Radon gas measurements

Figure 1. Variations in the hourly mean alpha-energy concentration during an integrating radon gas measurement of three weeks The alpha-energy concentration calculated from the radon level (4860 Bq/m3) and the typical equilibrium factor (0.45) is also given.

In the case of radon gas measurement, the major problem is the low sensitivity of existing instruments for accurate routine analysis at radon concentrations near the indoor average, which has a worldwide arithmetic mean of 40Bqm. At this concentration, in each liter of air, there will be 2.2 decays per minute of Rn. Even with further decays of the radon progenies, this implies low counting rates. Each a-particle decay of Rn is shortly followed by the a-particle decays of Po and Thus, there... 

Static sampling systems are defined as those that do not have an active air-moving component, such as the pump, to pull a sample to the collection medium. This type of sampling system has been used for over 100 years. Examples include the lead peroxide candle used to detect the presence of SO2 in the atmosphere and the dust-fall bucket and trays or slides coated with a viscous material used to detect particulate matter. This type of system suffers from inability to quantify the amount of pollutant present over a short period of time, i.e., less than 1 week. The potentially desirable characteristics of a static sampling system have led to further developments in this type of technology to provide quantitative information on pollutant concentrations over a fked period of time. Static sampling systems have been developed for use in the occupational environment and are also used to measure the exposure levels in the general community, e.g., radon gas in residences. 

Aside from the difficulty in correlating soil radon measurements with indoor radon measurements, various field studies have also shown that obtaining a representative soil gas measurement is difficult. Soil gas radon measurements were made with a permeameter in seven central Florida houses.42... 

Here we have only discussed the concentration of the radon gas. This is because the measurements have been made of this nuclide. However, the health effects are referred to the short-lived decay products. The equilibrium factor depends on the ventilation rate and the particle concentrations. 

It is noted that the ICRP has assumed a higher conversion coefficient between annual effective dose equivalent and radon concentration (ICRP, 1984) in recommending an action level for remedial measures in homes, i.e. 1 mSv y"1 per 10 Bq m"3 of equilibrium equivalent radon gas concentration (9 mSv per WLM). If this conversion coefficient were applied to our regional survey data, we would estimate, from the distribution parameters given in table 3, that about 15% of the residents of certain areas of Devon and... 

Ionization Chamber Method (DSC), The ionization chamber is one of the most common instruments for measuring radon gas. The chmaber was cylindrically shaped and had a 1.5 liter volume. Air samples were drawn through a dryer filled with CaCl and a filter to remove... 

Charcoal-Trap Method (ACC). The Charcoal-Trap Method has been used for sampling radon gas in the atmospheric air and for measuring radon emanation rate from the soil surface by some researchers (e. g. 

Flow-Type Ionization Chamber (PFC). The Flow -Type Ionization Chamber Method (PFC) has been developed for continuously measuring radon gas in the atmospheric air. The detail of the device has been described elsewhere (Shimo, 1985). Briefly, measurements are continuously carried out by drawing air through the detector at 1.0 2.0 /min. The ionization currentdue to alpha particles from radon and its daughters is detected with a vibrating reed electrometer (VRE) in the same manner as the DSC. The sensitivity... 

Together with the radon daughter measurements, nearly continuous measurements of the ventilation rate are performed by means of the release of N2O tracer gas and observation of its decay with an infrared spectrometer (Miran 101). Furthermore the aerosol concentration and size distribution are monitored every 20 to 30 min with an automated aerosol spectrometer (Raes et al.,1984). 

Equilibrium factors were estimated from simultaneous measurements of radon gas and daughters when available. A default equilibrium factor of 0.3 was used when simultaneous gas and daughter values were not available. The default equilibrium factor is based on reported data for Salt Lake City (EPA, 1974) and on data obtained in Edgemont, South Dakota (Jackson et al., 1985), for climatic conditions similar to those in Salt Lake City. 

