Shigehiro An

A design study of the neutron irradiation facility for boron neutron capture therapy

A design study of the neutron irradiation facility for boron neutron capture therapy was performed using two-dimensional transport calculations. Dose depth distributions in a phantom head were calculated for various neutron energies. The epithermal neutrons having the energies between 10 eV and 0.5 keV are suitable for the therapy. To obtain the epithermal neutron beam, the neutrons leaking downward through the central hole of the annular core TRIGA reactor were moderated through a mixture of heavy water with aluminum whose volume ratio is 15:85. Bismuth and lithium fluoride tile was used to remove gamma rays and thermal neutrons from the beam. Iron, borated polyethylene, and lead were used as the shield surrounding the moderation layer. When the epithermal neutron column is used, the maximum usable depth and irradiation time are 6.9 cm and 7.25 h, respectively, at a 2-MW level.

Design and safety study of power producing fusion-fission hybrid reactor

Abstract A power producing tokamak hybrid reactor was designed on the concept of fast fission blanket containing equilibrium plutonium. A pressure tube type blanket cooled with helium was adopted for the fuel blanket. The study includes nuclear and thermal hydraulic design of the blanket. The net electrical output is 723 MW. The blanket safety performance was analyzed on residual heat removal and accidental criticality. Transient thermal calculations were performed for emergency reactor shutdown, loss of coolant flow accident, loss of coolant accident and local blockage accident. Reactivity effects were also estimated for loss of coolant accident, steam ingress accident and blanket melt down.

Neutron streaming through a slit and duct in concrete shields and comparison with a Monte Carlo analysis

A series of measurements of about14-MeV deuterium-tritium neutrons streaming through a slit and a duct in concrete shields has been carried out using a Cockcroft-Walton-type neutron generator. Measured neutron energy spectra are compared with calculations in six configurations of the shields. The configurations are the simplified geometries of streaming paths of tokamak reactors, such as a divertor throat and a neutral beam injection port. The measured data were obtained with an NE-213 liquid scintillator using pulse shape discrimination methods to resolve neutron and gamma-ray pulse height data and using a spectral unfolding code to convert these data to energy spectra. The experiments were analyzed by a Monte Carlo code. The calculated neutron energy spectra slightly underestimate the measured data, especially in the range of 6 to 8 MeV. The agreement between the calculated and measured integral flux above 2.2 MeV ranges from 87.5 to 72.% depending on the configurations.

Study of epithermal neutron columns for boron neutron capture therapy

Abstract Optimal neutron energy for boron neutron capture therapy for treating brain tumors was studied. Epithermal neutrons gave lower dose at the brain surface and pentrated deeper than thermal neutrons. An epithermal neutron column and a reactor facility for boron neutron capture therapy were conceptually studied. Layers of alminum and heavy water whose volume ratio 85 15 were effective in decreasing fast neutrons while maintaining a high epithermal neutron level. An epithermal neutron column was experimentally developed at YAYOI reactor. It has been used for fundamental study of BNCT and radiation biology, although the beam intensity was not high enough to treat the patients due to the low reactor power.

Neutron and Gamma-Ray Penetrations in Thick Iron

Measurements of neutron and gamma-ray penetrations in an iron shield were performed up to a 60-cm depth in a tightly coupled source shield configuration with the fast-neutron reactor YAYOI as a source. Rates of neutron reactions and gamma-ray dose rates in the iron shield were obtained using activation foils and thermoluminescent dosimeters. Analyses of the experiments were made by using the DOT-III code with coupled neutron and gamma-ray cross sections from ENDF/B-IV and POPOP4 libraries. To obtain the source condition for the iron shield analyses, the calculated spectrum was adjusted to the measured reaction rates at the reactor shield boundary. The calculated neutron and gamma-ray distributions in the iron shield show fairly good agreement with the experiments. The effect of difference in Bondarenko-type self-shielding factors on the analyses of the iron shield is also shown.

Studies on the concepts of HTGR plants viable in Japan Part I: Outline of the activities

In Part I of this paper, the activities of the Research Association on the HTGR are outlined. A possible scenario based on HTGR plants viable in Japan is presented here as one of the main results of our studies.

Experimental Study on Fast-Neutron Streaming Through a Grid-Plate Shield of a Liquid-Metal Fast Breeder Reactor

Yoshiaki Oka (top left) (Dr. Eng. , University of Tokyo, 1974) is a member of the staff of the Nuclear Engineering Research Laboratory at the University of Tokyo. His interests include reactor shielding and reactor noise . Hiroaki Wakabayashi (top right) (Dr . Eng., University of Tokyo, 1967) is an associate professor in the Nuclear Engineering Research Laboratory at the University of Tokyo. His main interests include dynamic characteristics of fast pulse reactors. He is engaged in studies oi the pulsed operation of YAYOI. Shigehiro An (bottom left) (Dr. Eng., University of Tokyo, 1963) is a professor in the Nuclear Engineering Research Laboratory at the University of Tokyo. His interests include fast reactor safety and core physics design. Ikunori Suzuki (bottom right) (MS, nuclear engineering, Tokyo Institute of Technology , 1967) is employed by Kawasaki Heavy Industries and is a member of the Fast Breeder Reactor Development Project of the Power Reactor and Nuclear Fuel Development Corporation. He is responsible for the fast breeder reactor shielding design .

Fast neutron shielding and neutron transport studies at YAYOI

Abstract The fast neutron shielding experiments at the fast neutron source reactor YAYOI of the University of Tokyo were summarized. The experiments were grouped into the following four types; 1. (1)|experiments for shield design of fast breeder reactor, 2. (2)|fast neutron transmission experiments, 3. (3)|fast neutron streaming experiments, 4. (4)|neutron skyshine experiment. The experimental data are useful for shield design and assessing the accuracy of the calculational methods. The accuracy of numerical solution of the neutron transport equation by the discrete ordinates method were analysed. The effect of the uncertainty of the neutron cross sections and approximations in the computational method on the errors were assessed. The errors of multigroup approximation was dominant in the iron shield calculation.

Fast neutron source reactor, YAYOI

Abstract The characteristics of the fast neutron source reactor, YAYOI of the University of Tokyo are described. The results of major researches are summarized. Those are the studies of fast neutron shielding and neutron transport, development of standard neutron field, advanced neutron detection, measurement of decay heat, development of epithermal neutron columns for boron neutron capture therapy, on-line tritium recovery from fusion materials, fast neutron radiolysis of water, fast neutron radiography and behavior of actinides. Some of the off-pile studies are described. Those are the conceptual design study of advanced power reactors, electromagneto-mechanics, fluid dynamics of a free surface in liquid metal fast breeder reactors and development of computational techniques for nuclear engineering.

Coordination of nuclear developments in the Asia-Pacific region

Healthy, coordinated development of nuclear energy in the Asia-Pacific region requires the securing of human resources. This is an important component of development and should be well designed in advance, notwithstanding the fact that each country and area has its own unique system for nuclear research, education, and training. Differences are even more pronounced where preparedness for nuclear abnormal occurrences are concerned, despite the international impact of such incidents. From this point of view, we examine the current situation in international education and training of nuclear specialists, encompassing nuclear education and training systems, IAEA efforts, bilateral and multilateral transregional cooperation, and matters relating to national and transnational preparedness for nuclear abnormal occurrences. We present a proposal to create a regional center that would establish cooperation in nuclear research, education, training, and preparedness for abnormal occurrences.