Review of the microheterogeneous thoria‐urania fuel for micro‐sized high temperature reactors

Abstract

Summary This paper presents a systematic review of the micro‐modular thorium‐fueled high temperature reactors (HTR) loaded with duplex fuel pellet design. Specifically, each unique criterion of the design is discussed separately in an attempt to understand the combined advantages of the proposed reactor. Micro modular HTRs have great potential as a source of electricity or industrial heat in the future. The use of thorium not only improves its economic performance and safety, but also prolongs its operation. Nevertheless, the traditional seed‐and‐blanket configuration would not be able to maximize the thorium fuel burnup. As such, a new tristructural‐isotopic (TRISO) fuel based on duplex pellet designs were proposed instead. It should be noted that these duplex pellets were not practical for pressurized water reactor (PWR) technology due to its uneven power distribution which possibly leads to a very high local pellet temperature. However, this unorthodox inherent characteristics of the duplex pellets may actually suit the HTR burnup profile better due to its substantially higher thermal margin ‐ thus possibly enabling a relatively long operation of the HTR. The paper shall thereby provide a reasonably sound justification for the detailed technical investigations of the proposed reactor design.

A neutronic investigation of tristructural isotropic‐duplex fuel in a high‐temperature reactor prismatic seed‐and‐blanket fuel block configuration with reduced power peaking

“…The use of duplex pellet designs increased the ratio of neutron capture in fertile material to neutron absorption in fissile material, resulting in prolonged fuel burnup and core life 29,31,32 . This was demonstrated by previous studies in which there was a 15% burnup improvement through the use of duplex pellets in PWR synergistically with axial pellet arrangement and checkboard rod configuration 7,27 . Although it has excellent potential, research into the use of ThO 2 ‐UO 2 duplex fuel design in other types of reactors aside PWRs is insubstantial.…”

“…In fact, during the rapid commercialization of nuclear power reactors in the 1950s to the 1970s, 232 Th was extensively studied on prototype scales in different types of reactor technologies 6,7 . It should be noted that thorium reactor designs, specifically the high‐temperature reactors (HTRs) and light water reactors (LWRs) variant, utilize thorium in the forms of either molten salt (ThF 4 or ThCl 4 ) or solid fuels (ThO 2 ) 8 .…”

“…The above‐mentioned reactor configurations were based on the traditional UO 2 pellet design. An alternative configuration, such as one that is based on the tristructural‐isotopic (TRISO) fuel designs, would possibly offer unique technical advantages, which merit further investigations 7 . For example, TRISO fuels can potentially withstand extremely high fuel burn‐up.…”

A comparative analysis of the neutronic performance of thorium mixed with uranium or plutonium in a high‐temperature pebble‐bed reactor

“…22 According to the literature review, studies comparing the use of thorium-based fuel with various driver materials in HTGRs have often been conducted in prismatic block-type HTRs because of the flexible core that can support a wide range of fuel cycles. [35][36][37] Studies for PBR, on the other hand, have been conducted separately, and ThO 2 + UO 2 or ThO 2 + PuO 2 fuels have been widely used. 24,25,38,39 A recent comparative analysis between using HALEU (17 wt%) and ThO 2 + RGPuO 2 (RGPuO 2 content-37.6 wt%) in the PBR-HTR-10 reactor was conducted by Alzamly et al 40 Their results showed that core a fueled by ThO 2 + RGPuO 2 achieves a 24% longer fuel cycle than one fueled by HALEU (17 wt%).…”

Comparison of neutronic aspects in high‐temperature gas‐cooled reactor using ZrC and SiC Triso particle with 50 and 100 MWt power

“…One of the advantages is the high conversion of fertile to fissile in the thermal spectrum, increasing the utilization of the fuel. This high conversion rate is because U‐233, which is generated from the Th‐232 transmutation chain, emits more neutrons per absorption than U‐235 8 …”