Nuclear power—with its high energy density and low carbon footprint—is a source with which the international community has decades of experience. However, the challenges that come along with the technology have kept it from becoming a more dominant factor in the global energy mix. Geopolitical issues lie at the center of many of these challenges. Matters of safety, waste management, and proliferation are intrinsic to the technology. Although the carbon footprint of using nuclear fuels is smaller, there are still disadvantages of using nuclear fuel. The waste, while a much lower volume must be handled very carefully because of its radioactivity. Nuclear fuels require far more complicated systems to extract their energy, which calls for greater regulation.
About 440 reactors with combined capacity of over 390 GWe, require some 79,500 tonnes of uranium oxide concentrate containing about 67,500 tonnes of uranium (tU) from mines (or the equivalent from stockpiles or secondary sources) each year. This includes initial cores for new reactors coming online. The capacity is growing slowly, and at the same time the reactors are being run more productively, with higher capacity factors, and reactor power levels. However, these factors increasing fuel demand are offset by a trend for increased efficiencies, so demand is dampened – over the 20 years from 1970 there was a 25% reduction in uranium demand per kWh output in Europe due to such improvements, which continue today.Each GWe of increased new capacity will require about 150 tU/yr of extra mine production routinely, and about 300-450 tU for the first fuel load.
Looking ten years ahead, the market is expected to grow. The reference scenario of the 2019 edition of the World Nuclear Association’s Nuclear Fuel Report shows a 26% increase in uranium demand over 2020-30 (for a 22% increase in reactor capacity – many new cores will be required).
Mines in 2019 supplied some 63,273 tonnes of uranium oxide concentrate (U3O8) containing 53,656 tU, 80% of the utilities’ annual requirements . The balance is made up from secondary sources including stockpiled uranium held by utilities, and in the last few years of low prices those civil stockpiles have been built up again following their depletion over 1990-2005. At the end of 2018 they were estimated at almost 90,000 tU in Europe and the USA, about 120,000 tU in China, and about 70,000 tU in the rest of Asia.
With the main growth in uranium demand being in Russia and China, it is noteworthy that the vertically-integrated sovereign nuclear industries in these countries (and potentially India) have sought equity in uranium mines abroad, bypassing the market to some extent. Strategic investment in uranium production, even if it is not lowest-cost, has become the priority while world prices have been generally low. Russia’s ARMZ bought Canada-based Uranium One in 2013, and China holds equity in mines in Niger, Namibia, Kazakhstan, Uzbekistan and Canada.
Advances in breeder reactor technology could allow the current reserves of uranium to provide power for humanity for billions of years, thus making nuclear power a sustainable energy. However, in 2010 the International Panel on Fissile Materials said “After six decades and the expenditure of the equivalent of tens of billions of dollars, the promise of breeder reactors remains largely unfulfilled and efforts to commercialize them have been steadily cut back in most countries.” But in 2016, the Russian BN-800 fast-neutron breeder reactor started producing commercially at full power (800 MWe), replacing the previous BN-600. As of 2020, the Chinese CFR-600 is under construction after the success of the China Experimental Fast Reactor, based on the BN-800. These reactors are currently generating mostly electricity rather than new fuel because the abundance and low price of mined and reprocessed uranium oxide makes breeding uneconomical, but they can switch to breed new fuel and close the cycle as needed.
Peak uranium is the point in time that the maximum global uranium production rate is reached. After that peak, according to Hubbert peak theory, the rate of production enters a terminal decline. While uranium is used in nuclear weapons, its primary use is for energy generation via nuclear fission of the uranium-235 isotope in a nuclear power reactor. Each kilogram of uranium-235 fissioned releases the energy equivalent of millions of times its mass in chemical reactants, as much energy as 2700 tons of coal, but uranium-235 is only 0.7% of the mass of natural uranium. Uranium-235 is a finite non-renewable resource.
As well as existing and likely new mines, nuclear fuel supply may be from secondary sources including:
Recycled uranium and plutonium from used fuel, as mixed oxide (MOX) fuel .A key, nearly unique, characteristic of nuclear energy is that used fuel may be reprocessed to recover fissile and fertile materials in order to provide fresh fuel for existing and future nuclear power plants. Several European countries, Russia, China and Japan have policies to reprocess used nuclear fuel, although government policies in many other countries have not yet come round to seeing used fuel as a resource rather than a waste. Re-enriched depleted uranium tails.
Ex-military weapons-grade uranium, blended down. Military uranium for weapons was enriched to much higher levels than that for the civil fuel cycle. Weapons-grade material is about 97% U-235, and this can be diluted about 25:1 with depleted uranium (or 30:1 with enriched depleted uranium) to reduce it to about 4%, suitable for use in a power reactor. From 1999 to 2013 the dilution of 30 tonnes per year of such material displaced about 9720 tonnes U3O8 per year of mine production. Ex-military weapons-grade plutonium, as MOX fuel.
