English

The retrospective determination of radon exposure levels in dwellings by means of the measurement ofthe Po-210 surface activity is subject to various uncertainties. These result partly from the valuesassumed for the equilibrium factor F and for the unattached fraction f, and, more importantly, fromdifferences in the deposition velocities of short-lived decay products of Rn-222, caused by varyingconditions of turbulence.

The BfS Department of Radiation Protection performs official tasks in the field of radiation protectionfor man and his environment.

The work described in this paper is based upon the results of the recently completed National Surveyof Radon in Dwellings [1] carried out by the Radiological Protection Institute of Ireland (RPII).Measurements were carried out in 11,054 dwellings, located in 832 10 km grid squares across thecountry.

This paper presents the results of the National Survey of Radon in Dwellings carried out by theRadiological Protection Institute of Ireland (RPII). Radon measurements were carried out in 11,319houses throughout the country. Indoor annual average radon concentrations ranged from 10 Bq/m3 to1924 Bq/m3. The measurement data were grouped on the basis of the 10 km grid squares of the IrishNational Grid System and used to predict the percentage of dwellings in each grid square which exceedsthe Reference Level of 200 Bq/m3.

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.

A national radon survey is still lacking for Greece. Some Groups have done several more or lesslocal or extended radon surveys and valuable experience has been gained (Anagnostakis et al.1996, Papastefanou et al. 1997, Louizi 1997). After the first preliminary survey done by ourgroup (Geranios et al.

A preliminary indoor radon survey in Greece based on 258 passive detectors, to test the technique andthe statistics, is presented. This paper is an extension of an initial survey (Geranios et al. 1999). Themajority of the detectors were placed in schoolrooms and dwellings for a yearlong (June 1997-June1998). The part of our sample concerning the northern region of Greece tends to indicate higher radonconcentrations than the rest part of the country. The radon concentration distribution fits well to thetheoretically expected lognormal.

High concentrations of natural radionuclides in building materials result in high dose rate indoorsdue to radon and thoron exhalation and the ?-rays emitted from them. Among the naturalradionuclides contained in building materials, most attention has been given to 226Ra due to 222Rnexhalation and the subsequent internal exposure. In external dose calculations due to buildingmaterials it is usually assumed that there exists radioactive equilibrium among the radionuclides ofboth the uranium and thorium series.

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.