Fukaya, Yuji; Okita, Shoichiro; Kanda, Shun*; Goto, Masaki*; Nakajima, Kunihiro*; Sakon, Atsushi*; Sano, Tadafumi*; Hashimoto, Kengo*; Takahashi, Yoshiyuki*; Unesaki, Hironobu*
KURNS Progress Report 2021, P. 101, 2022/07
The Japan Atomic Energy Agency (JAEA) started the Research and Development (R&D) to improve nuclear prediction techniques for High Temperature Gas-cooled Reactors (HTGRs) in 2018. The objectives are to intro-duce the generalized bias factor method to avoid full mock-up experiment for the first commercial HTGR and to improve neutron instrumentation system by virtue of the particular characteristics due to a graphite moderation system. For this end, we composed B7/4"G2/8"p8EU(3)+3/8"p38EU in the B-rack of Kyoto University Critical Assembly (KUCA) in 2021.
Okita, Shoichiro; Fukaya, Yuji; Sakon, Atsushi*; Sano, Tadafumi*; Takahashi, Yoshiyuki*; Unesaki, Hironobu*
Proceedings of International Conference on Physics of Reactors 2022 (PHYSOR 2022) (Internet), 9 Pages, 2022/05
Okita, Shoichiro; Fukaya, Yuji; Sakon, Atsushi*; Sano, Tadafumi*; Takahashi, Yoshiyuki*; Unesaki, Hironobu*
Nuclear Science and Engineering, 7 Pages, 2022/00
Kumekawa, Hirokazu; Tsuboi, Hiroshi*; Unesaki, Hironobu*
Proceedings of INMM & ESARDA Joint Virtual Annual Meeting (Internet), 10 Pages, 2021/08
Since FM(C)T was proposed, nearly three decades have passed. Although numerous proposals have been made by many governments, institutions and experts, there has been no sign of convergence of opinions toward its realization. In the meantime, the TPNW entered into force in January 2021, which accentuates the gap between the global desire for the ultimate elimination of nuclear weapons and the hard reality. Realization of the FM(C)T is even more expected as a practical step for narrowing the gap. Although various proposals for the realization of FM(C)T were well summarized in the report by the high-level fissile material cut-off treaty expert preparatory group in 2018, it clearly indicates that further effort is needed in formulating proposals to bridge the existing gaps among various proposals based on the analysis of diverse opinions. Thus it could be concluded that, for the realization of the FM(C)T, what is missing is a strategy or logical steps to converge the diverse opinions into a consolidated proposal that should serve as a springboard for discussion. As the opinions are so diverse, it is impossible to satisfy all the relevant parties completely. There must be some level of compromises that each State has to make in order to bring the FM(C)T into reality. The questions should be how to prepare an optimal and realistic proposal that maximizes the chance to be agreed among key member states. The NPT has established a norm for nuclear non-proliferation together with comprehensive safeguards agreements and the norm is being further strengthened through the universalization of additional protocols. Compared with the effort for enhancing nuclear non-proliferation, advancement of nuclear disarmament has stagnated. Although the idea for TPNW was proposed after that for an FM(C)T, the TPNW has been realized. Compared with the TPNW, FM(C)T should be much more achievable target. From the historical perspective, the leadership of leading nations is now tested.
Takeuchi, Tomoaki; Yamamoto, Keiichi; Otsuka, Noriaki; Shibata, Hiroshi; Shibata, Akira; Takemoto, Noriyuki; Tsuchiya, Kunihiko; Sano, Tadafumi*; Unesaki, Hironobu*; Fujihara, Yasuyuki*; et al.
KURRI Progress Report 2014, P. 108, 2015/07
Investigation of a relation between output power and brightness of Cherenkov light of a specific fuel element at KUR by a CCD camera was performed due to a development of a real-time in-core measurement technique using Cherenkov light. The results indicate that the inhomogeneous distribution of output power and the shadow of the control-rod guide tubes and the other irradiation equipment have significant effects on the brightness of the Cherenkov light. These effects could be suppressed by using a number of cameras located at various positions.
