Determination of trace Al in silicon carbide by epithermal neutron activation.

An approach based on utilization of epithermal neutron activation analysis (ENAA) is proposed for determination of trace Al in silicon carbide (SiC) materials. The feasibility and restrictions of the ENAA were evaluated in terms of the associated uncertainties that resulted from counting and from propagation in calculations. Experimental measurements were carried out under the specified irradiation and measurement conditions, where the results of a set of SiC standards for accuracy testing were compared with the calculated uncertainties. It is shown that the epithermal neutron activation is a simple and reliable method practically useful for analysis of SiC containing Al in concentrations (f(Al)) higher than 10(-3) weight fraction by the use of a typical nuclear reactor; the associated uncertainties can be suppressed to less than 12%. The influences of neutron quality or the cadmium ratio in 27Al(n,gamma)28Al reaction on the applicable concentrations of Al in SiC are also predicted and discussed.