Masayo Inagaki

Methodology using a portable X-ray fluorescence device for on-site and rapid evaluation of heavy-atom contamination in wounds: a model study for application to plutonium contamination.

Workers decommissioning the Fukushima-Daiichi nuclear power plant damaged from the Great East Japan Earthquake and resulting tsunami are at risk of injury with possible contamination from radioactive heavy atoms including actinides, such as plutonium. We propose a new methodology for on-site and rapid evaluation of heavy-atom contamination in wounds using a portable X-ray fluorescence (XRF) device. In the present study, stable lead was used as the model contaminant substitute for radioactive heavy atoms. First, the wound model was developed by placing a liquid blood phantom on an epoxy resin wound phantom contaminated with lead. Next, the correlation between the concentration of contaminant and the XRF peak intensity was formulated considering the thickness of blood exiting the wound. Methods to determine the minimum detection limit (MDL) of contaminants at any maximal equivalent dose to the wound by XRF measurement were also established. For example, in this system, at a maximal equivalent dose of 16.5 mSv to the wound and blood thickness of 0.5 mm, the MDL value for lead was 1.2 ppm (3.1 nmol). The radioactivity of 239Pu corresponding to 3.1 nmol is 1.7 kBq, which is lower than the radioactivity of 239Pu contaminating puncture wounds in previous severe accidents. In conclusion, the established methodology could be beneficial for future development of a method to evaluate plutonium contamination in wounds. Highlights: Methodology for evaluation of heavy-atom contamination in a wound was established. A portable X-ray fluorescence device enables on-site, rapid and direct evaluation. This method is expected to be used for evaluation of plutonium contamination in wounds.

Time Trend Change of Air Dose Rate on Paved Areas in Fukushima City After the Fukushima Daiichi NPP Accident

The Kinki University Atomic Energy Research Institute investigated radioactive contamination resulting from the Fukushima Daiichi Nuclear Power Plant accident in urban areas of Fukushima City, Fukushima Prefecture, Japan. Activity measurement of the surface soil and a survey of the dose rate distribution in urban areas were performed. From the results of this research, dose rate changes in paved areas became clear, and gradients of the dose rate decrease for different paving materials were measured and analyzed.

Effect of spring water on the radon concentration in the air at Masutomi spa in Yamanashi Prefecture, Japan

The concentrations of 222Rn existing in air have been studied by using a convenient and highly sensitive Pico-rad detector system at Masutomi spa in Yamanashi Prefecture, Japan. The measurements in air were carried out indoors and outdoors during the winter of 2000 and the summers of 1999 and 2005. The concentrations of 222Rn in spring water in this region were measured by the liquid scintillation method. The concentrations of natural radionuclides contained in soils surrounding spa areas were also examined by means of the γ-ray energy spectrometry technique using a Ge diode detector to investigate the correlation between the radionuclides contents and 222Rn concentrations in air at each point of interest. The atmospheric 222Rn concentrations in these areas were high, ranging from 5 Bq/m3 to 2676 Bq/m3. The radon concentration at each hotel was high in the order of the bath room, the dressing room, the lobby, and the outdoor area near the hotel, with averages and standard deviations of the concentration of 441 ± 79 Bq/m3, 351 ± 283 Bq/m3, 121 ± 5 Bq/m3, and 23 ± 1 Bq/m3, respectively. The source of 222Rn in the air in the bath room is more likely to be the spring water than the soil. The spring water plays carries the radon to the atmosphere. Our measurements indicated that the 222Rn concentration in the air was affected by the 222Rn concentration in spring water rather than that in soil.

Migration of Radioactive Cesium to Water from Grass and Fallen Leaves

The TEPCO Fukushima Daiichi Nuclear Power Plant accident in March 2011 led to high amounts of emitted radioactive Cs being deposited on land by both rainwater and snowfall. In addition, a significant amount of Cs was deposited on the surface of leaves, and after the accident, both trees and grasses absorbed radioactive Cs through their roots. In order to assess the effect on water sources, it is therefore important to evaluate the amount of radioactive Cs migrating to the water from both grass and fallen leaves.

Study on Radioactive Cesium in Wild Mushroom

2011年 3月 11日の東日本大震災に伴う東京電力福島第 1 原子力発電所の事故によって、大量の放射性セシウムが大 気中に放出された、その一部は現在も福島県の浪江町、飯 舘村、南相馬市、川俣町などの地面に沈着しており、近畿 大学は震災直後から原子力研究所を中心として、川俣町に おける環境放射線の調査を川俣町と共同で行い、実態の把 握と対策の提言に資するデータの収集を行っている 。一 方、2012年 12月の朝日新聞の記事によると、青森県で採 取したきのこからも放射性セシウムが検出されたとしてい るが、検出された放射性セシウムは Cs-137のみで Cs-134 はなかったとしており 、事故後においても東北地方北部 で採取される野生きのこには、福島第一原発事故ではなく、 チェルノブイリ事故によってもたらされた放射性セシウム が検出されている可能性が高い。しかし、これまでに川俣 町の環境調査で測定された放射性セシウムとしては、Cs134も含まれていたことより 、検出された放射性セシウム は福島第一原発の事故により放出され、環境中に残留して いるものであることが強く示唆されている。 福島第一原発の事故以来、きのこは放射性物質の移行係 数が高い食品であるとの風評が流れたこともあり、特に野 生きのこや野外で栽培されているきのこは放射性物質濃度 が高い食品であるとされ、採取や販売が規制されてきた。 しかし、実際にはきのこの種類によっては放射性物質の濃 度は異なってくるといった研究報告 や、栽培方法の検 討により、野外で栽培されるきのこでも基準値以下に放射 セシウム濃度を低減した栽培法が開発されてきている に もかかわらず、いまだにきのこは放射性物質濃度、移行係 数ともに高い食品であると認識されている。また、マツタ ケやホンシメジのように植物の根に共生し、土から発生す る菌根性のきのこ (ectomycorrhizal mushroom; EM)は、シ イタケやエノキタケなどのように枯木や落葉から発生する タイプの腐生性きのこ (saprobic mushroom; SA)に比べて移 行係数が高く、高濃度の放射性物質を含むとため、食用に 供することができないとされている。 本研究では、福島県川俣町の計画的避難区域に指定され ている山木屋地区に自生しているきのこの放射能レベルの 研究論文