Otsuka, Noriaki; Takeuchi, Tomoaki; Yamamoto, Keiichi; Shibata, Akira; Kimura, Nobuaki; Takemoto, Noriyuki; Tanimoto, Masataka; Tsuchiya, Kunihiko; Sano, Tadafumi*; Unesaki, Hironobu*; et al.
KURRI Progress Report 2013, P. 215, 2014/10
Investigation of a relation between reactor power and brightness of Cherenkov light at Kyoto University Research reactor (KUR) by a CCD camera was performed due to a development of a real-time in-core measurement technique using Cherenkov light. Analyzing the brightness value of individual RGB color component at each pixel, some of the G and B brightness values reached the maximum value of 8-bit binary number, i.e. 255, above about 2-3 MW. Therefore, we corrected the G and B brightness values by the R signals whose brightness value did not saturate even at 5 MW, the maximum reactor power of KUR. Then, the total brightness value was in proportion to the reactor power after the correction. These results indicate the reactor power can be estimated by the observation of Cherenkov light.
Kimura, Nobuaki; Takeuchi, Tomoaki; Shibata, Akira; Takemoto, Noriyuki; Kimura, Akihiro; Naka, Michihiro; Nishikata, Kaori; Tanimoto, Masataka; Tsuchiya, Kunihiko; Sano, Tadafumi*; et al.
KURRI Progress Report 2012, P. 209, 2013/10
In research reactors, CCD cameras are used to observe reactor core for reactor operation management, e.g. to prevent debris from falling. In order to measure the reactor power and fuel burnup exactly by means of observation of Cherenkov light, the development of the on-line measurement device started in 2009. In this study, the wavelength and the absolute irradiance of the Cherenkov light were measured by a spectrometer, and the Cherenkov light was observed by the CCD camera. As a result, the measurement value is good agreement with the nominal value. On the other hand, the value by the visible imaging system was obtained the same tendency of nominal transmittance value of ND-filters.
Ishibashi, Kenji*; Uesaka, Mitsuru*; Morita, Koji*; Sato, Yasushi*; Iimoto, Takeshi*; Watanabe, Yukinobu*; Unesaki, Hironobu*; Yamano, Hidemasa
Nihon Genshiryoku Gakkai-Shi ATOMO, 55(7), p.403 - 406, 2013/07
Japan-Korea Exchange program has been successful and their joint sessions have been accompanying conferences. With this background, younger generation's communication has been recognized as important role in Japan and Korea's joint cooperation. Thus students and young researchers support program has started. Understanding the achievements and the current status is important, expecting unrelated areas and working groups to show interest and hopefully join this area of work.
Kimura, Nobuaki; Takemoto, Noriyuki; Nagata, Hiroshi; Kimura, Akihiro; Naka, Michihiro; Nishikata, Kaori; Tanimoto, Masataka; Tsuchiya, Kunihiko; Sano, Tadafumi*; Unesaki, Hironobu*; et al.
KURRI Progress Report 2011, P. 219, 2012/10
In research reactors, a CCD camera is used to observe reactor core for reactor operation management, e.g. to prevent debris falling. In order to measure the reactor power and fuel burnup exactly by means of observation of Cherenkov light and ray information, the development of the on-line measurement device has been started since 2009. In this study, as a part of development of in-reactor surveillance, wavelength and absolute irradiance of Cherenkov light were measured by spectroscopy, and Cherenkov light was observed by the CCD camera. The neutral density filters (ND-filters) were used to investigate the transmittance of Cherenkov light in these measurements.
Takemoto, Noriyuki; Tsuchiya, Kunihiko; Nagao, Yoshiharu; Kitagishi, Shigeru; Naka, Michihiro; Kimura, Akihiro; Sano, Tadafumi*; Unesaki, Hironobu*; Yoshimoto, Takaaki*; Nakajima, Ken*; et al.
KURRI Progress Report 2010, P. 204, 2011/10
no abstracts in English
Tsuchiya, Kunihiko; Kitagishi, Shigeru; Nagao, Yoshiharu; Takemoto, Noriyuki; Naka, Michihiro; Kimura, Akihiro; Sano, Tadafumi*; Unesaki, Hironobu*; Yoshimoto, Takaaki*; Nakajima, Ken*; et al.
