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Rn-MITIGATION IN A TRADITIONAL AUSTRIAN FARMHOUSE

H. Lettner, R. Rolle, R. Winkler, F. Steinhäusler
Institute of Physics and Biophysics, University of Salzburg
Hellbrunnerstrsse 34, 5020 Salzburg / Austria
e-mail: herbert.lettner@mh.sbg.ac.at

An Austrian farmhouse has been mitigated; it was built around the turn of the century in the
conventional farmhouse style of that time. Two main reasons for the high Rn concentrations found in
the building could be identified: the construction style, that allowed enhanced Rn transport from the
underlying soil into the building, and the furnace slag used as bulk material for the construction of the
ceiling and as filling material underneath the ground floor.
Prior to mitigation the Rn activity concentrations determined in the building varied between
700 Bq/m 3 (groundfloor) and 250 Bq/m 3 (upper floor) as a yearly average, with appr. twice as high
values in the heating season from October to April. Rn Mitigation was accomplished as a side issue of
a general renovation of the building which was done over a longer period that offered the unique
possibility to observe the influence and the effectiveness of the single renovation steps on Rn
reduction. From the main 3 different steps, (1) removing the bulk material of the ceilings, (2)
excavating the ground floor and replacing it by gravel and overlying concrete and (3), covering the
concrete with 5mm bituminous sealant the latter turned out to be most efficent, while step (1) and (2)
caused only minor reductions.