Design study of an irradiation experiment with inert matrix and mixed-oxide fuel at the Halden boiling water reactor

An effective way to reduce the large quantities of plutonium currently accumulated worldwide would be to use uranium-free fuel in light water reactors (LWRs) so that no new plutonium is produced. To test such a new fuel under reactor conditions and in comparison with standard mixed-oxide (MOX) fuel, an irradiation experiment is planned at the Halden boiling water reactor. The behaviour of three fuel rods consisting of uranium-free fuel will be investigated together with three rods made out of uranium-plutonium mixed-oxide fuel in the same assembly. The fuel compositions were adjusted so that all rods produce a similar power. Because of the moderation with D2O in the Halden reactor, two different surroundings of the considered assembly were examined to analyze the influence of the flux spectrum on the experiment. This showed that the influence of the spectrum on the material behaviour is negligible. The relation between assembly power and average neutron detector signal as well as the burnup or depletion function was calculated. The assumed power history was adapted to a usual LWR schedule. It is possible to reach a burnup of similar to 540 MW d kg(HM)(-1) with the uranium-free fuel and similar to 54 MW d kg(HM)(-1) with the MOX fuel after five years of irradiation, which is similar to the average burnup reached in commercial LWRs after four years of operation. (C) 1999 Elsevier Science B.V. All rights reserved.