KURRI Progress Report 2009, P. 196, 2010/10
no abstracts in English
Oba, Toshinobu; Inoue, Takeshi; Unesaki, Hironobu*
Proceedings of International Meeting on Reduced Enrichment for Research and Test Reactors 2008 (RERTR 2008) (Internet), 10 Pages, 2008/10
The current status of research and test reactors relevant to RERTR program is described. The reduced enrichment programs for the JRR-3, JRR-4 and JMTR of Japan Atomic Energy Agency (JAEA) were completed by 1999. The core of JRR-3 was converted from aluminide (UAl-Al) to silicide (USi-Al) in order to reduce the amount of spent fuel. The JRR-3 has been well operated with LEU fuel since 1990 and reached 55,400 MWD in December 2007 at the last operation cycle. Operation with 10 cycles (26 days/cycle) is scheduled for one year from July 2008 to July 2009. The JRR-4 is under shut down condition to replace reflector elements with new ones. It will restart in July 2009. The JMTR is under refurbishment of irradiation facilities. Kyoto University Research Reactor (KUR) has terminated its operation with HEU on February 2006. Shipment of all HEU spent fuel elements to the United States has been successfully completed. The full core conversion of KUR to LEU fuel, including fuel fabrication, is currently under progress and the reactor restart using LEU core is expected to be achieved in May 2009.
Yagi, Takahiro*; Misawa, Tsuyoshi*; Pyeon, C. H.*; Unesaki, Hironobu*; Shiroya, Seiji*; Kawaguchi, Shinichi*; Okajima, Shigeaki; Tani, Kazuhiro*
Proceedings of International Conference on the Physics of Reactors, Nuclear Power; A Sustainable Resource (PHYSOR 2008) (CD-ROM), 8 Pages, 2008/09
In order to insert a neutron detector in a narrow space such as a gap of between fuel plates and measure the fast neutrons in real time, a neutron detector with an optical fiber has been developed. This detector consists of an optical fiber whose tip is covered with mixture of neutron converter material and scintillator such as ZnS(Ag). The detector for fast neutrons uses ThO as converter material because Th makes fission reaction with fast neutrons. The place where Th can be uses is limited by regulations because Th is nuclear fuel material. The purpose of this research is to develop a new optical fiber detector to measure fast neutrons without Th and to investigate the characteristic of the detector. These detectors were used to measure a D-T neutron generator and fast neutron flux distribution at Fast Critical Assembly. The results showed that the fast neutron flux distribution of the new optical fiber detector with ZnS(Ag) was the same as it of the activation method, and the detector are effective for measurement of fast neutrons.
Sagawa, Hisashi; Koda, Nobuyuki; Hanawa, Nobuhiro; Maruo, Takeshi; Miyazawa, Masataka; Unesaki, Hironobu*; Nakagome, Yoshihiro*
IAEA-TECDOC-1593, p.121 - 128, 2008/06
In Japan, 1,712 of Research Reactor Spent Nuclear fuels (RRSNFs) have been transported to the US successfully since the receipt in accordance with the foreign research reactor spent nuclear fuel acceptance policy started in 1996. Especially, Japan Atomic Energy Agency (JAEA) carried out shipment to the US of eight times and of 1,283 fuel elements in total. This paper describes experiences of RRSNF transportation to the US in Japan.
Unesaki, Hironobu*; Ota, Kazunori; Inoue, Takeshi
Proceedings of International Meeting on Reduced Enrichment for Research and Test Reactors 2007 (RERTR 2007) (Internet), 11 Pages, 2007/00
The status of reduced enrichment program for research reactors in Japan will be reviewed. Among the fourteen research reactors and critical assemblies in operation in Japan, those concerned with the RERTR program are the JRR-3, JRR-4 and JMTR of Japan Atomic Energy Agency (JAEA) and KUR of Kyoto University Research Reactor Institute (KURRI). Reduced enrichment programs for the JRR-3, JRR-4 and JMTR of JAEA has been completed by 1999, and the reactors are being satisfactory operated using LEU fuels. In KURRI, the KUR has terminated its operation with HEU on February 2006. Licensing for the full core conversion of KUR to LEU fuel is under progress and the core conversion to LEU is expected to be completed in 2008.
