Ra-226 in building materials as a source of indoor radon in high-rise residential buildings in Russian cities.

The problem of indoor radon in high-rise buildings is mostly associated with exhalation from building materials. Characterization of the radon entry from building materials by diffusion is required to provide a proper control of the population indoor radon exposure. To analyze the relationship between the content of Ra-226 in building materials and the indoor radon concentration the results of the following surveys in high-rise buildings in Russian cities were used: 1) indoor radon (>1000 apartments), 2) natural radionuclides in the building materials in existing buildings by means of non-destructive field gamma spectrometry (100 apartments). The surveys were carried out in nine large cities in different climatic zones. The radon entry rate due to diffusion from building materials, D, normalized to Ra-226 activity concentration, Ra, is in the range of 0.2-0.6 (Bq/m3/h)/(Bq/kg), depending on the type of building materials and building construction. In new multi-story buildings, the typical D/Ra ratio can be assumed to be 0.4 (Bq/m3/h)/(Bq/kg). In new energy-efficient buildings, the ratio of the radon concentration to Ra-226 activity concentration is on average 2.1 times higher than in multi-story buildings of lower energy efficiency built before 2000. The average radon exhalation rate from the building materials, normalized to Ra-226 activity concentration, is estimated to be 0.25 Bq/m2/h.

Relationship between Ra-226 activity concentration in building materials and indoor radon concentration: An example of Russian high-rise residential buildings.

The worldwide trend toward the construction of high-rise buildings with high energy efficiency highlights the role of building materials as a source of indoor radon in the modern urban environment. The aim of the study is to analyze the relationship between the Ra-226 activity concentration in building materials and indoor radon concentration using the example of multi-story buildings in Ekaterinburg. Measurements of the activity concentration of natural radionuclides in building materials were carried out using a new non-destructive method. A radon survey conducted early provided the data on indoor radon concentrations in the same apartments. The obtained Ra-226 activity concentrations in building materials in high-rise buildings were found to be relatively low, ranging from 9.1 to 51 Bq/kg. The typical radon entry rate by diffusion from building materials for modern Russian multi-story buildings can be accepted as equal to 0.5 Bq/(m3∙h) per 1 Bq/kg of Ra-226 activity concentration. Ra-226 in building materials has been shown to be a primary source of indoor radon in modern high-rise buildings, where this factor can cause indoor radon concentrations above the reference level of 100 Bq/m3 at low air exchange rates. The activity concentration of Ra-226 in building materials should be considered a separate parameter for regulation within the national radiation protection systems.