Initial observations of fallout from the reactor accident at Chernobyl

Abstract

The fallout from the nuclear reactor accident at Chernobyl has been monitored at Studsvik, the Swedish energy research station located 75 km south of Stockholm. Here we present initial results of several different types of measurement. Gamma-ray spectrometry of samples of air, grass and milk reveals sixteen different nuclides, mainly volatile fission products. Radioactive particles up to ∼1 μm in diameter have been collected and analysed by electron microscopy; their form and composition lead to an estimate of ∼2,500°C for the temperature in at least part of the reactor core. The level of radioactivity in air has decreased from initial values of a few becquerels (disintegrations per s) per m³, to very low values, and the activity level on grass is also decreasing due to decay and weathering. The radiation doses due to the fallout will be small compared with those from natural sources (such as radon emission in buildings), and will not cause significant health effects.