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Journal Articles

Numerical investigations on the coolability and the re-criticality of a debris bed with the density-stratified configuration

Li, C.; Uchibori, Akihiro; Takata, Takashi; Pellegrini, M.*; Erkan, N.*; Okamoto, Koji*

Dai-25-Kai Doryoku, Enerugi Gijutsu Shimpojiumu Koen Rombunshu (Internet), 4 Pages, 2021/07

The capability of stable cooling and avoiding re-criticality on the debris bed are the main issues for achieving IVR (In-Vessel Retention). In the actual situation, the debris bed is composed of mixed-density debris particles. Hence, when these mixed-density debris particles were launched to re-distribute, the debris bed would possibly form a density-stratified distribution. For the proper evaluation of this scenario, the multi-physics model of CFD-DEM-Monte-Carlo based neutronics is established to investigate the coolability and re-criticality on the heterogeneous density-stratified debris bed with considering the particle relocation. The CFD-DEM model has been verified by utilizing water injection experiments on the mixed-density particle bed in the first portion of this research. In the second portion, the coupled system of the CFD-DEM-Monte-Carlo based neutronics model is applied to reactor cases. Afterward, the debris particles' movement, debris particles' and coolant's temperature, and the k-eff eigenvalue are successfully tracked. Ultimately, the relocation and stratification effects on debris bed's coolability and re-criticality had been quantitatively confirmed.

Journal Articles

Recent activities in the field of reactor physics

Fukushima, Masahiro; Tojo, Masayuki*

Journal of Nuclear Science and Technology, 56(12), p.1061 - 1062, 2019/12

 Times Cited Count:0 Percentile:0.34(Nuclear Science & Technology)

Reactor Physics that treat the essentials of how fission nuclear reactors work fundamentally has important roles on safe operations and design studies of various types of nuclear reactors. From the latest activities in the field of reactor physics, this report summarizes some outstanding researches and developments published in scientific journals including the Journal of Nuclear Science and Technology.

Journal Articles

Development of unstructured mesh-based numerical method for sodium-water reaction phenomenon in steam generators of sodium-cooled fast reactors

Uchibori, Akihiro; Watanabe, Akira*; Takata, Takashi; Ohshima, Hiroyuki

Journal of Nuclear Science and Technology, 54(10), p.1036 - 1045, 2017/10

 Times Cited Count:3 Percentile:40.62(Nuclear Science & Technology)

To evaluate a sodium-water reaction phenomenon in a steam generator of sodium-cooled fast reactors, a computational fluid dynamics code SERAPHIM, in which a compressible multicomponent multiphase flow with sodium-water chemical reaction is computed, has been developed. The original SERAPHIM code is based on the difference method. In this study, unstructured mesh-based numerical method was developed to advance a numerical accuracy for the complex-shaped domain including multiple heat transfer tubes. Numerical analysis of an underexpanded jet experiment was performed as part of validation of the unstructured mesh-based numerical method. The calculated pressure profile showed good agreement with the experimental data. Applicability of the numerical method for the actual situation was confirmed through the analysis of water vapor discharging into liquid sodium. The effect of use of the unstructured mesh was also investigated by the two analyses using structured and unstructured mesh.

JAEA Reports

Proceedings of the 2015 Symposium on Nuclear Data; November 19-20, 2015, Ibaraki Quantum Beam Research Center, Tokai-mura, Ibaraki, Japan

Iwamoto, Osamu; Sanami, Toshiya*; Kunieda, Satoshi; Koura, Hiroyuki; Nakamura, Shoji

JAEA-Conf 2016-004, 247 Pages, 2016/09

JAEA-Conf-2016-004.pdf:26.48MB

The 2015 Symposium on Nuclear Data was held at Ibaraki Quantum Beam Research Center, on November 19 and 20, 2015. The symposium was organized by the Nuclear Data Division of the Atomic Energy Society of Japan in cooperation with Nuclear Science and Engineering Center of Japan Atomic Energy Agency and North Kanto Branch of Atomic Energy Society of Japan. In the symposium, there were two tutorials, "Theory of Few-Body Systems and Recent Topics" and "Use of Covariance Data 2015" and four oral sessions, "Recent Research Topics", "Progress of AIMAC Project", "Present Status of JENDL Evaluated Files", and "Nuclear Data Applications". In addition, recent research progress on experiments, evaluation, benchmark and application was presented in a poster session. Among 99 participants, all presentations and following discussions were very active and fruitful. This report consists of total 46 papers including 13 oral and 33 poster presentations.

