A PWR Self- Contained Actinide Transmutation System

Abstract

Elements of the new Global Nuclear Energy Partnership (GNEP) initiative in the US call for the expansion of domestic use of nuclear power and the minimization of nuclear waste. To achieve both goals in the short term the transmutation of trans-uranic (TRU) elements in Combined Non- Fertile and Uranium (CONFU) PWR fuel assemblies is evaluated. These assemblies are composed of a mix of standard UO[subscript 2] fuel pins and pins made of recycled TRU in an inert matrix and are designed to fit in currently deployed PWRs. A CONFU-Self-Contained (CONFU-C) assembly is shown to achieve a net TRU destruction in a self-contained TRU multi-recycling system. The system may consist of as little as one currently operating reactor that does not depend on other reactors to supply it with its inventory of recycled TRU. This is considered a major advantage of the new design over its predecessors since it eliminates the need for designating a whole fleet of CONFU reactors to produce recycled TRU for the reactor under consideration. Degradation of fissile content of the multi-recycled TRU is compensated for by drawing from legacy TRU that already comes from standard UO2 spent fuel and the usage of fresh UO[subscript 2] fuel with different enrichments depending on fuel cooling time after discharge. A recycling strategy which uses a 4.5 year period of in core irradiation, followed by one of three cooling periods (6-, 18-, and 32-year) after discharge and reprocessing is considered. Calculations have shown the equilibrium CONFU-C assembly can have a net TRU destruction of approximately 20.6 (for the 6-yr cooling) and 2.7 (for the 18-yr cooling) kg of TRU per TWhe, as compared to 11.0 kg of TRU per TWhe for the CONFU-B with a 6-yr cooling period. This represents a net burning rate of ~13% (6-yr cooling) and 3% (18-yr cooling) of the TRU loaded per assembly compared to 8% for the CONFU-B design. However, Fuel Cycle Costs (FCC) for the equilibrium CONFU-C is shown to be 12.8 (6yr-cooling) and 14.2 (18yr cooling) mills/KWhe and that for the CONFU-B to be 12 mills/KWhe. Due to the relatively long cooling period of the third option (32 yr cooling), a CONFU-C assembly could not be designed to achieve net TRU destruction in a self-contained manner.