You wouldn’t know it from reading most papers, but the last five years have accommodated noteworthy developments in the chronically underreported world of next generation nuclear research. It is unfortunate that nuclear tends only to get airtime when journalists deign to dispense dismissive, undergraduate analysis, obligatorily set in the ‘wake’ of Fukushima and aimed at a caricature of the industry. The impression one gets from the nuclear landscape is actually one of careful optimism, an optimism built upon the sight of many bright lights on the next-gen horizon. The Liquid Fluoride Thorium Reactor (pronounced ‘lifter’ in acronymic form) is one of those bright lights, one that China is chasing, and one that Britain would do well to pay more attention to.
The LFTR is a type of Molten Salt Reactor: Molten Salt Reactors are Generation IV nuclear fission reactors that use molten salt as either the primary reactor coolant or as the fuel itself; they trace their origin to a series of experiments directed by Alvin Weinberg at Oak Ridge National Laboratory in the ‘50s and ‘60s. The LFTR is differentiated from other variants of the MSR by the fact that it runs on thorium rather than uranium, thorium being an element that is fertile rather than fissile, and which will transmute to fissile uranium-233 upon exposure to neutrons. Weinberg’s research was fruitful and instructive, and illuminated many solutions to the complex mechanical problems that are raised by the use of a liquid fuel, but Nixon nonetheless terminated research in ’69 (some say because of the unsuitability of thorium to the manufacture of nuclear weapons, though this claim is questionable). After enduring a long purgatory, MSR technology has experienced something of a renaissance in recent years: dust-cloaked Oak Ridge dossiers, long dormant in office drawers, are being re-examined by pioneering start-ups. The MSR movement gained considerable momentum in 2011 when the Chinese Academy of Sciences publicised its intention to commercialise a thorium-based MSR in 20 years (it is also developing non-thorium MSRs and solid fuel thorium reactors). The Shanghai Institute of Applied Physics has since employed 700 nuclear engineers in this service: a 10MW pilot LFTR is expected to be operationalised in 2025, with a 100MW version set to follow in 2035. Given that China theoretically has enough thorium to satisfy its energy needs for the next 20,000 years, this seems a sage application of resources.
Of course China still has much to do, there are obstacles to overcome and commercialisation will not be viable until the late 2020s, but it has nonetheless taken the plunge, undoubtedly motivated by considerable hypothetical advantages over conventional Pressure Water Reactors. According to Flibe Energy, headed by nuclear scientist Kirk Sorensen, thorium is so energy dense that 6600 tonnes of it could replace the ‘combined 5.3 billion tonnes of coal, 31.1 billion barrels of oil, 2.92 trillion cubic meters of natural gas, and 65,000 tonnes of uranium that the world consumes annually’. It is approximately 3X more abundant in the Earth’s crust than uranium, and significant quantities have already been extracted as the by-products of existing mining operations. Most compellingly, the energy output of a LFTR, per metric ton of thorium ore, is estimated to be 200X greater than the output of a Light Water Reactor (a type of PWR).
In addition to the advantages conferred by the use of thorium as a fuel, the design of the LFTR also delivers a host of benefits: the core, blanket, and primary cooling salt loops are all engineered to function at near atmospheric pressure and absent of water or steam, thus precluding the possibility of a Fukushima-style pressurised release. For this reason, the containment vessel also needn’t be much larger than the reactor itself, thereby alleviating construction costs and times. Crucially, liquid fuel is self-regulating: in the event of an increase in operating temperature the ‘thermal expansion of the liquid fuel and the moderator vessel containing it reduces the reactivity of the core’ (i.e. the more reactive the core becomes, the more the liquid fuel acts to reduce reactivity). Even some chaotic event, like an interruption in the supply of electricity to the plant, could be safely negotiated: a freeze plug, cooled by an electric fan, is installed in the base of the core vessel; if the supply of electricity to the plant is disturbed, the fan ceases to rotate and ‘the plug melts’, thus allowing the liquid fuel in the core to be safely evacuated into a ‘subcritical geometry’ inside of a catch basin (a subcritical geometry is an environment in which neutron losses exceed neutron production and the liquid fuel departs from a state of criticality, or self-sustaining fission).
China has been trailblazing in the world of next-gen nuclear for five years now: the fact that they are so aggressively chasing LFTR technology should excite our curiosity. The combination of ‘simpler fuel handling, smaller components, markedly lower fuel costs and significantly higher energy efficiency’ raise the prospects of attracting capital, and with the price of LFTR-generated electricity estimated to be 25% lower than the price of electricity generated by conventional nuclear power plants, the public would likely also be receptive. The government should engage Moltex Energy, a London-based company that has been a pioneer of Generation IV MSR technology, in an intellectual partnership to explore the mechanics, advantages, and disadvantages of a home-grown LFTR project. Given how mutually beneficial the collaboration between Oak Ridge National Laboratory and the Shanghai Institute of Applied Physics has been, the potential for a Sino-British partnership is real. Circumstances are auspicious: a little enterprise is now required.