Twenty samples of coal representing each of the seven major regions of the National Coal Board have been analysed for their natural radioactivity content. A variety of methods have been used to verify the results, but the major technique used was radiation spectrometry of 3 kg samples. The results indicate a mean value for uranium and radium activity in British coals of 14.5 Bq/kg, for thorium 12.5 Bq/kg and for potassium 150 Bq/kg. These are significantly lower levels of actinides than have been previously reported and represent only two thirds of those previously used as source terms for assessment of the radiological impact of fossil fuel burning in the U.K.. The content of potassium in U.K. coal is twice the accepted global mean but the radiological significance of this element is negligible. A subsidiary finding is that uranium and its daughter radium are in secular radioactive equilibrium in coal within the experimental error of the analysis.
Coal Potassium Radioisotopes