Use of the National Physical Laboratory ionization chamber type 1383A in neutron activation analysis

Abstract

The National Physical Laboratory γ-ionization chamber has been used for the measurement of chemical yield by re-irradiation in a method for the determination of arsenic by neutron activation analysis. Satisfactory accuracy and a precision of 1% were obtained with a single reading. Discrimination against other radioisotopes is achieved by irradiating for a short time and measuring at a total decay time of one mean life of the radionuclide to be determined; the resulting discrimination factor is given as a function of the half-life ratio. Maximum sensitivities for 66 elements with γ-emitting thermal neutron capture products were calculated for irradiation and decay times both equal to one half-life, and it is shown that the sensitivity for shorter irradiations at the selected time of measurement is a linear function of the irradiation time. More than a dozen elements were found suitable for determination at the milligram level by neutron activation followed by γ-ionization chamber measurement. The error from interfering elements can be directly estimated from their expected concentrations by means of the calculated sensitivities and discrimination factors presented in the paper.