LFTR: In Search of the Ideal Pathway to Thorium Utilization—Development Program and Current Status

Abstract

Thorium has gained substantial attention as a potential energy source that could rival and eventually replace fossil fuels as humanity’s primary energy source. This could not have come at a more opportune time as concerns about global climate change from CO₂ emissions and the specter of finite fossil fuel resources create serious challenges for the continuation of our advanced industrial societies, which are reliant on readily available and affordable energy. Thorium also potentially represents the catalyst with which the nuclear industry could reinvent itself and finally gain widespread public acceptance. There are many opinions on how to utilize thorium as a fuel, but the question of what constitutes an ‘ideal’ pathway has mostly been underemphasized. Many specific characteristics of the thorium fuel cycle can differ significantly depending on the conditions and methodologies of utilization; characteristics such as safety, efficiency, waste profile and volume, and fissile protection can vary greatly according to reactor design and utilization philosophy. With thorium, we have been given an opportunity to start over, a blank slate. Therefore, in imagining the ‘Thorium Economy’ to come, it behooves the scientific and engineering communities to consider the most ‘elegant’ solution physically possible—what constitutes the ‘ideal’ and is it possible to reconcile it with what is both economically and technically practical? The characteristics desired of an ‘ideal’ nuclear reactor, in the areas of safety, efficiency, economy, and sustainability, and the five key design choices that could enable such a reactor will be discussed. This will be followed by an overview of the liquid fluoride thorium reactor, a two-fluid molten salt reactor currently under development by Flibe Energy in the USA. LFTR is a direct descendant of the MSRE, which was developed at Oak Ridge National Laboratory (ORNL) in the USA during the 1960–70s. The rationales and scientific concepts for the choices made on the design of the LFTR and how it could potentially achieve many of the desired characteristics of the ‘ideal’ nuclear system will be the focus of this article.