Fast Burner Reactor Devoted to Minor Actinide Incineration

Abstract

This study proposes a new fast reactor core concept dedicated to plutonium and minor actinide burning by transmutation. This core has a large power level of ~1500 MW(electric) favoring the economic aspect. To promote plutonium and minor actinide burning as much as possible, total suppression of ²³⁸U, which produces ²³⁹Pu by conversion, and large quantities of minor actinides in the core are desirable. Therefore, the ²³⁸U-free fuel is homogeneously mixed with a considerable quantity of minor actinides.

From the safety point of view, both the Doppler effect and the coolant (sodium) void reactivity become less favorable in a ²³⁸U-free core. To preserve these two important safety parameters on an acceptable level, a hydrogenated moderator separated from the fuel and nuclides, such as W or ⁹⁹Tc, is added to the core in the place of ²³⁸U. Tungsten and ⁹⁹Tc have strong capture resonances at appropriate energies, and ⁹⁹Tc itself is a long-lived fission product to be transmuted with profit.

This core allows the achievement of a consumption rate of ~100 kg/TW(electric)·h of transuranic elements, ~70 kg/TW(electric)·h for plutonium (due to ²³⁸U suppression), and 30 to 35 kg/TW(electric)·h for minor actinides. In addition, ~14 kg/TW(electric)·h of ⁹⁹Tc is destroyed when this element is present in the core (the initial loading of ⁹⁹Tc is >4000 kg in the core).

The activity of newly designed subassemblies has also been investigated in comparison to standard fast reactor subassemblies (neutron sources, decay heat, and gamma dose rate). Finally, a transmutation scenario involving pressurized water reactors and minor actinide-burning fast reactors has been studied to estimate the necessary proportion of burner reactors and the achievable radiotoxicity reduction with respect to a reference open cycle.