Design of a pan-shape transuranic burner core with low sodium void reactivity

Abstract

The primary incentive for transmutation of transuranic (TRU) isotopes is to eliminate as many of them as possible from the ultimate geological repository stream via processing light water reactor (LWR) spent fuels and to recycle the man-made TRU as TRU burner fuel sources. The favorable features on a TRU burner core have been emphasized from the viewpoint of maximizing TRU burning potential, compatibility with breeder reactors in terms of geometry and overall safety performance, and low sodium void reactivity environment. There has been no such a TRU burner design that is superior to other candidate designs in every physics performances of interests. There has been some degree of compromises of physics performances and safety parameters in every design, and thus the best design is regarded as what has the least number of insignificant drawbacks, compared with typical breeder reactor cores of a similar power rating. A 1575 MWt TRU burner reactor core with a low sodium void worth has been developed by devising an unconventional pan-shaped active core design that is regarded as an innovative reactor concept. The core consists of two types of fuel subassemblies that differ in the height of the fueled region. This strategy has allowed extreme “pancaking” of the inner core region, while the radial dimension increase is limited by placing longer fuels in the outer core region. The fuel cycle analysis has been performed in the equilibrium cycle, consisting of external feed fuel with reprocessed typical LWR spent fuel and fissile makeup with self-recycled TRU nuclides. The neutronic performance characteristics obtained from the equilibrium cycle analysis show that it would work safely as well as economically, as measured in terms of burnup reactivity swing, peak power density, Doppler coefficient, TRU burning and sodium void worth. The core has relatively low double power peaks in both the inner and outer cores without enrichment zoning, and this makes an active core v...