ABSTRACT
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.