Reactor physics experiment in a graphite-moderation system for HTGR

Fukaya, Yuji; Goto, Minoru; Nakagawa, Shigeaki; Nakajima, Kunihiro*; Takahashi, Kazuki*; Sakon, Atsushi*; Sano, Tadafumi*; Hashimoto, Kengo*

Proceedings of International Conference on the Physics of Reactors; Transition To A Scalable Nuclear Future (PHYSOR 2020) (USB Flash Drive), 8 Pages, 2020/03

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). The objectives are to introduce a generalized bias factor method to avoid full mock-up experiment for the first commercial HTGR and to introduce reactor noise analysis to High Temperature Engineering Test Reactor (HTTR) experiment to observe subcriticality. To achieve the objectives, the reactor core of graphite-moderation system named B7/4"G2/8"p8EUNU+3/8"p38EU(1) was newly composed in the B-rack of Kyoto University Critical Assembly (KUCA). The core is composed of the fuel assembly, driver fuel assembly, graphite reflector, and polyethylene reflector. The fuel assembly is composed of enriched uranium plate, natural uranium plate and graphite plates to realize the average fuel enrichment of HTTR and it's spectrum. However, driver fuel assembly is necessary to achieve the criticality with the small-sized core. The core plays a role of the reference core of the bias factor method, and the reactor noise was measured to develop the noise analysis scheme. In this study, the overview of the criticality experiments is reported. The reactor configuration with graphite moderation system is rare case in the KUCA experiments, and this experiment is expected to contribute not only for an HTGR development but also for other types of a reactor in the graphite moderation system such as a molten salt reactor development.

Development of compact high field pulsed magnet system for new sample environment equipment at MLF in J-PARC

Watanabe, Masao; Nojiri, Hiroyuki*; Ito, Shinichi*; Kawamura, Seiko; Kihara, Takumi*; Masuda, Takatsugu*; Sahara, Takuro*; Soda, Minoru*; Takahashi, Ryuta

JPS Conference Proceedings (Internet), 25, p.011024_1 - 011024_5, 2019/03

https://doi.org/10.7566/JPSCP.25.011024

Recently, neutron scattering experiments have been rapidly progressed under high magnetic field. In the J-PARC, proto-type compact pulse magnet system with the power supply, the coil and the sample stick has been developed. Basic specifications of the power supply are as follows; maximum charged voltage with capacitor is 2 kV, maximum current is 8 kA, repetition rate is a pulse per several minutes and pulse duration is several msec. Maximum magnetic field in the coil is more than 30 Tesla. The sample stick is designed for Orange-Cryostat. In this presentation, We report the details of the pulsed magnet system and the performance of it on neutron scattering experiments at MLF beam line (HRC).

Experimental observation of temperature and magnetic-field evolution of the 4 states in CeFe revealed by soft X-ray magnetic circular dichroism

Saito, Yuji; Yasui, Akira*; Fuchimoto, Hiroto*; Nakatani, Yasuhiro*; Fujiwara, Hidenori*; Imada, Shin*; Narumi, Yasuo*; Kindo, Koichi*; Takahashi, Minoru*; Ebihara, Takao*; et al.

Physical Review B, 96(3), p.035151_1 - 035151_5, 2017/07

AA2017-0611.pdf:0.36MB

https://doi.org/10.1103/PhysRevB.96.035151

We revisit the delocalized character of the 4 states of CeFe in the ferromagnetically ordered phase by X-ray magnetic circular dichroism (XMCD) in X-ray absorption spectroscopy (XAS) with improved data quality using single crystals. Surprisingly, the Ce XMCD spectral shape changes significantly as a function of temperature and applied magnetic field, with no concomitant changes in the spectral shape of the Ce XAS as well as the Fe XAS and XMCD. This unusual behavior is characterized by the states in a 4 configuration mixed into the ground state. Such extreme sensitivity of the Ce 4 states to the external perturbations can be related to the magnetic instability toward an antiferromagnetic phase in CeFe. Our experimental data presented here provide valuable insights into the underlying physics in strongly-hybridized ferromagnetic Ce compounds.

