Conceptual capabilities of a pyroelectrochemical technology for the thorium engagament in the fast neutron reactor fuel cycle
The use of thorium in a combination with plutonium in nuclear power offers a solution to the problem of reducing the accumulation of long-lived transplutonium nuclides. Along with this, the existing uranium fuel cycle (UFC) has such disadvantage as vulnerability to unauthorized use of nuclear materials. The thorium fuel cycle (TFC) does not have these drawbacks.
The engagement of thorium in nuclear power is possible provided there is a respective technology to reprocess irradiated thorium. A fuel cycle based on thorium oxide may not differ in principle from the developed pyrochemical fuel cycle containing uranium and plutonium oxides. In a compact state, it is by electrolysis of molten salts from thorium-containing electrolytes that thorium oxide is most commonly obtained. Most of the studies into the physicochemical and electrochemical behavior of thorium in molten haloids of alkali and alkaline-earth metals were conducted in the 1960s and the 1970s.
Since an extensive experimental material has been accumulated by now to justify the use of pyroelectrochemical and chemical processes for regeneration of fuel in molten salts, then it has also been proposed that technologies to reprocess fuel in molten chlorides of alkali metals should be used resulting in a crystalline product that can be used for the fuel element fabrication.
Unlike uranium and plutonium, thorium has a simpler behavior in molten salt environments. In molten salts, thorium exists predominantly in the form of Th4+, and the mixture of uranium and thorium dioxides with a content of ThO2 of up to 50% can be obtained by electrolysis of molten salts.
Therefore, the existing amount of knowledge about the chemistry of thorium allows one to regard the use of pyrochemical processes in production of thorium oxide as highly promising, and the available data on the physicochemical properties of thorium and its compounds in high-temperature molten salts makes it possible to state that the pyroelectrochemical technology can be potentially used in production and reprocessing of thorium fuel.
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