The first Radon Risk Maps
|Location||International Geological Congress,oslo 2008|
|Holding Date||07 October 2008|
One of the first tasks of the Swedish Radon Commission, when it was established in 1997, was to prevent that new constructions for living and work were built on ground which could impose special risk for radon. At that time we had just found the first homes with high indoor radon concentrations due to transport of radon from the ground. These homes were built on landfill of uranium-rich alum shale. The Commission commissioned The Geological Survey of Sweden (SGU) to produce maps of areas with known enhanced concentrations of uranium in bedrock and soil. During three years SGU produced 250 so called GEO-radiation Maps in the scale of 1:50,000. However during the time when these maps were made our knowledge and understanding on how radon together with soil air is transported into buildings increased. Many houses on ground with no apparent enhanced uranium concentration were found at measurements of indoor radon. Evidently also permeability of the soil and house construction had a great impact on the risk for high indoor radon concentrations.
These findings resulted in development of a new type of maps, the Radon Risk Maps, which also took in consideration the radon concentration in soil air and the permeability of soils. The ground was classified according to the radon concentration in the soil air and the risk for in-leaking soil air in three classes: Low radon ground, Normal radon ground and High radon ground. This classification system has then world wide been followed by other states, each states using there own classification system, but more or less copying the Swedish system.
The presentation will give a comprehensive description on the Swedish Radon Risk Maps and the findings on which these are based.