The Physics of Spallation Processes

2.6. CONCLUSION “RESEARCH WITH NEUTRONS” 29The possibility of having a neutron source external to a nuclear system, will allowthe use of thorium in the future: a fuel much cleaner than uranium. This element isnot fissionable, but by capturing a neutron it can be transformed into 233 U, an isotopehaving favorable properties quite similar to the ones of 235 U, as for example being equallyfissionable and having resembling capture cross sections. The advantage is that thoriumneeds to capture 7 neutrons to transform itself into plutonium 239, which is almost impossiblegiven the fact that many other nuclear reactions are competing with capture ina subcritical core. Practically, over a thorium fast reactor lifetime only a few grams ofplutonium can be produced and an even lower quantity of the other transuranics, whichconstitute the most toxic part of a traditional uranium reactor’s waste. The huge amountof thorium available in the earth’s crust opens the way to a source of energy which isexploitable for thousands of years. For the Energy Amplifier, different strategies for thetransmutation of long-lived fission fragments are indicated. After 500 years the toxicityof the radioactive waste is below that produced by Coal burning to produce an equivalentamount of energy.For a detailed concept of the Energy Amplifier refer to refs. [AIP94, Rub96b, Rub95,Rub97, Pab97, IAEA97, ENEA01] and references therein.2.6 Conclusion “Research with Neutrons”Summarized the high intense spallation neutron source project is pioneering the mostadvanced fields for the science and technology of the 21st century. It is expected that thecollaboration of many European and international institutions with different experienceand knowledge will bring significant progress. From the scientific point of view the highestpower neutron source will be one of the most significant facilities in the world whichcan be utilized by pharmaceuticals, agriculture, materials science, physics, chemistry andgeneral industries. The aspect of transmutation processing has important socio-economicsignificance in determining the spent fuel policy of the next generation and is an urgentsubject that should be researched and developed systematically under worldwide cooperation.R&D is expected to be further promoted by enhancing cooperation of researchersworldwide. Already the feasibility studies [ess96-III, ess02-III] have approved that theESS-project has been well examined and elaborated. Technically the project could berealized within the planned costs. Scientific demands and requirements by the user communitycould well be met. As far as international positioning is concerned the projectcertainly would attract worldwide researchers as one of a small number of world-scaleresearch facilities.