Over the last 50 years or so the principal reason for reprocessing used fuel has been to recover unused plutonium, along with less immediately useful unused uranium, in the used fuel elements and thereby close the fuel cycle, gaining some 25-30% more energy from the original uranium in the process. This contributes to national energy security. A secondary reason is to reduce the volume of material to be disposed of as high-level waste to about one-fifth. In addition, the level of radioactivity in the waste from reprocessing is much smaller and after about 100 years falls much more rapidly than in used fuel itself.
Commercial reprocessing plants are operating in France and Russia with a combined capacity of about 2000 tonnes of heavy metal (tHM) per year. World reprocessing capacity would increase by 800 tHM with the restart of the Japanese plant at Rokkasho-Mura. Further capacity is under construction in Russia and China, and there are a number of other plants with small reprocessing capacities worldwide.
These are all considerations based on current power reactors, but moving to fourth-generation fast neutron reactors will change the outlook dramatically, and means that not only used fuel from today’s reactors but also the large stockpiles of depleted uranium (from enrichment plants, about 1.2 million tonnes end 2018) become a fuel source. Uranium mining will become much less significant.
Ural federal university: Scientists Discover a Technology For Reprocessing Nuclear Fuel
Scientists have obtained fundamental information useful for creating an advanced technology for reprocessing (regeneration) of spent nuclear fuel (SNF). With this technology, SNF can be reused in nuclear power plants (NPPs). This is extremely important, since the deposits of uranium – the main component of spent nuclear fuel – are small in nature. The discovery was made by chemists while working on the problem of separating actinides and lanthanides in chloride melts. An article about the research carried out and the results obtained was published in The Journal of Chemical Thermodynamics.
The goal of the scientists is to develop a pyrochemical method for reprocessing spent nuclear fuel in molten salt with subsequent extraction and reuse of uranium and plutonium in nuclear reactors, including fast neutron reactors. The latter belong to actinides. To restore the nuclear-physical properties of the fuel, it is necessary to clean it from fission products that “interfere” with the process. First of all, these are lanthanides. It is also necessary to remove the most dangerous elements – cesium and technetium.
In this regard, chemists are studying the electrochemical and thermodynamic properties of cerium compounds – one of the main fission products from the group of lanthanides – in a melt of lithium and potassium chlorides of eutectic composition. Used as a solvent, this melt is economical and has a low melting point. The optimum operating temperature of the melt is 450–500 degrees Celcium: an increase in temperature leads to the volatility of lithium chloride, in addition, the corrosion resistance of equipment deteriorates and energy costs increase.
The significance of the research is explained by Valery Smolenskiy, Chief Researcher of the Laboratory of Radiochemistry of the Institute of High Temperatures of the Ural Branch of the Russian Academy of Sciences, Senior Researcher of the Scientific Laboratory “Pyrochemical Technologies and Materials of a Closed Nuclear Fuel Cycle” of the Ural Federal University and the Institute of High Temperatures of the Ural Branch of the Russian Academy of Sciences.
“During the operation of a nuclear power plant, as a result of nuclear reactions, various fragmentation elements are formed, which have different degrees of activity and life expectancy. The most dangerous of them are isotopes of cesium and other lanthanides, as well as technetium, molybdenum, tungsten, and a number of noble metals. Among the dangerous elements and minor actinides are neptunium, americium, curium. During the operation of a nuclear reactor, lanthanides form only a few percent of the fuel volume, but at the same time they are highly active, dangerous and are the so-called “neutron poisons”, that is, they absorb the neutron flux. This leads to a decrease in the efficiency and safety of the reactor, ”the scientist states.
According to Valery Smolensky, the regenerated spent nuclear fuel intended for reuse at nuclear power plants and loading into reactors must be “clean” and not contain debris. Therefore, uranium and plutonium, which are part of the fuel, must be separated from fission products, in particular from lanthanides, including cerium. In addition, in countries that actively generate and use atomic energy, including Russia, there is a problem of accumulating nuclear waste: their storage is dangerous and costly, and the possibilities for storage are limited. This is also the reason for the development of technologies for processing spent nuclear fuel in molten salt. In our country, the task of reprocessing nuclear waste is supposed to be solved by creating a molten salt reactor-afterburner, in which the highly active and most dangerous fission products will be transmuted into inactive or short-lived elements.
In Russia, the task of reprocessing nuclear waste is supposed to be solved by creating a molten salt reactor-afterburner, in which the highly active and most dangerous fission products will be transmuted into inactive or short-lived elements. For the processing of low-level fuel with a long holding time, the PUREX process is currently used, based on the use of hydrometallurgical methods. The regeneration of high-level fuel with a short holding time must be carried out in radiation-resistant media, such as salt and metal melts.
Currently, SNF reprocessing uses mainly MOX fuel for thermal reactors, consisting of uranium oxides or mixed oxides of uranium and plutonium. The resulting fission products are also present in MOX fuel mainly in the form of oxides. Therefore, in the process of regeneration, it is necessary to know both the electrochemical and thermodynamic properties of oxygen and anoxic compounds of fragmentation elements, including cerium.
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