Natural Radioactivity Level and Exhalation Rates in Main Building Materials From Xining City

The specific activities of ⁴⁰K, ²²⁶Ra and ²³²Th and radon exhalation rates of building materials in Xining were determined by using low background multi-channel NaI(Tl) γ spectrometer and ERS-2-S radon-thoron analyzer, respectively. The results were evaluated in accordance with the relevant standard methods. The results show that the specific activities of ⁴⁰K, except for red-clay brick, gravel aggregate and sand, in the building materials are lower than the mean of local soil, while the specific activities of ²²⁶Ra and ²³²Th in red-clay brick, ash brick, aerated block and cement exceed the corresponding means of local soil. The values of internal exposure and external exposure indexes of the analyzed building materials are lower than 1 which can be used anywhere. While, the annual effective dose equivalent rate of some red-clay and aerated block samples are slightly higher than or close to the maximum limit of 1 mSv/a suggested by the European Commission. The radon (²²²Rn) exhalation rate of building materials is related to the level of ²²⁶Ra specific activity.