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Hakata ku, Japan
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Tashima H.,Japan National Institute of Radiological Sciences | Yoshida E.,Japan National Institute of Radiological Sciences | Nishikido F.,Japan National Institute of Radiological Sciences | Wakizaka H.,Japan National Institute of Radiological Sciences | And 8 more authors.
2015 IEEE Nuclear Science Symposium and Medical Imaging Conference, NSS/MIC 2015 | Year: 2015

There is a strong potential demand for high-sensitivity and low-cost brain positron emission tomography (PET) imaging that is applicable to early diagnosis of Alzheimer's disease. Therefore, we have proposed a high-sensitivity dedicated brain PET geometry composed of a helmet detector having a hemisphere shape and a chin detector, which we call helmet-chin PET. Because the shape of a human head is a sphere, the hemispherical arrangement of the detectors allows closer positioning of detectors and better sensitivity than the conventional cylindrical arrangement. In addition, adding detectors around the chin position significantly improves the sensitivity at the center where the cerebellum is located. For a proof-of-concept of the helmet-chin PET, we developed the first prototype of the helmet-chin PET using 4-layer depth-of-interaction (DOI) detectors. The helmet detector for the prototype system was realized by multiple rings having different numbers of detectors and a cross-shaped part covering the top. We used in total 54 DOI detectors, each of which consisted of 1,024 Zr-doped GSO crystals with dimensions of 2.8 × 2.8 × 7.5 mm3 and a high-sensitivity, 64-ch flat-panel photomultiplier tube. In performance evaluations, we determined there were uniform spatial resolutions of 3.0 mm by an analytical method and 1.4 mm by an iterative method. Peak sensitivity was measured as 10 % at a region near the top of the head, which was almost equivalent to the central sensitivity of the cylindrical PET composed of 120 DOI detectors. In addition, we performed an initial imaging test with a brain phantom and we reconstructed the images with and without the chin detector. We found the slice near the bottom of the helmet detector had strong noise without the chin detector, while the slice had good imaging performance with it, and the overall image quality was improved. Therefore, we concluded that the helmet-chin PET had high potential for realizing high-sensitivity, low-cost, and accurate brain imaging. © 2015 IEEE.

Naganawa H.,Japan Atomic Energy Agency | Kumazawa N.,Ibaraki University | Saitoh H.,ATOX Co. | Yanase N.,Japan Atomic Energy Agency | And 6 more authors.
Transactions of the Atomic Energy Society of Japan | Year: 2011

We tried the decontamination of surface soils for three types of agricultural land at Nagadoro district of Iitate-mura (village) in Fukushima Prefecture, which is highly contaminated by deposits of radionuclides from the plume released from the Fukushima Daiichi nuclear power plant. The decontamination method consisted of the peeling of surface soils solidified using a polyion complex, which was formed from a salt solution of polycations and polyanions. Two types of polyion complex solution were applied to an upland field in a plastic greenhouse, a pasture, and a paddy field. The decontamination efficiency of the surface soils reached 90%, and dust release was effectively suppressed during the removal of surface soils. © 2011 Atomic Energy Society of Japan, All Rights Reserved.

Sakamoto F.,Japan Atomic Energy Agency | Ohnuki T.,Japan Atomic Energy Agency | Kozai N.,Japan Atomic Energy Agency | Yamasaki S.,Japan Atomic Energy Agency | And 2 more authors.
Transactions of the Atomic Energy Society of Japan | Year: 2013

The local area distribution and relocation of radioactive cesium deposited in trees after the 2011 tsunami-related accident at the Fukushima Daiichi Nuclear Power Plant (FDNPP) have been studied by measuring the spatial distribution of cesium on/in trees by autoradiography analysis. Samples of trees were collected from places located between 4 and 55 km from FDNPP approximately 2, 8, 20, and 22 months after the accident. The autoradiography analyses of Cryptomeria japonica, Torreya nucifera, and Thujopsis dolabrata var. hondae samples collected approximately 2 and 8 months after the accident showed that radioactive Cs was mainly distributed as spots on the branches and leaves of the trees emerged before the accident, and was detected in negligible amounts in new branch and leaves that emerged after the accident. On the contrary, radioactive Cs was detected at the outermost tip of the branches in the trees collected 20 months after the accident. Morus alba samples collected 22 months after the accident contained radioactive Cs inside and outside their stems, even though no radioactive Cs was detected in their roots, strongly suggesting that a certain amount of radioactive Cs was translocated from the outside to the inside of stems. These results indicate that the distribution of radioactive Cs deposited on/in the trees gradually changes with time (scale: year). © 2013 Atomic Energy Society of Japan, All Rights Reserved.

