Hydrogen explosion occurred at Fukushima Dai-ichi nuclear power plants in Japan on 12―15th March, 2011. At the same time, lots of radioactive materials have been released including tritium(T), and caused serious environmental impacts. In order to investigate the effect of the accident of Fukushima Dai-ichi nuclear power plant on environment, we collected the short precipitation(hourly collected precipitation) and spring water for several years after the accident. As to the precipitation collected, T and radiocaesium were measured by using liquid scintillation counter and high-purity germanium detector, respectively. Furthermore, we also measured the concentration of ions(Na＋, Cl－, Ca2＋, and SO42－) in spring water. From the above-mentioned matters, the following points have been obtained:(1)The variation of T concentration in recent three years(2012, 2013 and 2014) can be clarified. (2)The effect of the accident on spring water in mountains around the Fukushima prefecture is so small. (3)As to the short precipitation on 15th March, 2011, the activity of radiocaesium was not detected, but the activity of T was detected significantly.
In order to estimate the human intake and the committed effective dose of several radioactive materials, the duplicate diet samples sampled from Saitama residents were analyzed. The average daily intakes of134Cs and 137Cs in 2011 were 0.43 and 0.48 Bq/person･day, and those in 2012 were 0.065 and 0.15 Bq/person･day. The committed effective doses in 2011 and 2012 are estimated to be 5.5 and 1.1μSv, respectively. The estimated dose in 2011 is almost 80 times higher than that before the occurrence of Fukushima Daiichi Nuclear Power Plant accident. However, it is found that this dose is less than 1% of the annual effective dose limit for members of the public (1mSv/year).
The muon, one of the elementary particles, plays a variety of roles in scientific research with its unique physical properties:having the mass between the proton and electron, one unit charge, spin 1/2, spin polarization etc. Commencement of the J-PARC MUSE facility in Japan has opened a new year of muon science. A brief introduction to the following articles is provided.
Polymer dynamics in solution is overviewed especially with the corresponding intermediate correlation functions and neutron spin echo results. The development of polymer dynamics is briefly explained, and the theoretical backgrounds for interpretations of the intermediate correlation functions based on Rouse and Zimm models are summarized. The intermediate correlation function for de Gennes's reputation model is also introduced. The experimental results with neutron spin echo technique are also shown, which are very helpful to understand the contributions of quasielastic neutron scattering for the progress of polymer dynamics.
This article presents the features of regional distributions and temporal changes in air dose rates and radionuclide deposition densities in Fukushima on the basis of analyses on large-scale environmental monitoring results using diverse methods. The continuity of decontamination effects is discussed according to repeated monitoring data after the decontamination model project. Further, some examples are shown on the projection of air dose rates together with the ecological half lives for different land uses.