In situ gamma spectroscopy to characterise building materials as radon and thoron sources

In situ gamma spectroscopy is widely utilised to determine the outdoor gamma dose rate from the soiland to calculate the natural and artificial radionuclide concentration and their contribution to the doserate. The application of in situ gamma spectroscopy in indoor environments can not supplyquantitative information about activity concentration of radionuclides in buildings materials, but thistechnique can provide interesting information about building materials as radon source. In fact, amethod based on analyses of gamma spectra data has been developed by the authors to provide, infield, quantitative estimation of disequilibrium in 226Ra and 228Ac sub-chains due to 222Rn and 220Rnexhalation. The method has been applied to data of gamma spectroscopy measurements carried outwith HPGe 26% in seven dwellings and one office in Rome. The first results of the data analysis showthat, as regards especially the 226Ra sub-chain disequilibrium, different building materials (tuff,concrete, etc. ...) can show very different characteristics. If, in addition to the spectrometric data, otherindoor environment parameters (indoor ? dose rates, room dimensions, wall thickness, etc. ...)(Bochicchio et al., 1994; Bochicchio et al., 1996a) are utilised in a room model, an evaluation of226Ra, 228Ac and 40K activity concentration and an estimation of 222Rn exhalation can be achieved.