Fujiia Y.,Tokyo Institute of Technology | Fujiia Y.,ATOX Co. | Kima S.-H.,Tokyo Institute of Technology | Kima S.-H.,Daegu Technopark Nano Convergence Practical Application Center | And 2 more authors.
Zeitschrift fur Naturforschung - Section C Journal of Biosciences | Year: 2013

A one hundred meter long ion-exchange chromatograph was used to establish rigorously the mass effects in the iron isotope fractionation in the Fe(II)-Fe(III) electron exchange equilibration.We used a highly porous, strongly basic anion exchange resin packed in glass columns. The abundance ratios of all natural iron isotopes, 54Fe, 56Fe, 57Fe, and 58Fe, in the effluent at the iron adsorption band boundary were measured with a mass spectrometer. The enrichment correlations among these isotopes were analyzed by three-isotope plots. The results clearly showed that the isotope fractionation of Fe(II)-Fe(III) is governed by the normal mass effect; the iron isotope fractionation is not proportional to the nuclear size, but proportional to the reduced mass difference of the pair of iron isotopes. © 2013 Verlag der Zeitschrift für Naturforschung, Tübingen.

Fujii Y.,Atox Co. | Nomura M.,Tokyo Institute of Technology | Kaneshiki T.,Tokyo Institute of Technology | Sakuma Y.,Tokyo Institute of Technology | And 3 more authors.
Isotopes in Environmental and Health Studies | Year: 2010

Benzo 18-crown-6-ether resin was synthesised by the phenol condensation polymerisation process in porous silica beads, of which particle diameter was ca 60μ Calcium adsorption chromatography was performed with the synthesised resin packed in a glass column. The effluent was sampled in fractions, and the isotopic abundance ratios of 42Ca, 43Ca, 44Ca, and 48Ca against 40Ca were measured by a thermo-ionisation mass spectrometer. The enrichment of heavier calcium isotopes was observed at the front boundary of calcium adsorption chromatogram. The mass dependence of mutual separation of calcium isotopes was analysed by using the three-isotope-plots method. The slopes of three-isotope-plots indicate the relative values of mutual separation coefficients for concerned isotopic pairs. The results have shown the normal mass dependence; isotope fractionation is proportional to the reduced mass difference, (M - M')/MM', where M and M' are masses of heavy and light isotope, respectively. The mass dependence clarifies that the isotope fractionations are originated from molecular vibration. The observed separation coefficient ε is 3.1×10-3 for the pair of 40Ca and 48Ca. Productivity of enriched 48Ca by crown-ether-resin was discussed as the function of the separation coefficient and the height equivalent to the theoretical plate. © 2010 Taylor & Francis.

Kawano T.,Japan National Institute for Fusion Science | Uda T.,Japan National Institute for Fusion Science | Yamamoto T.,ATOX Co. | Ohashi H.,ATOX Co.
Fusion Science and Technology | Year: 2011

For measuring the tritium concentration in water, a water monitoring system was developed. The monitoring system consists of a flow-cell detector, a pair of photomultiplier tubes, a circuit unit (including a highvoltage power supply and a coincidence counting module), a water flow pump and a multichannel pulse height analyzer. The flow-cell detector was fabricated using granular CaF 2(Eu), which was solid scintillation materials. The performance of the water monitoring system was examined with three water samples containing different tritium concentrations of 10, 50 and 100 Bq/ml, and linearity between the count rate and the tritium concentration was examined. The results suggest that our system reasonably works as a water monitor for measuring low level tritium concentration. This system is the first such real-time monitoring system able to measure tritium concentrations in water continuously flowing through the solid scintillation detector.

