Scientists of the Nuclear Technology Engineering School of Tomsk Polytechnic University are developing a technology on the basis of which it will be possible to create high-temperature gas-cooled thorium reactor units of low power, the TPU press service reports. In such installations, polytechnics are offered to burn weapons-grade plutonium, converting it into electrical and thermal energy. The heat energy produced on the thorium reactor can be further applied to the production of hydrogen on an industrial scale. And even on such installations it will be possible to desalinate water.
The results of the study are published in the journal Annals of Nuclear Energy (IF 1,312; Q2).
Thorium reactor installations can be used in those regions where there are no large water bodies and rivers, the presence of which is an indispensable condition for the construction of a classical reactor. For example, they can be used in arid areas, as well as in the north – in remote areas of Siberia and the Arctic.
“Any station, as a rule, is built on the river bank. The lake is not suitable for these purposes, as water must necessarily be flowing so that no harmful elements accumulate in it. From the river, water is collected for the needs of the nuclear power plant. In particular, it is used in the reactor core to cool it. In the thorium reactor installations, helium is used instead of water, carbon dioxide (CO2) or hydrogen can also come up. Thus, water is no longer needed to use, “says one of the authors of the article, Sergei Bedenko, assistant professor of the Engineering School of Nuclear Technology of TPU.
Fuel for a new type of reactor will be a mixture of thorium and weapons-grade plutonium.
“Weapon plutonium was produced in large quantities in the world even in the Soviet years. The cost of storing this fuel is very high, and it needs to be disposed of. In the US, it is rendered harmless by chemical methods and buried, and in Russia – burned in reactors. However, at the same time, some percentage of plutonium still remains, and it must be disposed of at radioactive waste disposal sites. Our technology will reduce this percentage. With its help, it will be possible to burn 97% of weapons-grade plutonium, – continues Sergei Bedenko. “And when all weapons-grade plutonium is disposed of, it will be possible to use uranium-235 or uranium-233 instead of it for thorium installations.”
It is noteworthy that the plant is capable of operating at low capacities (from 60W), for the active zone of the thorium reactor it will take quite a bit of fuel, and the percentage of its burn-up will be higher than that of existing reactors. After processing, 3% of the remaining weapons-grade plutonium will no longer represent a nuclear hazard. At the output a mixture of graphite, plutonium and decay products is formed, which will be very difficult to use for any other purpose. These remains can only be buried.
“Perhaps the main advantage of such installations will be that they are multi-purpose.
First, we efficiently utilize one of the most dangerous types of radioactive fuel with the thorium reactor, secondly, we get energy and heat, and thirdly, with its help, it will be possible to establish industrial hydrogen production, “summarizes Sergei Bedenko.
Scientists propose to receive hydrogen at the expense of helium, which, as already mentioned above, will replace water in the thorium reactor. In the active zone of the reactor, helium will be heated to a temperature of 1250 ° C, and then fed to a hydrogen production unit. According to polytechnics, the scale of hydrogen production at such a nuclear power plant will be much higher than in existing chemical plants. Another important advantage of the thorium plant will be that, depending on the needs of production, it will be possible to change the reactor power by increasing or decreasing the volumes of hydrogen produced.
And in general, according to scientists, the installation itself is times safer and more economical compared to traditional reactors.
The authors of the scientific article report that the advantages of such reactors include higher safety in comparison with traditional designs, increased efficiency (up to 40-50%), absence of phase transitions of the coolant, reduction in corrosion problems of working surfaces, the possibility of using different fuels and its overload in the process of reactor operation, simplified handling of spent nuclear fuel.
“First, the use of thorium in the reactor makes it possible to save money. In existing reactors, uranium is used, which is required to be enriched. This procedure is, perhaps, one of the most expensive in the nuclear industry. Thorium does not need to be enriched, and weapons-grade plutonium already contains the required concentration of fissile material. They can only be mixed and manufactured fuel pellets, – explains Sergey Bedenko. “By the way, such fuel can be used not only in thorium installations, but also on common VVER-1000 reactors.”
In addition, the very construction of thorium reactor installations contains much fewer elements than in classical reactors, which will make their construction several times cheaper. Scientists expect that such installations will be able to work out in the future not less than 10 – 20 years, and after the fuel has been worked out, the active zone of the thorium reactor can be either rebooted or disposed of.
“The initial costs for the construction of such facilities will prove to be quite substantial, but they will pay off due to the mass production of thorium-plutonium fuel, and also through the import of this technology to those countries where such installations are needed. For example, in such small countries as Vietnam or Korea, where to build a full-fledged nuclear power plant is expensive, “- says Sergei Bedenko.
In addition to hydrogen production, it will also be possible to desalinate water on thorium plants, which is important for those areas where there are problems with the availability of fresh water.
“In our article we tried, first of all, to draw the public’s attention to the fact that this technology must be developed in Russia. Now similar projects are already appearing in the USA, China, India, and Korea. And there is no doubt that the external market for the production of such plants will appear in a few years. In China, they are already producing similar fuel cells, a production line has been launched, and this year it is planned to launch the first low-power reactor. Its concept differs from the one we offer, on a number of parameters, but it is also high-temperature and can serve for the production of energy and hydrogen. However, in these installations it is planned to use not thorium, but uranium. The method proposed by us is even more effective due to the fact that thorium does not need to be enriched.
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