radon

Rad Elec Inc., located in Frederick, MD, USA is the only commercial producer of electret ionchambers (EIC) systems. These are distributed under the brand name of E-PERM, electret-passiveenvironmental radon monitors. Different versions of these are used in various applications, whichinclude: measurement of indoor/outdoor radon, thoron (220Radon), radon flux, radon in water, radiumin soil/building materials, environmental gamma radiation, tritium in air and on surfaces, alphacontamination on surfaces and in soil.

The application of a radon model is useful to understand the processes that drive the radon gasbehaviour from its sources to its accumulation indoors. Since in a given inhabited house the detailedknowledge of the values of all the parameters that affect indoor radon levels is not available, theresponse of the model has to be explored in a reference site in which all the parameters are supposedto be known. We call this site the reference configuration.

Radon goes through four stages from its formation until it reaches a living environment: i) itsgeneration in the source medium, ii) its migration in the source medium, iii) its entry into a dwelling,and iv) its accumulation indoors. Many parameters of different origin take part at each stage, and mostof them are time-dependent. In this paper we discuss the requirements that an ideal model, whichconstitutes a Global Dynamic Radon Model (GDRM), should fulfil to predict indoor radon levels inliving areas of inhabited houses.

The study aims at measuring the gamma activity concentration (226Ra, 232Th and 40K) of sub-slabfilling gravel of Finnish houses. This study forms a part of a wider study aiming at exploring factorsaffecting high indoor radon concentrations in Finnish dwellings. The gamma activity and radonemanation were measured from gravel samples sent from 229 Finnish municipalities, the gammaactivity was reported. Gamma activity was determined by HPGe gamma spectrometry. The averageradium and thorium concentrations of the filling gravel were 23 and 27 Bq/kg, respectively.

The council directive 96/29 EURATOM laying down the Basic Safety Standards for the protection ofthe health of workers and the general public against ionising radiation might force some Europeanwater supply companies to take technical measures for lowering the indoor air radon contents in theirwaterworks. A suitable method for this, is the installation of water aeration equipment to remove radondirectly from raw water and lead it out off the building.

From the end of 1996 through March 1999, the spatial and the temporal variability of the soil 222Rnconcentration was investigated at a 20m x 20m test field with porous soil in 0.5 m and 1.0 m depth atnine positions each and at 1m x 1m plots at four positions each. For this, soil gas was collected weeklyinto evacuated scintillation cells and was analysed subsequently for radon activity. In the 20m x 20mfield the spatial variability is characterised by coefficients of variation (C.V.) of 26% at 0.5m, and13% at 1.0 m depth. Within the 1m x 1m plots the C.V. Were 4% and 2%, i.e.

A study was made of radon-safe building in 300 Finnish low-rise residential buildings using data obtainedfrom a questionnaire study. The study also aims at finding the main defects in design andimplementation and how the guidance given on radon-safe building in slab-on-grade houses has beenfollowed. According to the guidance, the prevention of the flow of radon-bearing air from the soil intothe house is recommended to be carried out through installation of aluminized bitumen felt and use ofelastic sealants.

Experimentally, it has been observed that the radon emanation coefficient, determined for geologicaland construction materials, depends principally on the porosity and water content.

The Austrian radon mitigation joint research project SARAH (supported by the Austrian Ministry ofEconomy and the Government of Upper Austria), a two-year follow up study of the Austrian NationalRadon Project (NRAP), was started in 1996. Objectives of the research project were to find simple,cost effective experimental methods for the characterisation of the radon situation in dwellings and toevaluate technically and economically the implementation of state of the art remedial actions forAustrian house types.

Implanted long-lived radon decay products in glass surfaces have been used as a measure of pastradon exposure in homes. Special track-etch devices (so-called retro-detectors") attached to the glasssurface, have the ability to specifically measure the implanted activity of 210Po in-situ. Calibratingthese devices for 210Po is fairly straightforward, but the retro-detectors are also sensitive to thebackground activity of the glass substrate.