studies of a heterogeneous liquid--metal fast breeder reactor

The first physics measurements for a heterogeneous design of a 1000-MW (thermal) liquid--metal fast breeder reactor were made in the Zero Power Plutonium Reactor (ZPPR) during the last half of 1976. This benchmark assembly, ZPPR-7, had a central blanket zone as well as three internal blanket rings. Fuel zones had a single enrichment. Cores with heavy plutonium buildup in the internal blankets as well as cores with clean internal blankets were investigated. Such key physics parameters as k/sub eff/, most of the important reaction rates, control rod worths, sodium void reactivity, and material worths were studied in the ZPPR-7 program. Results verified the gain in breeding that were predicted for the heterogeneous arrangement. When design-level calculations were used, calculated-to-experimental biases were different from those that had been found for homogeneous cores