Faculty Profiles - URITANI Akira

Papers - URITANI Akira

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Measurement of the Thermal and Fast Neutron Flux in a Research Reactor with a Li and Th Loaded Optical Fibre Detector Reviewed

Y. Yamane, A. Uritani, T. Misawa, J. K-H. Karlsson and I. Pazsit

Nucl. Inst. and Methods Vol. A432 ( 2-3 ) page： 403-409 1999.8

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

The spatial dependence of thermal and fast neutron flux was measured axially in the core of a 1 MW research reactor. The measurements were made by a thin optical fibre detector with a neutron sensitive ZnS(Ag) scintillation tip. For thermal neutrons 6Li was used, whereas for fast neutrons 232Th was used as neutron converter. The spatial dependence was measured by moving the fibre axially with a uniform speed. The measurement takes a few minutes, compared to up to 10 h with the conventional wire activation method. Comparison with traditional measurements shows a good agreement.

放射線検出器のニューラルネットワーク波形識別におけるデータ入力間隔の最適化

酒井宏隆、瓜谷章、井口哲夫

放射線 Vol. 25 ( 2 ) page： 115-122 1999.4

Spherical Neutron Detector for Space Neutron Measurement Reviewed

S. Yamaguchi, A. Uritani, H. Sakai, C. Mori, T. Iguchi, H. Toyokawa, N. Takeda and K. Kudo

Nucl. Instr. and Methods Vol. A422 ( 1-3 ) page： 600-605 1999.2

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

A novel neutron detector has been developed to measure energy spectra of space neutrons in a spaceship. The detector consists of a spherical polyethylene moderator with a diameter of 30 cm and 19 pairs of 6Li- and 7Li-glass scintillators arranged along the orthogonal x-, y-, and z-axes of the sphere. The pairs can distinctively detect thermal neutrons in some radiation fields, where other radiation exists, by subtracting the number of detected events of the 7Li-glass scintillator from that of the 6Li-glass one. Hence the detector can clearly obtain the thermal neutron flux distribution in the spherical moderator even in such fields. The detector was applied to the measurement of monoenergetic and 252Cf neutrons. The characteristics of the detector were studied by comparison with the simulations.

Time-Spatial Neasurement by Using Position-Sensitive ³He Proportional Counter

Y. Kitamura, T. Misawa, H. Unesaki, S. Shiroya, A. Uritani and K. Ishitani

Nucl. Instr. and Methods Vol. A422 ( 1-3 ) page： 64-68 1999.2

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

Time-spatial neutron measurement was carried out by using a position-sensitive 3He proportional counter (PSPC) in the Kyoto University Critical Assembly. The data of the output pulses from the PSPC were acquired by a data acquisition system which was based on the LN-9000 system of Laboratory Equipment Corporation. In this system, the time and the position data of the neutron detection pulses were simultaneously accumulated by a personal computer. In the present study, the Rossi-α method, which was derived for time-domain neutron correlation analysis, was extended in order to process the measured two-dimensional data of time and space. The processed experimental results and a theoretical formula based on the one-group diffusion approximation neglecting the higher modes agreed well with each other, which indicates the present system is applicable for reactor physics experiments including reactor kinetics.

High Energy Resolution Spectrometer with Propotrional Counter and Si-Detector Telescope Type for 14MeV Neutrons in Plasma Diagnostics Reviewed

C. Mori, J. Goto, A. Uritani, H. Miyahara, Y. Ikeda, Y. Kasugai, J. Kaneko, M. Sasao, Y. Sakuma, K. Kudo and N. Takeda

Nucl. Instr. and Methods Vol. A422 ( 1-3 ) page： 75-78 1999.2

Measurement of Neutron and Gamma Ray Intensity Distributions with an Optical Fiber-Scintillator Detector

C. Mori, A. Uritani, H. Miyahara, T. Iguchi, S. Shiroya, K. Kobayashi, E. Takada, R. F. Flemming, Y. K. Dewaraja, D. Stuenkel, G. F. Knoll

Nucl. Instr. and Methods Vol. A422 ( 1-3 ) page： 129-132 1999.2

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

On the tip of an optical fiber, a very small amount of ZnS(Ag) scintillator mixed with neutron converter and adhesive paste was painted, which can be inserted into a narrow space and moved by a fiber-driving unit controlled with a personal computer. The presented method made it possible to measure neutron flux distributions in critical assemblies, research reactors or other neutron facilities with position resolution of less than 1 mm and in 10 min or so over a meter. As neutron converter, 6Li and 235U are good for thermal neutrons and 232Th is useful for fast neutrons. When a neutron converter is not used, the method can be applied to the measurement of γ-ray intensity distribution.

