Assessment of the natural radiological hazards in surface soil at high-background natural radiation areas in Northern Vietnam

Radiological hazard assessment is an important task. The natural radionuclides in 88 surface soil samples in/surrounding high-level natural radiation areas were measured using a high-purity germanium gamma-ray detector. The ²²⁶Ra, ²³⁸U, ²³²Th, and ⁴⁰K activities varied from 60.4 to 655, 59.3 to 643, 71.2 to 886, and 252 to 745 Bq/kg respectively. The highest radionuclides concentration was found in rare earth element mines, followed by uranium and metallic mines. There was an equilibrium between ²³⁸U and ²²⁶Ra with ²³⁸U/²²⁶Ra ratios equal to 1.01. The radiation hazard indices in the study soil samples were far higher than the world average values. (author)