Accelerator-driven systems: source efficiency and reactivity determination

Accelerator-driven systems (ADS) are being investigated and designed for transmutation of the long-lived nuclear waste. Application of ADS allows to safely transmute large fractions of minor actinides (MA) per reactor core, while the fraction in critical reactors is limited to a few percent due to the safety constraints. Additional imposed costs of ADS introduction into the nuclear fuel cycle can be decreased by improving their efficiency, particularly the external source efficiency. Design of the European Facility for Industrial Transmutation (EFIT) with transuranium (TRU) oxide fuel has been recently developed in the frame of the EUROTRANS project. In this thesis it is shown that the neutron and proton source efficiency of EFIT can be significantly improved by application of advanced TRU nitride fuel. Thanks to the good neutron economy of the nitride fuel, the EFIT core size can be reduced, which permits reducing the size of the spallation target. This provides a twice higher proton source efficiency and therefore lowers the demand for the proton accelerator current. Additionally, the nitride version of EFIT features two times lower coolant void worth improving the core safety. The pulsed neutron source (PNS) methods for ADS reactivity control have been studied experimentally at the YALINA facility in Minsk (Belarus) and shown good agreement with numerical simulation. The PNS methods will be most probably used for calibration of online reactivity monitoring system in future ADS