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

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. This paper aims to present a review of the duplex fuel pellets and its potential in a micro‐sized modular thorium HTR. The paper studies the Duplex fuel pellet: its design, historical development and technical issues. The authors present the basics of HTR thorium technology, and the technical challenges in adopting the Duplex fuel pellets into the MMR HTR which includes proposed design and analysis tools.