A comparative study of three different spallation target materials: lead, uranium and tungsten in the pebble bed ADS with TRISO fuel

Nuclear fission devices coupled to particle accelerators driven system (ADS) are being widely studied. These devices have many applications, including nuclear waste transmutation and production of hydrogen, both with significant social and environmental impact. The main objective of this work was to use probabilistic methods of computational modeling to simulate ADS geometry with TRISO fuel. Specifically, we were concern with a comparative study of three different spallation target materials: lead, uranium and tungsten in the pebble bed ADS with TRISO fuel. The variations of the neutron flux, the thermal power, the effective multiplication factor, and the isotopic composition of the TRISO fuel, during the stationary cycle for minor actinides and plutonium isotopes, were studied as a function of the simulated target materials. The refueling cycles during one year of reactor operation for each simulated target were determined by the decreasing of thermal power to a set minimum value. Modeling was performed using Monte Carlo code MCNPX 2.6e. From the analysis of the ADS geometry modeling with TRISO fuel we concluded that the extension of burning time without recharging in the reactor core obtained with the uranium spallation target is the key factor to reduce the mass of the plutonium isotopes and minor actinides in the core. The main future goal of this work is increase the core power for the three spallation target materials simulated. (author)