Guanheng Zhang (alumnus), Chris Keckler, Alejandra Jolodosky (former), Massimiliano Fratoni, Jasmina Vujic, Ehud Greenspan
This study assesses the feasibility of designing a Seed and Blanket (S&B) Sodium-cooled Fast Reactor (SFR) to generate a significant fraction of the core power from radial thorium-fueled blankets. The goals of this project support sustainability of the nuclear fuel cycle. The blanket operates in a Breed-and-Burn mode without exceeding currently-verified experimental radiation damage limits. The S&B core is designed to maximize the fraction of neutrons that radially leak into the subcritical blanket. The blanket makes beneficial use of the leaking neutrons for improved economics and resource utilization. Since the blanket fuel requires no reprocessing or remote fuel fabrication, a larger fraction of power from the blanket will result in a lower fuel cycle cost per unit of electricity generated. A unique synergism is found between a low conversion ratio seed and the breed-and-burn thorium blanket. The benefits of this synergism are maximized when using an annular seed surrounded by inner and outer thorium blankets.
Fuel cycle analysis of the S&B design, including basic fuel cycle parameters, nuclear waste characteristics (radioactivity, inhalation/ingestion toxicity), proliferation resistance, fuel cycle cost, and resource utilization, is conducted and compared with a reference Advanced Burner Reactor and Pressurized Water Reactors. The S&B cores can utilize 7% of thorium’s energy value without the need to develop irradiated thorium reprocessing capabilities. This is ~12 times the amount of energy that LWRs generate per unit weight of natural uranium mined, showing vast improvement in resource utilization over current systems.
Preliminary studies have found that the S&B core could establish several new fuel cycle options. Currently under investigation is the option of using the S&B design to burn minor actinides and plutonium from LWR spent fuel, which would greatly benefit the situation for geologic disposition of spent nuclear fuel and increasing the sustainability of nuclear power.