Significant Quantity Production Rates in Small Modular Reactors

This work assesses the time necessary to create a significant quantity of weapons-grade plutonium, given the reactor size over a broad range of small modular reactor (SMR) technology families. Given the avantgarde nature of current SMR development, it is impractical to consider every technological nuance. However, some meaningful contrasts can be made based on basic reactor physics characteristics. The rate at which plutonium is produced in a uranium-fueled reactor is primarily a function of the conversion ratio, power level, and plant availability factor. Currently, many SMR concepts considered as “advanced”, are being designed with at least one of the following traits: high conversion ratio, high power density, or multiyear to decades-long cycle lengths. These characteristics are generally thought to increase proliferation resistance, as they reduce the frequency at which a state can access in-situ bred plutonium. However, this premise does not apply to the breakout scenario. When the state is no longer bound to wait until the end of the declared cycle length, the time necessary to achieve one significant quantity of weapons-grade plutonium becomes highly relevant. In this study, four reactor technology families are explored: pressurized-water reactors, sodium-cooled fast reactors, high-temperature gas reactors, and molten-salt reactors. A 3D neutronics model for each reactor type was created based on available preconceptual design data found in the open literature. The plutonium production rate for each concept is contrasted as a function of the conversion ratio, power level, and plant availability factor.