Máté Szieberth

Investigation of the Energy Correlations of Spallation Neutrons by Monte Carlo Simulations

Earlier works have suggested that the energy correlations in a spallation source may influence the neutron noise measurements in an ADS. For the calculation of this effect not only the generally known and used one-particle spectrum is needed but also the so-called two particle spectrum, which describes also the energy correlations. Since measured data are not available for the energy correlation of the neutrons from a single spallation event, the physical models of the MCNPX code have been used to investigate the effect. The calculational model has been successfully validated with measurements of the number distribution of spallation neutrons. The simulated one- and two-particle energy distributions and spectra proved that the energy correlations exist and have an important effect in low multiplicity spallation events and in thin targets. On the other hand, for thick targets this effect appears negligible and the factorization of the two-particle spectrum seems an acceptable approximation. Further investigations are in hand to quantify the actual effect of the energy correlations on the neutron noise measurements.

Fuel cycle studies on the uranium utilization efficiency and minor actinide burning in gas cooled fast reactors

The gas cooled fast reactor (GFR) is a Generation IV reactor type considered as an alternative fast neutron reactor design aimed to improve the sustainability of nuclear energy by improved uranium utilization efficiency and opportunities for minor actinide burning.The following paper presents fuel cycle studies performed at the Budapest University of Technology and Economics for the assessment of the transmutational capabilities of the 2400 MWth GFR design in the framework of the GoFastR project. Based on the results of numerous (few thousand) core calculations, multidimensional regression method was used to develop a fast and flexible burnup calculation scheme which can be easily integrated into fuel cycle simulations. The burnup model was applied for the analysis of fuel cycle scenarios including a mixed fleet of GFRs and conventional LWRs. The equilibrium and transitional state properties of different recycling options were investigated in order to examine fuel utilization and trasmutational capabilites.

A Novel Molten Salt Reactor Concept to Implement the Multi-Step Time-Scheduled Transmutation Strategy

Nowadays the molten salt reactor (MSR) concept seems to revive as one of the most promising systems for the realization of transmutation. In the molten salt reactors and subcritical systems the fuel and material to be transmuted circulate dissolved in some molten salt. The main advantage of this reactor type is the possibility of the continuous feed and reprocessing of the fuel. In the present paper a novel molten salt reactor concept is introduced and its transmutational capabilities are studied. The goal is the development of a transmutational technique along with a device implementing it, which yield higher transmutational efficiencies than that of the known procedures and thus results in radioactive waste whose load on the environment is reduced both in magnitude and time length. The procedure is the multi-step time-scheduled transmutation, in which transformation is done in several consecutive steps of different neutron flux and spectrum. In the new MSR concept, named “multi-region” MSR (MRMSR), the primary circuit is made up of a few separate loops, in which salt-fuel mixtures of different compositions are circulated. The loop sections constituting the core region are only neutronically and thermally coupled. This new concept makes possible the utilization of the spatial dependence of spectrum as well as the advantageous features of liquid fuel such as the possibility of continuous chemical processing etc. In order to compare a “conventional” MSR and a proposed MRMSR in terms of efficiency, preliminary calculational results are shown. Further calculations in order to find the optimal implementation of this new concept and to emphasize its other advantageous features are going on.Copyright