Radium average concentrations

Fig. 9,20. Vertical distribution in the atmosphere of average concentrations of radium-226, lead-210, uranium and stable lead (after Kownacka et al., 1990).

The average concentrations of uranium and radium for the coarse, medium, and fine fractions are shown in Table 13. Radium was most concentrated in the fine fraction, and ANOVA verified that a significant difference existed among the sizes. The results in Table 13 also indicated differences in uranium concentrations with size fractions. However, ANOVA indicates these differences are not significant. Insufficient data were available to statistically analyze thorium data. 

As noted in Table I, average surface radium concentrations appear to vary by about a factor of 20. This can also be seen from the distributions from the NARR data. Soil permeabilities, on the other hand, have much larger variations, and thus, in principle, may have a greater influence on the spatial variations in average indoor radon concentrations that have been observed. As with the case of surface radium concentrations, the spatial variability of air permeabilities of soils is an important element in developing a predictive capability. 

The isotopes of thorium include mass numbers 223-234. 232Th has a half-life of 1.39 x 1010 years, See also Radioactivity. It emits an alpha-particle and forms meso-thorium 1 (radium-228), which is also radioactive, having a half-life of 6.7 years, emitting a beta-particle. Since 2 2Th captures slow neutions to form, by a series of nuclear reactions, >>U which is fissionable, thorium can be used as a fuel for nuclear reactors of the breeder type. Thorium occurs in earth minerals, an average content estimated at about 12 ppm. Findings of hc Apollo 11 space flight indicated that thorium concentrations in some lunar rocks are about the same as the concentrations in terrestrial basalts. 

Radium is a naturally-occurring metal and is almost ubiquitous at low concentrations in air, water, soil, rocks, and food. The median concentrations of radium-226 and radium-228 in drinking water are generally low, but there are geographic areas where higher concentrations of radium are known to occur. The utilization of coal and uranium has resulted in re-distributing radium in the environment, but the overall effects appear to be small. Estimated levels of average human exposure to radium of nonoccupational populations are presented in Table 5-1. 

TABLE 14—Average radium concentrations of phosphogypsum samples. pCHg. 

The radium concentration in phosphogypsum in Florida averaged 21 pCi/g, and its concentration was greatest in the fine sizes. 

Thirty-nine elements were detected in the phosphogypsum samples, but concentrations of the elements did not vary with depth within the stockpiles. Radium content averaged 21 pCi/g and varied inversely with particle size. 

Because radon is a gas, its occurrence in soil is most appropriately referred to as its occurrence in "soil-gas," which is in the gas or water-filled space between individual particles of soil. Factors that affect radon soil-gas levels include radium content and distribution, soil porosity, moisture, and density. However, soil as a source of radon is seldom characterized by radon levels in soil-gas, but is usually characterized directly by emanation measurements or indirectly by measurements of members of the uranium-238 series (National Research Council 1981). Radon content is not a direct function of the radium concentration of the soil, but radium concentration is an important indicator of the potential for radon production in soils and bedrock. However, Michel (1987) states that average radium content cannot be used to estimate radon soil-gas levels, primarily due to differences in soil porosity. 

SJ6 Radon (Rn) is the heaviest, and only radioactive, member of Group 8A(18) (noble gases). It is a product of the disintegration of heavier radioactive nuclei found in minute concentrations in many common rocks used for building and construction. In recent years, health concerns about the cancers caused from inhaled residential radon have grown. If l.OX lO atoms of radium (Ra) produce an average of 1.373X 10 atoms of Rn per second, how many liters of Rn, measured at STP, are produced per day by 1.0 g of Ra ... 

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