Determination of Neutron Fluxes and Spectrum Shaping Factors in Irradiation Sites of Ghana’S Miniature Neutron Source Reactor (mnsr) by Activation Method After Compensation of Loss of Excess Reactivty

Abstract

Accurate neutron flux values in irradiation channels of research reactors are very essential to their usage. The total neutron flux of the Ghana Research Reactor-1 (GHARR-1) was measured after a beryllium reflector was added to its shim to compensate for excess reactivity loss. The thermal, epithermal and fast neutron fluxes were determined by the method of foil activation. The experimental samples with and without a cadmium cover of 1-mm thickness were irradiated in the isotropic neutron field of the irradiation sites of Ghana Research Reactor-1 facility. The induced activities in the sample were measured by gamma ray spectrometry with a high purity germanium detector. The necessary correction for gamma attenuation, thermal neutrons and resonance neutron self-shielding effects were taken into account during the experimental analysis. By defining cadmium cutoff energy of 0.55 eV, Al-0.1% Au wires of negligible thickness were irradiated at 3 kW to determine the neutron fluxes of two irradiation channels, outer channel 7 and inner channel 2 whose Neutron Shaping Factor (α) were found to be (0.037 ± 0.001) and (-0.961 ± 0.034). The neutron flux ratios at the inner irradiation site 2 were found to be, (25.308 ± 3.201) for thermal to epithermal neutrons flux, (0.179 ± 0.021) for epithermal to fast neutrons flux and (4.528 ± 0.524) for thermal to fast neutrons flux, in the outer irradiation site 7, the neutron flux ratios were found to be, (40.865 ± 3.622) for thermal to epithermal neutrons flux, (0.286 ± 0.025) for epithermal to fast neutrons flux and (11.680 ± 1.030) for thermal to fast neutrons flux.

Tritium breeding mock-up experiments containing lithium titanate ceramic pebbles and lead irradiated with DT neutrons

“…6 Li atoms in the converter foil was measured with the help of 241 Am-Be neutron source of intensity 3.8 × 10 7 n/s and 7 cm thick HDPE moderator to thermalize the high energy source neutrons. The thermal plus epithermal neutron flux incident on the converter foil was 7.36 × 10 3 n/cm 2 /s measured with help of 197 Au (n, ␥) 198 Au reaction using Cd ratio technique [20]. The experimental uncertainty in the thermal flux at 1 level is ±4.14% which includes HPGe detector calibration (4%), cross-section uncertainty (0.67%) and statistical error on gamma counts (0.89%).…”

Characterization of Neutron Field in a Spherical Irradiation Facility

“…For this purpose a previously described small-sized neutron irradiator prototype based on a 5 Ci (1.85×10 11 Bq) Am-Be isotopic neutron source was prepared [1]. The use of the neutron irradiator presents the advantage of supplying a stable neutron flux over a long period [2][3][4], thus eliminating the need for using expensive neutron producing devices such as reactors or accelerators. This way makes the analyzing process became agile, practical and economic.…”