The thorium- based nuclear fuel cycle

Right from the start of the development of nuclear energy, thorium was considered a potential fuel to complement or even replace uranium, whose natural scarcity was initially feared. In fact, as we shall see in this article, thorium is not a genuine alternative to uranium, because unlike uranium, it does not possess an isotope that can be "fissile" by slow neutrons, but simply generates one, uranium 233 (U-233), by neutron capture in a nuclear reactor. This artificial element, which is relatively stable (half-life 160,000 years), is an excellent fissile isotope for "thermal" reactors. It is even better than uranium 235 (U-235) or plutonium 239 (Pu-239), hence the potential interest in thorium as a "fertile" nucleus. For this reason, the thorium cycle has always been the subject of significant study around the world, an overview of which is given in this article. We will also examine the advantages and disadvantages of using thorium in reactors, and the technological challenges that need to be overcome for industrial implementation of the thorium cycle.