Research on the incineration of plutonium in a modular HTR using thorium-based fuel

Abstract Large stockpiles of plutonium have accumulated globally. In order to avoid the production of second-generation plutonium during the reuse of this nuclear fuel, it can be incinerated in combination with the fertile material thorium instead of uranium. The coated-particle fuel of high-temperature reactors (HTR) allows a very high heavy metal burnup and thus it can achieve a very high incineration fraction of the initially loaded plutonium (∼86%) already during the first reuse in a modular pebble-bed HTR. Only a negligible amount of second-generation plutonium is bred from the small quantity of highly enriched uranium, which is used as make-up fissile material. An optimization of the fractions of Pu, U and Th contained in the fuel elements has been done on condition that a negative temperature coefficient of the reactivity has to be achieved over the whole range of operating temperature.