Characterization and application of Neutron Flux of a 370 GBq 241Am-Be irradiating systems

Abstract

Characterization of spatial neutron flux distribution above a 370 G B q 24 I Am - Ben e u t ron. sou r c e ina mod era tin gas s e m b I y has bee n performed experimentally; The source is surrounded by paraffin wax except for a cylindrical cavity along its axis, which also serves as the irradiation channel. This arrangement constitutes the so-called 'howitzer'.

The experimental method was based on foil activation, using industrial grade Aluminum foils and analytical grades of Indium foil and Dysprosium Oxide (DY203) pellet. The optimum flux positions for fast and thermal neutrons within the irradiation cavity were determined. The optimum thermal neutron fluxes lie between the distances 1.5 - 3.0 cm from the source. For bulk sample irradiation it is not edt hat meaningful thermal activation can a Is ob e achieved within the range of 0 - 6.0 cm from the source.

The fast neutron flux decreases exponentially with distance from the source. Some applications of the characterized irradiation facility were demonstrated; namely elemental analysis (for Si and Al concentrations) of geological specimens from Kanj era archaeological site, and the determination of hydrogen contents of some petroleum products in the Kenyan market. The determined Si and Al concentration were found to lie within the ranges 19.1± 9.9% - 69.9± 26.6% and 18.0± 30.4% - 46.2± 73.9% respectively.

On the other hand the hydrogen concentration in petroleum products was found to lie between 11.59± 0.36 13.90± 0.38 w%. This demonstrates important applications for which the characterized irradiation system could be useful. However, it must be stated that improvements have to be made inorder to minimize the large uncertainty as seen in the results.