Naturally occurring radioactivity in some Swedish concretes and their constituents - Assessment by using I-index and dose-model

The reference level for effective dose due to gamma radiation from building materials and constructionproducts used for dwellings is set to 1 mSv per year (EC, 1996, 1999), (CE, 2014). Given the specificconditions presented by the EC in report 112 (1999) considering building and construction materials, anI-index of 1 may generate an effective dose of 1 mSv per year. This paper presents a comparison of theactivity concentrations of 40K, 226Ra and 232Th of aggregates and when these aggregates constitute a partof concrete. The activity concentration assessment tool for building and construction materials, the Iindex,introduced by the EC in 1996, is used in the comparison. A comparison of the I-indices values arealso made with a recently presented dose model by Hoffman (2014), where density variations of theconstruction material and thickness of the construction walls within the building are considered. Therewas a ~16e19% lower activity index in concretes than in the corresponding aggregates. The model byHoffman further implies that the differences between the I-indices of aggregates and the concretes' finaleffective doses are even larger. The difference is due, mainly to a dilution effect of the added cement withlow levels of natural radioisotopes, but also to a different and slightly higher subtracted backgroundvalue (terrestrial value) used in the modeled calculation of the revised I-index by Hoffman (2014). Onlyvery minimal contributions to the annual dose could be related to the water and additives used, due tot heir very low content of radionuclides reported.QC 20210428