%0 Journal Article
%T Computational Model for the Neutronic Simulation of Pebble Bed Reactor¡¯s Core Using MCNPX
%A J. Rosales
%A A. Mu£¿oz
%A C. Garc¨ªa
%A L. Garc¨ªa
%A C. Brayner
%A J. P¨¦rez
%A A. Ab¨¢nades
%J International Journal of Nuclear Energy
%D 2014
%R 10.1155/2014/279073
%X Very high temperature reactor (VHTR) designs offer promising performance characteristics; they can provide sustainable energy, improved proliferation resistance, inherent safety, and high temperature heat supply. These designs also promise operation to high burnup and large margins to fuel failure with excellent fission product retention via the TRISO fuel design. The pebble bed reactor (PBR) is a design of gas cooled high temperature reactor, candidate for Generation IV of Nuclear Energy Systems. This paper describes the features of a detailed geometric computational model for PBR whole core analysis using the MCNPX code. The validation of the model was carried out using the HTR-10 benchmark. Results were compared with experimental data and calculations of other authors. In addition, sensitivity analysis of several parameters that could have influenced the results and the accuracy of model was made. 1. Introduction Very high temperature reactor (VHTR) designs offer promising performance characteristics. If realized, these concepts can provide sustainable energy, offer improved proliferation resistance, and are more easily safeguarded than current light water reactors (LWR). These designs also promise operation to high burnup and large margins to fuel failure with excellent fission product retention via the TRISO (tristructural-isotropic) fuel design. The higher temperature of operation for these concepts can support industrial process applications that cannot be easily supported by LWR technology [1]. Two VHTR concepts have been studied: the prismatic reactor, with block-type fuel elements, and the pebble bed reactor (PBR), with spherical fuel elements, as shown in Figure 1. Figure 1: Scheme of TRISO fuel for pebble bed and prismatic VHTR. In PBRs, the fuel is contained within graphite pebbles which form a randomly packed bed inside a graphite-walled cylindrical cavity. Due to the stochastic nature of this bed, the location of the individual pebbles is not well defined. The pebble bed in such a reactor for some type of calculations is often modeled as a homogeneous mixture of pebbles and coolants materials, with a uniform density throughout the core. Unfortunately, such a model does not include all the effects that the heterogeneity of the pebble bed entails, resulting in possible errors. Three of these effects are (1) the density fluctuations in the pebble bed near the wall, (2) the neutron streaming through the void space between the pebbles, and (3) the variations in the Dancoff factor near the edge of the pebble bed [2]. In the framework of a
%U http://www.hindawi.com/journals/ijne/2014/279073/