ACTINIDE BURNING IN A LEAD-BISMUTH-COOLED CRITICAL FAST REACTOR WITH ECONOMIC ELECTRICITY GENERATION *
A Lead Bismuth-cooled fast reactor concept for actinide burning and low-cost electricity production and excellent safety characteristics is proposed. The concept employs metallic thoriumbased fuel (Th-U-Pu-MA-Zr) in a 700 MWth core. The transuranics destruction rate per MWth-yr is 66% that of an accelerator-driven system using the same initial transuranics composition in fertile-free fuel. Coolant void reactivity mitigation is achieved through the use of streaming fuel assemblies and both the Doppler and fuel thermal expansion feedback are negative. The small negative fuel temperature and coolant temperature reactivity coefficients and negative core radial expansion coefficient provide self-regulating characteristics, so that the reactor is capable of inherent shutdown in major transients without scram, as in the Integral Fast Reactor (IFR). * This project is supported by an INEEL Laboratory Directed Research and Development Project.
Medium-Power Lead-Alloy Reactors: Missions for This Reactor Technology
Abstract A multiyear project at the Idaho National Engineering and Environmental Laboratory and the Massachusetts Institute of Technology investigated the potential of medium-power lead-alloy–cooled technology to perform two missions: (1) the production of low-cost electricity and (2) the burning of actinides from light water reactor (LWR) spent fuel. The goal of achieving a high power level to enhance economic performance simultaneously with adoption of passive decay heat removal and modularity capabilities resulted in designs in the range of 600-800 MW(thermal), which we classify as a medium power level compared to the lower [˜100 MW(thermal)] and higher [2800 MW(thermal)] power ratings of other lead-alloy–cooled designs. The plant design that was developed shows promise of achieving all the Generation-IV goals for future nuclear energy systems: sustainable energy generation, low overnight capital cost, a very low likelihood and degree of core damage during any conceivable accident, and a proliferation-resistant fuel cycle. The reactor and fuel cycle designs that evolved to achieve these missions and goals resulted from study of the following key trade-offs: waste reduction versus reactor safety, waste reduction versus cost, and cost versus proliferation resistance. Secondary trade-offs that were also considered were monolithic versus modular design, active versus passive safety systems, forced versus natural circulation, alternative power conversion cycles, and lead versus lead-bismuth coolant. These studies led to a selection of a common modular design with forced convection cooling, passive decay heat removal, and a supercritical CO2 power cycle for all our reactor concepts. However, the concepts adopt different core designs to optimize the achievement of the two missions. For the low-cost electricity production mission, a design approach based on fueling with low enriched uranium operating without costly reprocessing in a once-through cycle was pursued to achieve a long operating cycle length by enhancing in-core breeding. For the actinide-burning mission three design variants were produced: (1) a fertile-free actinide burner, i.e., a single-tier strategy, (2) a minor actinide burner with plutonium burned in the LWR fleet, i.e., a two-tier strategy, and (3) an actinide burner with characteristics balanced to also favor economic electricity production.
LMR design concepts for transuranic management in low sodium void worth cores
The fuel cycle processing techniques and hard neuron spectrum of the Integral Fast Reactor (IFR) metal fuel cycle have favorable characteristics for the management of transuranics; and the wide range of breeding characteristics available in metal fuelled cores provides for flexibility in transuranic management strategy. Previous studies indicate that most design options which decrease the breeding ratio also show a decrease in sodium void worth; therefore, low void worths are achievable in transuranic burning (low breeding ratio) core designs. This paper describes numerous trade studies assessing various design options for a low void worth transuranic burner core. A flat annular core design appears to be a promising concept; the high leakage geometry yields a low breeding ratio and small sodium void worth. To allow flexibility in breeding characteristics, alternate design options which achieve fissile self-sufficiency are also evaluated. A self-sufficient core design which is interchangeable with the burner core and maintains a low sodium void worth is developed. 13 refs., 1 fig., 4 tabs.