The BR2 reactor as NSUF affiliate infrastructure

The BR2 reactor, operated by the Belgian nuclear research centre SCK.CEN in Mol, Belgium, is a high flux material test reactor. The BR2 reactor offers a unique combination of high performance (access to thermal and fast neutron flux up to 1015n/cm²s and 6x1014(E>0.1MeV)n/cm²s respectively) and flexibility (the core configuration is adaptable on a cycle by cycle base to accommodate different irradiations).As the reactor is cooled by pressurized (1.2 MPa) water, the allowable heat flux on the fuel surface, exposed to the nominal primary flow, is 470 W/cm² for the driver fuel, up to 600 W/cm² in experimental-set ups cooled by the primary water. The fuel elements are tubular, with 6 concentric tubes, each made of 3 circular formed fuel plates. In the center of the fuel elements, there is sufficient space for an irradiation device.The different types of irradiation positions can be described as follows:• Irradiation positions inside fuel elements: these can be in standard 6 plate elements (F1) (diameter 25.4 mm) or dedicated 5 plate elements (F2) (diameter 32 mm) for more space. Typically, these positions yield the highest fast flux levels but limited space. The fluxes quoted in the table scale with the power level of the reactor and can vary depending on the position of the element and the burn-up level of the surrounding elements.• Irradiations in standard channels (S): flux levels will depend on the position of the channel in the reactor (total flux) and the thermal to fast flux ratio will be optimized by the number and burn-up of the surrounding fuel elements. All standard channels have a diameter of 84 mm; the flux level generally varies with the distance to the reactor's central flux trap.• Irradiation in large channels: there are 5 large channels (H), offering space up to 200 mm in diameter. These channels can contain a single irradiation rig (200 mm), 1 to 3 standard channels (84 mm) or a combination of a standard channel with 6 small channels (33 mm).• Irradiation in peripheral channels (P; 50 mm diameter), located at the edge of the reactor.For rapid turnaround experiments, a number of standardised irradiation devices are available for material and fuel irradiation. For larger projects (such as Consolidated Innovative Nuclear Research programmes) either standard devices or dedicated devices can be used.