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Advanced Nuclear Energy Research 先進原子力エネルギー研究グループ

(1)Research on New-Type Nuclear Reactors and Accelerator Driven Subcritical Reactors

1)Development of New-Type Nuclear Reactors

(Graduate School of Engineering)Tomoaki Kunugi, Zensaku Kawara

Plan and Achievement in FY2009

In order to realize high efficiency and safety for new-type nuclear reactors as promising advanced nuclear energy source, precise knowledge is essential on the coolant flow, which is gas-liquid two-phase flow in complex system. Measurement and analytical technology for multi-phase flow are needed as the fundamental technology. In this study, measurements are taken for the temporal-spatial behavior of gas-liquid interface at various two-phase flow regime by using two-phase flow experiment loop, and its experimental database are used for development of high-accurate and high-speed analytical technology on multiphase flow. In this year, numerical method which is available for more flexible grid system is investigated for gas-liquid multiphase flow by MARS method using collocated grid system, and interfacial transport method for unstructured grid system is created and validated. Moreover, investigation on speeding-up and parallelization by using GPU (Graphic Processing Unit) gives us a vision for development of large-scale and highly-efficient direct numerical method which also contains treatment for interaction between multiphase flow and structure. According to experimental work, measurement system for multiphase flow was sophisticated by optical probe system and flow visualization system with high resolution of spatial and temporal.

2)Research on Reactor Physics of Accelerator Driven Subcritical Reactors

(Research Reactor Institute)Tsuyoshi Misawa, Hironobu Unesaki, Ken Nakajima

Plan and Achievement in FY 2009

At a new Accelerator-Driven System (ADS) with the Fixed-Field Alternating-Gradient (FFAG) accelerator, on 4th March 2009, the high-energy neutrons generated by spallation reactions with 100 MeV proton beams, which had a few pA intensity at a tungsten target, were successfully injected into a solid-moderated and -reflected core (A-core) in thermal neutron field of Kyoto University Critical Assembly (KUCA). Unfortunately, the quality of injected proton beams was not satisfied the target goal of FFAG accelerator with 150 MeV energy and 1 μA average beam current enough. Especially, less 1% proton beam intensity was not effective for irradiation experiments and was not a sufficient external neutron source for maintaining neutron flux inside critical assembly. Using 3 detectors which located at near active core regions, however, the prompt and delayed neutron behaviors by proton injection are experimentally observed and the neutron beam characteristics at the beam duct are also watched by Gafchromic films. Under the subcritical condition with 0.76 %Δk/k, an In wire irradiation experiment is accomplished horizontally. The 115In(n,γ)116mIn reaction rate comparison is also performed by MCNPX simulation and its errors shows within the allowance of the experimental statistical errors. By numerical analysis, the feasibility of neutron shield and beam duct is verified and the performance change inside of critical assembly is investigated depend on the distance from tungsten target and injected proton energies. Finally, it is confirmed that the effect of different injected proton energy is not intensified because of well-thermalized KUCA core condition by sufficient polyethylene moderators and reflectors.

3)Development of FFAG Proton Accelerator

(Research Reactor Institute) Yoshiharu Mori, Yoshihiro Ishi

Plan and Achievement in FY 2009

In order to improve the beam quality and intensity, study of charge-exchange injection with negative hydrogen ions (H-ions) for 150MeV FFAG proton accelerator at KURRI, which has been developed for accelerator driven sub-critical reactor (ADSR). In this fiscal, two major subjects have been studied: (1) Development of thin carbon foils for charge-exchange injection, and (2) Evaluation and optimization of beam emittance growth during the charge-exchange injection. As for charge-exchange foil, procedure of making a thin carbon foil with 20μg/cm2 (~0.1μm) has been established and even much thinner foils with 10μg/cm2 is under development. The beam emittance growth due to the multiple scattering and straggling during the charge-exchange injection process has also been estimated with 6-D beam tracking simulation including ionization cooling effect and, as a result, the optimum condition between number of turns at injection and accumulated beam intensity was obtained.

4)Development of Materials for Accelerator Driven Subcritical Reactors

(Research Reactor Institute) Toshimasa Yoshiie, Qiu Xu

Plan and Achievement in FY 2009

The instrumentation of materials irradiation facility at FFAG proton accelerator in the Research Reactor Institute was finished. Commercial austenitic stainless steels and their model alloys were irradiated to 0.02dpa at room temperature. The defect structure was investigated by positron annihilation spectroscopy. There were little differences between Ni, N, Fe-Cr-Ni, Fe-Cr-Ni-Mn-Mo, Fe-Cr-Ni-Mn-Mo-Si, Fe-Cr-Ni-Mn-Mo-Si-Ti、Ti added US316. Main defects were ones which had smaller space than vacancies.

