Development of a High Flux Research Reactor with Assembly- Integral Flux Traps

In recent years, the demand for irradiation services has increased as research reactors face a number of challenges. These challenges include reduction in enrichment, the need for economical use of fuel, and the medical isotope crisis brought about by the temporary shutdowns of the NRU and HFR. These challenges have inspired the design of a revolutionary research reactor assembly concept making use of the new U-Mo monolithic fuel form. Each assembly consists of a trapezoidal plate-fueled region and integral triangular flux trap. When placed in a hexagonal core, this structure permits multiple orientations of the flux trap with respect to those surrounding it. As a result, multiple orientations, sizes and shapes of the flux trap are possible. These flux trap parameters can be adjusted to provide the spectra needed to meet ever-changing experimental needs. This assembly concept was applied to the development of a 5 MWth research reactor core, and optimized for peak thermal flux. During the design process, attention was given to making the design economical, manufacturable, and maintainable. The design was able to produce a maximum unperturbed thermal flux of 1.2 x 1014 neutrons/cm2 s, 70% higher than existing research reactors of the same power rating. Despite this optimization for thermal flux, the reactor is still capable of producing fast fluxes in excess of 1 x 1014 neutrons/cm2 s in other regions of the core. The response of the resulting core to thermal hydraulic transients was also analyzed. (author)