Improving accuracy in routine instrumental activation analysis

An INAA procedure for routine analysis of rock samples is described. Samples are irradiated in a rotating sample holder. Measurement of the induced gamma activity is performed using an automatic gamma spectrometer and the elemental concentrations are calculated by a computer. The analytical error is discussed and precision and accuracy evaluated experimentally. An average error of +-3-5% without considering counting statistics is obtained. The accuracy obtained in the present work can be considered an important improvement particularly since the analytical procedure is simple. Results for 19 elements in 8 international standard rocks are reported. A short discussion of the cost of the analysis is included. Without including the cost of maintenance of the reactor the cost is estimated to be about US $ 3.5-6.5 per sample. (T.G.)