Feasibility Study of 13 Thorium-Plutonium Mixed Oxide Core

Abstract EN

Thorium-plutonium mixed oxide (Th-MOX) fuel has become one of the most promising solutions to reduce a large and increasing plutonium stockpile.

Compared with traditional uranium-plutonium mixed oxide (U-MOX) fuels, Th-MOX fuel has higher consumption rate of plutonium in LWRs.

Besides, thorium based fuels have improved thermomechanical material properties compared with traditional U-MOX fuels.

Previous studies on a full Th-MOX core have shown reduced efficiency in reactivity control mechanisms, stronger reactivity feedback, and a significantly lower fraction of delayed neutrons compared with a traditional uranium oxide (UOX) core.

These problems complicate the implementation of a full Th-MOX core in a similar way as for a traditional U-MOX core.

In order to reduce and avoid some of these issues, the introduction of a lower fraction of Th-MOX fuel in the core is proposed.

In this study, one-third of the assemblies are Th-MOX fuel, and the rest are traditional UOX fuel.

The feasibility study is based on the Swedish Ringhals-3 PWR.

The results show that the core characteristics are more similar to a traditional UOX core, and the fraction of delayed neutrons is within acceptable limits.

Moreover, the damping of axial xenon oscillations induced by control rod insertions is almost 5 times more effective for the 1/3 Th-MOX core compared with the standard core.