Development of a short-term emergency assessment system of the marine environmental radioactivity around Japan

Kobayashi, Takuya; Kawamura, Hideyuki; Fujii, Katsuji*; Kamidaira, Yuki

Journal of Nuclear Science and Technology, 54(5), p.609 - 616, 2017/05

https://doi.org/10.1080/00223131.2017.1286272

The Japan Atomic Energy Agency has, for many years, been developing a radionuclide dispersion model for the ocean, and has validated the model through application in many sea areas using oceanic flow fields calculated by the ocean model. The Fukushima Dai-ichi Nuclear Power Station accident caused marine pollution by artificial radioactive materials to the North Pacific, especially to coastal waters northeast of mainland Japan. In order to investigate the migration of radionuclides in the ocean caused by this severe accident, studies using marine dispersion simulations have been carried out by JAEA. Based on these as well as the previous studies, JAEA has developed the Short-Term Emergency Assessment system of Marine Environmental Radioactivity (STEAMER) to immediately predict the radionuclide concentration around Japan in case of a nuclear accident.

Magnetic structure and quadrupolar order parameter driven by geometrical frustration effect in NdB

Yamauchi, Hiroki; Metoki, Naoto; Watanuki, Ryuta*; Suzuki, Kazuya*; Fukazawa, Hiroshi; Chi, S.*; Fernandez-Baca, J. A.*

Journal of the Physical Society of Japan, 86(4), p.044705_1 - 044705_9, 2017/04

https://doi.org/10.7566/JPSJ.86.044705

Neutron diffraction experiments have been carried out to characterize the magnetic structures and order parameters in an intermediate phase of NdB showing the successive phase transitions at K, K, and K. The observed patterns in phase II () are successfully explained by postulating a planar structure with static magnetic moments in the tetragonal -plane. We have found that the magnetic structure in phase II can be uniquely determined to be a linear combination of noncolinear "all-in/all-out"-type and "vortex"-type antiferromagnetic structures. We propose that the quadrupolar interaction holds the key to stabilizing the noncollinear magnetic structure and quadrupolar order. Here, the frustration in the Shastry - Sutherland lattice would play an essential role in suppressing the dominance of the magnetic interaction.

Influence of mesh non-orthogonality on numerical simulation of buoyant jet flows

Ishigaki, Masahiro; Abe, Satoshi; Shibamoto, Yasuteru; Yonomoto, Taisuke

Nuclear Engineering and Design, 314, p.326 - 337, 2017/04

AA2016-0575.pdf:1.57MB

https://doi.org/10.1016/j.nucengdes.2017.02.010

no abstracts in English

Selective extraction of Pt(IV) over Fe(III) from HCl with an amide-containing tertiary amine compound

Maeda, Motoki*; Narita, Hirokazu*; Tokoro, Chiharu*; Tanaka, Mikiya*; Motokawa, Ryuhei; Shiwaku, Hideaki; Yaita, Tsuyoshi

Separation and Purification Technology, 177, p.176 - 181, 2017/04

https://doi.org/10.1016/j.seppur.2017.01.002

Development of fuel temperature calculation code for HTGRs

Inaba, Yoshitomo; Nishihara, Tetsuo

Annals of Nuclear Energy, 101, p.383 - 389, 2017/03

https://doi.org/10.1016/j.anucene.2016.11.006

In order to ensure the thermal integrity of fuel in High Temperature Gas-cooled Reactors (HTGRs), it is necessary that the maximum fuel temperature in normal operation is to be lower than a thermal design target. In the core thermal-hydraulic design of block-type HTGRs, the maximum fuel temperature should be evaluated considering data such as thermal power, core geometry, power density and neutron fluence distributions, and core coolant flow distribution. The fuel temperature calculation code used in the design stage of the High Temperature engineering Test Reactor (HTTR) presupposes to run on UNIX systems, and its operation and execution procedure are complicated and are not user-friendly. Therefore, a new fuel temperature calculation code named FTCC which has a user-friendly system such as a simple and easy operation and execution procedure, was developed. This paper describes calculation objects and models, basic equations, improvement points from the HTTR design code in FTCC, and the result of a validation calculation with FTCC. The calculation result obtained by FTCC provides good agreement with that of the HTTR design code, and then FTCC will be used as one of the design codes for HTGRs. In addition, the effect of cooling forms on the maximum fuel temperature is investigated by using FTCC. As a result, it was found that the effect of center hole cooling for hollow fuel compacts and gapless cooling with monolithic type fuel rods on reducing the temperature is very high.

Reaction path and product analysis of sodium-water chemical reactions using laser diagnostics

Deguchi, Yoshihiro*; Muranaka, Ryota*; Kamimoto, Takahiro*; Takagi, Taku*; Kikuchi, Shin; Kurihara, Akikazu

Applied Thermal Engineering, 114, p.1319 - 1324, 2017/03

https://doi.org/10.1016/j.applthermaleng.2016.09.167

The purpose of this study aims to clarify the gas phase sodium-water reaction path and reaction products quantitatively. The counter-flow diffusion experiment device was employed to analyze the reaction path and reaction products using laser diagnostics. The main product of sodium-water reaction was determined to be NaOH and the sodium oxide was not notably measured compared with NaOH.

Preparation of Sr adsorptive fiber by impregnating with crown ether derivative for Sr measurement

Horita, Takuma; Asai, Shiho; Konda, Miki; Hanzawa, Yukiko; Saito, Kyoichi*; Fujiwara, Kunio*; Sugo, Takanobu*; Kitatsuji, Yoshihiro

Bunseki Kagaku, 66(3), p.189 - 193, 2017/03

https://doi.org/10.2116/bunsekikagaku.66.189

A Sr-selective adsorption fiber was prepared for rapid analysis of Sr content by using radiation-induced emulsion graft polymerization and subsequent chemical modification. A polyethylene fiber with a diameter of 13 m was first immersed in a methanol solution of an epoxy-group-containing vinyl monomer, glycidyl methacrylate (GMA), and polyoxyethylene sorbitol ester (Tween20) as a surfactant for graft-polymerization of GMA. Octadecylamine was then bound to a polymer chain extending from the fiber surface providing hydrophobicity to the polymer chain. Dicyclohexano-18-crown-6 (DCH18C6) was finally impregnated onto the polymer chain via a hydrophobic interaction between the octadecyl moiety of the polymer chain and the cyclohexyl moiety of DCH18C6. The fiber surface structure, characterized by DCH18C6 molecules loosely entangled with polymer chains, afforded realizes the rapid and selective adsorption of Sr ions with an adsorption rate approximately 100 times higher than that of a commercially available Sr-selective resin (Sr Resin).