(2)Research on Nuclear Fusion Reactors


(Institute of Advanced Energy)Tohru Mizuuchi

Plan and Achievement in FY 2009


1.Development of advanced diagnostic systems for fusion plasma

1-1 A microwave reflectometer system for detailed electron density profile measurement of fusion plasmas.

A charge exchange recombination spectroscopy (CXRS) system for the measurement of the high time/spatial resolved impurity ion temperature and plasma rotation velocity profiles,

2.Development of modules for an integrated code which is capable of performing hierarchical simulation for plasmas in a non-axisymmetric fusion reactor.

Progress in 2009

1-1.By introducing a Q-band amplifier, 200MHz modulation detector, phase detector, etc, we successfully measured the electron density profile in Heliotron J. We found that the electron density profile is hollow in low-density ECH plasmas and it is a peaked one in NBI plasmas.

1-2.A charge exchange recombination spectroscopy system has been developed for the measurement of the high time/spatial resolved impurity ion temperature and the rotation velocity profiles. In order to improve the spatial resolution, new sight lines are introduced by aligning them with the 3dimensional shape of the magnetically confined plasma. This optimization enables us to measure the ion temperature and rotation velocity profiles with the spatial resolution less than r=0.05, which contributes the detailed estimation of the radial electric field which is expected to control the plasma micro-turbulence.

2 .Development of an advanced three-dimensional MHD equilibrium cord with highly precise and a simulation cord for time evolution of plasma current density distribution is in progress. The three-dimensional MHD equilibrium cord, HINT2, is modified to improve the calculation precision and CPU time by using a simple cylindrical coordinate system instead of a complicated rotating helical one. As for the plasma current simulation code, a mutual inductance term is newly introduced in the code to increase predictivity of the simulation

2)Development of Integrated Tokamak Simulation Code

(Graduate School of Engineering)Atsushi Fukuyama

Plan and Achievement in FY 2009

As a part of the integrated tokamak modeling code, the Fokker-Planck component, which describes the time evolution of the momentum distribution functions of plasma species, was extended to include the effect of radial transport and the fast ion effect on fusion reaction rate as well as to reduce the computation time by parallel processing. It has enabled us to simulate the time evolution of multi-species momentum distribution functions (electrons, Deuterons, Tritons and alpha particles) in the presence of multi-scheme heating (wave heating, neutral-beam heating and alpha-particle heating) simultaneously.

3)Development of Compact Tokamak Fusion Reactor

(Graduate School of Energy Science)Takashi Maekawa

Plan and Achievement in FY 2009

Start-up experiment for advanced torus has been performed. In the experiment, the toroidal plasma current has been rapidly started-up by electron cyclotron heating and current drive in the Low Aspect ratio Torus Experiment (LATE) device. The experimental results show the current carrying fast electron tail is developed against the reverse voltage from self induction.


(Institute of Advanced Energy)Satoshi Konishi

Plan and Achievement in FY 2009


Based on the fusion-biomass hybrid concept that produces carbon neutral fuels from wastes, the research plan in the fiscal year 2009 intended the establishment of concrete design concept of the entire system, major components and to preliminary evaluate the feasibility.


Plasma and reactor major parameters are investigated using fusion system code, and the major radius 4.5m, thermal output 700MW tokamak was designed. These parameters are on the similar level of difficulty of currently constructed ITER as technical targets. Particularly plasma parameters and energy flux density on in-vessel components are moderate and technically achievable without significant breakthroughs. As the major components, liquid metal high temperature blanket, intermediate heat exchanger and tritium recovery system were designed using the simulation codes previously prepared. Entire system design with the coordinated material and energy balance and component designs were obtained with the understanding of the relationship between their parameters. These designs are supported with the ongoing experiments.
 These results satisfied the original research plan for the fiscal year 2009, and the outcome suggests that it is technically possible to introduce zero emission fuels as substitute of fossil oil before 2050 by fusion.