Kawano T.,Japan National Institute for Fusion Science | Ohashi H.,ATOX Co. | Hamada Y.,ATOX Co. | Jamsranjav E.,ATOX Co.
Nuclear Science and Techniques | Year: 2014

A monitoring system based on a CaF2 flow-cell detector was previously developed for measuring the tritium concentration in water. The flow-cell detector was fabricated using a granular CaF2(Eu) solid scintillator. In the present study, the effect of lead shielding on the measurement sensitivity was investigated. First, measurements were carried out both on tritium water and tritium-free water without the use of shielding. Counts were accumulated for either 600 or 10 000 s and the detection limits without shielding were calculated. Second, the effect of shielding was evaluated using background radiation. Lead blocks with a thickness of 5 cm were used as shielding materials. Full shielding around the entire measurement system reduced the background count by 53.8%. Approximating this to a background reduction of 2 times, the detection limit with full shielding was then calculated. It was concluded that 5-cm-thick lead shielding reduced the detection limit for tritium by at least 35%. © 2014, Science Press. All rights reserved.

Kawano T.,Japan National Institute for Fusion Science | Ohashi H.,ATOX Co. | Hamada Y.,ATOX Co. | Jamsranjav E.,ATOX Co.
Fusion Science and Technology | Year: 2015

A monitoring system based on a flow-cell detector was developed for measuring the tritium concentration in water. The flow-cell detector was fabricated using a granular CaF2 solid scintillator. This system does not use a liquid scintillation cocktail and does not generate radioactive organic liquid waste. Moreover, continuous real-time measurements are possible, in contrast to a liquid scintillation counting system, which requires batch measurements. For further development of the system, four flow-cell detectors were fabricated. They included a single 3-mm-diameter cell, three 3-mm-diameter cells in series, a single 5-mm-diameter cell, and three 5-mm-diameter cells in series. Continuously flowing water containing tritium at various concentrations was passed through the flow cells, and tritium count were measured for 600 and 10000 s. Investigating the relation between the count rate and concentration, the three 5-mm-diameter cells were most sensitive, with a linear relation maintained down to approximately 2 Bq/mL and 10 Bq/mL for 10000- and 600-s measurements, respectively.

Takeishi T.,Kyushu University | Kotoh K.,Kyushu University | Kawabata Y.,Kyushu University | Tanaka J.-I.,Kyushu University | And 2 more authors.
Fusion Science and Technology | Year: 2015

In the decommissioning project of tritium handling laboratories or/and facilities, oils such as used in the vacuum pumps have been left conventionally in their comprehensive facilities. Existence of oils, especially highly-contaminated with tritium, is becoming one of the serious problems in projects for decommissioning tritium handling laboratories because of no disposal way of the tritiated waste oils. Experiments using bubblers were carried out to examine the tritium contamination and decontamination of a volume of rotary-vacuum-pump-oil. Contamination of pump oil was observed by bubbling with tritiated water vapor and tritiated hydrogen gas. And then, subsequent decontamination of tritiated oil was processed by bubbling with pure water vapor and dry argon gas. The bubbling with water vapor was more effective than with the dry gas. Experimental results show that the water vapor bubbling in an oil bottle can remove tritium efficiently from the contaminated oil into another water-bubbling bottle. © 2015, American Nuclear Society. All rights reserved.

Tada K.,Nagaoka University of Technology | Kawamoto S.,Nagaoka University of Technology | Yamada N.,Nagaoka University of Technology | Kimura T.,Nagaoka University of Technology | And 3 more authors.
2015 IEEE 42nd Photovoltaic Specialist Conference, PVSC 2015 | Year: 2015

A robotic crawler for on-site inspection of disconnection failure of crystalline silicon photovoltaic (PV) module was prototyped and tested in actual PV array. Magnetic flux sensors that traced the interconnector lines of the PV module successfully detected disconnection failures. Based on the inspection result by manual inspection, robotic inspection achieved failure predictive value of 90%; however, the test revealed issues such as inspection errors due to line tracing errors of the sensor in the robot. Optimal sensor placement in the robot was investigated aiming for more robust disconnection failure detection. © 2015 IEEE.

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