Using the 186-keV peak for 226 Ra activity concentration determination in Hungarian coal-slag samples by gamma-ray spectroscopy

The uranium isotopic abundance and the 238 U– 226 Ra secular equilibrium were determined in nine Hungarian coal slag samples. The 226 Ra activity concentration was measured based on the radon decay products and also the 226 Ra peak at 186 keV. Secular equilibrium existed in eight samples, whereas one sample showed a slight disequilibrium. The direct and fast measurement using only the 186 keV peak was validated which can be used after measuring the uranium isotopic ratio and verifying the 238 U– 226 Ra secular equilibrium. This method can be used to measure the 226 Ra content of high number of samples from the same geochemical background.