An intrinsically safe facility for forefront research and training on nuclear technologies — Burnup and transmutation

Abstract

The currently dominant open fuel cycles have resulted in the gradual accumulation of (relatively) large quantities of highly radioactive or fertile materials in the form of depleted uranium, plutonium, minor actinides (MA) and long-lived fission products (LLFP). For low-activity wastes a heavily shielded surface repository is required. Spent fuel can be instead directly buried in deep geological repositories or reprocessed in order to separate U and Pu and eventually also MA and LLFP from other materials. These elements can be further burnt by modern reactors but not yet in sufficient quantities to slow down the steady accumulation of these materials in storage. Using ADS, the residual long-lifetime isotopes can be transmuted by nuclear reactions into shorter-lifetime isotopes again storable in surface repositories. However, in order to perform transmutations at a practical level, high-power reactors (and consequently high-power accelerators) are required; particularly, a significant transmutation can be reached not only by increasing the beam current to something of the order of a few tens of mA, but also by increasing the beam energy above 500MeV in order to reach the spallation regime. Such high-power infrastructures require intermediate test facilities with lower power and higher safety level for the investigation of their dynamics and transmutation capabilities: the ADS proposed in this study could accomplish many of these constraints.