Natural radioactivity level in graphite samples from the Cătălinul deposit, Parâng Mountains, Romania: sources identification and radiological risk assessment

Abstract

Twenty graphite samples (amorphous and crystalline flake types of graphite) were collected from the ore storage of the Catalinul deposit and, the 238U, 232Th, 40K naturally occurring radionuclides have been investigated by gamma-ray spectrometry. The mineral contents of selected graphite samples were examined using a scanning electron microscope (SEM). The radiological hazard parameters: radium equivalent activity (Raeq), absorbed gamma dose rates in air (DR), and external hazard index (Hex) were calculated and compared with international safety limits. Radiometric data showed average specific activities for 238U, 232Th and, 40K of 80.40, 49.69 and, 124.21 Bq kg–1 for amorphous graphite respectively, 38.53, 76.25 and, 241.12 Bq kg–1 for flake graphite. Zircon, rutile, uraninite, coffinite, urano-thorite, and monazite are the main radioactive element bearing minerals. The mean of the radiological hazard parameters: Raeq – 262.22 (Bq kg–1), DR – 123.72 (nGy/h), and 0.7 – Hex do not exceed the recommended values by UNSCEAR.