Radon methods

A site suspected to contain a waterborne source of radon should not be avoided solely on the basis of the existence of radon. Methods can be utilized to alleviate any problem that may arise from waterborne radon. 

The amount of particles determine the quantity of decay products that stay in the air (equilibrium fraction, F) and the fraction of activity associated with the "unattached or ultrafine mode of the size distribution (fDot) These decay products are certainly harmful at high concentrations but we cannot yet detect the effects at normal levels because the vast majority of lung cancer death are due to smoking. Models predict that potentially 9000 lung cancer deaths per year in the United States are due to indoor radon. Methods are currently available and new methods are being developed and tested for lowering the levels of radon in indoor air. 

The second method is based on the amount of radon gas in the surface ocean. Radon gas is generated by the decay of Ra. The concentration of the parent Ra and its half-life allow calculation of the expected radon gas concentration in the surface water. The observed concentration is 70% of expected, so 30% of the radon must be transferred to the atmosphere during its mean lifetime of six days. Correcting for differences in the diffusivity of radon and CO2 allows an estimation of the transfer rate for CO2. The transfer rates given by the method and the radon method agree within 10%. 

Grammakov, A.G., 1934. Emanation (radon) method of search, investigation and reconnaissance of radioactive objects. Tr. TSNIGRI 7 (in Russian). 

Smith, A.Y., Barretto, P.M.C., and Poumis, S., 1976. Radon methods in uranium exploration. In Exploration for Uranium Ore Deposits. IAEA, Vienna, pp. 185-211. 

A key issue when comparing different techniques for measuring SGD is the need to define the fluid composition that each method is measuring (i.e., fresh, saline, or brackish SGD). For example, whereas hydrogeological techniques are estimates of fresh SGD, the radium and radon methods include a component of recirculated seawater. Therefore, it is often not possible to directly compare the utility of these techniques. Instead, they should be regarded as complementary. 

Figure 7 Plot comparing variations in SGD at Shelter Island, NY, between an automated seepage meter and the continuous radon method.

Smith A. Y. Barretto P. M. C. and Pournis S. Radon methods in uranium exploration. Reference 5, 185-211. 

Grangeat P. Mathematical framework of cone beam three-dimensional reconstruction via the first derivative of the Radon transform.. Math. Methods in Tomography, V.1947 of Springer Lecturre Notes in Math-cs, Springer-Verlag, Berlin, 1991, p.66-97. 

Another efficient and practical method for exact 3D-reconstruction is the Grangeat algorithm [11]. First the derivative of the three-dimensional Radon transfomi is computed from the Cone-Beam projections. Afterwards the 3D-Object is reconstructed from the derivative of the Radon transform. At present time this method is not available for spiral orbits, instead two perpendicular circular trajectories are suitable to meet the above sufficiency condition. 

Krypton difluoride cannot be synthesized by the standard high pressure-high temperature means used to prepare xenon fluorides because of the low thermal stabitity of KrF. There are three low temperature methods which have proven practical for the preparation of gram and greater amounts of KrF (141—143). Radon fluoride is most conveniently prepared by reaction of radon gas with a tiquid halogen fluoride (CIE, CIE, CIE, BrE, or lE ) at room temperature (144,145). 

Growing concern about the risks posed by indoor radon has underscored the need for dependable radon-resistant residential construction techniques. In response to this public health exposure, the U.S. EPA has developed and demonstrated a variety of methods that have been used to reduce radon levels in existing homes.2,8 Many of these methods could be applied during construction, involve less labor and financial investments, and provide greater homeowner satisfaction and safety than would a radon-reduction technique installed after the home is built and occupied. 

In theory, the application of radon barriers should be adequate to avoid elevated radon levels in houses. In practice, however, a backup radon mitigation system has been found essential for maintaining indoor radon concentrations below 4 pCi/L in most homes studied. In the recent radon-resistant residential construction projects conducted by U.S. EPA and/or private builders, several of the homes designed to be radon resistant have contained radon concentrations above 4 pCi/L. In each of those houses, a backup system consisting of an active (fan-assisted), or passive (wind-and-stack-effect-assisted), SSD system was installed at the time of construction. When mechanical barriers failed to adequately control radon, the soil depressurization methods were made operational. 