Molecular dynamics simulations of cesium adsorption on illite nanoparticles

Lammers, L.*; Bourg, I. C.*; Okumura, Masahiko; Kolluri, K.*; Sposito, G.*; Machida, Masahiko

Journal of Colloid and Interface Science, 490, p.608 - 620, 2017/03

https://doi.org/10.1016/j.jcis.2016.11.084

no abstracts in English

Swelling pressure and leaching behaviors of synthetic bituminized waste products with various salt contents under a constant-volume condition

Irisawa, Keita; Meguro, Yoshihiro

Journal of Nuclear Science and Technology, 54(3), p.365 - 372, 2017/03

https://doi.org/10.1080/00223131.2016.1273143

Development of methods for recovering uranium from sludge-like uranium generated in decontamination of metal wastes

Ohashi, Yusuke; Tanaka, Yoshio; Tsunashima, Yasumichi; Ikeda, Yasuhisa*

Journal of Nuclear Science and Technology, 54(3), p.382 - 390, 2017/03

https://doi.org/10.1080/00223131.2016.1260065

Sludge-like uranium wastes (SUWs) have been generated with neutralization of acidic aqueous solutions used for decontamination of metal wastes containing a large amount of iron. We have examined the method for recovering uranium from such SUWs using -2-pyrrolidone (NCP) as a precipitate. As a result, it was found that precipitation ratios (PRs) of uranium in the solutions prepared by dissolving SUWs in HNO is 97.7% at [NCP]/[U(VI)] = 20, and that the PRs of iron, aluminum, fluorine, and sulfate species are less than 1%. This indicates that uranium species are precipitated selectively. The content ratios of U, Fe, Ca, F, and S in the materials after calcining precipitates obtained at [NCP]/[U(VI)] = 20 were in accordance with the conditions of uranium ore concentrate. From these results, it is expected that highly purified uranium can be efficiently recovered from SUWs by using NCP as the precipitant.

Neutron powder diffraction study on the magnetic structure of NdPdAl

Metoki, Naoto; Yamauchi, Hiroki; Kitazawa, Hideaki*; Suzuki, Hiroyuki*; Hagihara, Masato*; Frontzek, M. D.*; Matsuda, Masaaki*; Fernandez-Baca, J. A.*

Journal of the Physical Society of Japan, 86(3), p.034710_1 - 034710_5, 2017/03

https://doi.org/10.7566/JPSJ.86.034710

Magnetic structure of NdPdAl has been studied by means of neutron powder diffraction. We observed remarkable magnetic reflections with the modulation vector = (1/2 0 0) below the ordering temperature = 1.2 K. We found a collinear magnetic structure of Nd moment of 2.9(1) at 0.3 K parallel to the -axis, where the ferromagnetically ordered planes stack with four Nd layer period of ++-- sequence along the direction with the distance between adjuscent Nd layers to be . This is very similar to CePdAl with = (0.23 0.23 0) and the Ce moment parallel to the -axis. These structures with in-plane modulation is a consequence of the two dimensional nature of fermi surface topology in this family, coming from unique crystal structure with very long tetragonal unit cell and large distance 7 between the rare earth layers separated by Al and two Pd layers.

Evaluation of influence of splay fault growth on groundwater flow around geological disposal system

Takai, Shizuka; Takeda, Seiji; Sakai, Ryutaro*; Shimada, Taro; Munakata, Masahiro; Tanaka, Tadao

Nihon Genshiryoku Gakkai Wabun Rombunshi, 16(1), p.34 - 48, 2017/03

https://doi.org/10.3327/taesj.J16.003

In geological disposal, direct effect on geological repositories by active faults is avoided at a stage of site characterization; however, uncertainty remains for avoidance of faults derived from the active faults, which are concealed deep under the ground and difficult to detect in advance. In this research, the influence of growth of undetected splay faults on natural barrier in a geological disposal system, which will caused by attack of the faults in the future, was evaluated. We investigated examples of splay faults in Japan and set conditions for growth of splay faults. Furthermore, we assumed a disposal site composed of sedimentary rocks and made a hydrogeological model of growth of splay faults. We carried out groundwater flow analyses, changing parameters such as location and depth of repository and growth velocity of splay faults. The results indicate that main flow path from the repository is changed into upward flow along the splay fault due to its growth and the average velocity to the ground surface becomes one or two orders of magnitude higher than that before its growth. The results also suggest that the splay fault growth leads into the possibility of downward flow of oxidizing groundwater from ground surface area.

Prospects for researches on environmental and health effects of the Fukushima Dai-ichi NPP accident

Hirouchi, Jun; Okura, Takehisa; Satoh, Daiki

Nihon Genshiryoku Gakkai-Shi ATOMO, 59(3), p.152 - 155, 2017/03

no abstracts in English

Applicability of the two-angle differential method to response measurement of neutron-sensitive devices at the RCNP high-energy neutron facility

Masuda, Akihiko*; Matsumoto, Tetsuro*; Iwamoto, Yosuke; Hagiwara, Masayuki*; Satoh, Daiki; Sato, Tatsuhiko; Iwase, Hiroshi*; Yashima, Hiroshi*; Nakane, Yoshihiro; Nishiyama, Jun*; et al.

Nuclear Instruments and Methods in Physics Research A, 849, p.94 - 101, 2017/03

https://doi.org/10.1016/j.nima.2016.12.031

Quasi-monoenergetic high-energy neutron fields induced by Li(p,n) reactions are used for the response evaluation of neutron-sensitive devices. The quasi-monoenergetic high-energy field consists of high-energy monoenergetic peak neutrons and unwanted continuum neutrons down to the low-energy region. A two-angle differential method has been developed to compensate for the effect of the continuum neutrons in the response measurements. In this study, the two-angle differential method was demonstrated for Bonner sphere detectors, which are typical examples of moderator-based neutron-sensitive detectors, to investigate the method's applicability and its dependence on detector characteristics. Through this study, the adequacy of the two-angle differential method was experimentally verified, and practical suggestions were made pertaining to this method.

Degradation behavior of surface-mounted LED by irradiation

Takeuchi, Tomoaki; Otsuka, Noriaki; Uehara, Toshiaki; Kumahara, Hajime*; Tsuchiya, Kunihiko

QST-M-2; QST Takasaki Annual Report 2015, P. 80, 2017/03

https://repo.qst.go.jp/records/73804

no abstracts in English

Dynamic behavior of secondary electrons produced by a high-energy electron in liquid water

Kai, Takeshi; Yokoya, Akinari*; Fujii, Kentaro*; Watanabe, Ritsuko*

Yodenshi Kagaku, (8), p.11 - 17, 2017/03

It is thought to that the biological effects such as cell death or mutation are induced by complex DNA damage which are formed by several damage sites within a few nm. We calculated dynamic behavior of secondary electrons produced by primary electron and positon of high energy in water whose composition ratio is similar to biological context. The secondary electrons induce the ionization or electronic excitation near the parent cations. The decelerated electrons about 10% are distributed to their parent cations by the attractive Coulombic force. From the results, we predicted the following formation mechanism for the complex DNA damage. The electrons ejected from DNA could induce the ionization or the electronic excitation within the DNA. The electrons attracted by the Coulombic force are pre-hydrated in water layer of the DNA. The pre-hydrated electrons could induce to the DNA damage by dissociative electron transfer. As the results, the complex DNA damage with 1 nm could be formed by the interaction of not only the primary electron or positon but also the secondary electrons.

