Study of large sample neutron activation analysis using photoneutrons an an americium-beryllium neutron source

Conventional instrumental neutron activation analysis (INAA) typically involves analysis of small material portions of about 100 to 500 mg mass. Not until recently, INAA on large sample was not performed because of the absence of adequate correction methods for neutron self-shielding and gamma-ray attenuation in the sample. Large sample INAA compliments and significantly extends the analytical tools available for multi-elemental studies. In this work, the feasibility of large sample (sample in the range of 0.5 g to 5 g) INAA using americium-berylium (241Am-Be) neutron source and photoneutrons produced in the Ghana Research Reactor -1 (GHARR-1) is studied. The nominal photoneutron flux in GHARR-1 is in the order of 107 n/cm2.s1 and the 241Am-Be neutron source has flux in the order of 104 n/cm2.s1. The gamma-ray detector efficiency for the large samples were determined. Correction for gamma-ray self attenuation in the sample was determined using experimentally determined linear attenuation coefficients via transmission measurements. The correction for the neutron self-shielding with the sample was also determined from measurement of neutron flux depression. A good agreement could not be obtained between the concentration values when the results of samples analyzed using the technique of LS-INAA (employing photoneutrons and 241Am-Be neutron source) were compared with that of conventional INAA of the same sample. (au)