JAEA Reports

Proceedings of the 2014 Symposium on Nuclear Data; November 27-28, 2014, Conference hall, Hokkaido University, Sapporo Japan

Aikawa, Masayuki*; Iwamoto, Osamu; Ebata, Shuichiro*; Kunieda, Satoshi; Nakamura, Shoji; Koura, Hiroyuki

JAEA-Conf 2015-003, 332 Pages, 2016/03

JAEA-Conf-2015-003.pdf:30.22MB

The 2014 Symposium on Nuclear Data was held at Conference Hall, Hokkaido University, on November 27 and 28, 2014. The symposium was organized by the Nuclear Data Division of the Atomic Energy Society of Japan, Hokkaido Branch of the Atomic Energy Society of Japan, and Nuclear Reaction Data Centre, Faculty of Science, Hokkaido University in cooperation with Nuclear Science and Engineering Directorate of Japan Atomic Energy Agency. In the symposium, there were two tutorials, "Cross section measurement strategy for long lived fission product" and "Physics and Nuclear Data in Radiation Therapy" and four sessions, "A Neutron TOF Measurement Instrument desired by Nuclear Data Community", "Recent Topics", "Application of Nuclear Data", and "Nuclear Theory and Nuclear Data". In addition, recent research progress on experiments, evaluation, benchmark and application was presented in a poster session. Among 88 participants, all presentations and following discussions were very active and fruitful. This report consists of total 62 papers including 2 tutorials, 16 oral and 44 poster presentations.

JAEA Reports

Proceedings of the International Conference on Physics of Reactors (PHYSOR 2014); September 28-October 3, 2014, Kyoto, Japan

Suyama, Kenya; Sugawara, Takanori; Tada, Kenichi; Chiba, Go*; Yamamoto, Akio*

JAEA-Conf 2014-003, 76 Pages, 2015/03

JAEA-Conf-2014-003.pdf:5.13MB
JAEA-Conf-2014-003-appendix(CD-ROM).zip:360.78MB

Japan Atomic Energy Agency organized an international conference PHYSOR 2014 on the reactor physics which is one of basic researches in the nuclear engineering, in cooperation with Research Reactor Institute of Kyoto University. PHYSOR is the world's largest scale international conference in the reactor physics field. It originates in the conference held in Marseille, France in 1990, which originally had been organized in the United States as a Physics of Reactors Topical Meeting of the reactor physics division of the American Nuclear Society every two years. More than 500 papers had been submitted and finally 472 papers were presented in the conference after the paper review process. This report contains the presented papers, which the PHYSOR organizing committee has decided to publish in an official JAEA report with the permission by authors, except for several selected papers to be published in the Journal of Nuclear Science and Technology of the Atomic Energy Society of Japan.

Journal Articles

Nuclear technology and potential ripple effect of superconducting magnets for fusion power plant

Nishimura, Arata*; Muroga, Takeo*; Takeuchi, Takao*; Nishitani, Takeo; Morioka, Atsuhiko

Fusion Engineering and Design, 81(8-14), p.1675 - 1681, 2006/02

 Times Cited Count:3 Percentile:25.6(Nuclear Science & Technology)

In a fusion reactor plant, a neutral beam injector (NBI) will be operated for a long time, and it will allow neutron streaming from NBI ports to outside of the plasma vacuum vessel. It requires the superconducting magnet to develop nuclear technology to produce stable magnetic field and to reduce activation of the magnet components. In this report, the back ground of the necessity and the contents of the nuclear technology of the superconducting magnets for fusion application are discussed and some typical investigation results are presented, which are the neutron irradiation effect on Nb$$_{3}$$Sn wire, the development of low activation superconducting wire, and the design concept to reduce nuclear heating and nuclear transformation by streaming. In addition, recent activities in high energy particle physics are introduced and potential ripple effect of the technology of the superconducting magnets is described briefly.

