S. Subbotin1 , S. Lukashenko1 , K. Zelenskiy1 , V. Romanenko1 , V. Suprunov1
1Institute of Radiation Safety and Ecology, National Nuclear Centre, Kurchatov, Kazakhstan
Results of a study of groundwater in areas of underground nuclear explosions (UNE) at the Semipalatinsk test site (STS) have shown a presence of high concentrations of 137Cs and 90Sr (hundreds of Bq/kg), which can be found only near the areas of the UNE. At a distance of 200 m from the epicenter of the explosion radionuclide concentration is reduced to a fraction of Bq/kg. At the same time, tritium concentration remains sufficiently high, with values, which depend on the characteristics of the geological structure and hydrogeological conditions. Quantitative values of tritium more than 7 Bq/kg are observed at distances up to 20 km from the epicenter of UNE. Tritium is part of tritiated water and is not adsorbed by rocks at migration. So, tritium can significantly move in a short period from UNE region with ground water. During on-site inspections in regions like STS measurements of tritium concentration in ground water allows one conclude the presence of a UNE at a 20 km radius. The presence of 137Cs and 90Sr in ground water allows the more precise placement of the UNE epicenter.