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  • Author or Editor: K. Masumoto x
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Abstract  

Fullerenes, C60 and C70, were irradiated by 8 and 10 MeV deuterons. The irradiated samples were dissolved in CS2 and filtered to remove insoluble by-products. Finally, radioactive fullerenes and products, such as fullerene dimers, trimers labeled with13N, were isolated and detected in the liquid phase by radiochromatography. This suggests that the energy rich13N atoms successfully incorporated into the fullerene cages and that the disrupted cages reacted with neighboring cages.

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Abstract  

We studied the production of nine typical organic analytical reagents labeled with11C,13N and18F by irradiation with charged particles and bremsstrahlung and the purification of labeled compounds with HPLC and sublimation. As a result, we found that six reagents, α-naphthol, β-naphthol, quinoline, α-nitroso-β-naphthol, 8-hydroxyquinoline, and 1,10-phenanthroline H2O could be labeled with11C by bombarding a mixture of each reagent and boron with protons. More than 10% of the11C was successfully exchanged with carbon atoms in the original reagents. We also found that sublimation is useful for purifying 8-hydroxyquinoline labeled with11C. The extraction property of11C-labeled 8-hydroxyquinoline between water and chloroform could be easily monitored by radioactivity measurement.

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Abstract  

The spatial distribution of neutrons was measured at the muon science laboratory of KEK by the activation detector method using an imaging plate for the radioactivity measurement. It was confirmed that this method is highly sensitive to detect the average neutron dose of 10 µSv/h. The distribution of thermal and epithermal neutrons was also measured in the experimental room. The cadmium ratio inside the experimental room is one except for the neutron leakage point. The spatial distribution of neutrons inside the concrete shield of KENS was measured by the same method. Aluminum and gold foils were used for the measurement of fast and thermal neutrons, respectively. Two dimensional change of the reaction rate of the 27Al(n,α)24Na reaction shows a good agreement with the results calculated by the Monte Carlo simulation using MARS14 code. Thermal and epithermal neutron flux ratio on the beam axis was measured by the cadmium ratio method. The flux ratios were about 30 and almost constant for every slot except for the surface of the shield, because the cadmium ratio is 2. This method was very useful to measure the activity of many pieces of detector simultaneously without any efficiency and decay correction. Wide dynamic range and high sensitivity are also the merit of this method.

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Abstract  

A new internal standard method coupled with the standard addition method for PIXE analysis has been developed. In its basic principle, this method is characterized by that a suitable element present initially in the sample is used as an internal standard, and further the comparative standard is prepared by applying the standard addition method to the duplicated sample. When a sample contains Wa g of trace element A to be determined together with an element B which is usable as an internal standard, and when the comparative standard is prepared by adding an exactly known amount of element A, W a * g, to the duplicated sample, the absolute concentration of Wa can easily be determined by the following equation even if the above sample and comparative standard are irradiated separately by a different number of protons Wa=W a * /[(R*/R)-1] where R and R* are ratios of net photopeak counts due to the characteristic X-rays from the element A and B in the irradiated sample and comparative standard, respectively. The usefulness of the method was examined through determination of Cu, Zn, Rb and Sr in two biological materials, such as spinach and orchard leaves. As a result, this method was demonstrated to be sensitive, highly reproducible and reasonably accurate.

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Abstract  

For decommissioning of the cyclotron and electron synchrotron facilities, the residual radioactivity in surface and core samples of concrete, collected from various parts of buildings, was determined by gamma-ray spectrometry. It was found that the concrete samples were activated mainly by neutrons and that the major radioisotopes were 152Eu, 60Co, 134Cs, 22Na and 54Mn. The maximum activity induced by thermal neutron capture was observed at the depth of 10 cm in the concrete wall near the deflector of the cyclotron. Tritium was also produced by the neutron reaction, because its concentration was proportional to the activities of 152Eu and 60Co. The surface dose rates inside the accelerator room were also monitored to define the decontamination area. The surface dose rate was proportional to the residual radioactivity, such as 60Co. A careful evaluation was very useful in order to minimize the radioactive waste during decontamination.

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Abstract  

Activation is one of the severe problems at the high-energy accelerator facilities. By using gamma-ray spectrometry and activation detector technique, we could obtain important information on (1) nuclear reactions, (2) energy spectra of secondary particles, (3) penetration behavior of secondary particles in shield wall, (4) historical record of beam loss occurred in the accelerator rooms. It was concluded that the technique and knowledge of activation analysis are very useful to solve the radiation protection problems at the accelerator facilities.

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Abstract  

A dedicated NAA calibration method was developed for the determination of the neutron spectrum monitor elements Co, Au and Lu in alloyed wires and foils, with an accuracy of better than 1%. The method does not require quantitative micropipetting for preparing the standards, and leads to vanishing errors caused by flux inhomogeneities and by differences in counting geometry and gamma attenuation. Its performance was tested by analysing various NIST, IRMM and RX aluminium-based materials with certified or specified Co, Au or Lu content.

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Abstract  

Highly selective and sensitive γ-ray detection was performed by coincidence and anticoincidence event analysis after list-mode data acquisition using an HPGe spectrometer equipped with NaI(Tl) and plastic scintillation detectors. In order to obtain the most suitable detection of specific nuclides, coincidence or anticoincidence spectra could be freely constructed by extracting events with particular time and energy correlations. Although the detector arrangement of this system was the same as that of a typical Compton suppression spectrometer, background counts were drastically reduced and γ-rays of particular nuclides could be selectively detected by using γ-γ, γ-X, γ-X-X, and γ-β+ coincidences.

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Abstract  

The internal standard method coupled with the standard addition method has been applied to photon activation analysis and proton activation analysis of minor elements and trace impurities in various types of iron and steel samples issued by the Iron and Steel Institute of Japan (ISIJ). Samples and standard addition samples were once dissolved to mix homogeneously, an internal standard and elements to be determined and solidified as a silica-gel to make a similar matrix composition and geometry. Cerium and yttrium were used as an internal standard in photon and proton activation, respectively. In photon activation, 20 MeV electron beam was used for bremsstrahlung irradiation to reduce matrix activity and nuclear interference reactions, and the results were compared with those of 30 MeV irradiation. In proton activation, iron was removed by the MIBK extraction method after dissolving samples to reduce the radioactivity of56Co from iron via56Fe(p,n)56Co reaction. The results of proton and photon activation analysis were in good agreement with the standard values of ISIJ.

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Abstract  

A comprehensive study on the yields of photonuclear reactions of various types has been performed, and sensitivities and the effects of interferences in multielement photon-activation analysis have been evaluated by bremsstrahlung activation of many elements with maximum energies ranging from 30 to 60 MeV. The applicability and reliability of the method were demonstrated by analyzing standard round-robin samples and then by presenting the elemental abundances in several geological, biological and environmental materials. The method was almost insensitive to matrix effects and was assessed to be promising for nondestructive multielement determination of the materials of wide variety, giving good reproducible results for 20 or more elements.

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