Abstract
This report compares the available experimental neutron flux data in the High Flux Isotope Reactor
(HFIR) to computational models of the HFIR loosely based on the experimental loading of cycle
400. Over the last several decades, many materials irradiation experiments have included fluence
monitors which were subsequently used to reconstruct a coarse-group energy-dependent flux
spectrum. Experimental values for thermal and fast neutron flux in the flux trap about the midplane
are found to be 1.78±0.27 and 1.05±0:06 ·1E15 n/cm²·sec, respectively. The reactor physics code
MCNP is used to calculate neutron flux in the HFIR at irradiation locations. The computational
results are shown to correspond to closely to experimental data for thermal and fast neutron flux
with calculated percent differences ranging from 0:55 — 13.20%.