Distribution of radioactive nuclides of boring core samples extracted from concrete structures of reactor buildings in the Fukushima Daiichi Nuclear Power Plant

Since the start of the severe accidents at the Fukushima Daiichi Nuclear Power Plant in March 2011, concrete surfaces within the reactor buildings (RBs) have been exposed to radioactive contaminants. Released radionuclides still remain too high to permit entry into some areas of the RBs to allow the damage to be assessed and to allow carrying out the restoration of lost safety functions, decommissioning activities, etc. In order to clarify the situation of this contamination in the RBs of Units 1, 2 and 3, samples of contaminants were collected and subjected to analyses to determine the surface radionuclide concentrations and to characterize the radionuclide distributions in the samples. Especially, decontamination tests on the boring core sample of Unit 2 were conducted to quantitatively determine the effectiveness of several basic decontamination techniques. As a result of the tests, the level of radioactivity of this sample was reduced with the removal of ∼97% of the contamination present near the samp...