Operating limits for the ultra-high-flux reactor

The need for a neutron-producing source that will provide steady-state fluxes of at least 1.0 x 1016 n/cm2 x s has caused a critical review of thermal-hydraulics limits for plate-type cores. A high-intensity neutron sources will be used in various aspects of material, biological, and fundamental physics research. Because the neutron flux is nearly an order of magnitude larger than present plate-type reactors, the power density for the Ultra-High-Flux Reactor (UHFR) is also an order of magnitude larger. To save costs, the use of existing data and experience with an aluminum plate-type fuel was selected. The UHFR is basically a cylindrical core, double-donut, split axially with each axial section 15.2 cm high and a heavy-water-filled space of 15.2 cm between each section. The core is small, 43 cm o.d. with a volume of ∼ 40 ell and a power density at beginning of life (BOL) of nearly 10 MW/ell. The core thermal hydraulics are summarized. Even though the UHFR will have a much larger neutron flux and hence heat flux over existing facilities, adequate margins still exist in the thermal-hydraulics limits to allow safe operation