Technique de datation des échantillons riches en uranium par les séries de l'uranium en utilisant la spectrométrie gamma à basse énergie

Abstract

Dating technique of samples rich in uranium by the series of the uranium by using the gamma spectrometry with low energy

In this work, a dating technique by the series of the uranium using the gamma spectrometry with Flow energy (<100 keV) was improved so that it could be applicable to samples rich in uranium. It consists in reducing the sample to a hasty of hydroxides containing the isotopes of the uranium and the thorium. This technique allowed to measure directly in a geologic sample rich in uranium, and without any correction due to the autoabsorption or to the geometry of counting and to the interferences of the lines gamma, 

Th/²³⁴U, ²³⁴U/238U and ²³¹Pa/235U activity ratios necessary to date a sample by the methods of radioactive imbalance in the families of the uranium (²³⁰Th/²³⁴U, and ²³¹Pa/²³⁵U). Activity ratios and age measured by this technique are comparable to those obtained by means of the suitable alpha spectrometry for this kind of measures. The gamma  spectrometry with low destructive energy allowed, in this work, to date a sample rich in uranium, from the same spectrum, by 2 methods of radioactive imbalance (^{230Th/234U and 231Pa/235U). What will allow to avoid the radioactive pollution problem for laboratories which also handle the samples of weak activities}