Hoger Onderwijs Reactor (HOR)

The HOR is an open pool-type research reactor, using MTR-fuel assemblies and low-enriched Uranium-235 (< 20%) as fuel. The core is composed of 20 fuel assemblies and 4 control assemblies. It is equipped at three sides with a row of Be-reflector assemblies acting as neutron reflectors. The reactor provides neutron radiation to a variety of facilities for radioisotope production and neutron activation analysis. It is also equipped with six horizontal beam-tubes in two sets of three at opposite sides of the core mainly used for neutron scattering experiments. The two larger beam tubes are equipped with stacked-mirror neutron guides (neutron guide system) to obtain clean beams of thermal neutrons with low contamination by fast neutrons and gamma rays. One neutron guide system provides two beams for experiments in the reactor hall. The other neutron guide system provides 4 neutron beams to the experiment hall, adjacent to the reactor hall. Measuring 25 x 40 m, this hall provides ample space with low radiation background for beam experiments. Finally, one of the beam-tubes is used by the source of variable-energy positrons (POSH). These positrons are led into the experiment hall as well.