Simulation of nuclear fuel cycle options are important in order to evaluate the sustainability of future nuclear systems and to support strategic decisions about the back-end of the fuel cycle and nuclear energy developments. The main challenge of fuel cycle studies is that the evaluation of different strategies can only be performed by knowing the detailed composition of the final waste, which requires the tracking of a large number of isotopes in the fuel cycle and the accurate determination of the spent fuel composition. For this purpose, fast and accurate burnup models are needed such as the FITXS method developed at the Institute of Nuclear Techniques of BME, which is based on the parametrization of one-group microscopic cross-sections as functions of the detailed fuel composition. While the burnup model was elaborated for several thermal and fast reactor types with the use of polynomial fitting, further developments are planned to extend its capabilities for Accelerator Driven Systems (ADS).
The ADS is a perspective nuclear system that can be used for the transmutation of minor actinides from spent nuclear fuel. The concept consists of a high energy proton accelerator, a heavy metal spallation target and a subcritical reactor core. Due to the subcriticality of the core, the ADS fuel can be loaded with much higher minor actinide content than conventional fast reactors, which is favorable for burning minor actinides from legacy spent Light Water Reactor fuel. A possible organization of advanced nuclear fuel cycles is the so-called double strata fuel cycle, which contains conventional thermal and fast reactors, as well as Accelerator Driven Systems, and the ADSs are used to burn minor actinides from the spent fuel of both fast and thermal reactors. Besides the minor actinide burning ADS has also favorable properties for the implementation of the Th-U fuel cycle, where 233U fissile material is bred from 232Th fertile material. Designs for this purpose often include breeding blanket which further complicates the fuel cycle and its simulation.
The aim of the doctoral research is to contribute the development of the FITXS method and develop burn-up models based on publicly available ADS conceptual designs. The complexity of the task lies in the fact that both high energy reactions in the spallation target and the neutron transport in the subcritical core has to be simulated in a coupled way and in a calculation flow efficient enough to run for a few thousands of core compositions requested for the cross-section parametrization. This task will require the use and couple several deterministic and Monte Carlo neutron transport codes. Developments to the FITXS methodology are also needed to optimize the calculation efforts needed for the parametrization. The developed burnup model has to be integrated in complex nuclear fuel cycle models in order to investigate scenarios involving double strata fuel cycles, evaluate the performance of ADS in minor actinide burning or Th-breeding and compare them with other nuclear systems. Quantification of the effect of uncertainties in technological parameters and material properties on the fuel cycle simulation results should also be part of the evaluations.
reactor physics knowledge, good programming skills, English language skills