JAEA Reports

Fast reactor nuclear physics parameters calculation code system "EXPARAM"

Iijima, Susumu*; Kato, Yuichi*; Takasaki, Kenichi*; Okajima, Shigeaki

JAERI-Data/Code 2004-016, 91 Pages, 2004/12

JAERI-Data-Code-2004-016.pdf:7.45MB

The calculation code system "EXPARAM" was designed to analyze the experimental results systematically measured at the fast critical assembly (FCA). Some calculation codes developed independently in JAERI and in US research institutes were collected and arranged as the fast reactor physics calculation code system. The multi-group core calculation code and the perturbation calculation code based on the diffusion theory and the transport theory calculate the reactor physics parameters such as eigenvalue, reaction rate, Doppler reactivity worth and sodium void worth. The dynamic physics parameters such as prompt neutron lifetime and effective delayed neutron fraction are also calculated. Input and Output data of calculation codes are transferred to each other using a direct access file on UNIX computer system.

Journal Articles

Introduction to modern nodal method and discontinuity factor

Okumura, Keisuke

Nihon Genshiryoku Gakkai Dai-36-Kai Robutsuri Kaki Semina Tekisuto, p.81 - 102, 2004/08

The modern node method which uses a discontinuous factor has come to be widely used recently in the reactor core analyses of commercial light water reactors. The basic theory, numerical computation technique and examples of calculation results are explained for biginners of the modern nodal method.

Journal Articles

Analysis of benchmark results for reactor physics of LWR next generation fuels

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$$_{2}$$ 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.

JAEA Reports

Experimental study on accelerator driven subcritical reactor, JAERI's nuclear research promotion program, H12-031 (Contract research)

Shiroya, Seiji*; Misawa, Tsuyoshi*; Unesaki, Hironobu*; Ichihara, Chihiro*; Kobayashi, Keiji*; Nakamura, Hiroshi*; Shin, Kazuo*; Imanishi, Nobutsugu*; Kanazawa, Satoshi*; Mori, Takamasa

JAERI-Tech 2004-025, 93 Pages, 2004/03

JAERI-Tech-2004-025.pdf:6.69MB

In view of the future plan of Research Reactor Institute, Kyoto University, the present study consisted of (1) the transmission experiments of high energy neutrons through materials, (2) experimental simulation of ADSR using the Kyoto University Critical Assembly(KUCA), and (3) conceptual neutronics design study on KUR type ADSR using the MCNP-X code. Through the present study, valuable knowledge on the basic nuclear characteristics of ADSR, which is indispensable to promote the study on ADSR, was obtained both theoretically and experimentally. For the realization of ADSR, it is considered to be necessary to accumulate results of research steadily. For this purpose, it is inevitable (1) to compile the more precise nuclear data for the wide energy range, (2) to establish experimental techniques for reactor physics study on ADSR including subcriticality measurement and absolute neutron flux measurement, and (3) to develop neutronics calculation tools which take into account the neutron generation process by the spallation reaction and the delayed neutron behavior.

JAEA Reports

Activity report of Working Party on Reactor Physics of Subcritical System; October 2001 to March 2003

Research Committee on Reactor Physics

JAERI-Review 2004-006, 164 Pages, 2004/03

JAERI-Review-2004-006.pdf:11.76MB

Under the Research Committee on Reactor Physics, the Working Party on Reactor Physics of Subcritical System (ADS-WP) was set in July 2001 to research reactor physics of subcritical system such as Accelerator-Driven System (ADS). The WP, at the first meeting, discussed a guideline of its activity for two years and decided to perform theoretical research for the following subjects: (1) study of reactor physics for a subcritical core, (2) benchmark problems for a subcritical core and their calculations, (3) study of physical parameters affecting to set subcriticality of ADS, and (4) study of measurement and surveillance methods of subcriticality of a subcritical core. The activity of ADS-WP continued up to March 2003. In this duration, the members of the WP met together eight times, including four meetings jointly held with the Workshop on Accelerator-Driven Subcritical Reactor at Kyoto University Research Reactor Institute. This report summarizes the result obtained by the above WP activity and research.

