A windowless multiwire proportional counter was installed at AIST to determine alpha and beta particle emission rates for 100mm×150mm surface sources. The detector system was characterized and its parameters were optimized. In addition, the uncertainties in the alpha and beta particle emission rates measurements were estimated.
55Fe movement in plant root was analyzed by applying the real-time imaging system (VIM-micro) developed for conventional β-ray emitters coupled with the fluorescent microscope. The sensitivity of VIM-micro to the 55Fe detection was apparently higher than that of the imaging plate. Only 2 minutes of integration time allowed the clear visualization of 55Fe distribution in the root. Ten kBq/μL of 55Fe was applied to the bottom part of the root of Arabidopsis and a rice plant. Then, 60 images of the root were taken over 2 hours. In both plants, 55Fe was preferentially accumulated in the root tip area. The inactivated root, which was pre-treated either with the metabolic inhibitor or with boiling, was also prepared to evaluate the contribution of the biological activity on the 55Fe accumulation. The result indicates that the intensive accumulation of 55Fe in the root tip area of the active normal root after 30 minutes is the consequence of the biological activity. Thus, it is suggested that Fe is actively transported to the root tip area, which is the important sink tissue.
A mixed breed pig that was raised at a farm within 20km of the Fukushima Daiichi nuclear power plant on the day of the accident was moved to a clean area 17days after the accident, slaughtered and sampled 41days after arriving at the clean area. The γ-ray spectrum of belly, ham, loin, and heart were measured using a Ge semiconductor detector. Even though the animal had been kept in a clean area for 41days, contamination with radioisotopic caesium was detected in pork. The pig had been kept inside a piggery and had been fed non-contaminated imported feed in both Fukushima and clean area of its all life. Broadcasts reported that feeding rice straw poses a risk of radioactive contamination of beef in Japan, but rice straw might not be the sole source of contamination. For the safety of future generations, it is necessary to monitor not only beef but also other animal products for food safety.
In addition to information and estimation of nitrogen input and release at global and regional levels, accumulated information of natural abundances of 15N(δ15N) over 40 years has revealed new findings of ecosystems' nitrogen metabolisms and dynamics. One of such new findings is that tropical rain forests are rich in nitrogen and that the big-size leguminous trees do not fix nitrogen. The further measurements of δ15N in the various ecosystems in Asia, Africa and South America may improve the knowledge on quantitative nitrogen dynamics.
From results of radionuclide analysis for tiger globefish cultivated on the surface of the sea around the Genkai nuclear power plant, it was confirmed that tiger globefish took 137Cs into their bodies and this radionuclide mainly accumulated in their muscle and bone via seawater as a mediation route. Radionuclide analysis of 137Cs as a tracer for marine life, is extremely useful as the basic data to understand behavior of the artificial radionuclides in the environment.
Although brachytherapy is an invasive modality, it can reduce the difference between the clinical and planning target volumes and obtain very concentrated dose distribution onto the tumor by the inverse square low of distance and dose. Brachytherapy is the supreme of high precision radiation therapy. Image-guided therapy is being implemented in high-dose rate brachytherapy, and the newly introduced radionuclides, such as 125I have opened now indications in brachytherapy.