Assembly-level analysis of heterogeneous Th–Pu PWR fuel

Abstract

This study compares homogeneous and heterogeneous thorium-plutonium (Th-Pu) fuel assemblies (with high Pu content-20 wt%), and examines whether there is an increase in Pu incineration in the latter. A seed-blanket configuration based on the Radkowsky thorium reactor concept is used for the heterogeneous assembly. This separates the thorium blanket from the uranium seed, or in this case a plutonium seed. The seed supplies neutrons to the subcritical thorium blanket which encourages the in-situ breeding and burning of 233 U, allowing the fuel to stay critical for longer, extending burnup of the fuel. While past work on Th-Pu seed-blanket units shows superior Pu incineration compared to conventional U-Pu mixed oxide fuel, there is no literature to date that directly compares the performance of homogeneous and heterogeneous Th-Pu assembly configurations. Use of exactly the same fuel loading for both configurations allows the effects of spatial separation to be fully understood. It was found that the homogeneous fuel with and without burnable poisons were 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, 233 U breeding is faster, thereby contributing to a much larger fraction of total power produced by the assembly. In contrast, 233 U build-up is slower in the homogeneous case and therefore Pu burning is greater. This 233 U begins to contribute a significant fraction of power produced only towards the end of life, thus extending criticality, allowing more Pu to burn.

The effect of Am241 on UK plutonium recycle options in thorium-plutonium fuelled LWRs – Part I: PWRs

“…While there are notable downsides to the Th-fuel cycle, specifically the lack of commercial infrastructure and the reduced worth of certain control materials (du Toit & Naicker, 2018) (Alhaj, et al, 2016) (Lau, et al, 2014) (Insulander Bjork, et al, 2013 (Fridman & Kliem, 2011) (Lamarsh & Baratta, 2001), it may warrant further investigation. Th-Pu only recycle has been studied in depth (Zainuddin, et al, 2017) (Alhaj, et al, 2016) (Zainuddin, et al, 2016) (Tucker, et al, 2015) (Yun, et al, 2010) (Mittag & Kleim, 2011) (Schram & Klaassen, 2007) (Sorensen, et al, 2006) (Kim & Downar, 2002) (Galperin, et al, 2000). However, it is Th-Pu-MA recycle that is of more interest with respect to UK Pu management due to the previously mentioned build-up of Am241.…”

Comparison of homogeneous and heterogeneous thorium fuel blocks with four drivers in advanced high temperature reactors

“…Past studies prove a superior incineration of plutonium on thorium/plutonium seed‐blanket configurations, compared to the traditional MOX fuel in PWR . Recently, a comparison analysis between homogeneous and heterogeneous thorium/plutonium fuel assemblies (with high Pu content‐20 wt%) was conducted by Zainuddin et al It was found that the homogeneous fuel with and without burnable poisons could achieve much higher plutonium incinerations than heterogeneous fuel configurations, and could still attain a reasonably high discharge burnup.…”