Radon emanation rate studies: inter-laboratory standard reference materials and the effects of powdering and pelletizing
Radon emanation rates, J, and compositions of materials from the Canadian Certified Reference Materials Project (CCRMP) indicate that the fraction of the Rn produced that escapes, E, is usually 1% to 8% and the 23SU decay chain is nearly in secular equilibrium. For some Chinese ore standards, E values are higher than for the CCRMP materials. Standard ore tailings have 21°Pb concentrations higher than expected from their 226Ra concentrations and Rn escape rates (12 - 34%). Biological materials have E -100%, their ash E =0%. Pelletizing ore powders at 20 000 lb/in2 reduces J by only 20 - 40% but only 2% of Rn escapes from pressed Li 2B 4O 7 pellets and 0.01 -0.04% from fused Na 38 4O 7 or Li 2B 4O 7 discs. Large, difficult-to-explain random variations in J are observed in some situations but several highly reproducible ways of measuring emanation rates have been found.