The 222 Rn concentration in exhaust air is being measured at underground uranium mines in the Grants, New Mexico area. The objective of the work is to determine relationships between U 3 0 8 production and the mine characteristics and practices relative to 222 Rn emission. Concentrations in the vent air from two mines ranged from 90 nCi/m 3 to 3800 nCi/m 3 during a month of observations. Diurnal radon emission patterns were seen from each mine which were inversely related to barometric pressure. The average diurnal emission patterns on weekends when no mining occurred were very similar to those on weekdays during active mining, indicating that the mining activities had little short-term effect on those radon emissions. The radon emission rate from each mine vent showed a correlation with the associated ventilated surface area and the cumulative tons of U 3 0 8 extracted there and a higher correlation with cumulative tons of ore extracted. Grab samples of vent air collected at 14 additional mines in the Grants area showed radon concentrations from 7 nCi/m 3 to 21,000 nCi/m 3 •

Estimated Radon Emission From Waste Following Closure of the Mines. Piles at Four Mines Estimated Radon Storage Piles Release from Six Mine 10. Estimated Radon Release in Mine Water From Six Mines 11. Relationship Between Radon Emission and Mine Production C.l Distribution of Grab Sampling Times and Associated Biases C.2 lntercomparison of Vent Flow Measurements Using Different Instruments

The concentrations of 226Ra and 222Rn (214Pb) were measured as a function of depth within a uranium mill tailings pile by in situ y-ray spectrometry. Radon diffusion and exhalation rates were determined from the concentration gradients by employing an integral solution of the diffusion equation that accomqodates a nonuniform depth distribution of the parent radium. Radon diffusion coefficients of 0.0002 and 0.0017 cm2 s-l and exhalation rates of 60-275 atoms cm-2 s-l were determined for two locations with differing soil moisture content. This method evaluates diffusion and exhalation parameters from radon concentration changes that have occurred over time periods of several days. It, therefore, integrates shortterm variations due to changes in atmospheric and meteorological conditions that would ordinarily be measured by methods involving surface radon collection or accumulation techniques commonly applied to field studies.Release of 222Rn (hereafter called radon) from uranium mill tailings to the atmosphere results in one source of radiation exposure to populations as a consequence of the uranium mining and processing industry. Radon is the daughter of (hereafter called radium), which, not being depleted by the uranium extraction process, is associated with the spent feed material which is disposed to a tailings pile. Being a noble gas, radon can be produced in or diffuse into the interstitial pores of the soil column, and diffuse upward through the soil surface, escaping to the atmosphere. Any assessment of the radiological impact of the exhaled radon requires knowledge of its rate of release and the influence of various physical and meteorological parameters on this rate.A variety of approaches have been used to evaluate the quantities of radon released to the atmosphere from general soil areas or from specific sites. Most of these involve collection and subsequent analysis of radon or radon daughters from the air a t or above the soil surface. A common method involves direct accumulation in a container that is sealed to the soil surface, followed by removal of an aliquot for radon analysis ( I , 2). Countess ( 3 ) and Megumi and Mumuru ( 4 ) describe methods by which radon is absorbed directly onto a layer of activated charcoal placed on the soil surface. By definition, the radon concentration in the air column above a soil surface is equal to its flux across the soil--air interface. Determination of the atmospheric radon or radon daughter inventory as a measure of flux has been employed by many investigators; e.g., see ref 5 and 6. While these techniques afford useful data on instantaneous radon emanation, they provide little or no information concerning total radon exhalation or the diffusion parameters involved in migration of radon to the soil surface. We took a more mechanistic approach, basically measuring the changes of concentration of radium and radon, as its 214Pb daughter, as a function of depth in the soil column by in situ y-ray spectrometry. From the rate of change of parentdaughter concentratio...