Neutron-physical characteristics and fuel utilization in a sodium-cooled fast reactor with high-density fuel at the initial stage of the transition to a closed cycle

Abstract

The results of neutron-physical investigations of a fast reactor using high-density fuel (UC) at the initial stage of the transition to a closed fuel cycle are presented. Validation is given for the possibility of making the transition to a closed fuel cycle with self-supply of fissile nuclei starting with the first recycle.The high density of the fuel used in fast reactors makes it possible to improve the neutron-physical characteristics and to use the fuel more efficiently.In some western countries, India, China, and South Korea intensive research is being conducted to develop fast reactors using different kinds of fuel. Experiments performed on the Phoenix reactor (France) studying nitride and carbide fuels showed the advantage of the latter type. Investigations of carbide fuel in a closed fuel cycle are continuing as part of the Generation IV international program as well as in a program with France, USA, and Japan collaborating to build FBR by 2020-2025 [2].India has made substantial advances in perfecting carbide fuel. Burnup 100-150 MW·days/kg has been achieved in the FBTR fast reactor with uranium-plutonium carbide fuel, irradiated fuel with burnup 25, 50, and 100 MW·days/kg has been reprocessed using a novel technology based on the Purex process [3]. Further improvements will require using metallic (alloyed) fuel in a closed fuel cycle: PFBR-500 (startup by 2020, India) [4] and KALIMER-600 (South Korea) [5].Different promising fuel compositions including carbide fuel (UC, PuC, UPuC) have been investigated in our country. A series of experiments with carbide fuel has been performed at the Research Institute for Nuclear Reactors and burnup 10.4% h.a. has been achieved [6]. Reassuring results have also been obtained for metallic alloyed uranium-plutonium-zirconium fuel, and a technology for fabricating fuel elements with such fuel has been perfected [7]. A federal targeted program has the BN-800 reactor starting up in 2012. The implementation of a closed fuel cycle based on this reactor is still not completely clear. Consequently, in order to transition to a closed fuel cycle taking account of the operation of this reactor in an open cycle it is helpful to compare the neutron-physical characteristics of the core with several types of fuel in order to determine its dimensions and the optimal parameters of the fuel assemblies.The present article together with [8] presents a conceptual investigation of this question for oxide and carbide fuels. In [8], optimization of fuel-assembly composition and core characteristics was performed for oxide duel and BN-800 oper-