Natural radioactivity and dose assessment in coal samples collected from Sulaymaniyah city in Iraqi Kurdistan region

Abstract

In this study, a total of eleven coal samples were collected from different locations in the Sulaymaniyah city markets to determine three natural radioactivity concentrations (²²⁶Ra, ²³²Th, and ⁴⁰K). The measurements were performed using a High Purity Germanium (HPGe) detector. The findings revealed that the mean activity concentrations for ²²⁶Ra, ²³²Th, and ⁴⁰K were 2.2 ± 0.3, 1.1 ± 0.3, and 255.3 ± 5.0 Bq kg⁻¹, respectively. The maximum activities of ²²⁶Ra and ²³²Th were 4.7 ± 1.3 and 2.1 ± 0.6 Bq kg⁻¹ in grape trees from Ukraine, respectively, while the maximum activity of ⁴⁰K was 387.0 ± 7.1 Bq kg⁻¹ in the oak tree from Penjween, Iraq. Based on the study’s results, the levels of natural radionuclides in each sample were below the worldwide accepted limit of 35, 30, and 400 Bq kg⁻¹ for ²²⁶Ra, ²³²Th, and ⁴⁰K as reported by UNSCEAR. The radiological hazard indices such as radium equivalent (Ra_eq), absorbed dose rate (D), external hazard index (H_ex), and gamma index (Iγ) were also below the international recommended limits according to UNSCEAR and IAEA. The findings showed that all coal samples under investigation are safe for an applications in Sulaymaniyah due to low concentrations of natural radioactivity in the samples.