JAEA Reports

Basic concept of Common reactor physics Code Systems; Final report of working party on Common reactor physics Code Systems (CCS)

Research Committee on Reactor Physics

JAERI-Review 2004-003, 152 Pages, 2004/03

JAERI-Review-2004-003.pdf:5.8MB

A working party was organized for two years (2001-2002) on common reactor physics code systems under the Research Committee on Reactor Physics of JAERI. This final report is compilation of activity of the working party on common reactor physics code systems during two years. Objectives of the working party is to clarify basic concept of common reactor physics code systems to improve convenience of reactor physics code systems for reactor physics researchers in Japan on their various field of research and development activities. We have held four meetings during 2 years, investigated status of reactor physics code systems and innovative software technologies, and discussed basic concept of common reactor physics code systems.

JAEA Reports

Study on the analyses of the reactor physics benchmark problem for the LWR next generation fuels

Research Committee on Reactor Physics

JAERI-Research 2004-004, 409 Pages, 2004/03

JAERI-Research-2004-004.pdf:28.53MB

This report summarizes the second phase (FY2001-2002) activity of "the Working Party (WP) on Reactor Physics for LWR Next Generation Fuels". The next generation fuels mean the ones aiming at further extended burn-up such as 70GWd/t over the current design. In the WP, the benchmark activity has been conducted to investigate and improve the calculation accuracy of the nuclear characteristics of the next generation fuels. In the second phase activity, all benchmark results were compiled and compared. Based on the comparison, the present status of calculation accuracy for the next generation fuels has been confirmed, and the factors causing the calculation differences were analyzed in detail. Moreover, analyses of the post irradiation and critical experiments with the codes used in the benchmark were reviewed, and future experiments and research subjects necessary to reduce the calculation differences were discussed and proposed.

JAEA Reports

Nuclear Energy System Department annual report; April 1, 2002 - March 31, 2003

Department of Nuclear Energy System

JAERI-Review 2003-023, 232 Pages, 2003/09

JAERI-Review-2003-023.pdf:16.58MB

The Department has carried out researches and developments (R&Ds) of innovative nuclear energy system and their related fundamental technologies to ensure the long-term energy supply in Japan. The report deals with the R&Ds of an innovative water reactor, called Reduced-Moderation Water Reactor (RMWR), which has the capability of multiple recycling and breeding of plutonium using light water reactor technologies. In addition, as basic studies and fundamental researches of nuclear energy system in general, described are intensive researches in the fields of reactor physics, thermal-hydraulics, nuclear data, nuclear fuels, and materials. These activities are essential not only for the R&Ds of innovative nuclear energy systems but also for the improvement of safety and reliability of current nuclear energy systems. The maintenance and operation of reactor engineering facilities belonging to the Department support experimental activities.

Journal Articles

Update status of benchmark activity for reactor physics study of LWR next generation fuels

Unesaki, Hironobu*; Okumura, Keisuke; Kitada, Takanori*; Saji, Etsuro*

Transactions of the American Nuclear Society, 88, p.436 - 438, 2003/06

In order to investigate the calculation accuracy of the nuclear characteristics of LWR next generation fuels, the Research Committee on Reactor Physics organized by JAERI has proposed "Reactor Physics Benchmark for LWR Next Generation Fuels". The next generation fuels aim at very high burn-up of about 70GWd/t in PWR or BWR with UO$$_{2}$$ or MOX fuels whose fissile enrichments may exceed the Japanese regulatory limitations for the current LWR fuels such as 5wt.% U-235. Until now, twelve organizations have pariticipated in the benchmark activity. From the comparison with the cell burn-up calculation results using different codes and library data, status of the calculation accuracy and future subjects are clarified.

JAEA Reports

Nuclear Energy System Department annual report

Department of Nuclear Energy System

JAERI-Review 2003-004, 236 Pages, 2003/03

JAERI-Review-2003-004.pdf:16.34MB

This report summarizes the research and development activities in the Department of Nuclear Energy System during the fiscal year of 2001 (April 1, 2001 - March 31, 2002). The Department has been organized from April 1998. The main research activity is aimed to build the basis of the development of future nuclear energy systems. The research activities of the Department cover basic nuclear data evaluation, conceptual design of a reduced-moderation water reactor, reactor physics experiments and development of the reactor analysis codes, experiment and analysis of thermal-hydrodynamics, energy system analysis and assessment, development of advanced materials for a reactor, lifetime reliability assessment on structural material, development of advanced nuclear fuel, design of a marine reactor and the research for a nuclear ship system. The maintenance and operation of reactor engineering facilities belonging to the Department are undertaken. The activities of the research committees to which the Department takes a role of secretariat are also summarized in this report.

