Innovative model of annular fuel design for lead-cooled fast reactors

Abstract

The results of an investigation of the analytical solutions of the default – solid fuel and innovative – annular fuel approach are summarized in this paper. Innovative annular fuel concept is described in details and shows that it is a promising technology in terms of safety aspects. Liquid metal cooled reactors are considered to burn used nuclear fuel from conventional nuclear power plants or processed weapon grade plutonium and therefore, higher safety standards must be assured.

During the design process seven fuel assemblies with annular fuel elements were created. The investigation was conducted in case of both commonly used fuel lattices i.e. square and hexagonal, moreover effect of spacer grids was taken into considerations. Results show that the annular fuel is superior in case of maximum fuel temperature, which is up to 757 °C lower than in default base design – with use of spacer grids. The most promising designs are hexagonal lattice with 91 fuel elements and square lattice 18 × 18, where the maximum temperatures are 822 °C and 732 °C, while pressure drop of 185 kPa and 128 kPa, respectively.

The square lattice proved better performance according to our evaluation, it is possible to obtain very similar or smaller pressure drop than default – solid fuel – design. Hence, use of the same or even smaller coolant pumps is possible in case of annular fuel elements. Moreover, the innovative fuel also allows to overpower reactor up to 110% of nominal power, while securing all safety limits. Therefore, it is promising concept and further investigation would be interesting.