Transmutation for a nuclear revival
Will the next generation of accelerator-driven nuclear reactors signal a nuclear revival, despite the problems encountered by Japanese reactors in the aftermath of the earthquake and tsunami which hit the archipelago? They effectively allow for better management of products from traditional power stations, by recycling fissile material such as uranium and plutonium and transforming long-life waste products through transmutation (minor actinides). Natural transmutation of radio-elements is very slow: for example, several hundreds of thousands of years are required for a plutonium atom to be transformed into lead. Burying them in the earth while waiting for their radio-toxicity to disappear is, therefore, not a satisfactory solution. New generation reactors offer a faster and safer solution: by irradiating the radioelements which cannot be recycled, they are transformed into waste with a shorter life.
The process of transmutation is based on the nuclear reactions of spallation, a subject which Davide Mancusi, a researcher in the ULg's Astrophysics, Geophysics and Oceanology Department (AGO), has been studying for several years. Etymologically speaking, 'spallation' means 'extraction'. A spallation reaction consists of sending a high energy particle, often a proton, into a nucleus which then ejects different sorts of particles. Among these particles are neutrons which can be added to nuclear station waste for transformation. The spallation reaction leaves behind it a residual hot nucleus which will de-excite itself. Two forms of de-excitation are possible: fission and evaporation.