Gyroscopic factor of rare earth metals

Ogata, Yudai; Chudo, Hiroyuki; Ono, Masao; Harii, Kazuya; Matsuo, Mamoru; Maekawa, Sadamichi; Saito, Eiji

Applied Physics Letters, 110(7), p.072409_1 - 072409_4, 2017/02

https://doi.org/10.1063/1.4976998

Interaction of rare earth elements and components of the Horonobe deep groundwater

Kirishima, Akira*; Kuno, Atsushi*; Amamiya, Hiroki; Kubota, Takumi*; Kimuro, Shingo*; Amano, Yuki; Miyakawa, Kazuya; Iwatsuki, Teruki; Mizuno, Takashi; Sasaki, Takayuki*; et al.

Chemosphere, 168, p.798 - 806, 2017/02

https://doi.org/10.1016/j.chemosphere.2016.10.133

For better understanding of the migration behavior of minor actinides (MA) in deep groundwater, the interaction of doped rare earth elements (REEs) and components in Horonobe deep groundwater was studied. Appx. 10 ppb of rare earth elements, i.e., Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Tm and Yb were doped to the sample groundwater collected from a packed sections in borehole drilled from 140 m depth experiment drift of Horonobe underground research laboratory (URL), Hokkaido, Japan. Then, that groundwater was sequentially filtrated by 0.2 micron pore filter, 10 kDa, 3 kDa and 1 kDa of nominal molecular weight limit (NMWL) ultrafilters by keeping inert condition. After that, the filtrate solutions were analyzed by ICP-MS to determine the concentrations of retained REEs at each filtration steps, while the used filters were analyzed by the neutron activation analysis (NAA) and TOF-SIMS element mapping to know the amount and chemical speciation of trapped fraction of the REEs on each filter. A remarkable relation between the retention ratios of REEs in the filtrate solutions and the ionic radius was observed, i.e., smaller rare earth element solves more in liquid phase under the Horonobe groundwater condition. NAA and TOF-SIMS analyses revealed that certain portions of REEs were trapped by 0.2 micron pore filters as rare earth phosphates which corresponded with the predicted predominant species by a chemical equilibrium calculation for the Horonobe groundwater condition, while small portions of colloidal REEs were trapped by 10 kDa and 3 kDa NMWL ultrafilters. The result suggested that phosphate anion plays an important role in the chemical behavior of REEs in saline (seawater based) groundwater, which could be referred for the prediction of migration behavior of trivalent actinide released from the repository of radioactive waste in far future.

Experimental investigation of the influence of Mo contained in stainless steel on Cs chemisorption behavior

Di Lemma, F. G.; Nakajima, Kunihisa; Yamashita, Shinichiro; Osaka, Masahiko

Journal of Nuclear Materials, 484, p.174 - 182, 2017/02

https://doi.org/10.1016/j.jnucmat.2016.11.031

Chemisorption phenomena can affect fission products retention in the nuclear reactor vessel during a Severe Accident (SA). This paper will describe the influence of molybdenum contained in type 316 stainless steel (SS) on Cs chemisorption. Our experiments showed the formation of Cs-Mo compounds in addition to CsFeSiO, observed previously on SS304. The results of high temperature stability tests on the deposits are also presented. These tests aimed at simulating the revaporization of FP from structural materials during a SA. From our results, it can be inferred that Cs-Mo deposits may revaporize, contributing as a delayed source to the radioactive release.

Improvement of neutron startup source handling work by developing new transportation container for High-Temperature engineering Test Reactor (HTTR)

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

https://doi.org/10.1080/00223131.2016.1255574

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.

Positron annihilation in the near surface of room temperature ionic liquids

Hirade, Tetsuya; O'Rourke, B. E.*; Kobayashi, Yoshinori*

Journal of Physics; Conference Series, 791(1), p.012029_1 - 012029_4, 2017/02

https://doi.org/10.1088/1742-6596/791/1/012029

We tried to observe the positron annihilation rates near surface of (room temperature ionic liquids) IL's, such as N,N,N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl)imide (TMPA-TFSI) by use of the perpendicular slow positron beamline installed at AIST. The vaper pressure of TMPA-TFSI is very small and hence it is possible to measure the positron annihilation rate in vacuum chamber directly. This represents the first energy variable experimental results of the positron annihilation rate at the near surface of an IL. The triplet positronium annihilation rate seems to be larger at nearer region to the surface of the IL's.

Research progress at the Slow Positron Facility in the Institute of Materials Structure Science, KEK

Hyodo, Toshio*; Wada, Ken*; Mochizuki, Izumi*; Kimura, Masao*; Toge, Nobukazu*; Shidara, Tetsuo*; Fukaya, Yuki; Maekawa, Masaki*; Kawasuso, Atsuo*; Iida, Shimpei*; et al.

Journal of Physics; Conference Series, 791(1), p.012003_1 - 012003_8, 2017/02

https://doi.org/10.1088/1742-6596/791/1/012003

no abstracts in English

Algebraic design of multi-dimensional transfer function using transfer function synthesizer

Kawamura, Takuma; Idomura, Yasuhiro; Miyamura, Hiroko; Takemiya, Hiroshi

Journal of Visualization, 20(1), p.151 - 162, 2017/02

https://doi.org/10.1007/s12650-016-0387-1

In this paper, we propose a novel transfer function design interface for multivariate volume rendering. In the conventional multivariate volume rendering, GUI based transfer function design interfaces were limited to two-dimensional variables space. In order to design higher dimensional transfer functions in an interactive and intuitive manner, a Transfer Function Synthesizer (TFS) is developed. On the TFS, multi-dimensional transfer functions are generated by algebraic synthesis of one-dimensional transfer functions, which are designed based on the conventional GUIs or algebraic expressions. The TFS enables not only multivariate volume rendering but also general visualization techniques such as surface visualization and image composition within the framework of volume rendering. The TFS is implemented on the remote visualization system PBVR, and applied to various multivariate scalar volume data generated from nuclear applications.

