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RETROSPECTIVE ASSESSMENT OF HISTORIC RADON CONCENTRATIONS IN NORWEGIAN DWELLINGS BY MEASURING GLASS IMPLANTED Po-210 – AN INTERNATIONAL FIELD INTERCOMPARISON

Aleksandar Birovljev 1 , Rolf Falk 2 , Ciara Walsh 3 , Francesca Bissolo 4 , Flavio Trotti 4 , James P.
McLaughlin 3 , Johan Paridaens 5 , Hans Vanmarcke 5 and Anikken Heiberg 1
1 Norwegian Radiation Protection Authority, (NRPA) Østerås, Norway 2 Swedish Radiation Protection Institute, (SSI) Stockholm, Sweden 3 Physics Dept, University College Dublin, (UCD) Ireland 4 CRR-ULSS 20 Veneto region, (CRR) Verona, Italy 5 SCK-CEN, Boeretang 200, B-2400 Mol, Belgium

The first Norwegian study of historic radon concentrations in 17 dwellings in the high radon areas in
Norway has been conducted as part of an international field intercomparison during 1998. The
investigation is part of SINI (an acronym for Sweden, Italy, Norway and Ireland) international
collaboration on retrospective radon measurements in several European countries having different
climates and living conditions. The retrospective radon concentration is estimated via measurements
of Po-210, the long-lived decay product of Rn-222 implanted in glass surfaces of objects like pictures,
mirrors, cabinet-glass etc, the method called “surface trap”. Three different surface trap techniques to
assess the implanted Po-210 activity and two different procedures to estimate retro radon from Po-210
data were used. The Po-210 and the retrospectively estimated radon results agree reasonably well over
a wide range of concentrations. Historic radon concentrations were also estimated from analysis of a
smaller number of “volume trap” samples (pieces of spongy materials), and the results compared to
those from “surface traps. The retro radon results correlate with contemporary radon results with
correlation coefficient of 0.877. To evaluate uncertainty in Po-210 measurements due to varying
position on the glass a study of spatial homogeneity of three sample glasses was conducted and
variations between 12% and 18% were found.
Key words: retrospective radon estimates, Po-210, surface traps, Norway, intercomparison