Abstract
Present constructions of uranium-graphite spherical fuel elements (SE) for the VGR-50 and VG-400 high temperature gas-cooled reactors (HTGR) being designed in the USSR, which are based on using coated fuel particle elements (CP) are unified to a large degree (outer diameter 60 mm, cladding thickness 5 mm) and differ in loading and uranium enrichment, as well as in density of matrix graphite (MG), whose values are determined by the neutron-physical features of nuclear devices. The characteristic of SE operation in the reactor VGR-50 is their repeated (up to 2000 cycles) circulation through the core and irradiator, connected by ball-leads. Therefore strict requirements are imposed on their dynamical strength and wear resistance as well as on their operability under different temperature conditions
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