Influence of inlet velocity condition on unsteady flow characteristics in piping with a short elbow under a high-Reynolds-number condition

Ono, Ayako; Tanaka, Masaaki; Kobayashi, Jun; Kamide, Hideki

Mechanical Engineering Journal (Internet), 4(1), p.16-00217_1 - 16-00217_15, 2017/02

http://doi.org/10.1299/mej.16-00217

In the design of the Advanced Sodium-cooled Fast Reactor in Japan, the Reynolds number in the primary hot leg (H/L) piping reaches 4.210. Furthermore, a short elbow is used in the H/L piping to achieve a compact plant layout. In the H/L piping, flow-induced vibration is a concern due to the excitation force caused by pressure fluctuation in the short elbow. In this report, the influence of inlet velocity condition on the unsteady velocity characteristics in the short elbow was studied by controlling the flow patterns at the elbow inlet. Measured velocity distributions indicated that the inlet velocity profiles affected a circumferential secondary flow, which then affected an area of flow separation at the elbow. It was also found that the velocity fluctuation at low frequency components observed upstream of the elbow could remain in downstream of the elbow though its intensity was attenuated.

Progress of thermal hydraulic evaluation methods and experimental studies on a sodium-cooled fast reactor and its safety in Japan

Kamide, Hideki; Ohshima, Hiroyuki; Sakai, Takaaki; Tanaka, Masaaki

Nuclear Engineering and Design, 312, p.30 - 41, 2017/02

https://doi.org/10.1016/j.nucengdes.2016.09.026

In the framework of the Generation-IV International Forum, the safety design criteria (SDC) incorporating safety-related Research and Development results on innovative technologies and lessons learned from Fukushima Dai-ichi Nuclear Power Plants accident has been established to provide the set of general criteria for the safety designs of structures, systems and components of Generation-IV Sodium-cooled Fast Reactors (Gen-IV SFRs). A number of thermal-hydraulic evaluations are necessary to meet the concept of the criteria in the design studies of Gen-IV SFRs. This paper focuses on four kinds of thermal-hydraulic issues associated with the SDC, i.e., fuel subassembly thermal-hydraulics, natural circulation decay heat removal, core disruptive accidents, and thermal striping. Progress of evaluation methods on these issues is shown with activities on verification and validation (V and V) and experimental studies towards commercialization of SFR in Japan. These evaluation methods are planned to be eventually integrated into a comprehensive numerical simulation system that can be applied to all possible phenomena in SFR systems and that can be expected to become an effective tool for the development of human resource and the handing our knowledge and technologies down.

Dislocations near elastic instability in high-pressure body-centered-cubic magnesium

Winter, I. S.*; Poschmann, M.*; Tsuru, Tomohito; Chrzan, D. C.*

Physical Review B, 95(6), p.064107_1 - 064107_9, 2017/02

https://doi.org/10.1103/PhysRevB.95.064107

At high pressure, Mg is expected to transform to the body centered cubic (BCC) phase. We use density functional theory to explore the structure of type dislocation cores in BCC Mg as a function of pressure. As the pressure is reduced from the region of absolute stability for the BCC phase, the dislocation cores spread. When dislocation cores overlap the displacements of columns of atoms resemble the nanodisturbances observed in TiNb alloys known as Gum Metal. The ideal tensile strength of BCC Mg is also computed as a function of pressure. Despite its low shear modulus, BCC Mg is predicted to be intrinsically brittle at absolute zero.

Two-body wave functions and compositeness from scattering amplitudes; General properties with schematic models

Sekihara, Takayasu

Physical Review C, 95(2), p.025206_1 - 025206_16, 2017/02

AA2016-0539.pdf:1.06MB

https://doi.org/10.1103/PhysRevC.95.025206

Unitization for portability of emergency response surveillance robot system; Experiences and lessons learned from the deployment of the JAEA-3 emergency response robot at the Fukushima Daiichi Nuclear Power Plants

Kawatsuma, Shinji; Mimura, Ryuji; Asama, Hajime*

ROBOMECH Journal (Internet), 4, p.6_1 - 6_7, 2017/02

https://doi.org/10.1186/s40648-017-0073-7

It was cleared that portability of emergency response reconnaissance robot had been very important. So, RESQ-A robots, which had been developed by Japan Atomic Energy Research Institute (present Japan Atomic Energy Agency), had been considered from the view point of portability. After Fukushima Daiichi NPPs' accidents occurred, JAEA had modified a RESQ-A robot to JAEA-3 robot in order to meet the anticipated situation of the accidents. However, actual situation was beyond the anticipated situation, and additional modification was required. The actual confused situation was many rubble were scattered and temporary cables and hoses were constructed in the reactor buildings, so that reconnaissance robots should be conveyed by operators through limited route, should be reassembled in short time and should be able to remove cable and tiers for reduce the operators' exposure dose during maintenance. JAEA modified again JAEA-3 robot system, with cooperation of operators from Fukushima Daiichi NPPs. It was lesson learned that emergency response reconnaissance robot needed to be unitized for portability, and "Unitization Policy for emergency response reconnaissance robot" was developed.

Effect of specimen size and oxygen partial pressure on creep characteristics for mod. 9Cr-1Mo steel

Kanayama, Hideyuki; Hiyoshi, Noritake*; Ito, Takamoto*; Ogawa, Fumio*; Wakai, Takashi

Zairyo, 66(2), p.86 - 92, 2017/02

https://doi.org/10.2472/jsms.66.86

This study presents creep characteristics of Mod. 9Cr-1Mo steel with various sized specimens and environment. Creep tests were performed using three different sizes of specimen and three different type of testing environment. Specimens are a bulk specimen which has 6mm diameter and 30mm gage length, a miniature specimen which has 2mm diameter and 10mm gage length and a thin plate specimen which has 0.76mm thickness, 1.5mm width and 7.62mm gage length. Three different type of testing environment are air, 99.99% Ar gas and vacuum. In the same environmental condition, there was no effect of specimen size on time to rupture. Time to rupture of Mod. 9Cr-1Mo steel in Ar gas was shorter than that in air and vacuum. Oxide thickness is not dominant factor in time to rupture. Fracture mode at specimen surface in Ar gas might be dominant factor in shorter time to rupture. Effect of specimen size and environment on creep strength of Mod. 9Cr-1Mo steel was evaluated on the basis of thinning.

