Ryugo S. Hayano

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The largest concern on the cesium-137 ((137)Cs) deposition and its soil contamination due to the emission from the Fukushima Daiichi Nuclear Power Plant (NPP) showed up after a massive quake on March 11, 2011. Cesium-137 ((137)Cs) with a half-life of 30.1 y causes the largest concerns because of its deleterious effect on agriculture and stock farming, and,(More)
The Fukushima Dai-ichi NPP accident contaminated the soil of densely-populated regions in Fukushima Prefecture with radioactive cesium, which poses significant risks of internal and external exposure to the residents. If we apply the knowledge of post-Chernobyl accident studies, internal exposures in excess of a few mSv/y would be expected to be frequent in(More)
BABYSCAN, a whole body counter for small children with a detection limit for (137)Cs of better than 50 Bq/body, was developed, and the first unit has been installed at a hospital in Fukushima, to help families with small children who are very much concerned about internal exposures. The design principles, implementation details and the initial operating(More)
Using the first WBC unit installed in Fukushima Prefecture after the accident, the radiocesium body burdens of 566 high-risk residents of Minamisoma city were measured in July 2011 at the Minamisoma Municipal General Hospital. The analysis of the data was challenging because this chair-type, WBC unit, did not have sufficient shielding against background(More)
Resettlement to their radiation-contaminated hometown could be an option for people displaced at the time of a nuclear disaster; however, little information is available on the safety implications of these resettlement programs. Kawauchi village, located 12-30 km southwest of the Fukushima Daiichi nuclear power plant, was one of the 11 municipalities where(More)
Maintaining low levels of chronic internal contamination among residents in radiation-contaminated areas after a nuclear disaster is a great public health concern. However, the efficacy of reduction measures for individual internal contamination remains unknown. To reduce high levels of internal radiation exposure in a group of individuals exposed through(More)
BABYSCAN, a whole-body counter (WBC) for small children was developed in 2013, and units have been installed at three hospitals in Fukushima Prefecture. Between December, 2013 and March, 2015, 2707 children between the ages of 0 and 11 have been scanned, and none had detectable levels of radioactive cesium. The minimum detectable activities (MDAs) for(More)
After a major radioactive incident, accurate dose reconstruction is important for evaluating health risks and appropriate radiation protection policies. After the 2011 Japan Fukushima nuclear incident, we assessed the level of agreement between the modeled and directly measured dose and estimated the uncertainties. The study population comprised 520 school(More)
Physical laws are believed to be invariant under the combined transformations of charge, parity and time reversal (CPT symmetry). This implies that an antimatter particle has exactly the same mass and absolute value of charge as its particle counterpart. Metastable antiprotonic helium (pHe(+)) is a three-body atom consisting of a normal helium nucleus, an(More)
After radioactive incidents, the exposure risk in daily activities among children is a major public concern. However, there are limited methods available for evaluation of this risk, which is essential to future health risk management. To this end, this study assessed the relationship between behavioral patterns of school children and radiation exposure for(More)