Changes of ambient gamma-ray dose rate in Katsushika Ward, metropolitan Tokyo before and after the Fukushima Daiichi Nuclear Power Plant Accident

Katsushika Ward in the eastern part of metropolitan Tokyo was the Tokyo area with the highest deposition of artificial radionuclides after the nuclear accident at the Fukushima Daiichi Nuclear Power Plant. A car-borne survey of the air kerma rate was conducted for all of the ward and the results were compared with measurements done in 2005. The mean air kerma rate in 2014 was 59 ± 12 nGy h⁻¹ and that was 50% higher than the rate in 2005 (p < 0.01). Additionally, the environmental half-life was estimated to be 1.9 years from the transition of ambient equivalent dose rate after the accident for data published by the Katsushika Ward Office

Large enhancement of superconducting transition temperature in single-element superconducting rhenium by shear strain

Finding a physical approach for increasing the superconducting transition temperature (Tc) is a challenge in the field of material science. Shear strain effects on the superconductivity of rhenium were investigated using magnetic measurements, X-ray diffraction, transmission electron microscopy, and first-principles calculations. A large shear strain reduces the grain size and simultaneously expands the unit cells, resulting in an increase in Tc. Here we show that this shear strain approach is a new method for enhancing Tc and differs from that using hydrostatic strain. The enhancement of Tc is explained by an increase in net electron–electron coupling rather than a change in the density of states near the Fermi level. The shear strain effect in rhenium could be a successful example of manipulating Bardeen–Cooper–Schrieffer-type Cooper pairing, in which the unit cell volumes are indeed a key parameter

Database of the radioactivity of norm used as industrial raw materials

Most ores used as industrial raw materials are imported mainly because Japan has poor natural resources. The activity concentrations in these materials should be investigated to evaluate the radiation exposure of workers. In this study, imported industrial raw materials were collected, and the activity concentrations in these resources were measured by using inductively coupled plasma mass spectrometry and gamma ray spectrometry. Furthermore, a database of activity concentrations of NORMs was developed by referring to the measured results as well as referring to the literature, and a database on the web was published. The purpose of the database is to relieve anxieties among the general public and to provide extensive data regarding NORM for researchers and regulators. The database provides more than 900 activity concentrations in worldwide NORMs at no fee. (NORM database; http://www.nirs.go.jp/db/anzendb/NORMDB/ENG/index.php)

Natural radioactive nuclides in cigarettes and dose estimation for smokers

210Po and 210Pb contained in cigarettes might contribute to an increase in an effective dose. This article reports the effective dose of radionuclides to smokers based on results of a review of various parameters related to dose estimation for smokers. The annual effective dose to smokers was found to be 0.27 mSv year-1, which was lower than an intervention exemption level(1 mSv year-1)given in International Commission on Radiological Protection (ICRP Publ.82)

Database of activity concentration in NORMs used as industrial raw materials in Japan

Natural radioactive nuclides, such as Uranium-238 (238U), Thorium-232 (232Th), and Radium-226 (226Ra), are widely distributed in the environment. Zirconium (Zr) ore, titanium (Ti) ore, and phosphate (P) ores which are generally used as industrial raw materials, contain radioactive nuclides in a relatively high concentration. The International Commission on Radiological Protection (ICRP) 1990 Recommendations recommended that an occupational exposure to some of NORMs should be controlled. However, the current extent of the industrial use of NORMs is not clearly perceived, because the activity concentrations in NORMs have a wide distribution from low to high level, and NORMs are used for a variety of purposes. Because Japan has poor natural resources, most ores used as industrial raw materials are imported significantly. There can be a case that workers handling imported raw materials would be exposed to high levels of radiation without being aware of it. The activity concentrations in the materilas should be investigated to evaluate the radiation exposure of workers. In this study, we collected imported industrial raw materials, and measured the activity concentrations in these resources by using ICP-MS (inductively-coupled plasma mass spectrometry) and gamma ray spectrometry. Furthermore, we developed a database of activity concentrations of NORMs by referring to the measured results as well as referring to literatures, and published a database on the web. The purpose of the database is to relieve anxieties among the general public and to provide extensive data regarding NORM for researchers and regulators. The database is providing more than 1000 pieces of activity concentrations in NORMs at no fee. (NORM database; http://www.nirs.go.jp/db/anzendb/NORMDB/ENG/index.php)

Radiation survey along two trails in Mt. Fuji to investigate the influence of the radioactive contamination due to the Fukushima nuclear accident

Mt. Fuji is located approximately 300 km southwest of the Fukushima Daiichi Nuclear Power Stations. We performed the radiation survey along two main Mt. Fuji\u27s trails from 4:30 to 18:30 on July 9, 2011. We climbed the Yoshida trail from the Fuji-Subaru Line fifth station (2,300 m in altitude) to the Yoshida-Subashiri top (3,720 m in altitude) and descended the Subashiri trail from the Yoshida-Subashiri top to the Subashiri new fifth station (2,000 m in altitude) on foot while measuring gamma rays. The dose rate 1 m above ground measured using a NaI (Tl) scintillation survey meter were within the range from 0.03 &micro;Sv/h to 0.05 &micro;Sv/h throughout our measuring trip. We used a NaI (Tl) scintillation spectrometer for gamma-ray pulse height spectra measurement. The gamma-ray pulse height spectra obtained at least 2,500 m in altitude on both of the Yoshida and Subashiri trail showed the peaks of two radioactive cesium isotopes (Cs-134 and Cs-137) and natural radioactive nuclides. It was confirmed that a radioactive plume released from the Fukushima Daiichi Nuclear Power Stations had arrived at least 2,400m above sea level of Mt. Fuji.International Symposium on Environmental monitoring and dose estimation of residents after accident of TEPCO\u27s Fukushima Daiichi Nuclear Power Station

Natural radioactivities in iron and nickel ores imported into Japan and the dose assessment for workers handling them

In Japan, Fe and Ni ores are imported from foreign countries to be used as industrial raw materials for manufacturing industrial products like stainless steel. A part of these ores might contain high radioactivity, and then workers handling these ores would be exposed to radiations without being aware of it. Activity concentrations in these ores should be measured to evaluate the radiation exposure of workers. In this study, Fe and Ni ores used as industrial raw materials were collected from iron and steel companies, and the activity concentrations of 238U series, 232Th series and 40K in these ores were determined using ICP-MS and gamma ray spectrometry. The activity concentrations of 238U series, 232Th series and 40K in these ores samples were lower than the IAEA values. The doses to workers handling these ores were estimated using methods for dose assessment given in a report by the European Commission. In each scenario, a maximum value of annual effective doses for them was estimated to be about 6.8 &#61620; 10-6 Sv, which was lower than intervention exemption levels (annual dose: 1.0 &#61620; 10-3 Sv) given in ICRP Publication 82

Exposure assessment of workers using industrial NORM in Japan

In this study dose assessment of workers using typical industrial NORMs was carried out to obtain information for the future regulation system in Japan. Annual effective dose to workers was estimated using results of measurement of ambient dose rate and activity concentration of NORM in raw materials, products, and aerosols, as well as concentrations of 222Rn and 220Rn decay products in the environments of worksites of plant processing zirconium ore, monazite and titanium ore in Japan. From the results of dose assessment, relationship between concentration of NORM and average annual dose to worker was discussed