A Spin-crossover phenomenon depending on the environment around an iron atom for the assembled coordination polymers

Nakashima, Satoru*; Kaneko, Masashi

Advances in Chemistry Research, Vol.36, p.171 - 195, 2017/01

Spin-crossover (SCO) phenomena of the assembled coordination polymers are introduced. When the bridging ligand is flexible like 1,2-bis(4-pyridyl)ethane, 1,3-bis(4-pyridyl)propane, a variety of assembled structure can be obtained, depending on the conformer of the ligand and the guest molecules. Guest-dependent SCO phenomena of the assembled iron complexes are shown. Density functional theory is applied to know the cause of guest-dependent SCO phenomena. The validity of an iron mono-nucleus model is evaluated for the coordination polymers. It is shown that SCO occurs or not depends on the local structure around iron ion.

The Role of low-temperature organic matter diagenesis in carbonate precipitation within a marine deposit

Miyakawa, Kazuya; Ishii, Eiichi; Hirota, Akinari*; Komatsu, Daisuke*; Ikeya, Kosuke*; Tsunogai, Urumu*

Applied Geochemistry, 76, p.218 - 231, 2017/01

https://doi.org/10.1016/j.apgeochem.2016.11.001

no abstracts in English

Analysis of Cs, Cs and K in the certified reference material of Brown Rice by -ray spectrometry using a Ge detector, 2; Uncertainty evaluation

Yonezawa, Chushiro*; Shirono, Katsuhiro*; Haraga, Tomoko

Bunseki Kagaku, 66(1), p.27 - 37, 2017/01

https://doi.org/10.2116/bunsekikagaku.66.27

no abstracts in English

Assessment of the functions of the impervious plug based on several monitoring results for groundwater recovery experiment

Matsui, Hiroya; Mikake, Shinichiro; Ikeda, Koki; Sasaki, Sadao

Dai-14-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (Internet), 6 Pages, 2017/01

Japan Atomic Energy Agency (JAEA) has been conducting the groundwater recovery experiment to develop the methodology to estimate the recovery of geological environment after drift closure at GL-500m in Mizunami Underground Research Laboratory, Gifu prefecture, Japan. For the experiment, the impervious concrete plug was constructed to keep a recovered water pressure. The authors assessed the functions of the pluge based on monitoring and interpretation of the several kinds of measurements inside and outside of the plug during groundwater recovery process in a drift. As the results, the design concept and the expected function of the impervious plug assessed almost satisfied and it is supposed no problem will occur on the groundwater recovery experiment for several months.

Estimation of rock mass stress state based on the convergence measurement result during tunnel excavation

Kamemura, Katsumi*; Aoyagi, Kazuhei; Nago, Makito*; Sugawara, Kentaro*; Matsubara, Makoto*

Dai-14-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (Internet), 6 Pages, 2017/01

In the design of deep underground structures such as high-level radioactive waste disposal repositories, the estimation of rock mass stress state is important as well as the estimation of mechanical characteristics of rock mass. This study establishes a practical and effective method for estimating in situ stress based on the convergence measurement results obtained during gallery construction of URL. The convergence was measured in various directions of the URL loop gallery at 350 m depth, and this will allow determination of the stress state over a large area using a back analysis method. In order to improve the accuracy of initial stress estimation, the relationship between convergence measurement results and geological situation of existing fractures were studied. The analysis results show good agreement with the in situ stress state results reported in previous studies and confirm the applicability of the proposed method.

Numerical analysis of the grout injection conducted in the ventilation shaft of the Horonobe Underground Research Laboratory

Nakashima, Hiroyoshi*; Koyama, Tomofumi*; Tatsuta, Keisuke*; Katayama, Tatsuo*; Aoyagi, Kazuhei

Dai-14-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (Internet), 6 Pages, 2017/01

In this study, we created the three dimensional model based on equivalent continuum approach to study the penetration length and enhancement of the hydraulic conductivity of the rock mass. The developed numerical model was applied to the in situ grout injection conducted in the ventilation shaft of the Horonobe Underground Research Laboratory. We evaluated the hydraulic conductivity of the rock mass after the grout operation. As a result, hydraulic conductivity of the highly permeable fault was decreased in 4 orders of magnitude, which is almost consistent with the in situ hydraulic conductivity obtained from in situ Luegeon test after the grout injection. Thus the simulation method described in this paper can be applied to the evaluation of the efficiency of in situ grout injection.

Inferring partial orders of nodes for hierarchical network layout

Wu, H.-Y.*; Takahashi, Shigeo*; Miyamura, Hiroko; Ozahata, Satoshi*; Nakao, Akihiro*

Electronic Imaging, 2017(1), p.118 - 130, 2017/01

https://doi.org/10.2352/ISSN.2470-1173.2017.1.VDA-395

Extracting hierarchical structures from networks provides us with an effective means of visualizing them, especially when they contain complicated node connectivities such as those in traffic and distributed networks. This paper presents an algorithm for inferring such partial orders by optimizing the network hierarchies along flow paths that are given as input. We study several network examples to demonstrate the feasibility of the proposed approach including course dependency charts, railway networks, and P2P networks.

Comprehensive study on initial thermal oxidation of GaN(0001) surface and subsequent oxide growth in dry oxygen ambient

Yamada, Takahiro*; Ito, Joyo*; Asahara, Ryohei*; Watanabe, Kenta*; Nozaki, Mikito*; Nakazawa, Satoshi*; Anda, Yoshiharu*; Ishida, Masahiro*; Ueda, Tetsuzo*; Yoshigoe, Akitaka; et al.

Journal of Applied Physics, 121(3), p.035303_1 - 035303_9, 2017/01

https://doi.org/10.1063/1.4974458

Initial oxidation of GaN(0001) epilayers and subsequent growth of thermal oxides in dry oxygen ambient were investigated by means of X-ray photoelectron spectroscopy, spectroscopic ellipsometry, atomic force microscopy and X-ray diffraction measurements. It was found that, whereas initial oxide formation tends to saturate at temperatures below 800C, selective growth of small oxide grains proceeds at dislocations in the epilayers, followed by noticeable grain growth leading to rough surface morphology at higher oxidation temperatures. This indicates that oxide growth and its morphology are crucially dependent on the defect density in the GaN epilayers. Structural characterizations also revealed that polycrystalline - and -phase GaO grains in an epitaxial relation with the GaN substrate are formed from the initial stage of the oxide growth. On the basis of these experimental findings, we also developed a comprehensive model for GaN oxidation mediated by nitrogen removal and mass transport.

