Comparative assessment of theoretical and experimental measurement of photo neutron flux level in GHARR-1 after shutdown

Direct photo-neutron source strength was evaluated for the Miniature Neutron Source Reactor (MNSR) in subcritical condition in the GHARR-1 facility. Two different static methods were applied for comparison. A theoretical method based on the use of MCNP code and an experimental method based on foil activation technique. The latter has been found to be most convenient method for neutron flux measurement. The method depends only on the activity of a bare and cadmium covered foil if the irradiation positions are known. Photo-neutron flux level was determined theoretically using MNCP after measuring neutron flux at shutdown; and experimentally using Neutron Activation Analysis (NAA) technique also at shutdown with great care. The values obtained from the theoretical and experimental measurements are tabulated in Table 2. The results recorded were validated using biological peach leave and a geological rock sample. The results after validation for Mn concentration in the samples were 87 ± 1 μg/g and 432 ± 23 μg/g, respectively. Results for the two methods were in good agreement. Realization of photo-neutron source existence due to beryllium reflector was also experienced.