New Pulse Shape Analysis Method with Multi-shaping Amplifiers Reviewed

H. Sakai, A. Uritani. K. Inoue, Y. Takenaka, C. Mori and T. Iguchi

Nucl. Instr. and Methods. Vol. A421 ( 1-2 ) page： 316-321 1999.1

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

A novel pulse-shape analysis method that uses similarity to recognize an individual pulse shape is presented in this paper. We obtain four pulse heights by using four linear amplifiers with different shaping time constants. We treat a combination of the four pulse heights as a pattern vector. A similarity of the pulse shape can be obtained by comparison between the pattern vector and a discriminant vector which was given in advance. Each pulse shape is analyzed by using the similarity. The method has been applied for the improvement of characteristics of a CdZnTe semiconductor detector. The characteristics of the energy spectrum of the CdZnTe detector such as the photopeak efficiency or the peak-to-valley ratio are improved after the correction procedure with the similarity.

コンプトンカメラによるガンマ線イメージング

瓜谷章

放射線 Vol. 25 ( 1 ) page： 87-92 1999.1

実践！放射線計測応用技術[6][原子炉分野]試験・研究炉、臨界装置、加速器炉

森千鶴夫、瓜谷章

原子力eye Vol. 45 ( 6 ) page： 64-67 1999

Pulse Shape Recognition for CdZnTe Semiconductor Detector by Using Multi-shaping Amplifiers Method with Neural Network Algorithm

H. Sakai, A. Uritani, C. Mori, T. Iguchi

Nuclear Science Symposium Conference Record, 1999 IEEE Vol. 1 page： 662 - 665 1998.10

Language：English

A new pulse shape recognition method with multi-shaping amplifiers, combined with a neural network algorithm, has been developed, where four pulse heights are sampled from one signal pulse through four linear amplifiers with different shaping time constants. The four pulse heights are used as characteristic parameters to recognize the pulse shape with a neural network. This method has been applied to signal processing for a CdZnTe semiconductor detector to improve the deteriorated energy spectra caused by pulse height deficits due to the different mobilities of electrons and holes in the detector. The neural network recognizes the pulse shape patterns and provides the corrective magnification factors of the pulse heights. After the corrective procedure, the energy spectrum for 137Cs gamma-rays is improved from 9.3 keV to 7.4 keV in the energy resolution (FWHM) of the 662 keV gamma ray photopeak. The photopeak becomes a considerably symmetrical shape without a low-energy tail. It has been verified that this method is simple and useful for pulse shape analyses, which can be used for many other applications.

Evaluation of Counting Loss and Its Correction for Small Pulses in the Internal Counting with Proportional Counters Reviewed

C. Mori, Y. Wu, T. Agemura, A. Uritani, H.Miyahara, T. Suzuki and M. Yoshida

International J. Applied Radiation and Isotopes Vol. 49 ( 9-11 ) page： 1107-1111 1998.9

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

In the absolute radioactivity determination of gaseous samples using the internal gas counting method with proportional counters, evaluation of counting losses of pulses whose pulse heights are lower than the discrimination level is very important to obtain high accuracy. Counting losses due to wall effect and to very low energy of a β-ray were evaluated by experiment and EGS4 Monte Carlo calculation. The calculated results agreed well with experimental results when parameters in the EGS4 code were properly chosen; which shows the calculation code is able to be applied to other radioactive nuclides and other measurement conditions for the evaluation of counting losses.

Novel Pulse Shape Analysis Method by Using Similarity Reviewed

Y. Takenaka, A. Uritani , K. Inoue, H. Sakai and C. Mori

International J. Applied Radiation and Isotopes Vol. 49 ( 9-11 ) page： 1219-1223 1998.9

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

A novel pulse-shape-analysis method that uses the similarity of patterns to recognize individual pulse shapes is presented. The principle of this method is described. The method has been applied to improve the gamma-ray energy spectrum of a CdZnTe semiconductor detector. The energy spectrum has been improved with increased photopeak efficiency and better energy resolution.

Improvement of Precision in Quantitative Measurement of Radioactivity with Imaging Plate Reviewed

T. Suzuki, C. Mori, K. Yanagida, A. Uritani, H.Miyahara, M. Yoshida and F. Takahashi

International J. Applied Radiation and Isotopes Vol. 49 ( 9-11 ) page： 1127-1130 1998.9

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

To obtain a high precision in radiation or radioactivity measurements with an imaging plate, the photo-stimulated luminescence intensity must be large. To get the highest intensity, we reread an imaging plate repeatedly and summed each intensity for the purpose of reducing the variation of the measured intensities. A great improvement of the precision in the measurement was achieved with the method of repeated readings when the time interval between each reading is more than about 1 h.

