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Ono, Masato; Kozawa, Takayuki; Fujimoto, Nozomu*
JAEA-Technology 2019-012, 15 Pages, 2019/09
JAEA-Technology-2019-012.pdf:2.83MB
The High Temperature Engineering Test Reactor has a neutron source of 
Cf to start up the reactor and to confirm count rates of wide range monitors. The half-life of Cf is short, about 2.6 years, so it is necessary to replace at an appropriate time. In order to estimate the period to replace, it is necessary to consider not only the half-life but also the fluctuation of the count rate of the wide range monitor to prevent alarm. For that reason, the method has been derived to predict a minimum count rate from relationship between the count rate and the standard deviation of the count rate of the wide range monitors. As a result of predicting the count rate using this method, it was found that the minimum count rate reaches to 3.0cps in 2022 and 1.5 cps in 2024. Therefore, it is necessary to exchange Cf by 2024.
Shimazaki, Yosuke; Sawahata, Hiroaki; Shinohara, Masanori; Yanagida, Yoshinori; Kawamoto, Taiki; Takada, Shoji
Journal of Nuclear Science and Technology, 54(2), p.260 - 266, 2017/02
Times Cited Count：2 Percentile：19.65(Nuclear Science & Technology)The High-Temperature engineering Test Reactor (HTTR) has three neutron startup sources (NSs) in the reactor core, each of which consists of Cf with 3.7 GBq and is contained in a small capsule, installed in NS holder and subsequently in a control guide block (CR block). The NSs are exchanged at the interval of approximately 7 years. The NS holders are transported from the dealer's hot cell to the reactor facility of HTTR using a transportation container. The loading work of NS holders to the CR blocks is subsequently carried out in the fuel handling machine maintenance pit of HTTR. Technical issues, which are the reduction and prevention of radiation exposure of workers and the exclusion of falling of NS holder, were extracted from the experiences in past two exchange works of NSs to develop a safety handling procedure. Then, a new transportation container special to the NSs of HTTR was developed to solve the technical issues while keeping the cost as low as that for overhaul of conventional container. As the results, the NS handling work using the new transportation container was safely accomplished by developing the new transportation container which can reduce the risks of radiation exposure dose of workers and exclude the falling of NS holder.
Shinohara, Masanori; Ishitsuka, Etsuo; Shimazaki, Yosuke; Sawahata, Hiroaki
JAEA-Technology 2016-033, 65 Pages, 2017/01
JAEA-Technology-2016-033.pdf:11.14MB
To reduce the neutron exposure dose for workers during the replacement works of the startup neutron sources of the High Temperature Engineering Test Reactor, calculations of the exposure dose in case of temporary neutron shielding at the bottom of fuels handling machine were carried out by the PHITS code. As a result, it is clear that the dose equivalent rate due to neutron radiation can be reduced to about an order of magnitude by setting a temporary neutron shielding at the bottom of shielding cask for the fuel handling machine. In the actual replacement works, by setting temporary neutron shielding, it was achieved that the cumulative equivalent dose of the workers was reduced to 0.3 man mSv which is less than half of cumulative equivalent dose for the previous replacement works; 0.7 man mSv.
Shimazaki, Yosuke; Ono, Masato; Tochio, Daisuke; Takada, Shoji; Sawahata, Hiroaki; Kawamoto, Taiki; Hamamoto, Shimpei; Shinohara, Masanori
Proceedings of International Topical Meeting on Research Reactor Fuel Management and Meeting of the International Group on Reactor Research (RRFM/IGORR 2016) (Internet), p.1034 - 1042, 2016/03
In High Temperature Engineering Test Reactor (HTTR), three neutron holders containing Cf with 3.7 GBq for each are loaded in the graphite blocks and inserted into the reactor core as a neutron startup source which is changed at the interval of approximately ten years. These neutron holders containing the neutron sources are transported from the dealer's hot cell to HTTR using the transportation container. The holders loading to the graphite block are carried out in the fuel handling machine maintenance pit of HTTR. There were two technical issues for the safety handling work of the neutron holder. The one is the radiation exposure caused by significant movement of the container due to an earthquake, because the conventional transportation container was so large (
1240 mm, h1855 mm) that it can not be fixed on the top floor of maintenance pit by bolts. The other is the falling of the neutron holder caused by the difficult remote handling work, because the neutron holder capsule was also so long (155 mm, h1285 mm) that it can not be pulled into the adequate working space in the maintenance pit. Therefore, a new and low cost transportation container, which can solve the issues, was developed. To avoid the neutron and 
ray exposure, smaller transportation container (820mm, h1150 mm) which can be fixed on the top floor of maintenance pit by bolts was developed. In addition, to avoid the falling of the neutron holder, smaller neutron holder capsule (75 mm, h135 mm) with simple handling mechanism which can be treated easily by manipulator was also developed. As the result of development, the neutron holder handling work was safely accomplished. Moreover, a cost reduction for manufacturing was also achieved by simplifying the mechanism of neutron holder capsule and downsizing.
