Study on nuclear activities by the measurement of residual radioactivity

Abstract

Caesium-137, caesium-134, cobalt-60, and some other radioisotopes were introduced into the atmosphere as a result of nuclear activities such as nuclear test explosions, the failure of the nuclear power plant, and the leakage of the radioactive waste. In fact test explosions taking place in various areas of the world mostly occurred in the fifties and sixties. It can be assumed that the resulting total fallout of¹³⁷Cs into the Earth surface has been almost uniformly even over large regions. On the contrary the fallout resulting from a single power plant accident or nuclear test explosion differed, greatly depending on the migration of the radioactive cloud in the subsequent days after the nuclear accident and occurrence of rainfalls or aerosols fallout introducing the radioisotopes directly onto the Earth surface. Preliminary results of the research program in the Radioanalysis Research Laboratory are presented. About 300 samples of plants, soil, water, and fertilizer were analyzed for isotopes of¹³⁷Cs,¹³⁴Cs,⁶⁰Co, and⁴⁰K using a single γ-ray spectrometer employing 10% HPGe detector and the Compton suppression spectrometer. Large differences in the concentrations of¹³⁷Cs and⁶⁰Co have been observed. The results gave us information on the nuclear activities in various localities.