The used fuel discharged from nuclear power plants constitutes the main contribution to nuclear waste in countries which do not undertake reprocessing. As such, its disposal requires isolation from the biosphere in stable deep geological formations for long periods of time (some hundred thousand years) until its radioactivity decreases through the process of radioactive decay. Ways for significantly reducing the volumes and radiotoxicities of the waste and to shorten the very long times for which the waste must be stored safely are being investigated. This is the motivation behind the partitioning and transmutation (P&T) activities worldwide. This paper addresses the potential impact of P&T on the long-term disposal of nuclear waste. In particular, it evaluates how realistic P&T scenarios can lead to a reduction in the time required for the waste to be stored safely. The calculations have been done independently by three research groups: ITU and FZK in Germany, and by the CEA in France.
Powerful tabletop lasers are now available in the laboratory and can be used to induce nuclear reactions. We report the first demonstration of nuclear fission using a high repetition rate tabletop laser with intensities of 10 20 W/cm 2 . Actinide photo-fission has been achieved in both 238 U and 232 Th from the high-energy bremsstrahlung radiation produced by laser acceleration of electrons. The fission products were identified by time-resolved γspectroscopy.
Intense laser-plasma interactions produce high brightness beams of gamma rays, neutrons and ions and have the potential to deliver accelerating gradients more than 1000 times higher than conventional accelerator technology, and on a tabletop scale. This paper demonstrates one of the exciting applications of this technology, namely for transmutation studies of long-lived radioactive waste. We report the laser-driven photo-transmutation of long-lived 129 I with a half-life of 15.7 million years to 128 I with a half-life of 25 min. In addition, an integrated cross-section of 97±40 mbarns for the reaction 129 I(γ ,n) 128 I is determined from the measured ratio of the (γ ,n) induced 128 I and 126 I activities. The potential for affordable, easy to shield, tabletop laser technology for nuclear transmutation studies is highlighted.
The electrical resistivity and specific heat of samples of 241Am and 243Am are reported. The electrical resistivity at room temperature is reduced compared with the value for plutonium, while the power law exponent at low temperatures is increased. The electronic specific heat coefficient is lower than for the lighter actinides. These features lead to the conclusion that americium is the first of the actinides in which the 5 f electrons are essentially localized. Anomalies occur in the electrical resistivity and in the specific heat in the region of 60 K, the cause of which is unknown.
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