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
SUPPLY OF THORI UM OXI DE, SHORT TONS OF TH02 FIGURE 1. lB. Domestic Thorium Supply Curve 500,000 illustrates high and low cost estimates for each deposit. Deposits are arrayed by plotting production costs in increasing order except for Lemhi Pass. The Lemhi Pass deposit shows a decrease in cost because Lemhi Pass is mined in two stages. Costs for the first stage of mining are higher because a lower grade of ore is developed. As mining progresses, higher grades of ore are accessed (second stage) and production costs decrease. The supply curve illustrates that sufficient amounts of thorium exist to supply a domestic thorium-reactor economy.
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