Spectrum-dose conversion operator of NaI(Tl) and CsI(Tl) scintillation detectors for air dose rate measurement in contaminated environments

Tsuda, Shuichi; Saito, Kimiaki

Journal of Environmental Radioactivity, 166(Part 3), p.419 - 426, 2017/01

https://doi.org/10.1016/j.jenvrad.2016.02.008

Air dose rate monitoring in the environment has been performed since the Fukushima Dai-ichi Nuclear Power Plant accident happened. In the measurement, NaI(Tl) and CsI(Tl) scintillation detectors are used, which are usually used in nuclear power plants and calibrated in a uniform irradiation condition in a radiation calibration field. In general, however, the detector responses are dependent on incident direction and in reality, the incident direction of the photons is not uniform in the environment. In this study, to evaluate the dependence of dose on the photon incident direction, the spectrum - dose conversion operator (G(E) function) for air kerma in a semi-infinite radiation field were obtained using the PHITS code for commonly used NaI(Tl) and CsI(Tl) scintillation detectors. The results indicate that the commonly used scintillation detectors overestimate the doses by a maximum of 40% for mono-energetic photons but under the real environment, one could obtain the dose in the semi-infinite radiation field within 20%.

Implementation of muon interaction models in PHITS

Abe, Shinichiro; Sato, Tatsuhiko

Journal of Nuclear Science and Technology, 54(1), p.101 - 110, 2017/01

https://doi.org/10.1080/00223131.2016.1210043

There are several researches for application of muons, e.g. the visualization of inner-structure of nuclear reactors by using high-energy cosmic-ray muons, nuclear transmutation of long-lived fission products (LLFPs) and nondestructive elemental analysis by using low-energy negative muon. In this study, we construct models for muon interactions (i.e., bremsstrahlung, electron-positron pair production, muon photonuclear interaction, and negative muon capture reaction) and implement them into PHITS in order to make PHITS available for investigations of muon application. The improved PHITS agrees well with experimental data not only for the vertical intensities of cosmic-ray muons in water and standard rock, but also for neutron production by muon photonuclear interaction and negative muon capture reaction. The improved PHITS can also reproduce the cross-section of radionuclide production by muons passing through a concrete wall very well. These results indicate the applicability of the improved PHITS to the shielding design of muon facilities in which estimations of attenuation length and induced radioactivity are important.

Correction of the thermal neutron capture cross section of Am obtained by the Westcott convention

Mizuyama, Kazuhito; Iwamoto, Nobuyuki; Iwamoto, Osamu

Journal of Nuclear Science and Technology, 54(1), p.74 - 80, 2017/01

https://doi.org/10.1080/00223131.2016.1208593

Applicability of polyvinylpolypyrrolidone adsorbent to treatment process of wastes containing uranium

Ohashi, Yusuke; Harada, Masayuki*; Asanuma, Noriko*; Ando, Shion; Tanaka, Yoshio; Ikeda, Yasuhisa*

Journal of Radioanalytical and Nuclear Chemistry, 311(1), p.491 - 502, 2017/01

https://doi.org/10.1007/s10967-016-5017-9

In order to assess the feasibility of method for recovering U from wastes containing uranium (scrap uranium) using polyvinylpolypyrrolidone (PVPP) adsorbent, we have examined the adsorption and desorption behavior of metal species in HCl aqueous solutions dissolving scrap uranium. It was found that the U(VI) species are selectively adsorbed onto PVPP regardless of the presence of a large amount of Na(I) and Al(III), that the adsorbed U(VI) species are desorbed from PVPP column selectively by water. Pure uranium was efficiently recovered from the eluates. From these results, the PVPP resin is expected to be used as the adsorbent in the treatment process of scrap uranium.

Reduced-shifted conjugate-gradient method for a Green's function; Efficient numerical approach in a nano-structured superconductor

Nagai, Yuki; Shinohara, Yasushi*; Futamura, Yasunori*; Sakurai, Tetsuya*

Journal of the Physical Society of Japan, 86(1), p.014708_1 - 014708_9, 2017/01

https://doi.org/10.7566/JPSJ.86.014708

no abstracts in English

Alloy design and mechanical properties; First-principles calculations of dislocation core

Tsuru, Tomohito

Materia, 56(1), p.5 - 13, 2017/01

http://doi.org/10.2320/materia.56.5

Elements strategy becomes important to investigate alternative materials of rare metals. We have dedicated to establish a new approach based on computational methods. In the present paper, we propose two approaches based on first-principles and theory of dislocations. These methods are introduced to magnesium alloys.

Investigation of error estimation method of observational data and comparison method between numerical and observational results toward V&V of seismic simulation

Suzuki, Yoshio; Kawakami, Yoshiaki*; Nakajima, Norihiro

Mechanical Engineering Reviews, 4(1), p.15-00525_1 - 15-00525_18, 2017/01

https://doi.org/10.1299/mer.15-00525

The method to estimate errors included in observational data and the method to compare numerical results with observational results are investigated toward the verification and validation (V&V) of a seismic simulation. For the method to estimate errors, it is found that errors are caused by the resolution, the linearity, the temperature coefficient for sensitivity, the temperature coefficient for zero shift, the transverse sensitivity, the seismometer property, the aliasing, and so on. Thus, it is needed to estimate errors individually for those factors and integrate them. For the method to compare numerical results with observational results, it is found that six methods have been mainly proposed in existing researches. Evaluating those methods using nine items, advantages and disadvantages for those methods are arranged. The method is not well established so that it is necessary to employ those methods by compensating disadvantages and/or to search for a solution to a novel method.

Hydrogenation of iron in the early stage of Earth's evolution

Iizuka, Riko*; Yagi, Takehiko*; Goto, Hirotada*; Okuchi, Takuo*; Hattori, Takanori; Sano, Asami

Nature Communications (Internet), 8, p.14096_1 - 14096_7, 2017/01

AA2016-0524.pdf:0.73MB

https://doi.org/10.1038/ncomms14096

Density of the Earth's core is lower than that of pure iron and the light element(s) in the core is a long-standing problem. Hydrogen is the most abundant element in the solar system and thus one of the important candidates. However, the dissolution process of hydrogen into iron remained unclear. Here we carry out high-pressure and high-temperature in situ neutron diffraction experiments and clarify that when the mixture of iron and hydrous minerals are heated, iron is hydrogenized soon after the hydrous mineral is dehydrated. This implies that early in the Earth's evolution, as the accumulated primordial material became hotter, the dissolution of hydrogen into iron occurred before any other materials melted. This suggests that hydrogen is likely the first light element dissolved into iron during the Earth's evolution and it may affect the behaviour of the other light elements in the later processes.

Cesiated surface H ion source; Optimization studies

Ueno, Akira

New Journal of Physics (Internet), 19(1), p.015004_1 - 015004_15, 2017/01

https://doi.org/10.1088/1367-2630/aa52e3

In order to satisfy the increasing intensity requirements of high-energy and high-intensity proton accelerators for an H ion beam with small transverse normalized rms emittances of around 0.25 mmmrad, diverse parameters possibly reducing the emittances were optimised. Such as the plasma electrode shape and temperature, the radio-frequency (RF) matching network for the igniter plasma, the filter-field strength and distribution, the strength of the axial magnetic field around the beam extraction hole, the cesiasion procedure and the cesium (Cs) density, impurity elements, and so on, were optimized with H ion sources for the Japan Proton Accelerator Research Complex (J-PARC). By optimizing each parameter step by step, the J-PARC cesiated RF-driven H ion source successfully produced the world brightest class beam with 95% beam transverse normalized rms emittances of 0.24 mmmrad and an intensity of 66 mA.

