LARGE-SAMPLE NEUTRON-ACTIVATION ANALYSIS - PRESENT STATUS AND PROSPECTS

Neutron activation analysis is attractive for trace-element determinat ions in large samples. Facilities for reactor irradiation and gamma-ra y spectrometry of kilogram-size cylindrical samples are described. The thermal neutron flux is ca. 5.10(12) m(-2).s(-1) with a Phi(th)/Phi(e pi) > 10(4), so neutron self-thermalization can be neglected. The corr ection for the neutron attenuation within the sample is derived from m easurement of the neutron flux depression just outside the sample. Cor rection for gamma-attenuation in the sample is performed via linear at tenuation coefficients derived via transmission measurements. Also the natural radioactivity in the sample is taken into account. Examples a m given of materials to which large sample INAA has been applied succe ssfully, and further lines of development and exploration are indicate d.