Emanation coefficient

Morawska L, Philhps CR (1992) Dependence of the radon emanation coefficient on radium distribution and internal stractnre of the mineral. Geochim Cosmochim Acta 57 1783-1797 Neretnieks I (1980) Diffusion in the rock matrix an important factor in radionuclide retardation J Geophys Res 88 4379-4397... 

The ratio of mobile radon to the total radon produced is referred to as the emanating fraction or emanation coefficient. The range of observed emanation coefficients is indicated in Table I. The effect of moisture on the emanation coefficient has been noted by several authors (Thamer fill al.. 1981 Strong and... 

The emanating power or coefficient of rocks or soil is defined as the proportion of the radon activity per unit bulk volume which is in the interstitial gas. The emanating coefficients of rocks and soils vary greatly. Barretto et al. (1972) found values ranging from 0.01 to 0.26 for... 

If ps (kg m-3) is the bulk soil density, AR (Bq kg-1) the specific activity of radium in the soil, a the emanating coefficient, and A (s-1) the decay constant of radon, then PsARa atoms, or psARaX Bq of radon, enter the interstitial air per m3 of soil volume per second. At depth in the soil, the rates of entry and radioactive decay of radon are equal, so its activity in interstitial air is... 

Exercise 14.4 On what arguments is it claimed that most of the produced radiogenic helium is released from the rocks and dissolved in the associated groundwater (i.e., the helium emanation coefficient is close to 1) ... 

Average radon emanation coefficients in different media for nine different ores... 

A soil with 5 pCi/g of Ra, has an emanation coefficient of 0.20, an average porosity of 0.3, and a solid density of 2.7 g/cm. Therefore, the bulk density is about 1.9 g/cm. Calculate the average Rn concentration in the soil gas, assuming secular equilibrium. 

The fraction of radon atoms released into rock or soil pore space from a radium-bearing grain is called the emanation coefficient (also called emanation factor or emanating power). Typical emanation coefficients for rocks and soils range from 0.05 to 0.7. The grain size, the shape, and the soil moisture are important factors. 

Following the publication of the first example of fluorous biphase catalysis by Horvath and Rabai in 1994 [1], the immediate focus was to develop catalysts that would exhibit very biased partition coefficients with respect to fluorous and organic solvents. Such liquids are normally immiscible at room temperature. This was done by attaching ponytails of the formula (CH2)m(CF2) -iCF3 (abbreviated (CH2)mRf )> including arrays emanating from silicon atoms [2]. Catalysis was then effected at elevated temperatures, where fluorous and organic solvents are commonly miscible, with prod-uct/catalysis separation at the low-temperature two-phase limit. 

The gel point is directly connected with the branching coefficient ab, defined as the probability that a given branch (emanating from a branch point) leads to a branch point. 

Corollaries. (1) Coefficients of the characteristic equation cannot contain terms having simultaneously direct and inverse weights (e.g. they cannot have ft2+1>2 ) and the terms containing weights of two reaction-arcs emanating from the same point. 

Figure 1 Schematic diagram of a molecular beam machine. A gas at elevated pressure emanates from an orifice. The gas stream is collimated in three differential pumping stages to reduce the gas load on the target chamber. Only the part of the gas stream that reaches the target though all collimators is indicated as shaded. In the UHV target chamber a crystal is positioned in the beam path. The pressure and the target chamber and particles reflected or desorbed from the sample surface are detected by particle detectors. Inert beam flags can be moved into the beam to determine the beam intensity and the sticking coefficient. From Kleyn [22],...

Emanation power, emanation efficiency, coefficient of emanation, percent emanation, and escape-to-production ratio all mean the same thing, namely the fraction of Rn atoms formed in a solid that escape from the solid. 

Tanner s reviews on the migration of Rn in the ground (Tanner, 1964a, 1978, 1980) contain a detailed description of the processes responsible for Rn emanation and migration and an excellent summary of diffusion studies and coefficients therefore this topic will not be discussed here in detail. The emanation processes of recoil and diffusion release Rn into pore spaces of minerals and rocks, permitting diffusion and mechanical transport to move Rn away from its source. Typical diffusion constants of Rn in various media are listed in Table 1 l-I. From the many diffusion studies carried out it is evident that diffusion alone cannot move Rn beyond about 8 m within the lifetime of a Rn atom. A simple approximation of the distance-time relationship is given by = pDt, where S = distance, D = diffusion coefficient and t = time. Thus, assuming a typical diffusion constant of 0.05 cm /sec., after six half-lives or 23 days, only 1.5% of a Rn... 

Assume the dry deposition velocity over a New England forest for particles emanating from a midwestern U.S. power plant averages 0.5 cm/sec on a certain day. The scavenging coefficient in a rain-forming cloud over the forest is 10 3/sec. If the cloud is 500 m in vertical extent, what is the equivalent wet deposition velocity, Vw, for rainout of the particles ... 

The part a B emanating from the bubble formation is based on the heat transfer coefficient aB in nucleate boiling in free flow. However because the temperature rise in the boundary layer of a forced flow is steeper than in free flow nucleate boiling, more heat will be released from the wall by conduction and the bubble formation will be partially suppressed in comparison to that in free flow. Chen accounted for this effect with a suppression factor S < 1, which the heat transfer coefficient aB in nucleate boiling in free flow is multiplied by, a B = SaB. 

The correlation coefficient between o(exp) and BB I (the second most important index) is 0.7980. The ease of rotational or oscillational motions around a backbone bond emanating from an atom which is singly bonded to all of its neighbors increases with decreasing (8/8v), as is shown in Figure 12.5 for the first-row atoms C, N and O in bonding environments in which... 

In this equation D (m2.s 1) represents the radon diffusivity, X the radioactive decay constant (s 1), C (Bq.m3) the radon concentration in the pore space, R (Bq.kg1) the radium concentration in the material, p (kg.m3) the bulk density of the dry material, E (dimensionless) the radon emanation power coefficient for the pore spaces, s (dimensionless) the total porosity and 0 (dimensionless) the moisture. The solution of the diffusion equation for an homogeneous medium represents the flux release from the waste material to the surface, Jt (Bq.m 2.s ). For a system without cover we obtain (Rogers, 1984) ... 

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