radon

The effectiveness of various insulating materials for limiting radon entry into houses has beeninvestigated experimentally in 90 existing houses and in laboratory conditions. Each material hasbeen evaluated according to several aspects - placeability, durability, tear resistance and diffusionproperties. The results of the radon diffusion coefficients measurement in more than 80 insulatingmaterials are summarized. We have found out that great differences exist in diffusion properties,because the diffusion coefficient varries within four orders from 10-13 m2/s to 10-10 m2/s.

The Austrian Radon Project (ARP) is aimed to investigate and measure systematically the indoorradon concentration in about 0.5% of all Austrian homes. With the information from this surveyareas of enhanced indoor radon concentration can be identified and people living in such areasshould be encouraged to mitigate their homes. The radon potential is introduced by normalizingthe observed radon data to a standard situation. By mapping the radon potential an overview on thegeological risk for enhanced indoor radon concentrations will be available.

A data set of long-term radon measurements in about 2200 houses in southern Belgium has been collectedin an on-going national Rn survey. The spatial variation of indoor Rn concentrations is modelled byvariograms. A radon distribution map is produced using the lognormal kriging technique. A GIS is usedto digitise, process and integrate a variety of data, including geological maps, Rn concentrationsassociated with house locations and an administrative map etc. It also allows to evaluate the relationshipsbetween various spatial data sets with the goal of producing radon risk maps.

It is estimated that more than 5000 householders in the UK have taken steps to reduce high radonlevels in their homes. In 1993 a number of homes with successful remedies installed were asked toparticipate in a study to determine the long term reliability of those systems. This involved the annualremeasurement of the radon concentration in each dwelling.

A soil gas measurement method developed earlier [1] was applied to boreholes drilled to belowfoundation depth. Radon concentration and permeability were measured at 50 cm intervals. Inradon prone areas permeability showed to increase with depth over several orders of magnitude,indicating a low permeability top layer with a thickness of 0.5 m and more. A radon availabilityindex (RAI) was empirically defined and the maximum RAI of each boring proved to be a reliableindicator for radon problems in nearby houses.

Within the Belgian Radon Programme the Belgian Building Research Institute is responsible for theinvestigation of techniques for prevention and mitigation of radon problems in dwellings. One of themost regular actions is the installation of a sub-slab depressurisation (SSD) system. As there are noready-to-use systems available on the Belgian market, a system has to be designed for every specificsituation.

Measurements of indoor radon (222Rn) concentrations were carried out by using LR-115 II solid statenuclear track detectors (SSNTD). One hundred forty detectors were placed randomly in Patras housesfor two periods of three months exposure, from December 1996 to November 1997. The observedmean radon values compared with the standard recommended values are low, while the maximumrecorded value is found to be within the limits. The influence of seasonal variation as well thedistance from the ground on radon level were also investigated.

Two methods for determining the 222Rn diffusion coefficient in building materials are presented.Experimentally, the measurement of radon release rates under well-controlled conditions, using aflush and adsorption technique, underlies both methods. However, the theoretical principle of thetwo methods differs. The first method uses samples with a cubical or rectangular geometry andhas, as a prerequisite that a 100% radon tight surface covering method is available.

The International Commission on Radiological Protection (ICRP) recommends the use of a singleconversion factor, derived from epidemiological studies of exposure to uranium miners, for thedetermination of the effective dose from inhalation of radon progeny. Dosimetric models of radonprogeny inhalation predict that the dose conversion factors (DCF) are dependent upon the form ofthe radon progeny activity size distribution. The measurement of these activity size distributions isdifficult and an alternative approach has been proposed.

Soil radon concentrations together with climatic and seismic data were continuously observed in theKanto area (Japan). During fall 1998, several typhoons and earthquakes occurred. In the meanwhile,continuous measurements of the following parameters were carried out: air pressure, temperature inthe air and in the soil, humidity in the soil, wind speeds, wind direction, rainfall and earthquakesmagnitudes.Data were analyzed using time-series analysis method, i.e. Correlation and Spectrum Analysis, so asto point out the possible relationship between radon and an environmental variable.