Chiba, Go; Unesaki, Hironobu*
Annals of Nuclear Energy, 33(13), p.1141 - 1146, 2006/09
In the present paper, we have proposed an improved method to produce the probability table needed for the resonance self-shielding calculations with the sub-group method. The method is based on an relation between the effective cross sections and cross section moment, which was obtained from numerical analyses. Using the proposed method, we can obtain more accurate probability table with less number of points than the conventional method.
Nakagome, Yoshihiro*; Unesaki, Hironobu*; Sagawa, Hisashi
Proceedings of 27th International Meeting on Reduced Enrichment for Research and Test Reactors 2005 (RERTR 2005) (Internet), 10 Pages, 2006/00
no abstracts in English
Kinase, Masami; Sagawa, Hisashi; Nakagome, Yoshihiro*; Unesaki, Hironobu*
Proceedings of International Meeting on Reduced Enrichment for Research and Test Reactors 2006 (RERTR 2006) (Internet), 10 Pages, 2006/00
The reduced enrichment programs for the JRR-3M, JRR-4 and JMTR of Japan Atomic Energy Research Institute (JAERI) has been completed until 1999. The KUR of Kyoto University Research Reactor Institute (KURRI) has been partially completed and is still in progress under the Joint Study Program with Argonne National Laboratory (ANL). The JRR-3M using LEU silicide fuel elements has done a functional test by the Japanese Government in 2000, and the property of the reactor core was satisfied. JAERI established a "U-Mo fuel ad hoc committee" for feasibility study concerning future LEU fuel instead of the silicide fuel in 2001, and an installation of the U-Mo fuel was estimated from 2012, even the irradiation tests are carried out successfully. The U.S. Policy of Foreign Research Reactor Spent Nuclear Fuels is strongly expected to expand the policy until U-Mo fuel installed. The Japanese Government approved a cancellation of the KUHFR Project in February 1991, and in April 1994 the U.S. Government gave an approval to utilize HEU fuel in the KUR instead of the KUHFR. Therefore, the KUR will be operated with HEU fuel until March 2006, then the full core conversion with LEU fuel will be done. All KUR spent fuel elements will be sent to the U.S. by March 2008.
Ishikawa, Masayori*; Kumada, Hiroaki; Yamamoto, Kazuyoshi; Kaneko, Junichi*; Bengua, G.*; Unesaki, Hironobu*; Sakurai, Yoshinori*; Tanaka, Kenichi*; Kosako, Toshiso*
Nuclear Instruments and Methods in Physics Research A, 551(2-3), p.448 - 457, 2005/10
A wide range thermal neutron detector was developed based on the Scintillator with Optical Fiber (SOF) detector which has been previously used for thermal neutron monitoring during boron neutron capture therapy irradiation. With this new detector system we intended to address the issues of real-time thermal neutron flux measurement and the simultaneous measurement of a wide range of thermal neutron flux in a BNCT irradiation field which were difficult to implement with the gold wire activation method. A good agreement between the thermal neutron flux measured by the gold wire activation method and the paired SOF detector system was observed. However, measurements which would normally take a few days to perform with the gold wire activation method were obtained in just about 15 min using the SOF detector system. We also confirmed the dynamic range of linearity for the SOF detector system to be in the order of magnitude of 1e-4.
Kitada, Takanori*; Okumura, Keisuke; Unesaki, Hironobu*; Saji, Etsuro*
Proceedings of International Conference on Physics of Fuel Cycles and Advanced Nuclear Systems; Global Developments (PHYSOR 2004) (CD-ROM), 8 Pages, 2004/04
Burnup calculation benchmark has been carried out for the LWR next generation fuels aiming at high burnup up to 70 GWd/t with UO and MOX. Based on the submitted results by many benchmark participants, the present status of calculation accuracy has been confirmed for reactor physics parameters of the LWR next generation fuels, and the factors causing the calculation differences were analyzed in detail. Moreover, the future experiments and research subjects necessary to reduce the calculation differences were discussed and proposed.