(3)Development of Advanced Nuclear Materials

1)Research on Thermal Diffusivity Estimation of Irradiated Ceramics

(Graduate School of Engineering)Masafumi Akiyoshi

Plan and Achievement in FY 2009

Material that survives under severe irradiation environment is the key factor to develop the future fusion reactor and other nuclear applications, such as high-temperature gas cooling fission reactor. Especially, these reactors are designed to operate at high-temperature to achieve higher generation efficiency or to actualize direct hydrogen production, and ceramics are one of the candidate materials. Thermal diffusivity is one of the most important factors for materials used at high temperature, but it has been reported that the thermal diffusivity of neutron-irradiated ceramics showed significant degradation. Changes after the irradiation that depend on the irradiation conditions were clarified step by step with the past study, still changes during the irradiation is not estimated, and that inhibit to obtain the guide to develop materials.
The thermal diffusivity at the irradiation temperature is evaluated from the dependence of thermal diffusivity on measurement temperature, and it can be considered to represent the thermal diffusivity during irradiation with several assumptions. In this work, 30MeV electron accelerator is used to induce defects to ceramic materials at several temperatures and irradiation dose, and then the thermal diffusivity of post-irradiation specimens is measured at room temperature. Specimens are radio activated with the irradiation, so all measurements are operated in radiation controlled area at Radiation Laboratory, Uji campus.
All α-Al2O3, AlN, β-Si3N4、β-SiC specimens showed degradation in thermal diffusivity with the irradiation dose, while the error in the measurement was relatively large, so the dependence on the irradiation temperature was not clear. It was caused by the specimen size, that is, very smallφ3×0.5mm specimen was used to measure the thermal diffusivity. So, factor with the specimen thickness or escape beam with laser flash that depend on a setting of jigs were not resolved.

2)Improvement of In-situ Observation System of Irradiation Defects

(Graduate School of Engineering)Hidetsugu Tsuchida

Plan and Achievement in FY 2009

Nowadays, positron annihilation method is widely used to investigate the irradiation defects, and expected to clarify the behavior of irradiation defects under the irradiation environment. In previous works, the behavior of irradiation defects has been analyzed by measurements of post irradiation specimen, but behavior during the irradiation is little studied. So, we have been trying in-situ observation of defects during ion-beam irradiation using tandem accelerator in Radiation Laboratory, Uji campus. But still time resolution of positron annihilation lifetime measurement is not enough good, and each measurement required very long time, so improvement of the system is required.
In this year, positron annihilation lifetime of fused quartz during the irradiation using the measurement system improved in the last year. Ion beam irradiation was performed using Cockcroft-Walton tandem accelerator with condition of 3MeV H+ to 1014ions/cm2. With this measurement, it was found that long-lifetime component of positron was reduced during the irradiation. The mechanism was now under study, though it was possible that the charge state of defects was changed by the irradiation and it restrain the formation of positronium.

3)Development of Advanced Oxide Dispersion Strength Ferritic Steels

(Institute of Advanced Energy)Akihiko Kimura

Plan and Achievement in FY 2009


The objective of this research is to develop innovative nuclear materials as a basic technology to realize safe and efficient operation of advanced nuclear systems under zero-emission of CO2 scenario. In 2008, material development was performed for ODS steels to improve performance of the materials, and a 16Cr-2W ODS steel was selected as a candidate of fusion blanket structural materials. The objective of this year is to develop adequate joining techniques for nano-oxide dispersion strengthened steels, which is considered to be critical technology to fabricate blanket.

Research Plan and Results

 Ph.D course students discussed on the requirements for structural materials for advanced nuclear systems and fusion blanket systems, and it was concluded that ODS steels were very feasible to apply them to advanced nuclear systems and fusion blanket systems as structural material. It was also concluded that joining technology was one of the critical techniques for the application. They discussed on joining methods and selected the followings as candidate joining methods for ODS steels: 1) TLP: transient liquid phase, 2) SSDB: solid diffusion bonding, 3) FS: friction stirring, 4) PR: pressurized resistivity. Joint performance was evaluated by tensile test and impact fracture test. In both of TLP and SSDB, tensile strength of the joints was almost same as those of base metal. However, tensile elongation of the TLP joint was reduced to almost a half of the base metal, while that of SSDB joints showed same tensile ductility as base metal. Impact fracture tests sometime showed a superior characteristic feature of SSDB than base metal. Thus, SSDB method is considered to be the most adequate joining method for ODS steels.
 R&D of reduced activation ferritic steel (RAFS), which was considered to be the candidate structural material for fusion blanket systems, started under this program. Because the temperature window of the RAFS application is limited, design margin is small in the case of the application of RAFS to advanced blanket systems. To expand the design margin, the coupling application of RAFS and ODSS will be effective, since the temperature window of the ODSS application is much wider than RAFS. The joining technique of RAFS and ODSS is essential for the coupling utilization of those two steels