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Taniguchi, Naoki; Suzuki, Hiroyuki*; Nakanishi, Tomoaki*; Nakayama, Takenori*; Masugata, Tsuyoshi*; Tateishi, Tsuyoshi*
Zairyo To Kankyo, 56(12), p.576 - 584, 2007/12
The long term hydrogen absorption behavior and the possibility of hydrogen embrittlement were studied for titanium overpack for high level radioactive waste disposal. The results of galvanostatic cathodic polarization tests showed that as the cathodic current density is lowered, the amount of absorbed hydrogen for a constant cathodic charge was increased as well as hydrogen permeated into inside of titanium. The hydrogen absorption ratio for a cathodic current density equivalent to the corrosion rate under anaerobic condition was estimated to nearly 100 percent, and the amount of absorbed hydrogen for 1000 years was evaluated to be 400 ppm. The mechanical property of titanium containing hydrogen depended on not only hydrogen concentration but also hydrogen distribution type. The more hydrogen distribution is uniform, the degree of embrittlement was larger. It was expected that the rupture of titanium overpack with 6 mm thickness would be initiated if the crack size in titanium is over about 2-3 mm under the stress corresponds to yield strength.
Nakashima, Hiroshi; Shibata, Tokushi; Nakane, Yoshihiro; Masukawa, Fumihiro; Matsuda, Norihiro; Iwamoto, Yosuke; Hirayama, Hideo*; Suzuki, Takenori*; Miura, Taichi*; Numajiri, Masaharu*; et al.
Proceedings of 14th Biennial Topical Meeting of the ANS Radiation Protection and Shielding Division (CD-ROM), p.267 - 282, 2006/00
no abstracts in English
Nakashima, Hiroshi; Nakane, Yoshihiro; Masukawa, Fumihiro; Matsuda, Norihiro; Oguri, Tomomi*; Nakano, Hideo*; Sasamoto, Nobuo*; Shibata, Tokushi*; Suzuki, Takenori*; Miura, Taichi*; et al.
Radiation Protection Dosimetry, 115(1-4), p.564 - 568, 2005/12
Times Cited Count：8 Percentile：49.16(Environmental Sciences)The High Intensity Proton Accelerator Project, named as J-PARC, is in progress, aiming at studies on the latest basic science and the advancing nuclear technology. In the project, the high-energy proton accelerator complex of the world highest intensity is under construction. In order to establish a reasonable shielding design, both simplified and detailed design methods were used in the shielding design of J-PARC. This paper reviews the present status of the radiation safety design study for J-PARC.
Ito, Yutaka*; Hirade, Tetsuya; Hamada, Eisaku*; Suzuki, Takenori*; Ito, Yasuo*
Acta Physica Polonica A, 95(4), p.533 - 538, 1999/04
no abstracts in English
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and digital methodsHashi, Yohei; Hirade, Tetsuya; Suzuki, Takenori*
no journal, ,
Positron Annihilation Lifetime was measured by - coincidence method with a digital storage cscilloscope(DSO). A photodiode was used to detect the positron injected into a sample from a source. Two sets of a photomultiplier tube and a scintillator were used to detect annihilation rays emitting to opposite directions from the sample. This - coincidence lifetime measurement was first attempt and the signal-to-noise ratio became better than the conventional lifetime measurement by - coincidence method.
Komuro, Yo; Hirade, Tetsuya; Suzuki, Ryoichi*; Odaira, Toshiyuki*; Muramatsu, Makoto*; Suzuki, Takenori*
no journal, ,
Many ions and the excess electrons are formed by the injected positron just before the thermalization of that positron in a small area (it is called spur or blob) in condensed matter. The positron has a chance to form positronium (Ps) with one of the excess electrons. According to the model of Ps formation in the spur (blob), the initial encounter pairs of an electron and a positron will form Ps in short time. Some of the positrons have some possibility to form Ps after diffusion in several hundreds pico-seconds. There were experimental results that were interpreted as a Ps thermalization by a group in Germany more than 10 years ago. However, we have believed that some of the results were caused by the delayed Ps formation and have successfully obtained the experimental evidence of the delayed Ps formation by applying electric fields on the sample, fused quartz.
Komuro, Yo; Hirade, Tetsuya; Suzuki, Ryoichi*; Odaira, Toshiyuki*; Muramatsu, Makoto*; Suzuki, Takenori*
no journal, ,
The injected positrons to condensed materials form a very small area where they deposit much energy and some tens of ion-electron pairs are formed. This area is called a positron spur or blob. Positrons have a possibility to form positronium at this area. Some of the positrons are isolated from the excess electrons when they thermalized. They will have smaller possibility to form positronium and longer time to form positronium. Therefore the positronium formation by the isolated positrons from excess electrons can be easily inhibited by applying the external electric fields. We have found this expected phenomena by applying the external electric fields.
