In nuclear technology, neutron data are fundamental for a variety of applications. The field which relies the most on neutron data is by far nuclear energy. In recent years, new studies have been triggered by the urgent need to find safe, clean and possibly economic energy supplies to progressively replace fossil fuels, so to limit emissions of CO2, responsible of the so-called greenhouse effect, i.e. an increase of the average global temperature and related climatic changes. In this respect, an important role in the mix of energy sources of the future could be played by nuclear energy, in particular in developing countries. However, together with some advantages, nuclear energy by fission presents also some disadvantages. The major drawbacks affecting current technology are the low efficiency in the use of uranium resources and the abundant production of high-level nuclear waste, mostly made of long-lived fission fragments and trans-uranium (TRU) actinides.
Since a few years, new systems are being investigated, which could allow to overcome the limitations of current nuclear reactors. A promising solution to the waste problem is the use of subcritical Accelerator Driven Systems (ADS), in which isotopes with long lifetime are transmuted in stable or short-lived nuclei by means of neutron-induced reactions (mainly capture and fission). In this scheme, high-current, high-energy proton or deuteron accelerator supplies the neutron flux necessary to sustain the transmutation reactions. Together with R&D on high-current accelerators, progresses in the knowledge of basic nuclear data related to the transmutation process are also for ADS
Another possibility being investigated are the so-called Generation IV fast nuclear reactors. The main concept of Gen IV reactors is the partial or full recycling of transuranium actinides, so to achieve a higher efficiency in the utilization of uranium resources and, especially, minimize the final volume of high-level nuclear waste to be stored in geological repositories. As for ADS, new data on capture, fission and inelastic reactions for several isotopes, in particular for actinides, are needed for the development of Gen IV reactors.
Finally, studies are now being performed on alternative fuel cycles. An interesting possibility is the use of the Th/U cycle, eventually in conjunction with ADS and/or with Gen IV systems. The advantages of this fuel cycle are the availability of Th, which is 3 to 4 times more abundant than uranium in the Earth crust, and the low production of Pu and heavy actinides.
The design of advanced nuclear energy systems requires accurate neutron data for a large number of isotopes. In particular, high-accuracy, high-resolution cross-section data are needed on neutron induced reactions (capture, fission and inelastic reaction) for several actinides, long-lived fission fragments and structural materials. Many of these needs can be addressed at the n_TOF facility at CERN. The very high instantaneous neutron flux of this CERN installation is particularly convenient for measurements of radioactive isotopes, such as minor actinides present in the nuclear waste. In the first experimental campaign, several measurement on capture and fission cross-section have been performed on various long-lived U, Pu, Np, Am and Cm isotopes, of outmost importance for project of nuclear waste transmutation and for next generation nuclear energy systems. More measurements on other components of the nuclear waste are already planned for the next few years, while a second experimental area with an even higher neutron flux will allow to perform difficult measurements on short-lived radionuclides of interest for various technological applications.