proton superfluidity in neutron star matter; Impact of bulk propertiesTanigawa, Tomonori; Matsuzaki, Masayuki*; Chiba, Satoshi
Physical Review C, 70(6), p.065801_1 - 065801_7, 2004/12
Times Cited Count：9 Percentile：51.36(Physics, Nuclear)We study the proton pairing gap in neutron star matterputting emphasis on influence of the Dirac effective mass and theproton fraction on the gap within the relativistic Hartree-Bogoliubovmodel. The gap equation is solved using the Bonn-B potential as aparticle-particle channel interaction. It is found that the maximalpairing gap 
is 1-2MeV, which has a strongcorrelation with the Dirac effective mass. Hence we suggest that itserves as a guide to narrow down parameter sets of the relativisticeffective field theory. Furthermore, the more slowly protons increasewith density, the lower the peak of the gap and the wider thesuperfluid range become.
Nakagawa, Tsuneo
JAERI-Data/Code 2003-016, 89 Pages, 2003/11
JAERI-Data-Code-2003-016.pdf:3.0MB
The data storage and retrieval system for neutron-induced reaction data NESTOR2 was developed. NESTOR2 was written in Fortran77, and can be used on workstations with UNIX and personal computers with Windows. Input data to NESTOR2 are those in EXFOR which are compiled and maintained under the international collaboration for nuclear data. By using the retrieval code, they can obtain lists of data index, numerical data and comment information and data files of numerical data. The present report explains the system and provides a user's manual of NESTOR2.
pairing and its dependence on background density in a relativistic Hartree-Bogoliubov modelTanigawa, Tomonori; Matsuzaki, Masayuki*; Chiba, Satoshi
Physical Review C, 68(1), p.015801_1 - 015801_8, 2003/07
Times Cited Count：16 Percentile：68.45(Physics, Nuclear)We calculate a pairing gap in binary mixed matter of nucleons and 
hyperons within the relativistic Hartree-Bogoliubov model since a recent experiment suggests a weaker attraction than before, which has a significant impact on properties of neutron stars in various aspects. Lambda hyperons to be paired up are immersed in background nucleons in normal state. A phenomenological interaction, which is derived relativistically from the Lagrangian of the system, is adopted to the gap equation. It is found that at background density 
the pairing gap is very small, and that denser background makes it rapidly suppressed. This result suggests a mechanism, specific to mixed matter dealt with relativistic models, of its dependence on the nucleon density.
Chiba, Satoshi
JAERI-Conf 2001-012, 116 Pages, 2001/09
JAERI-Conf-2001-012.pdf:6.33MB
The third symposium on Science of Hadrons under Extreme Conditions, organized by the Research Group for Hadron Science, Advanced Science Research Center, was held at Tokai Research Establishment of JAERI on January 29 to 31, 2001. The symposium was devoted for discussions and presentations of research results in wide variety of hadron physics such as nuclear matter, high-energy nuclear reactions, quantum chromodynamics, neutron stars,supernovae, nucleosynthesis as well as finite nuclei to understand various aspects of hadrons under extreme conditions. Twenty two papers on these topics, including a special talk on the present status of JAERI-KEK joint project on high-intentisy proton accelerator, presented at the symposium aroused lively discussions among approximately 40 participants.
Fujimoto, Nozomu; Yamashita, Kiyonobu
JAERI-Research 99-059, p.43 - 0, 1999/11
JAERI-Research-99-059.pdf:2.51MB
no abstracts in English
