Natural activities of U-238, Th-232 and K-40 in building materials

Seven kinds of building materials were analysed for U-238, Th-232 and K-40 using a direct gamma-counting method. The activity concentrations measured for U-238 (30-448 Bq kg(-1)) and K-40 (328-7541 Bq kg(-1)) were greater tha n the world average activity for soil (25 and 370 Bq kg(-1), respectively) for all building materials analysed, while the activity concentrations of T h-232 were found to exceed the average of 25 Bq kg(-1) (soil) for red-clay brick (51 Bq kg(-1)) and ceiling asbestos sheet materials (162 Bq kg(-1)). The calculated Ra equivalent activities (Ra-eq) for all materials are highe r than the world average value for soil (89 Bq kg(-1)). For red-clay brick and ceiling asbestos, the Ra-eq values are found to exceed the limit of 370 Bq kg(-1), equivalent to a gamma-dose of 1.5 mSv yr(-1). (C) 1999 Elsevier Science Ltd. All rights reserved.