Measurement of Eigenvalue Separation by Using Position Sensitive Proportional Counter Reviewed

K. Ishitani, Y. Yamane, A. Uritani, T. Iguchi and S. Shiroya

Annals of Nuclear Energy Vol. 25 ( 10 ) page： 721-732 1998.6

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

Eigenvalue separation is an important index of power reactor stability in the view of neutronics. In recent years, a long, slender Position Sensitive Proportional Counter has been developed. By using this proportional counter, the spatial neutron flux distribution of a nuclear reactor can be measured rapidly. Using these characteristics, we intend to develop the experimental method evaluating eigenvalue separation as an index for reactor stability. A method based on spatial integrals of neutron flux measured at a subcritical system with an external source is proposed. To verify this method, experiments were carried out at Kyoto University Critical Assembly. It was confirmed that eigenvalue separation can be evaluated within a relative error of 10%.

講座　放射線防護用機器　XVII.　放射線管理計測技術の最近の進歩　1.位置感応型検出器とその応用

瓜谷章、飯田孝夫、森千鶴夫

Vol. 47 ( 2 ) page： 155-165 1998

Pulse Shape Recognition with Neural Network Algorithm

H. Sakai, A. Uritani, C. Mori and T. Iguchi

Proceedings of the 12th Workshop on Radiation Detectors and Their Uses page： 28-37 1998

Improvement of Energy Spectrum Characteristics of CdZnTe Semiconductor Detector by means of Digital Waveform Processing with neural network algorithm Reviewed

H. Sakai, Y. Takenaka, A. Uritani, K. Inoue and C. Mori

Nuclear Instruments and Methods Vol. A400 ( 2-3 ) page： 401-408 1997.12

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

We have studied the improvement of gamma-ray energy spectrum characteristics of a CdZnTe semiconductor detector by means of a neural network algorithm. The neural network recognizes the pulse shapes and determines the corrective magnification factors of pulse heights. After the corrective procedure with the network, the gamma-ray energy spectra of some radioisotope sources become more ideal with better energy resolution.

Performance of a Spherical Neutron Counter for Spectroscopy and Dosimetry Reviewed

H. Toyokawa, M. Yoshizawa, A. Uritani, C. Mori, N. Takeda and K. Kudo

IEEE transaction Vol. NS-44 ( 3 ) page： 788-791 1997.6

Language：English Publishing type：Research paper (scientific journal)

A spherical neutron counter for spectroscopy and dosimetry has been developed. The counter consists of a spherical polyethylene moderator and three slender 3He position-sensitive proportional counters. Rough measurements of neutron fluence spectra and ambient dose equivalents, H*(10), have been done in the moderated-neutron field of JAERI. Characteristics of the counter are examined and compared with those of a Bonner sphere neutron spectrometer.

An Electronically Collimated Gamma Camera with a Parallel Plate Collimator for Tc-99m Imaging Reviewed

A. Uritani , N. H. Clinthorne, J. E. Gormley J. W LeBlanc, W L. Rogers, D. K. Wehe and S. J. Wilderman

IEEE Transaction Vol. NS-44 ( 3 ) page： 894-898 1997.6

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

We present a new idea to apply a parallel plate collimator to an electronically collimated gamma camera, to reduce the complexity of image reconstruction. Back projected images obtained experimentally and using Monte Carlo simulations are shown. Using the collimator, backprojected images of single low-energy gamma-ray emitters can be obtained with larger signal-to-noise ratio than those obtained without the collimator. The results show that this method is useful in obtaining Tc-99m images.

Characteristics and Correction of the Fading of Imaging Plate Reviewed

T. Suzuki, C. Mori, K. Yanagida, A. Uritani, H.Miyahara, M. Yoshida and F. Takahashi

J. Nucl. Sci. Technol. Vol. 34 ( 5 ) page： 461-465 1997.5

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

When the latent images formed by exposure with incident particles in the phosphor of Imaging Plate (IP) are irradiated with laser beam, photo-stimulated luminescence (PSL) is emitted and read through a photomultiplier. PSL intensity fades with increasing the elapsed time between the exposure and the PSL reading. When the IP is read successively, the PSL intensities decrease with the number of reading times. The tendency of the decreasing becomes gradual with increasing the elapsed time after exposure. The multiple successive reading method gives the means of the correction of the fading.

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