Due to difficulties often encountered in sealing subfloors and insulating pipes in crawlspace houses, which rarely have a poured floor slab, another radon-resistant alternative that can be applied after construction should be considered. This mitigation technique is a variation of the successful SSD methods used in basements. Polyethylene sheeting is often used as a moisture barrier applied directly over the soil in crawlspaces. The polyethylene sheeting can be used as a gastight barrier that forms a small-volume plenum above the soil where radon collects. A fan can be installed to pull the collected soil gas from under the sheeting and exhaust it outside the house. 

The first problems on the list are not specific to radon control but are encountered on nearly every construction job. In spite of quality control and communication problems and the understandable wariness builders show when asked to build something in a different way, the residential construction industry has responded to new techniques, materials, and public demands. The average house being built today is very different from a home built 20 years ago. If a product or a method can be demonstrated to reliably keep radon out without presenting significant problems with cost, scheduling, or installation, many builders would learn to use it. The major difficulty faced by mechanical barrier approaches is the thoroughness that seems to be required to ensure that no radon problem will occur. 

In addition to the above measurements, indexes using soil concentrations in combination with permeability measurements have been suggested by some researchers.4142 As elaborated on later in this section, these methods have been successful in establishing relationships between some of the site measurements and indexes, and indoor radon concentrations for specific areas and regions. 

In order to focus on more of the basic research problems related to radon, a symposium was organized in conjunction with the 191th National Meeting of the American Chemical Society. This volume presents most of the reports given at that symposium. There are five major groups of reports occurrence, measurement methods, physical and chemical properties of radon and its decay products, health effects, and mitigation of radon levels. 

Several papers present reviews of measurement methods or improvements in existing methods. Yamashita et al. (1987) present the description of a portable liquid scintillation system that can be used for thoron (Rn-220) as well as radon (Rn-222) in water samples. Thoron measurements have not been made for houses where radon in water may be a significant source. Such an instrument could be useful in making such determinations as well as in studying geochemical problems as described in this report. A review of measurement methods by Shimo et al. (1987) and of development and calibration of track-etch detectors (Yonehara et al., 1987) are also included. Samuelsson... 

Knutson, E.O., A.C. George, L. Hinchliffe, and R. Sextro, Single Screen and Screen Diffusion Battery Method for Measuring Radon Progeny Size Distributions, 1-500 nm, presented to the 1985 Annual Meeting of the American Association for Aerosol Research,... 

Samuelsson, C., A Critical Assessment of Radon-222 Exhalation Measurements Using the Closed-Can Method, this volume (1987). 

The dimensionless group Pep is essentially the ratio of the rate of convective transport to the rate of diffusive transport. Similarly, Nr describes the relative importance of radioactive decay to convective flow as a method of removing radon from the soil pores. In the case of Pep >>1/ diffusion can be neglected and the first term in equation (1) drops out. If in addition Nr >>1, then radioactive decay can be neglected as a removal term. If Pep 1, then diffusive radon migration dominates, and the second term in equation (1) can be neglected. 

Numerous radon and radon decay measurements in houses are now being made by a large number of private and governmental organizations. In order to assure valid and consistent measurements, it is important that proven methods be used following standardized procedures. To address this need, EPA issued "Interim Indoor Radon and Radon Decay Product Measurement Protocols" and established a Radon/Radon Progeny Measurement Proficiency program. 

In February 1986, EPA issued a document (Ronca-Battista et al., 1986) titled "Interim Radon and Radon Decay Product Measurement Protocols," describing seven methods for measuring radon and its decay products in houses. The methods addressed are those that have been evaluated by EPA and found to be satisfactory other methods may be added as they are reviewed by EPA. In addition, portions of the document may be revised as new information and data becomes available. 

Kusnetz H.L., 1956, Radon Daughters in Mine Atmospheres, a Field Method for Determing Concentrations, Ind.Hyg.Quart., 17, 85-88. 

Swedjemark, G.A., Radon and its decay products in housing - estimation of the radon daughter exposure to the Swedish population and methods for evaluation of the uncertainties in annual averages, Thesis, Department of Radiation Physics, University of Stockholm (1985). 

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