Development of simple estimation method for the influence of parameter uncertainty of probability distributions against evaluation result of probabilistic fracture mechanics

Okajima, Satoshi; Takaya, Shigeru; Asayama, Tai

Nihon Kikai Gakkai Rombunshu (Internet), 83(845), p.16-00434_1 - 16-00434_13, 2017/01

http://doi.org/10.1299/transjsme.16-00434

no abstracts in English

Development of spin-wave-like dispersive excitations below the pseudogap temperature in the high-temperature superconductor LaSrCuO

Matsuura, Masato*; Kawamura, Sho*; Fujita, Masaki*; Kajimoto, Ryoichi; Yamada, Kazuyoshi*

Physical Review B, 95(2), p.024504_1 - 024504_6, 2017/01

https://doi.org/10.1103/PhysRevB.95.024504

Search for the Glueball in and decays

Jia, S.*; Tanida, Kiyoshi; Belle Collaboration*; 170 of others*

Physical Review D, 95(1), p.012001_1 - 012001_13, 2017/01

AA2016-0474.pdf:1.26MB

https://doi.org/10.1103/PhysRevD.95.012001

Effect of storage environment on hydrogen generation by the reaction of Al with water

Wang, Y.-Q.*; Gai, W.-Z.*; Zhang, X.-Y.*; Pan, H.-Y.*; Cheng, Z.-X.*; Xu, P. G.; Deng, Z.-Y.*

RSC Advances (Internet), 7(4), p.2103 - 2109, 2017/01

AA2016-0521.pdf:1.55MB

https://doi.org/10.1039/C6RA25563A

What can we measure by radiation measurement instruments?

Takeyasu, Masanori

Tomioka Hoshasen Joho Matome Saito (Internet), 2 Pages, 2017/01

http://tomioka-radiation.jp/2017/01/24/radiation-measuring.html

Some radiation measurement instruments are lent out to the residents in Tomioka-machi, Fukushima. In this paper, it is explained that the kinds of those instruments, their purposes, the attention points on their uses and the interpretation of the measurement results by those instruments.

Numerical simulation of surface energy and water balances over a semiarid grassland ecosystem in the West African Savanna

Quansah, E.*; Katata, Genki; Mauder, M.*; Annor, T.*; Amekudzi, L. K.*; Bliefernicht, J.*; Heinzeller, D.*; Balogun, A.*; Kunstmann, H.*

Advances in Meteorology, 2017, p.6258180_1 - 6258180_11, 2017/00

AA2016-0147.pdf:2.3MB

https://doi.org/10.1155/2017/6258180

An accurate prediction in the energy partitioning of the net solar radiation into latent and sensible heat fluxes over arid and semiarid regions is one of the challenges in land surface study in weather and climate simulations. Numerical simulations of surface energy and water balances were carried out using a one-dimensional multi-layer atmosphere-SOil-VEGetation (SOLVEG) model for selected days of the dry and rainy seasons over a savanna grassland ecosystem in Sumbrungu in the Upper East region of Ghana. The results for the investigated period between both seasons showed that the model overall reproduced the diurnal changes in the observed net radiation, sensible heat flux, latent heat flux, and ground heat flux. The statistics for the above variables as the correlation coefficient, root mean square error, and normalized standard deviation between the observations and calculations in the dry and wet periods suggest that the model was able to simulate the observed energy fluxes, soil evaporation, and transpiration in savanna grassland ecosystems.

Effect of interaction of embedded crack and free surface on remaining fatigue life

Katsumata, Genshichiro*; Lacroix, V.*; Li, Y.

AIMS Materials Science, 3(4), p.1748 - 1758, 2016/12

https://doi.org/10.3934/matersci.2016.4.1748

Gamma radiation resistance of spin Seebeck devices

Yagmur, A.*; Uchida, Kenichi*; Ihara, Kazuki*; Ioka, Ikuo; Kikkawa, Takashi*; Ono, Madoka*; Endo, Junichi*; Kashiwagi, Kimiaki*; Nakashima, Tetsuya*; Kirihara, Akihiro*; et al.

Applied Physics Letters, 109(24), p.243902_1 - 243902_4, 2016/12

https://doi.org/10.1063/1.4971976

Thermoelectric devices based on the spin Seebeck effect (SSE) were irradiated with gamma () rays with the total dose of around 310 Gy in order to investigate the -radiation resistance of the devices. To demonstrate this, Pt/NiZnFeO/Glass and Pt/BiYFeO/GdGaO SSE devices were used. We confirmed that the thermoelectric, magnetic, and structural properties of the SSE devices are not affected by the -ray irradiation. This result demonstrates that SSE devices are applicable to thermoelectric generation even in high radiation environments.

A Trajectory generation method for mobile robot based on iterative extension-like process

Kawabata, Kuniaki

Artificial Life and Robotics, 21(4), p.500 - 509, 2016/12

https://doi.org/10.1007/s10015-016-0305-6

In this paper, we propose a trajectory generation method for mobile robot based on iterative extension-like process. Due to use mobile robots in the real world, trajectory generation must be done depending on the faced situation on each occasion. Proposed method enables online iterative trajectory extension process based on a low-order polynomial curve named as trajectory segment. The waypoints on the existing trajectory segment and a waypoint designated every fixed interval are the constraints to trigger the trajectory extension. For maintaining the smooth continuity of the trajectory, the velocity state must be sustained at the connecting point. Resultantly, the trajectory segments are organized into a single smooth trajectory.

Erratum; Effects of OH activity and temperature on the dissolution rate of compacted montmorillonite under highly alkaline conditions [Clay Minerals, vol.51, p.275 (2016), Corrected Fig. 7.]

Sawaguchi, Takuma; Tsukada, Manabu; Yamaguchi, Tetsuji; Mukai, Masayuki

Clay Minerals, 51(5), P. 815, 2016/12

http://claymin.geoscienceworld.org/content/51/5/815

ERRATUM; Effects of OH activity and temperature on the dissolution rate of compacted montmorillonite under highly alkaline conditions [Clay Minerals, vol.51, p.275 (2016), Corrected Fig. 7.]

First ionization potential of the heaviest actinide lawrencium, element 103

Sato, Tetsuya; Asai, Masato; Borschevsky, A.*; Stora, T.*; Sato, Nozomi*; Kaneya, Yusuke; Tsukada, Kazuaki; Dllmann, C. E.*; Eberhardt, K.*; Eliav, E.*; et al.