- positron annihilation lifetime measurement by use of digital oscilloscopeHirade, Tetsuya; Hashi, Yohei; Yachi, Hironari; Suzuki, Takenori*
no journal, ,
Recently, - positron annihilation lifetime measurement has been possible by use of Ge-68 positron emitter and avalanche photo diodes(APD). APD is placed between Ge-68 source and a sample and detecting positrons injecting into the sample. This information is used as a start signal and the stop signal is obtained by detecting one or both of the annihilation -rays. The detection rate of positrons is about 80% and then it is possible to reduce the random coincidence background. We have succeeded to reduce 40% of the background.
Taniguchi, Naoki; Suzuki, Hiroyuki*; Yui, Mikazu; Nakanishi, Tomoaki*; Nakayama, Takenori*; Masugata, Tsuyoshi*; Tateishi, Tsuyoshi*
no journal, ,
Titanium (including titanium alloy) is one of the candidate materials of overpacks for geological disposal of high-level radioactive waste, and required long term integrity against the groundwater for more than 1000 years. As the corrosion of titanium occurs, hydrogen is generated since the deep underground environment is originally low oxygen concentration condition. There is a possibility that the titanium overpack will be attackd by the hydrogen embrittlement due to long term hydrogen absorption. In this study, the amount of hydrogen and the possibility of embrittlement were investigated based on the experimental data on the corrosion rate, hydrogen absorption behavior, mechanical proparty of titanium containing hydrogen.
Nakashima, Hiroshi; Shibata, Tokushi; Sawahata, Kei; Miyamoto, Yukihiro; Nakane, Yoshihiro; Masukawa, Fumihiro; Seki, Kazunari; Sato, Koichi; Oguri, Tomomi*; Hirayama, Hideo*; et al.
no journal, ,
Aiming at studies on the latest basic science and the advancing nuclear technology, the J-PARC (Japan Proton Accelerator Research Complex) project is in progress, and the high-energy proton accelerator complex of the world highest intensity is under construction. Because of its very high beam power and its energy as well as the large-scale accelerator complex, we have encountered some difficult radiation problems in the radiation safety design. This paper reviews the radiation safety policy and methods for the design to overcome the problems on the radiation safety and the status of the radiation safety estimation for licensing of J-PARC.
Yachi, Hironari; Hashi, Yohei; Hirade, Tetsuya; Suzuki, Takenori*
no journal, ,
Recently, it is becoming possible to apply digital oscilloscopes for positron annihilation lifetime measurement instead of use of analogue circuit (NIM modules). More than 1 million sets of wave signals from -ray detectors constructed by scintillaters and photomultiplier tubes are recorded by a digital oscilloscope and analyzed afterward by a personal computer. More than 1 million events of positron annihilation are accumulated on a multi channel analyzer (MCA) for 2-4 hours to construct one lifetime spectrum in the case of the conventional analogue lifetime measurement system. However, it is possible to measure 100 times longer time, i.e. to accumulate 100 times more counts, because of the much better stability of the positron annihilation lifetime measurement system by digital oscilloscopes. Although it is clear that the system by digital oscilloscopes is very stable, There is no indication how much it is stable and how we can construct stabler and better systems. We studied these things and can conclude that we should apply one electric power supply for all detectors and higher voltage to the detectors and full range measurement (8bit) can give better time resolution.
Shibata, Tokushi; Nakashima, Hiroshi; Nakane, Yoshihiro; Masukawa, Fumihiro; Matsuda, Norihiro; Miura, Taichi*; Numajiri, Masaharu*; Suzuki, Takenori*; Takeuchi, Yasunori*
no journal, ,
J-PARC (Japan Proton Accelerator Research Complex) consists of a 400 MeV LINAC, a 3 GeV synchrotron, a 50 GeV synchrotron and three experimental halls for material and life science, hadron physics and neutrino physics. The radiation safety design for J-PARC is based on calculations on radiation outside the shielding, on the boundary of the controlled area and on the cite boundary. In order to study the accuracy of different methods and make clear the differences among different methods, some benchmark analyses on beam dump, bulk shielding, streaming and activation experiments were carried out. The activation of air, cooling water and the activation of soil and its effect to underground water have been also estimated. Since J-PARC is a complex accelerator facility, an interlock system is important for radiation safety. To prevent unintended radiation exposure, a carefully designed system was incorporated.
