Prediction and measurement of neutron energy spectrum in a material test research reactor

The objective of this work is to calculate and measure the neutron energy spectrum in the Pakistan Research Reactor-1 (PARR-1), which is a typical Material Test Reactor (MTR) fueled with low enriched uranium. The method of multiple foil activation was used with the adjustment code MSITER, a modified version of the code STAYʹSL, to obtain the experimentally measured spectrum. The calculated spectrum, which was used as pre-information in the adjustment procedure, was obtained through modeling the core and its surroundings in three-dimensions and the use of the transport code WIMS-D/4 and the diffusion code CITATION. A comparison between the calculated and measured spectra shows that the ratio of measured to calculated flux density in the thermal region (E less-than-or-equals, slant0.5 eV) is 0.998. This ratio is 1.02 for resonance (1/E) region (0.5 eV < E less-than-or-equals, slant 0.5 MeV) and 0.932 for the fast region (E > 0.5 MeV). This result is compared with other published results that report an agreement within 10 to 30% between the calculated and measured spectra.