Radioactive materials, primarily radiocaesium (134Cs+137Cs), were released into the environment by the Fukushima Dai-ichi Nuclear Power Plant accident in March 2011. The proportion of the soybean plants that had an activity concentration of radiocaesium over 100 Bq/kg was higher than that of other crops. To examine the reason why the activity concentration of radiocaesium in soybeans was higher, the concentration distributions of Cs in soybean seeds were analyzed using two methods, X-ray fluorescence microscopy and radioluminography with 137Cs. Moreover, the Cs concentration of each organ and the ratio of absorbed Cs to seeds in matured soybeans were examined. The results of the two experiments show that Cs was uniformly distributed in the soybean seeds, as was potassium, both of which likely accumulated in the cotyledon. In addition, approximately 40% of absorbed Cs was accumulated in the soybean seeds. Conversely, it is reported that rice accumulates Cs only in part of its grain and that the accumulation in the grain is lower than that in soybeans. It has been suggested that soybean seeds have a large capacity for Cs accumulation, and this is one of the reasons why the activity concentrations of radiocaesium in soybeans are higher than that in other crops.
An anion-exchange fiber capable of rapidly capturing proteins was prepared by radiation-induced emulsion graft polymerization. Glycidyl methacrylate emulsified with a surfactant Tween 20 was graft-polymerized onto pre-irradiated polyethylene fiber. Subsequently, some of epoxy groups of the graft chain were reacted with diethylamine. The 2.0-cm high column charged with the resultant diethylamino-type anion-exchange fiber exhibited a dynamic binding capacity (DBC) for 76 mg of bovine serum albumin (BSA) per mL of the column at a space velocity (SV) of BSA solution of 60 h−1. The DBC of the anion-exchange-fiber-packed column at an SV of 1200 h−1, 33 mg-BSA/mL, was 35 fold higher than that of a commercially available anion-exchange bead (DEAE Sepharose Fast Flow)-packed column with an identical column height with the fiber-packed column. This advantage of the fiber over the bead will result from the localization of the graft chain at the periphery of the fiber.
Gafchromic® films (Ashland Inc.) have been widely used for dosimetry in radiation therapy using X rays and γ rays, and are now applied to the measurements and evaluations of various ion beams. A high-dose model, named HD-V2, is available to the measurements for the ion beams with the short-range penetrations, since its active layer is not laminated by a protection layer. However, an optical-density (OD) response curve of the film to the fluence must be determined for each ion species and its incident energy, because the response is not proportional to the fluence. In this paper, a simple method for obtaining the relative beam intensity distribution using the γ-ray dose response curve was studied on the basis of the similarity of 60Co γ-ray and ion-beam irradiation response curves for the purpose of simplified measurements of the beam intensity distribution. We showed, as a result of the measurement using a flatbed image scanner ES-10000G, that the OD responses of various ion beams (selected ranges of linear energy transfer: 5.5 keV/µm–11 MeV/µm) corresponded to the 60Co γ-ray irradiation response curve within certain OD ranges and that the range was up to about 0.7 and 0.5 in the red and green channels of the film, respectively. Thus, it is possible to obtain the relative intensity distribution of various ion beams using the γ-ray irradiation response curve without obtaining a response curve of each ion beam.
The current limits for radioactive materials (sum of 134Cs and 137Cs) in food were set taking into account the radiation dose from 134Cs, 137Cs, 90Sr, 106Ru and Pu. Although the limits were based on the concentration ratio of radionuclides in soil etc., it was assumed that radiation doses from radioactive caesium (134Cs+137Cs) were equal to that from other radionuclides in regard to sea foods. In this study, we evaluate the contribution to the radiation dose from 134Cs+137Cs and others. The contribution of radionuclides other than radioactive caesium was less than that assumed when the limits were set.
223Ra is one of the most attractive radionuclides for radiopharmaceutical applications such as cancer therapy. To ensure reliable activity measurements of 223Ra radiopharmaceuticals in Japan, the National Metrology Institute of Japan (NMIJ) has developed a national primary standard with cooperative work with Japan Radioisotope Association. Liquid scintillation counting with CIEMAT/NIST method is applied in the present study. 223Ra counting efficiency is the sum of the detection efficiencies in proportion to the emission rates of radiation. The activity of 223Ra was obtained with respect to the counting efficiency and count rate.