Investigation on the radioactivity level of natural rock in Lhasa

Objective: To investigate the radioactivity level of natural rocks in Lhasa in order to obtain the radionuclide contents and availiability of the rock. Methods: Radiation monitoring and sampling were carried out in the natural rock mining area in Lhasa, and the contents of radionuclides in the samples were analyzed. Both internal and external exposure indexes were calculated, and the rocks were classified according to the relevant national standards on building materials. Results: The average specific activity of ⁴⁰K, ²²⁶Ra, ²³²Th and ²³⁸U in the rock samples were 912, 59.0, 77.1, and 64.4 Bq/kg, respectively. Internal and external exposure indexes were both less than 1. Conclusions: The radioactivity level in natural rocks in Lhasa were lower than the national levels. The natural rocks could be used as main building materials and Class A decoration materials. (authors)