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Matsuba, Kenichi
no journal, ,
no abstracts in English
Fukaya, Yuji
no journal, ,
The spent fuel characteristics of the reduced-moderation water reactor (RMWR) have been investigated using the SWAT and ORIGEN codes. RMWR In the estimation, the ORIGEN libraries for RMWR were necessary, but there were no open ones. Therefore, they were produced in this study by using the SWAT code. In order to investigate the characteristics of the RMWR spent fuel, the decay heat, the radioactivity and the content of each nuclide were evaluated with ORIGEN using these libraries. In this study, the spent fuel characteristics of other types of reactor were also evaluated with ORIGEN. The decay heat and the radioactivity of the RMWR spent fuel are lower than those of full-MOX-LWRs and FBR, and are the same level as those of the high burn-up PWR. In addition, from the waste disposal point of view, the characteristics of the heat generation FP elements, the platinum group metals, Mo and the long-lived FPs (LLFPs) were also investigated.
Cs derived from Nagasaki atomic bomb; The Sedimentation in Nishiyama reservoir for the last 60 years and the distribution in surface soil at presentKokubu, Yoko; Yasuda, Kenichiro; Magara, Masaaki; Miyamoto, Yutaka; Sakurai, Satoshi; Usuda, Shigekazu; Yamazaki, Hideo*; Yoshikawa, Shusaku*; Nagaoka, Shinji*
no journal, ,
In order to determine sedimentation of plutonium and Cs derived from Nagasaki atomic bomb for the last 60 years, we measured 
Pu/
Pu ratio and Pu and Cs concentration in a sediment core collected at Nishiyama reservoir in Nagasaki city. A layer where plutonium and Cs deposited immediately after the detonation was specified in the core. Even at present, the plutonium and Cs from the atomic bomb are continuously being deposited together with those of the atmospheric nuclear tests. We also measured the ratios in soils collected at eastern part of Nagasaki prefecture and Kumamoto prefecture and so on to determine the detailed distributions of the plutonium. The ratios in soils collected in the Shimabara peninsula, Kumamoto city and Aso city were relatively lower than value of global fallout from atmospheric nuclear tests. It indicates that the atomic bomb plutonium was deposited between 2 km and about 100 km east from the hypocenter.
Ishikawa, Masao; Itoga, Toshio*; Okuji, Toshio*; Nakhostin, M.*; Baba, Mamoru*; Shinohara, Koji; Hayashi, Takao; Sukegawa, Atsuhiko; Nishitani, Takeo
no journal, ,
Line-integrated neutron emission profiles are routinely measured using Stilbene neuron detectors (SNDs) in JT-60U tokamak. Although the SND has excellent pulse shape discrimination (PSD) property between neutrons and 
rays, the maximum count rate is limited up to 
10
cps due to its analog circuit. To overcome this issue, a digital signal processing (DSP) system using a flash ADC has been developed. In this system, anode signals from the photomultiplier of the SND are directory stored and digitized in the Flash ADC. Then, the PSD is performed using software. The DSP system has been installed in JT-60U and started to measure neutrons in deuterium experiments. As a result, it is confirmed that the DSP system is successfully measured neutron fluxes with count rate up to 10
cps.
Kajita, Shin; Ono, Noriyasu*; Takamura, Shuichi*
no journal, ,
The effects of a transient heat load on damaged tungsten due to helium plasma irradiation have been investigated using a ruby laser with long pulse duration in the divertor simulator NAGDIS-II. Helium holes/bubbles, which were formed in the surface region of powder metallurgy tungsten due to the exposure to the helium plasma, disappeared after the laser pulse irradiation to the tungsten surface with sufficient pulse energy. When a tungsten coated graphite was exposed to the helium plasma, the surface was covered with arborescent nanostructured tungsten containing many helium bubbles inside the structure. Melting traces were found on the surface after the laser pulses irradiated the surface even though the pulse energy was sufficiently lower than that for melting bulk tungsten.
Okano, Masanori; Nemoto, Hirokazu*; Jitsukata, Shu*; Yamada, Keiji; Sakai, Toshio
no journal, ,
no abstracts in English
Takamatsu, Kuniyoshi; Takeda, Tetsuaki; Nakagawa, Shigeaki
no journal, ,
Safety demonstration tests using the HTTR are in progress to verify the inherent safety features and to improve the safety technology and design methodology of high temperature gas-cooled reactors (HTGRs). The numerical analysis code was developed to analyze the reactor dynamics including the flow behavior in the HTTR core. We have modified this code to use a model with four parallel flow channels and twenty temperature coefficients in the core. This paper describes an analytical result of the loss of partial coolant flow test using the newly developed code. The analytical result of transient reactor power shows good agreement with the measured value during the test. Moreover, this paper refers to an analytical result of the loss of coolant flow test. The reactor power decreases to decay heat level due to the negative reactivity feedback effect of the core. Although the reactor power becomes critical again later, the peak power value is very small.
Sanada, Yukihisa; Hashimoto, Tetsuo*
no journal, ,
no abstracts in English
Aoyagi, Noboru; Nagaishi, Ryuji; Esaka, Fumitaka; Yamada, Reiji
no journal, ,
Interfacial reaction on chrysotile in acidic aqueous solutions which is promoted by irradiation of 
Co -ray or electron beam was studied by analyzing the production of hydrogen gas and morphological alteration offibril structure. The amount of generated hydrogen gas was proportional to the dose of irradiation and larger than the other particles such as alumina or silica known as a reactive surface donor for radicals. An expedited reaction in which chrysotile fibrous structure fell apart and come into particles was found more in SEM-EDX measurement with increasing the concentrations of sulfuric acid as 0.2M, 0.4M, 0.8M and 2.0M.