radon

The average indoor radon concentration in Finnish flats is 80 Bq/m3. Typically walls have been madeusing concrete elements. Building materials are the dominant source of indoor radon. However, in theflats of the lowest floor, with a floor slab in direct ground contact, the main source of radon is oftenthe inflow of radon bearing soil air. The number of these ground contact flats is less than 10 % of thetotal number of flats. The average indoor radon concentration of these ground contact flats is 150Bq/m3.

Since 1994 the Radiological Protection Institute of Ireland has been conducting a pilot programme ofpersonal monitoring of workers in workplaces with high radon concentrations. Initially theprogramme involved staff employed by the operators of commercial show caves, but in January 1999it was extended to incorporate non-show cave workers when employees in aboveground offices in twosmall Departments in an Irish University were included.Personal monitoring of show cave staff confirmed the fact that employees in two caves receivedannual radiation doses in excess of 4 mSv.

The Megalopolis lignite field basin in southern Greece, with Megalopolis-A and B lignite-firedpower plants in operation (total 900 MW), has been repeatedly investigated during the past 25years by the Nuclear Engineering Section of the National Technical University of Athens (NESNTUA).The present work aims at an integrated radioenvironmental approach leading to the doseassessment to the public and to the plants staff.

The Nuclear Engineering Section of the National Technical University of Athens undertook the organisation of a European building material radon exhalation rate intercomparison exercise in the framework of the European Research into Radon In Construction Concerted Action (ERRICCA). The intercomparison started in June 1998 and it was concluded in February 1999. Twenty participants from 13 countries took part. The exercise focused on the radon exhalation rate determination from a concrete slab, specially constructed to produce radon surface flux well below 10 mBqm-2s-1.

^ Department of Experimental Physics, University College Dublin, Dublin 4, IrelandCase-control studies on lung cancer and radon in dwellings have been conducted in North Americaand Europe, including one study in Lazio region, in Central Italy. Great attention is generally devotedto the reduction in the uncertainty in radon exposure assessment because it can give rise to relevantuncertainty in the estimated risk. One of the main potential sources of uncertainty is the use ofcontemporary radon concentration measurements as estimators of past concentration values.

A first review of the numerous data on the areas in Italy where high radon concentration in dwellingshave been found is presented here. The data were obtained from the national survey and from severallocal surveys carried out in areas where high radon concentration values were expected, on the basis ofthe national survey results or of geological considerations. The analysis is restricted to data obtainedwith long-term measurements.

About two hundred volume traps were retrieved from dwellings in various radon prone areas inEurope. They were analysed for the purpose of retrospective radon assessment. Emphasis is put onspecific problems encountered when using field samples as opposed to laboratory exposed samples. Itwas seen that in very dusty circumstances, direct penetration of radon decay products from the outsideto the centre of the volume traps calls for extra caution. Rinsing the samples is proposed as a solutionand was tested in field and laboratory conditions, showing good results.

One could say that the Spanish Radon Program began in 1988 with the development of a nationalsurvey on indoor radon in Spanish houses. Today, 10 years later, many activitites by differentinstitutions and Universities have been carried out and a good information about the radon problemhas been achieved. Spain consists of 50 provinces which are amalgamated to form 17 autonomousregions. In this paper, we show the results of a major research and development program which is stillin progress.

Several kinds of studies have been carried out concerning building materials.The granitic region can be considered as a significant part of the country. In recent years graniticmaterials are being used as ornements or integrated on the walls inside the houses, producing highindoor radon levels. Studies of different coverings for granitic materials were tested employing incolorpaintings in order to reduce the radon exhalation from such granitic stones, without modifying theirappearance.

This paper presents the experimental results of utilizing a flexible thin-film membrane as a passivebarrier to radon gas diffusion. Nine commercially available membranes of various compositions andthicknesses were evaluated as retardant to radon gas diffusion. The radon gas concentration ratiosacross the thin-film membranes alone and in combination with an adjacent concrete sample (effectivediffusion coefficient) were measured in a laboratory system with state-of-the-art instrumentation.