Natural radionuclide content in building materials and gamma dose rate in dwellings in Cuba

An extensive research project to investigate the radioactive properties of Cuban building materials was carried out because there is a lack of information on the radioactivity of such materials in Cuba. In the framework of this project 44 samples of commonly used raw materials and building products were collected in five Cuban provinces. The activity concentrations of natural radionuclides were determined by gamma ray spectrometry using a p-type coaxial high purity germanium detector and their mean values were in the ranges: 9–857 Bq kg−1 for 40K; 6–57 Bq kg−1 for 226Ra; and 1.2–22 Bq kg−1 for 232Th. The radium equivalent activity in the 44 samples varied from 4 Bq kg−1 (wood) to 272 Bq kg−1 (brick). A high pressure ionisation chamber was used to measure the indoor absorbed dose rate in 543 dwellings and workplaces in five Cuban provinces. The average absorbed dose rates in air ranged from 43 nGy h−1 (Holguín) to 73 nGy h−1 (Camagüey) and the corresponding population-weighted annual effective dose due to external gamma radiation was estimated to be 145 ± 40 μSv. This value is 51% lower than the effective dose due to internal exposure from inhalation of decay products of 222Rn and 220Rn and it is 16% higher than the calculated value for the typical room geometry of a Cuban house.