A. Terakawa

MEASURES AGAINST RADIOACTIVE CONTAMINATION DUE TO FUKUSHIMA FIRST NUCLEAR POWER PLANT ACCIDENTS PART III: REMOVING AND DECONTAMINATION OF CONTAMINATED SOIL

We studied the structure of radioactive cesium distribution in soil and found the exponential dependence. This behavior could be explained theoretically. We developed a useful method to decontaminate the soil contaminated with radioactive cesium atoms. We applied our method to the contaminated school yards of elementary schools of Marumori town and decontaminated total area of about 7000 m2.

Prototype of high resolution PET using resistive electrode position sensitive CdTe detectors

We developed resistive electrode position sensitive CdTe detectors and a prototype PET camera which included them in order to achieve a high sensitive semiconductor PET camera. It was determine that a high resistive electrode on a CdTe detector could be made by changing a thickness of an electrode metal. 1-dimensional position sensitive detectors were made by this method, and a good position resolution of 1.2 mm FWHM was confirmed. The prototype camera was built with these detectors. Reconstructed images of 22Na were obtained with the prototype. Resolutions are 0.8 mm (FWHM) in transaxial, and 1.6 mm (FWHM) in axial.

The 17,18O(p, n)17,18F reaction at Ep = 35 MeV

Abstract The 17,18 O(p, n) 17,18 F reactions were studied at E p = 35 MeV. Neutron spectra were measured at laboratory angles between 0° and 140°. Results were compared with distorted-wave calculations using the shell-model wave functions. For the 17 O(p, n) reaction, cross-section magnitudes as well as the angular-distribution shapes were well described by the calculation. On the other hand, normalization factors of 0.60 were required for the spin-flip excitations observed in the 18 O(p, n) reaction leading to the ground (1 + ), 1.700 MeV (1 + ) and 2.100 MeV (2 − ) states. Possible origins of such differences were discussed.

Development of a WDX-μ-PIXE system for chemical state mapping

In this paper, we have developed a wavelength dispersive X-ray spectrometer microparticle-induced X-ray emission (WDX-μ-PIXE) system combining a microbeam system with high spatial resolution and wavelength dispersive X-ray (WDX) spectrometry with high-energy resolution for chemical state mapping. A Von Hamos geometry was used for the WDX system to achieve higher detection efficiency and energy resolution. The system consists of a curved crystal and a CCD camera. The WDX system was installed in a newly developed microbeam system. The energy resolution of the WDX system was 0.67 eV for Si-Kα1 (1740 eV). Si-Kα1,2 and Si-Kβ X-ray spectra from various Si compounds were measured and chemical shifts related to chemical states were clearly observed. The system was applied to the chemical state analysis of clay particles. After elemental mapping of the clay particles using a conventional μ-PIXE system with a Si(Li) detector, particles to be analyzed were selected and analyzed sequentially with the WDX system. Si-Kβ spectra from clay particles were obtained. The microscopic spatial distribution of elements and chemical state of the clay particles were sequentially measured with high energy and spatial resolution using a microbeam.

MEASURES AGAINST RADIOACTIVE CONTAMINATION DUE TO FUKUSHIMA FIRST NUCLEAR POWER PLANT ACCIDENTS PART II: MEASUREMENT OF SPACE RADIATION DOSE RATES AND EXAMINATION OF CONTAMINATION IN FOOD

The space radiation dose rates at several points in Miyagi prefecture and their time dependencies were measured. Radiation exposure was mainly caused by 131I at the earlier stage of Fukushima first nuclear power accidents and then by 134Cs and 137Cs. We inspected radioactive contamination for food produced in Miyagi prefecture and Fukushima city. As the result, almost all food were safe.

MEASURES AGAINST RADIOACTIVE CONTAMINATION DUE TO FUKUSHIMA FIRST NUCLEAR POWER PLANT ACCIDENTS PART I: DAMAGE SITUATION OF THE GREAT EAST JAPAN EARTHQUAKE

The great East Japan earthquake consisted of three catastrophes. The first one was the earthquake, the second one was the tsunami and the third one was nuclear power plant accidents. The magnitude 9 was recorded. After the earth quake, huge tsunami waves of above 16m height hit the east coast of Northeastern Japan. Many people died and many things were lost. The tsunami caused the accident of Fukushima first nuclear power plant which resulted in a serious radioactive pollution.

Development of a high-current microbeam system

We report on the development of a high-current microbeam system for wavelength-dispersive X-ray micro particle-induced X-ray emission (WDX-μ-PIXE) for chemical state mapping. The microbeam system is composed of two slits and a quadrupole doublet lens mounted on a heavy rigid support. The microbeam system is installed immediately after a switching magnet. A beam brightness of 2.4 pA⋅μm−2⋅mrad−2⋅MeV−1 is obtained at a half-divergence of 0.1 mrad. A beam current of more than 300 pA is obtained for object sizes of 40×10 μm2 with a half-divergence of 0.2 mrad, which corresponds to a beam spot size of 1×1 μm2. The calculated spot size of the beam was 1×1 μm2 and the measured spot size was 1×1.5 μm2. The WDX-μ-PIXE system with the microbeam system is now operational.

An X-ray pinhole camera using metallic radioisotopes emitting only characteristic X-rays

We developed an X-ray pinhole camera using a radio-isotope source that emits only X-rays.We investigated the performance of this system using a 55Fe source with phantom samples. We then applied it to investigate the movement of a 55Fe tracer in Japanese mustard spinach. We obtained X-ray images of the 55Fe tracer in the spinach samples, and found that 55Fe accumulated in the plant.

Prototype of TlBr detector array for ultra high resolution PET

We developed a prototype of TlBr semiconductor detector array for high resolution PET scanner with less than 1mm FWHM. We obtained an energy resolution of ∼20% FWHM for 511 keV and a coincidence time resolution of ∼50nsec FWHM at a detector bias 100V. This result expects the capability of application of TlBr detector array to a high resolution PET scanner. The TlBr detector arrays with the present time resolution performance can be applied to a small PET scanner for the PET study using small animals such as rats and mice.

µ-CT IMAGES OF THE EGG OF DROSOPHILA

We are developing a µ-CT (micro computed tomography) which enables to observe the interior of living small insects. In this study, we applied the µ-CT to get CT images of the egg of drosophila, since the drosophila is applied to various basic studies, such as gene research. The interior of the living egg was observed and it was uniform. In the case of the dried egg, the shell and the interior structure were confirmed. This result comes from the growth of the living egg.