Neutron flux characterization of a peripheral target position in the High Flux Isotope Reactor

The High Flux Isotope Reactor at the Oak Ridge National Laboratory provides the highest steady-state thermal neutron flux in the western world for a wide range of experiments and for isotope production. The highest available fluxes are located in a flux trap region created inside the nested fuel elements. The experimentally determined thermal and the empirically obtained epithermal flux values along the vertical axis of the peripheral target position were fit to cosine curves, with the thermal flux ranging from 1.1×1015 ns−1 cm−2 at outer positions to 1.5×1015 ns−1 cm−2 at the center. The corresponding epithermal flux ranged from 3.5×1013 to 7.5×1013 ns−1 cm−2, respectively. The fast neutron flux (Engreater-or-equal, slanted0.32 MeV in two positions and Engreater-or-equal, slanted1.5 MeV in two other positions) was not, vert, similar6×1014 ns−1 cm−2, corresponding to a fast to thermal ratio of not, vert, similar0.4.