Keywords: uranium concentrations, gamma ray spectrometry, secular equilibrium, isotopic ratio, Iran, surface soil, antitank shells, low radiation, environmental pollution, health risks, depleted uranium
Determination of uranium concentration in surface soil samples of Iran
The use of uranium-tipped antitank shells during the Iraq war (2003) caused serious concerns in Iran and the international media over possible contamination of the Iranian environment and consequent long-term health effects. After a shell explosion, uranium is discharged by fire into the air in the form of oxidised particles, which can be dispersed over a radius of several kilometres. Gamma ray spectrometry was used to determine uranium concentrations in soil samples collected from ten sites in Iranian sectors near the Iraqi border. All surface soil samples were taken from the top 5 cm from each site. The concentrations of 238U were assessed from 63 keV and 92 keV emissions of its first daughter nuclide, 234Th. To assess the isotopic ratio of 238U/235U, a secular equilibrium was ensured and the concentration of 235U under 186 keV was deduced. The 226Ra was determined through 295 keV and 352 keV gamma rays of 214Pb. The concentrations of 238U and activity ratios of 238U/235U were determined. The average of measurement activity ratio was 20.0, very close to the value of 21.5 for natural uranium, while the activity ratio of depleted uranium can be as high as 76.9. The analysis of ten surface soil samples from Iranian sites near the Iraqi border showed that uranium isotopes are in natural abundances.