A laboratory study of radon emanation from domestic uranium ores

Laboratory measurements of radon emanation were made by a slightly modified sealed-can gamma-only method of radiometric assaying for equivalent uranium. When a sample is sealed in a container, the percentage build-up of gamma activity of the radon daughters, lead-214 and bismuth-214, from sealing time to equilibrium is equal to the percentage build-up of radon-222 and thus to the percentage emanation and may be calculated from two measurements at suitable times. The use of drill-core samples allows the partial assessment of radon problems before mining begins. The measured radon emanation from individual samples ranges from less than 1% to 91%. The average values of samples from various domestic mining areas range from 8% to 57%. Factors appearing to affect emanation are; (1) porosity and permeability; (2) ore grade; (3) uranium mineral species (seldom controlling); (4) crystal or particle size; (5) lithology (coalified wood emanates less than sandstone, mudstone emanates more); (6) radium mineralogy; (7) geologic age; (8) mobility of deposits; and (9) moisture content. The dominance of one or more of these factors determines the effectiveness of specific control measures. (author)