Nuclear Technology / Volume 157 / Number 2 / February 2007 / Pages 120-131
Technical Paper / Fission Reactors
A small reactor has the potential to be utilized as a power source to meet diverse social needs and reduce capital risks. In remote areas, populations tend to be small, and an economic power grid may not be available. In such situations, a small power source with a capacity of less than 50 MW(electric) without refueling is attractive since the costs for fuel transfer to such a site are expensive. In the present study, a metal fuel core with a lifetime of 30 yr and a simple reactor plant design has been proposed. The local burnup reactivity change in every core region is minimized by adjusting the zirconium content and the smear density of the three-core region to achieve a 550°C core outlet temperature. At the end of the cycle, the burnup reactivity is evaluated to be 1.1% of (dk/kk'), achieving a 30-yr core life. The reactor vessel is dramatically simplified by eliminating a fuel-handling system. The number of main cooling loops is reduced to one by installing dual electromagnetic pumps in the primary sodium circuit. The nuclear steam supply system mass, at 309 tonnes, shows that the present loop-type concept can more dramatically reduce material mass than that of the previous pool-type concept of 484 tonnes. The rough estimation of the electricity cost shows that this concept will be competitive for remote sites. Transient analyses show that a self-actuated shutdown system enhances the passive safety features, thus ensuring reactor integrity in anticipated transient without scram events.