Neutronic performance of proliferation hardened thorium fusion breeders

Production of denaturated fissile fuel in a thorium fusion breeder has been investigated by mixing the fertile fuel with natural-UO2 and LWR (light wa ter reactors) spent nuclear fuel. Four different coolants (pressurised heli um, Flibe 'Li2BeF4', natural lithium and Li17Pb83 eutectic) are selected fo r the nuclear heat transfer. In order to obtain a power flattening in the f issile-fertile zone, the UO2- or the spent fuel-fraction in the mixed oxide (MOX) fuel has been gradually increased in radial direction. Power plant o peration periods between 13 and 29 months are evaluated to achieve a fissil e fuel enrichment similar to4%, under a first-wall fusion neutron energy cu rrent of 5 MW m(-2) (plant factor of 100%). For a plant operation over 4 ye ars, enrichment grades between 6.0 and 11.5% are calculated for the investi gated MOX fuel and coolant compositions. The U-238 component of natural-UO2 can provide a limited proliferation hardening only for the U-233 component , whereas, the homogenous mixture of ThO2 with a small quantity of (>4%) LW R spent nuclear fuel remains all-over non-prolific for both, uranium and pl utonium components. (C) 2001 Elsevier Science B.V. All rights reserved.