This talk will explore the possible use of Thorium as a fuel source for nuclear reactors, which could make use of this element instead of Uranium which will be increasingly hard to mine at a cost effective rate over the coming 100 years. Thorium reactors will require different technologies to Uranium reactors, and this talk will explore the different fuel cycle using the latest UK research.
Currently, the vast majority of the world’s nuclear energy systems are fuelled with uranium. At 2011 consumption rates, the reserve of uranium ore that is available at US$80/kgU is expected to be exhausted within 80 years. Expectations that the world’s uranium ore reserves (excluding uranium contained in seawater) would be totally consumed range between 150–500 years. It begs the question: how best can this finite reserve of uranium be extended? The majority of the global fleet of nuclear reactors are light water reactors that mainly comprise pressurised water reactors and boiling water reactors. At present, these technologies mainly operate ‘open’ nuclear fuel cycles: where uranium ore is mined and milled, enriched such that it contains 3–5% 235U (cf. ~0.7% 235U contained in natural uranium), fabricated into fuel and loaded into the reactor. The fuel typically stays within the reactor for 3–5 years before being discharged and cooled, with a view to being directly disposed in a deep geological repository. With open nuclear fuel cycles, no reprocessing of the spent nuclear fuel takes place. Spent nuclear fuel can be reprocessed — in ‘closed’ nuclear fuel cycles — to extract unburnt uranium, plutonium, and other fissile isotopes; however, the savings in uranium ore and volume of spent nuclear fuel has to be traded-off against the much greater economic cost and added potential for diversion and proliferation. Given these barriers, it is expected that ‘open’ nuclear fuel cycles will still dominate in the near-term. It is been suggested that thorium, an element lighter than uranium, has the potential to become a future nuclear fuel. Thorium has traditionally been associated with closed nuclear fuel cycles, where fissile 233U that has been bred in the reactor is separated and refabricated into fresh nuclear fuel. However, given the aforementioned barriers, an open question remains as to whether thorium can be adopted in open nuclear fuel cycles and advantages and disadvantages this may yield. This talk will introduce the status of the world’s nuclear energy technologies, geological reserves of uranium and thorium, and the differences and trade-offs between ‘open’ and ‘closed’ nuclear fuel cycles. Technologies that could potentially use thorium and enriched uranium in open nuclear fuel cycles are outlined, before detailing the results of fuel-cycle modelling (performed with the UK National Nuclear Laboratory code ‘ORION’) to compare the material flow, characteristics of the spent nuclear fuel, economics, and an assessment of the proliferation-resistance of three different thorium-uranium-fuelled systems to a reference uranium-fuelled system. A number of counter-intuitive results that affect how thorium may be incorporated in the near-term will be presented, with an outward look towards thorium in closed nuclear fuel cycles and novel nuclear energy technologies.