Characterizing Limited-Separations Fuel Cycles Using Breed-and-Burn Reactors

A fuel cycle option is evaluated in which fuel bred in breed-and-burn (B&B) reactors is used to start up additional B&B reactors, with the fuel being recycled using limited-separations processes instead of full actinide reprocessing. This fuel cycle aims to minimize processing requirements and proliferation risk while still being able to achieve exponential growth and high uranium utilization. The neutron excess concept is applied to compute the starting fuel requirements of new B&B reactors, allowing fleet doubling times to be estimated. A simple analytic expression for doubling time is derived, which is applied to example B&B reactors using a hypothetical core composition. It is found that larger reactors are able to achieve shorter doubling times because of their smaller starter fuel requirements per unit power. Several variant fuel cycle configurations are examined, and their doubling times are computed.