Assembly-level analysis of heterogeneous Th-Pu PWR fuel

It was found that the homogeneous fuel with and without burnable poisons was able to achieve much higher Pu incinerations than the heterogeneous fuel configurations, while still attaining a reasonably high discharge burnup. This is because in the heterogeneous cases, 233U breeding is faster, thereby contributing to a much larger fraction of total power produced by the assembly. In contrast, 233U build-up is slower in the homogeneous case and therefore Pu burning is greater. This 233U begins to contribute a significant fraction of power produced only towards the end of life, thus extending criticality, allowing more Pu to burn.