Journal Articles

Development of Reduced-Moderation Water Reactor (RMWR) for sustainable energy supply

Iwamura, Takamichi; Okubo, Tsutomu; Kureta, Masatoshi; Nakatsuka, Toru; Takeda, Renzo*; Yamamoto, Kazuhiko*

Proceedings of 13th Pacific Basin Nuclear Conference (PBNC 2002) (CD-ROM), 7 Pages, 2002/10

In order to ensure sustainable energy supply in Japan, the reduced-moderation water reactor (RMWR) has been developed by JAERI since 1998. MOX fuel assemblies with tight lattice arrangement are used to increase the conversion ratio. In order to establish negative void reactivity coefficient, the core should be short and flat to increase neutron leakage from the core. The core designs were accomplished to a large core with 1,356MWe and a small core with 330MWe. For both cores, negative void coefficient and natural circulation cooling of the core were realized. To confirm thermal-hydraulic feasibility, critical heat flux experiments were performed using 7-rod bundles with the gap width of 1mm and 1.3mm. The results indicated that enough cooling was assured for the tight lattice core. Further R&D studies, including large scale thermal-hydraulic experiments, reactor physics experiments, development of high burn-up fuel cladding material and simplified reprocessing technology, are necessary to realize commercial introduction of RMWR by 2020's for the replacement of current generation LWRs.

Journal Articles

Benchmark results of burn-up calculation for LWR next generation fuels

Okumura, Keisuke; Unesaki, Hironobu*; Kitada, Takanori*; Saji, Etsuro*

Proceedings of International Conference on the New Frontiers of Nuclear Technology; Reactor Physics, Safety and High-Performance Computing (PHYSOR 2002) (CD-ROM), 10 Pages, 2002/10

In order to investigate the calculation accuracy of the nuclear characteristics of LWR next generation fuels, the Research Committee on Reactor Physics organized by Japan Atomic Energy Research Institute has proposed "Reactor Physics Benchmark for LWR Next Generation Fuels". The next generation fuels aim at very high burn-up of about 70GWd/t in PWR or BWR with UO2 or MOX fuels whose fissile enrichments may exceed the Japanese regulatory limitations for the current LWR fuels such as 5wt.% U-235. Twelve organizations have carried out the analyses of the benchmark problems with different codes and data, and their submitted results have been compared. As a result, status of accuracy with the current data and method and some problems to be solved in the future were clarified.

Journal Articles

Simple estimation method of $$gamma$$-ray dose using low neutron-sensitive TLD (UD-170LS) for Intra-Operative Boron Neutron Capture Therapy (IOBNCT)

Yamamoto, Kazuyoshi; Kumada, Hiroaki; Torii, Yoshiya; Kishi, Toshiaki; Yamamoto, Tetsuya*; Matsumura, Akira*

Research and Development in Neutron Capture Therapy, p.499 - 503, 2002/09

In order to estimate the maximum gamma-ray dose in the brain in Intra-Operative Boron Neutron Capture Therapy (IOBNCT), this study was conducted for (1) the development of low neutron-sensitive TLD (UD-170LS-T2), (2) the correlation of capture gamma-ray dose profile in a phantom for various collimator sizes, and (3) the formula for simple estimation of maximum gamma-ray dose on IOBNCT. The sensitivity of TLD, as $$^{60}$$Co $$gamma$$-ray equivalent, for thermal neutron was 5.1$$pm$$0.8$$times$$10$$^{-14}$$($$^{60}$$Co-Gycm$$^{2}$$)The average relative deviations between predicted and measured $$gamma$$-ray dose for the mixed epithermal-thermal neutron beam in the phantom were $$pm$$8.5%. The accuracy of the $$gamma$$-ray dose determination in the clinical BNCT may be improved by this simple method.

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