Evaluation of gamma radiation exposure in a room from construction material

The presence of radioactivity in building materials can be a potential hazard from external exposure to gamma and beta radiation. Indoor radiation comes mainly from the activity concentration of the natural radionuclides of ²³⁸U, ²³² Th and ⁴⁰K in building materials. The calculations presented in this paper indicate if clay bricks containing average activity concentrations of 35, 72 and 585 Bq kg^-1of ²²⁶Ra, ²³²Th and ⁴⁰K respectively are used to construct walls of a room of dimensions 3 m x 3 m x 0.1 m and 3.6 m x 3 m x 0.1 m the annual effective gamma radiation dose to a person with an occupancy factor of one is 1.65 mSv. This result can therefore be regarded as an upper limit on the expected exposure. Considering average activity concentrations of 55, 56 and 39 Bq kg^-1 for ²²⁶ Ra, 129, 50 and 44 Bq kg^-1 for ²³²Th, 1349, 1436 and 1725 Bq kg^-1 for ⁴⁰K for granite, Lanka and Royal Ceramic floor tiles respectively the annual gamma exposure due to these floor materials is 92, 69 and 61 nSv. The results suggest the exposure from the floor materials to be insignificant. The annual effective dose from construction materials is directly proportional to the activity concentration of the radionuclides present in the construction materials.

doi:10.4038/sljp.v1i0.171

Sri Lankan Journal of Physics, Vol.1 (2000) 73-79