Gamma radiation dose from building materials in HBRA regions of Ramsar

Introduction: The main natural contributors to external exposure from gamma rays are 226Ra, 232Th and 40K. Ramsar, an Iranian northern city in Mazandaran Province has some high background radiation areas (HBRA) due to the presence of considerable amount of 226Ra along with its decay products brought to the Earth surface by numerous hot springs. Many residents of these areas have used local stone as a convenient building material. The main objective of this research is to quantify the inventories of natural radionuclides in natural building materials and to estimate the indoor/outdoor absorbed dose rate and annual effective dose equivalent due to gamma radiation from 226Ra, 232Th and 40K in building materials in these regions. Methods: Methods Building materials were collected from different areas of Ramsar. Exploranium- GR-130 miniSPEC survey-meter was used in the selection process of samples. The specific activities were determined by a gamma spectrometry system using a hyper pure germanium detector with a relative efficiency of 40% and a resolution of 1.87 keV at 1.332 MeV. Calibration sources used were IAEA reference materials RGU-1, RGTh-1, and RGK-1. The measurements were carried out at the Environmental Radiological Protection Division of the National Radiation Protection Department (NRPD) at the Atomic Energy Organization of Iran (AEOI). Results: Results The mean activity concentrations of 226Ra, 232Th and 40K were 9384±4897, 30±11 and 310±75 Bq kg-1, respectively. The average outdoor and indoor absorbed dose rates are estimated as 26261±5638 nGy h-1 and 55842±11993 nGy h-1 , respectively. The annual indoor effective dose ranges from 0.04 to 384.85 mSv with an average value of 273.94±58.83 mSv, whereas the annual outdoor effective dose ranges from 0.01 to 45.25 mSv with an average value of 32.21±6.91 mSv. Conclusion: Results indicate that the estimated average annual indoor/outdoor effective dose for the study area is much higher than the worldwide average figure of 0.41/0.07 mSv reported by UNSCEAR. It can therefore be concluded that an assessment of the radiological hazard of using these building materials is crucial.