DESIGN AND MODELLING OF OXIDE FUEL FOR INCINERATION OF AMERICIUM AND PLUTONIUM IN AN EXPERIMENTAL ADS
The interest to the accelerator-driven subcritical systems (ADS) devoted to the incineration of plutonium and minor actinides is a subject of study around the world. Since 1997, the Belgian Nuclear Research Centre SCK·CEN is performing the pre-design studies aiming at the development of a small experimental ADS called MYRRHA which could be a step towards a prototype design of an ADStransmuter. In the present article, some results of the preliminary modelling of the behaviour of the fuel pins, filled with (Am0.5Pu0.5)O2-x dissolved in ThO2 matrix and with the same fuel in YSZ matrix, under typical ADS operation conditions are discussed and compared with the behaviour of MOX. Modelling has been performed with the fuel performance code MACROS-II which is under development and testing at SCK·CEN. A care was taken to model correctly the re-distribution of transuranium elements, fission products and helium within the fuel pellets and to their impact on the fuel performances.
Blanket design studies for maximizing the discharge burnup of liquid metal cooled ATW systems
Abstract This paper presents the results of neutronic design studies of lead–bismuth eutectic (LBE) and sodium cooled accelerator transmutation of waste (ATW) blankets. These studies have focused primarily on maximizing the discharge burnup under key thermal-hydraulic and material-related design constraints. Subject to the design constraints on the peak linear power, the maximum coolant velocity, the maximum volume fraction of transuranic (TRU) elements in the dispersion fuel, and the peak fast fluence, design studies have been performed for 840 MW ATW blankets. From these studies, it has been found that the unconstrained discharge burnup for a fixed fuel residence time increases monotonically as the fuel volume fraction and blanket size decrease. The results also show that the discharge burnup is proportional to the peak fast fluence. These indicate that the maximum discharge burnup is primarily determined by imposed design constraints. The maximum discharge burnup achievable under the peak fast fluence limit has been found to be ∼28% for the LBE system, and ∼30% for the sodium system. The optimum fuel volume fraction appears to be ∼0.21 and ∼0.32 for LBE and sodium systems, respectively.
Blanket Design Studies of a Lead-Bismuth Eutectic-Cooled Accelerator Transmutation of Waste System
Abstract The results of blanket design studies for a lead-bismuth eutectic (LBE)-cooled accelerator transmutation of waste system are presented. These studies focused primarily on achieving two important and somewhat contradictory performance objectives: First, maximizing discharge burnup, so as to minimize the number of successive recycle stages and associated recycle losses, and second, minimizing burnup reactivity loss over an operating cycle, to minimize reduction of source multiplication with burnup. The blanket is assumed to be fueled with a nonuranium metallic dispersion fuel; pyrochemical techniques are used for recycle of residual transuranic (TRU) actinides in this fuel after irradiation. The key system objective of high-discharge burnup is shown to be achievable in a configuration with comparatively high power density and relatively low burnup reactivity loss. System design and operating characteristics that satisfy these goals while meeting key thermal-hydraulic and materials-related design constraints have been preliminarily developed. Results of the performance evaluations indicate that an average discharge burnup of ~27% is achieved with a ~3.5-yr fuel residence time. Reactivity loss over the half-year cycle is 5.3%Δk. The peak fast fluence value at discharge, the TRU fraction in the charged fuel, and the peak coolant velocity are well within the assumed design limits. Owing to its use of nonuranium fuel, this proposed LBE-cooled system can consume light water reactor-discharge TRUs at the maximum rate achievable per unit of fission energy produced (~1.0 g/MWd).