Radioactivity analysis of metal samples taken from pipes of the Fugen, 4

Haraga, Tomoko; Tobita, Minoru*; Takahashi, Shigemi*; Ishimori, Kenichiro; Kameo, Yutaka

JAEA-Data/Code 2015-025, 52 Pages, 2016/03

JAEA-Data-Code-2015-025.pdf:1.92MB

Fugen Nuclear Power Station was shut down and now is under decommissioning. Many radioactivity concentration data of dismantled materials have to be accumulated to calculate the scaling factors of radioactive wastes and verify that the cleared dismantled materials conform to the clearance levels. A simple and rapid radioactivity determination method for radioactive waste samples was developed in Department of Decommissioning and Waste Management. For the demonstration, the simple and rapid radioactivity determination method was applied to metal samples, which were taken from dismantled pipes of Fugen. This report summarizes the radioactivity data obtained from the analysis of those samples.

Neutron irradiation effect of high-density MoO pellets for Mo-99 production, 2

Nishikata, Kaori; Ishida, Takuya; Yonekawa, Minoru; Kato, Yoshiaki; Kurosawa, Makoto; Kimura, Akihiro; Matsui, Yoshinori; Tsuchiya, Kunihiko; Sano, Tadafumi*; Fujihara, Yasuyuki*; et al.

KURRI Progress Report 2014, P. 109, 2015/07

http://www.rri.kyoto-u.ac.jp/PUB/report/PR/ProgRep2014/CO3.pdf

As one of effective applications of the Japan Materials Testing Reactor (JMTR), JAEA has a plan to produce Mo by (n,) method ((n,)Mo production), a parent nuclide of Tc. In this study, preliminary irradiation test was carried out with the high-density molybdenum trioxide (MoO) pellets in the hydraulic conveyer (HYD) of the Kyoto University Research Reactor (KUR) and the Tc solution extracted from Mo was evaluated. After the irradiation test of the high-density MoO pellets in the KUR, Tc was extracted from the Mo solution and the recovery rate of Tc achieved the target values. The Tc solution also got the value that satisfied the standard value for Tc radiopharmaceutical products by the solvent extraction method.

Radioactivity analysis of metal samples taken from pipes of the Fugen, 3

Haraga, Tomoko; Tobita, Minoru*; Takahashi, Shigemi*; Sakatani, Keiichi; Ishimori, Kenichiro; Takahashi, Kuniaki

JAEA-Data/Code 2014-007, 52 Pages, 2014/06

JAEA-Data-Code-2014-007.pdf:28.47MB

Fugen Nuclear Power Station was shut down and now is under decommissioning. Many radioactivity concentration data of dismantled materials have to be accumulated to calculate the scaling factors of radioactive wastes and verify that the cleared dismantled materials conform to the clearance levels. A simple and rapid radioactivity determination method for radioactive waste samples was developed in Nuclear Cycle Backend Directorate. For the demonstration, the simple and rapid radioactivity determination method was applied to metal samples, which were taken from dismantled pipes of Fugen. This report summarizes the radioactivity data obtained from the analysis of those samples.

Study on mechanism of inner duct wall failure within fuel subassembly during core disruptive accidents in an LMFBR; Results of parametric analyses for heat transfer

