Groundwater dating with tritium is an important substantiation of groundwater research. The application of tritium measurement can be expected to be a new research industry. The precipitation tritium data by monthly sampling have been observed for 56 years in Tokyo area, and it has been shown as an open access database in the web site of National Institute of Radiological Sciences. The tritium concentration of groundwater recharge should be necessary for groundwater dating. It was estimated from the annual maximum and minimum concentrations in the database by using the theoretical equation and area constants proposed in our previous paper. This paper presents the tritium concentration table of groundwater recharge at four sampling sites widely dispersed across Japan, i.e., Sapporo, Niigata, Tokyo, and Matsuyama. The tritium concentration table with logical significance should be useful for hydrological study.
Nurses in charge received additional radiation exposure from the patients with intravenous FDG injection when FDG-PET/CT with contrast media was performed. The exposure dose was measured about 1.5μSv per examination on average. There was not a large difference among those when the mean exposure dose of each nurse was compared. There was a tendency that the exposure dose was less, as work years of the nurses in charge of PET/CT with contrast were longer. Consideration of radioactivity distribution in the PET/CT examination room has a potential to reduce radiation exposure dose of the nurses in charge.
We have proposed a new theory on passive γ assay for 238U determination of uranium-contaminated waste drums generated in the decommissioning of nuclear facilities. According to this theory, regardless of the inhomogeneity of waste matrix density or uranium source distribution, we can accurately determine the amount of 238U contained in drums nondestructively using count rates of γ-rays of two energies(1001keV and 766keV) emitted from 238U progeny nuclide 234mPa. This technique is aimed final at introducing into the commercially available γ-ray measuring device. In this paper, we have verified the theory using the commercially available γ-ray measuring device by tests under various simulated waste drums conditions. We used the γ-ray measurement system made from CANBERRA:Qualitative and Quantitative (Q2) Low Level Waste Assay Systems. The application validity of this evaluation technique was shown.
We developed a method for easily and rapidly determining the concentration of 137Cs in irrigation water for paddy fields by a germanium detector. A Caesium Rad Disk Pack and a Rad Disk sampler were used to separate radiocaesium by a particle size and to concentrate radiocaesium on a Caesium Rad Disk and a pre-filter. Concentration of 137Cs in irrigation water was determined at a detection limit of 0.2Bq kg−1 with a detection time of 4000 seconds.
We have observed artificial radionuclides originated from the TEPCO Fukushima Daiichi Nuclear Power Plant accident. This paper presents our monitoring results(March to May, 2011) for (1) γ-ray dose rate (2) airborne radioactivity (3) radioactivity deposited onto the basin and (4) radioactivity in tap water. Regarding γ-ray dose rate, no increase was observed. A small amount of artificial radioactivity(131I, 134Cs, 136Cs, 137Cs and 132Te) was found from airborne dust samples. While 131I was detected two weeks after the accident, 134Cs and 137Cs were detected three weeks after. Integrated amount of activity was 14mBq/m3 for 131I, 11mBq/m3 for 134Cs and 9.5mBq/m3 for 137Cs. The monitoring results indicated that a plume with relatively high radioactivity passed through our monitoring station during April 6 - 7. Atmospheric diffusion simulation analyses reveal this. 131I, 134Cs and 137Cs were also measured from monthly-monitored deposition. Total depositions for three months were 4.2Bq/m2 for 131I, 0.85Bq/m2 for 134Cs and 0.84Bq/m2 for 137Cs. No artificial radionuclide was found for tap water samples. The dose from these artificial radionuclides was estimated to be 0.23μSv/y, which was too small to cause health effects.
The basic research of diluted magnetic semiconductor(DMS) or insulator(DMI) is promoted for development of future spintronics. It is indispensable to clarify what kind of state the magnetic ion doped in the oxides exists or whether it exists, like a cluster or a distributed ion. Mössbauer's scattering methods of conversion electron Mössbauer spectrometry(CEMS) and nuclear resonance inelastic scattering(NIS) as well as a conventional transmission method give unique information by the use of about 1% 57Fe ion as a probe of the valence state, magnetic structure, and local vibrational density of state(VDOS) distribution in DMS and DMI. The relation between the hyperfine structure of Mössbauer spectra and the room temperature ferromagnetism of transparent oxides such as TiO2, SnO2, ITO, IZO, SiO2 and Al2O3 is discussed.
The Subcommittee on Survey of Nuclear Medicine Practice in Japan has performed a nationwide questionnaire surveys every five years since 1982. The latest questionnaire survey was performed in June 2012. The estimated total number of the annual examinations was 1.15 millions, 19% less than that of the last survey in 2007. The scintigraphic examination most frequently performed was bone scintigraphy, followed by myocardial and brain perfusion scintigraphy in order. The number of PET studies and radionuclide targeted therapies increased by 40% and 62%, respectively, as compared to the 2007's survey. The increase was attributable to growing uses of commercially delivered FDG, and the newly started radionuclide targeted therapy for patients with metastatic bone tumor or malignant lymphoma, in addition to 131I therapy for patients with thyroid cancer or Graves' disease. The number of in vitro radioassays has been decreasing continuously since 1992.