Risk Assessment of Swedish Concrete as a Construction Material in Relation to Naturally Occurring Radiation from Different Aggregates

Abstract

The European Commission (EC) has, since 1996, prescribed regulations concerning ionizing radiation from building materials. The current threshold value suggested for free circulation of building materials without restrictions are 1 mSv/year (EC 2013). By use of full scale concrete slabs of dimensions 1.5 m × 1.5 m × 0.15 m, an empirical approach is suggested for the calculation of Activity Index (I-index) of naturally occurring ionizing radioactivity from building materials. The concrete slabs simulate a pre-cast concrete wall. Measurements of ⁴⁰K, ²²⁶Ra and ²³²Th are performed in order to assess the I-index, equivalent dose (AEDE), equivalent dose rate (AEDR) and some common international indices. The results indicate that ~70 % of the investigated building materials are in agreement with the stipulated levels set out by UNSCEAR (2000) for outdoor conditions. In relation to the I-index, 6 out of the 10 concrete slabs satisfactorily met the safety criterion (Activity Index < 1). Some aggregates fail to comply with the stipulated threshold value (EC 2013). The cause is not only a significant uranium source (²²⁶Ra), but more frequently an increased level of ²³²Th in some of the investigated concrete mixes. By and large, most indices are comparable and give a similar indication of a construction/building materials risk to produce naturally ionizing radiation to habitants. The study further suggests that an empirical approach by use of a field gamma spectrometer results in a good linear correlation with results achieved from laboratory gamma ray spectrometry analysis and consequently the empirical approach could as such be used to approximately calculate the I-index.