Toyooka, Junichi; Endo, Hiroshi*; Tobita, Yoshiharu; Takahashi, Minoru*

Nihon Genshiryoku Gakkai Wabun Rombunshi, 13(2), p.35 - 50, 2014/05

https://doi.org/10.3327/taesj.J13.011

In the design of future sodium-cooled fast reactor, a design measure to prevent severe re-criticality events even in case of core disruptive accidents is considered. This design adopts inner duct within the fuel sub-assembly that should allow molten fuel ejection out of the core region. The effectiveness of this design is dependent on failure time of the duct and it depends significantly on heat transfer from the melting core materials to the duct. In the previous study by the authors, heat transfer from molten fuel/steel mixture to the inner duct was evaluated with a computer model simulation for an in-pile experiment performed in IGR (Impulse Graphite Reactor) focusing on demonstration of the design effectiveness. In the present study, possible uncertainties in the assumption and model parameters in the previous study were evaluated so that validity of the main conclusion of the previous study could be confirmed and re-enforced. This confirmation consisted of evaluation of necessary fuel-to-steel heat transfer area, effect of hydrodynamic fragmentation of steel droplets, steel-vapor condensation heat transfer onto the duct surface and fuel crust formation. Furthermore, possible effect of variation in fuel designs and transient scenarios to the heat transfer was evaluated changing steel volume fraction as the initial boundary conditions. It was concluded that the previous study was appropriate in representing the realistic situation and the conclusions in the previous study were enforced. An additional set of analysis showed that possible under-estimation of heat transfer from fuel/steel mixture to the duct could be enhanced with a condition where steel volume fraction is less. Future model improvement is preferable for this characteristic.

Radioactivity analysis of metal samples taken from pipes of the Fugen

Kameo, Yutaka; Haraga, Tomoko; Ishimori, Kenichiro; Shimada, Asako; Tobita, Minoru*; Takahashi, Shigemi*; Takahashi, Kuniaki

JAEA-Data/Code 2010-028, 32 Pages, 2011/02

JAEA-Data-Code-2010-028.pdf:1.62MB

The Fugen Nuclear Power Station was shut down and decommissioning of the Fugen has been implemented. To calculate the scaling factor of radioactive waste or advance the clearance of dismantled materials, a large number of radioactivity concentration data of dismantled materials have to be accumulated. For these reasons, the simple and rapid radioactivity determination method was applied for metal samples, which were taken from pipes of the Fugen. The present report is summarized analytical procedures and obtained radioactivity data of the Fugen pipe samples.

Plan and reports of coupled irradiation (JRR-3 and JOYO of research reactors) and hot facilities work (WASTEF, JMTR-HL, MMF and FMF); R&D project on irradiation damage management technology for structural materials of long-life nuclear plant

Matsui, Yoshinori; Takahashi, Hiroyuki; Yamamoto, Masaya; Nakata, Masahito; Yoshitake, Tsunemitsu; Abe, Kazuyuki; Yoshikawa, Katsunori; Iwamatsu, Shigemi; Ishikawa, Kazuyoshi; Kikuchi, Taiji; et al.

JAEA-Technology 2009-072, 144 Pages, 2010/03

JAEA-Technology-2009-072.pdf:45.01MB

"R&D Project on Irradiation Damage Management Technology for Structural Materials of Long-life Nuclear Plant" was carried out from FY2006 in a fund of a trust enterprise of the Ministry of Education, Culture, Sports, Science and Technology. The coupled irradiations or single irradiation by JOYO fast reactor and JRR-3 thermal reactor were performed for about two years. The irradiation specimens are very important materials to establish of "Evaluation of Irradiation Damage Indicator" in this research. For the acquisition of the examination specimens irradiated by the JOYO and JRR-3, we summarized about the overall plan, the work process and the results for the study to utilize these reactors and some facilities of hot laboratory (WASTEF, JMTR-HL, MMF and FMF) of the Oarai Research-and-Development Center and the Nuclear Science Research Institute in the Japan Atomic Energy Agency.

Study on Three-Dimensional Seismic Isolation System Applied to Advanced Nuclear Power Plants, 5; Study on Development Planning

Takahashi, Kenji; Kato, Asao*; Ito, Kei; Fushimi, Minoru*; Fujita, Takafumi*; Inoue, Kazuhiko*

Dynamics and Design Conference 2005 (D&D 2005) Koen Rombunshu (CD-ROM), 6 Pages, 2005/09

In order to reduce the cost of plant design and construction, and to enhance the credibility, a study for Three-Dimensional isolation system was permormed. There are two types of isolation system. One is a 3D entire building isolaiton system. The other is a vertical isolation system which is added on the horizontal entire building isolation system. For both systems, outlines of development,requirements of the sytems, process of the verification tests, test results and applicabilities to the fast breeder reactor are mentioned.