By Danny Brooks
November 6, 2019
WUWEI, Gansu Province, China — Late last April, two employees of the government-backed Shanghai Institute of Applied Physics were sacked after permitting the performance of a Taoist ritual at a groundbreaking ceremony for an experimental nuclear reactor. The dismissals are more or less typical of the officially atheist Chinese Communist Party, but the site, and the reactor they hope to build there, are not.
The reactor being developed is a Thorium Molten Salt Reactor (TMSR). Based on Cold War technology that until recently had been relegated to the dustbin of history, TMSRs provide a compelling alternative to nuclear reactors in use today, and could provide the means by which China achieves energy independence in the 21st century. They run on an alternate fuel cycle as compared to traditional uranium reactors and — critically for a desert region like Gansu — don’t require vast amounts of water to operate.
Traditional nuclear reactors typically use fuel consisting of solid uranium pellets stacked closely together in hundreds of rods. A moderator, usually consisting of graphite or water, ensures the reaction remains critical. Meanwhile, control rods, made up of substances which absorb neutrons without fissioning, ensure the stability of the reaction. This process is extremely delicate while also being very inefficient. As the fuel and the fuel cladding both consist of solid materials, they are subject to damage from both radiation and the escape of gaseous fission products resulting from the reaction. Damage resulting from this process severely limits the useful lifetime of the fuel, with only about 3% of the fuel’s potential energy being harnessed before it is too damaged for further use. Such inefficiencies are one of the leading causes of the nuclear industry’s intractable waste-disposal problem. Waste products from current reactors remain toxic for tens of thousands of years, requiring centuries long storage mechanisms in order to protect people and the environment from its effects. In Gansu Province, China is investigating the possibility of storing such waste in an underground facility. Meanwhile in the U.S., efforts to license and operate the Yucca Mountain Nuclear Waste Repository in Nevada have been stymied for years.
Thorium, the fuel source for the experimental reactor being developed in Gansu, is three to four times more abundant in nature than uranium, with the largest concentrations found in India. Its capacity as a reactor fuel was first demonstrated with the completion of the Molten Salt Reactor Experiment conducted at the Oak Ridge National Laboratory in Tennessee in the 1960s. Thorium itself is not fissile — it is what physicists call “fertile.” This means that it alone is not sufficient to sustain a nuclear reaction — but when bombarded with neutrons, either from a small starter-sample of the uranium used in traditional reactors, or from neutrons emitted by a particle accelerator, thorium-232 transforms into thorium-233, which decays to uranium-233. Though uranium-233 does not exist in nature, it is a fissile isotope of uranium with numerous properties that make it an ideal material for nuclear reactor fuel.
The combination of the high availability of low-cost natural gas, increasingly affordable renewable energy resources, and safety concerns sharpened by the Fukushima disaster in 2011 has contributed to many countries slowing or ceasing nuclear reactor development. Indeed, in the U.S. many reactors are set to shut down ahead of their originally planned retirement dates. For China, however, natural gas extraction is still in its infancy, making Beijing largely reliant on imported fuels. Furthermore, renewables everywhere remain challenged by intermittency problems resulting from uneven wind and solar generation. The thorium fuel cycle offers a number of safety and logistical benefits, and could be a means by which China addresses these issues while reducing CO2 emissions. Thorium reactors use molten fluoride salts instead of water as a coolant. Conventional water-cooled reactors must operate at pressures often in excess of 300 atmospheres to maintain the liquid form of the coolant water at such high temperatures. Molten salts, however, remain in liquid form for a much wider range of temperatures. This means that reactors using this design can be operated at near-atmospheric pressures, reducing engineering complexity and limiting the threat of a Fukushima-like nuclear disaster.
Thorium also offers the advantage of being a liquid fuel, offering efficiency and safety improvements as compared to traditional reactors.According to Kirk Sorensen, a former NASA aerospace engineer and chief technologist at FLIBE energy, a firm undertaking market and engineering research in connection with TMSRs, liquid-fueled reactors can use nearly 100%of their fuel. As a result, these reactors generate one-thousandth of the waste of uranium reactors while also decaying more quickly into non-radioactive elements. Additionally, the fuel-burning cycle features passive safety mechanisms. As the fuel reacts, it generates heat, causing it to expand and become less dense. As the fuel loses density, its reactivity decreases, causing it to lose heat and contract. When it contracts, it becomes denser and therefore more reactive — a self-regulating cycle emerges. Furthermore, the waste heat of TSMRs can be used to power industrial processes, including water desalination, which could prove critical in addressing water shortages in China’s northern regions in the decades to come. Should China adopt widespread use of this technology it could help usher in a new age of abundant, safe, and clean energy.
Prospects for China
Despite all of its advantages, the development of thorium reactor technology has been tepid. Today the nuclear industry remains technologically locked into using a fuel cycle that is less safe, less efficient, and less viable in the long term. Presently the industry has no incentive to change its approach to nuclear energy generation. In the U.S., research into advanced reactor designs all but ceased at the end of the 1960s, as a result of a funding cut to the Atomic Energy Commission. Notably, early researchers also failed to pursue the technology, as thorium cannot be used in the creation of nuclear weapons — the driving impetus of the Manhattan Project.
China and India’s goals for meeting emissions reductions amid rapid urbanization and growing power-demand have spurred the recent development of Asian thorium technology. In order to meet guidelines set by the Intergovernmental Panel on Climate Change (IPCC), China has pledged to reach peak carbon emissions by 2030. However, today the country relies heavily on imported coal and natural gas while meeting only about 3.6%of its power demand with nuclear energy. The country has a number of good reasons to pursue the development of thorium reactors and nuclear energy generally. According to Roger Raufer, Professor of Energy Resources and Environment at the Hopkins-Nanjing Center at Johns Hopkins SAIS, “China has an air quality problem and a CO2 problem. They also have power demand spread over large, concentrated areas, and needs that can’t be 100% met with intermittent power sources like wind and solar.”
Should the Gansu experimental reactor project prove successful, thorium-based nuclear power could be a means by which Beijing achieves energy independence and sustainability for decades to come. The South China Morning Post reports that China has invested 2 billion yuan in the last few years in molten salt research alone, and, according to the International Energy Agency, “about two-thirds of the 60 GW of nuclear power capacity currently under construction [will be] completed by 2020, of which two-thirds is in Asia Pacific (almost half is in China alone).” Thorium’s worldwide abundance portends fundamental shifts in energy politics should it receive widespread support — any country that develops it successfully could achieve a high degree of energy independence over the next decades. Beyond China, projects in India, the Netherlands, and resurgent interest in the United States suggest that, for experimental nuclear reactors, the future is bright.