One crucial problem of nuclear energy is the production of radioactive waste. The radiotoxicity of spent nuclear fuel is dominated by plutonium and other minor actinides (see figure 1). New generation IV reactors with a closed fuel cycle shall minimize the amount of long-lived radioactive waste.
Figure 1: Radiotoxicity of spend nuclear fuel © Salvatores, NEA report 6090, 2006
One possibility of reducing the storage time of radioactive waste is the transmutation of long-lived isotopes into short-lived isotopes. This can be done by bombarding them with neutrons. The ability of transmutation of a generation IV reactors depends crucially on the neutron spectrum (the neutron energy) used in the reactor. Plutonium and minor actinides (which produce most of the radiotoxicity - see figure 1) are fissionable in a fast neutron spectrum. The fission products have much shorter half lives (102 yr) compared to plutonium or other minor actinides (up to 105 yr) leading to a shorter storage time of the radioactive waste.
Figure 2: Radiotoxicity of spent nuclear fuel with and without transmutation © Salvatores, NEA report 6090, 2006
If all plutonium of the spent nuclear fuel is recycled and fissioned, the radiotoxicity can be reduced up to factor of 10. Furthermore it can be reduced up to a factor of 100, if all minor actinides are burnt (see figure 2 - the circles, crosses and stars represent the radiotoxicity after different transmutation processes).
Precise cross sections for nuclear reactions with fast neutrons are necessary for the development of generation IV reactors and dedicated accelerators. Especially precise data for inelastic neutron scattering on reactor materials (iron) and fission cross sections for plutonium and minor actinides of are needed.
For this reason the joint research project TRAKULA deals with experiments with fast neutrons, gamma spectroscopy of transmutation products and fission experiments with minor actinides.