Concentrations of radon gas were measured using scintillation cells of 150 ml capacity fitted with two self closing vacuum connectors (EDA Instruments Inc., Toronto). The cells were filled by flushing with filtered room air. Flushing was carried out for several minutes to ensure complete filling. The cells were left for... 

The radon production rate for a dwelling, or for an individual room, is not constant with time, as it is affected by meteorological and other conditions. Average radon production rates based on longer term integrated measurements of radon gas concentration would have resulted in slightly different values from those reported here. However, this parameter is less variable than "grab" sample determinations of the concentration of radon or its decay products. 

Radon s main use is as a short-lived source of radioactivity for medical purposes. It is collected from the decay of radium as a gas and sealed in small glass capsules that are then inserted at the site of the cancer. It is also used to trace leaks in gas and liquid pipelines and to measure their rate of flow. The rate at which radon gas escapes from the Earth is one measurement that helps scientists predict earthquakes. 

Radon is present in the air and soil. It can leak into the indoor environment through dirt floors, cracks in walls and floors, drains, joints, and water seeping through walls. Radon can be measured by using charcoal containers, alpha-track detectors, and electronic monitors. Results of the measurement of radon decay products and the concentration of radon gas are reported as working levels (WL) and picocuries per liter (pCi/L), respectively. The continuous exposure level of 4 pCi/L or 0.02 WL has been used by USEPA and CDC as a guidance level for further testing and remedial action [33]. 

Miinnich, K. O., W. B. Clarke, K. H. Fisscher, D. Flothmann, B. Kromer, W. Roether, U. Siegenthaler, Z. Top, and W. Weiss, Gas exchange and evaporation studies in a circular wind tunnel, continuous radon-222 measurements at sea, and tritium/helium-3 measurements in a lake . In Turbulent Fluxes Through the Sea Surface, Wave Dynamics and Predictions, H. Favre and K. Hasselmann, Eds., Plenum, New York, 1978, pp. 151-165. 

Early experiments in liquids were quite variable for many reasons. The conductivity technique, which was used in the gas phase to measure dose, was not applicable to the liquid phase. Reactions were measured using dissolved radium salts or radon gas as the ionization source. Some thought the chemistry was due to the reactions with radium however, it was soon recognized that it was the emitted rays that caused the decomposition. Both radium and radon could cause radiation damage. Because the radon would be partitioned between the gas and liquid phase, the amount of energy that was deposited in the liquid depended critically on the experimental conditions such as the pressure and amount of headspace above the liquid. In addition, because the sources were weak, long irradiation times were necessary and products, such as hydrogen peroxide, could decompose. 

There have been hundreds of radon profiles measured in the surface ocean. Examples are presented in Fig. 10.5. These data are used to determine the gas exchange mass transfer coefficient by calculating a mass balance for Rn. The change in concentration (mol m ) of Rn in surface waters with time integrated to the depth, z, at which secular equilibrium is achieved, usually 200 m or less, is equal to the sum of three terms production by the integrated Ra concentration, and losses due to radioactive decay (mol m d ) and flux to the atmosphere ... 

Radon is continually produced in small amounts in the uranium radioactive decay sequence (Section 26-11). Radon gas is so unreactive that it eventually escapes from the soil. Measurable concentrations of radon, a radioactive gas, have been observed in basements of many dweUings. 

Radon is a radioactive gas produced when radium in soil and rock decays. It is a known carcinogen. The data above show radon levels measured in a community in Australia. Select a method for graphing these data. Explain the reasons for your choice, and graph the data. 

Lucas cell A cylindrical container for measuring radon gas that has a quartz window for transmitting scintillations at one end, has all other internal walls coated with ZnS(Ag) powder that responds with scintillations to alpha particles, and has a stopcock for connection to a pump to create a vacuum and then admitting a gas sample. 

Only two soil-gas measurements for United States locations were found in the literature one from Spokane, Washington, with soil-gas radon from 189 to 1,000 pCi radon-222/L of air (7,000 to... 

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