EPJ Web of Conferences, 131, p.05001_1 - 05001_6, 2016/12

https://doi.org/10.1051/epjconf/201613105001

Ionization efficiency in a surface ionization process depends on the first ionization potential of the atom. Based on the dependence, the ionization potential of the atom can be determined. We measured ionization efficiencies of fermium, einsteinium, mendelevium, and lawrencium by using a newly developed gas-jet coupled surface ion-source. The ionization potential of the elements have not been determined so far due to their low production rates and/or their short half-lives. Based on a relationship between the ionization efficiency and the ionization potential obtained via measurements of short-lived lanthanide isotopes, the ionization potentials of these actinide elements have been successfully determined.

Thermochronological contribution to the Crustal Dynamics Project

Tagami, Takahiro*; Sueoka, Shigeru; Kohn, B. P.*; Fukuda, Shoma*

Fisshion, Torakku Nyusureta, (29), p.1 - 2, 2016/12

http://ftrgj.org/FTNLs/FTNLparts/tagami16.pdf

no abstracts in English

Report on 40th Annual Meeting of Fission Track Research Group in Japan

Sueoka, Shigeru

Fisshion, Torakku Nyusureta, (29), p.29 - 34, 2016/12

http://ftrgj.org/FTNLs/FTNLparts/sueokakiji16.pdf

no abstracts in English

Characteristics of micro transfer paths and diffusion phenomena in the matrix of deep crystalline rock

Ishibashi, Masayuki; Sasao, Eiji; Hama, Katsuhiro

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 23(2), p.121 - 130, 2016/12

http://doi.org/10.3327/jnuce.23.2_121

Matrix diffusion is one of the important phenomena for safety assessment of radioactive waste disposal because it has an effect of retarding the mass transport in crystalline rocks. Although there is not enough knowledge on the matrix diffusion in unaltered (intact) rocks around fractures. Intact granitic rocks around fractures are affected by primary alteration related to hydrothermal fluid resulting from crystallization of granitic magma. Therefore, detailed observations were carried out to clarify the effects of primary alteration focused on the intact granite around fractures sampled from the MIU, central Japan. The results of observation provide that the micropores are formed in plagioclases affected by primary alteration and have the potential of acting as matrix diffusion paths. This is indicating the possibility that intact granitic rock around fractures in an orogenic belt such as Japan have also the retardation functions due to matrix diffusion.

Additional information to report on site tour of the Fukushima Daiichi Nuclear Power Station

Suto, Toshiyuki

Genshiryoku, hoshasen Bukaiho (Internet), (19), P. 15, 2016/12

The Tritiated Water Task Force under METI's Committee on Countermeasures for Contaminated Water Treatment for Fukushima Daiichi Nuclear Power Plant (1F) reported that the option of post-dilution offshore release could dispose the tritiated water at a smallest cost in the shortest amount of time. The amount of tritium in the contaminated water at 1F was compared with ones released from nuclear power plants and reprocessing plants as some help for grasping its level of magnitude.

Report on the Workshop "Radiation Research Based on Computer Simulation" held at the 59th Annual Meeting of the Japanese Radiation Research Society

Sato, Tatsuhiko; Hamada, Nobuyuki*

Hoshasen Seibutsu Kenkyu, 51(4), p.397 - 401, 2016/12

A workshop entitled "Radiation Research Based on Computer Simulation" was held at the 59th annual meeting of the Japanese Radiation Research Society. Approximately 50 participants attended the workshop, and six speakers gave a talk about their computational radiation biology studies. The title of the presentations are "Research on DNA damage and track structure simulation", "Study of cellular response based on stochastic model for simulating irradiated and non-irradiated cells", "Effectiveness of mathematical model for low-dose radiation effect", "Research on particle therapy based on cell surviving fraction model", "Development of model for natural induction of cataract", and "Mathematical model for carcinogenesis considering the differences of temporal and spatial doses". In the workshop, possible future collaborations were intensively discussed. This report briefly summarizes the outline of the workshop.

Simultaneous recovery and separation of rare earth elements in ferromanganese nodules by using

Fujimoto, Jun*; Tanaka, Kazuya; Watanabe, Naoko*; Takahashi, Yoshio*

Hydrometallurgy, 166, p.80 - 86, 2016/12

https://doi.org/10.1016/j.hydromet.2016.09.005

We examined recovery of REEs in Fe-Mn nodules by using (Fe-reducing bacterium). In this method, Fe-Mn nodule decomposition and REE recovery were achieved simultaneously in a single solution system. Fe-Mn nodules were reductively decomposed in NaCl solution under anaerobic conditions with daily addition of sodium lactate as an electron donor. During the decomposition of Fe-Mn nodule, REEs released from the Fe-Mn nodule were adsorbed on bacterial cells. Of the conditions studied here, the best REE adsorption rates were obtained with 0.5M NaCl solution at pH7 with daily addition of 1 mmol sodium lactate.

Solvent extraction and synergistic effect using an ionic liquid

Okamura, Hiroyuki; Shimojo, Kojiro

Ion Ekitai Kenkyu Saizensen To Shakai Jisso, p.220 - 227, 2016/12

Solvent extraction is a separation method based on the difference in the distribution of solutes between two immiscible liquid phases. Recently, ionic liquids have been widely investigated as novel extraction media. Solvent properties of an ionic liquid can be adjusted by combination of a cationic and an anionic component. It is, therefore, possible to provide an attractive reaction field as an extraction medium. In this article, specific extraction phenomena observed in the ionic liquid extraction system for metal ions were introduced.

The Effect of oxidation-and-quenching process during a LOCA on the behavior of the oxidation and embrittlement of Zircaloy-4 cladding under reheating transients

Miwa, Hideki; Amaya, Masaki

Journal of Nuclear Science and Technology, 53(12), p.2090 - 2097, 2016/12

https://doi.org/10.1080/00223131.2016.1198730

Two-sided oxidation tests, ring compression tests and semi-integral quench tests on Zircaloy-4 cladding specimens were conducted under the temperature transient conditions simulating a post-quench reheat transient in order to evaluate the effect of high temperature oxidation and quenching during a LOCA on the behavior of the oxidation and embrittlement of the cladding under a loss of long-term-core-cooling condition. Test specimens prepared from non-irradiated Zircaloy-4 cladding tube were oxidized at a temperature between 1173 and 1473 K in steam flow and quenched by soaking the specimen in room temperature water. By using the test specimens, re-heating tests were performed in steam flow at a temperature between 1173 and 1473 K. The suppression of oxide layer growth and weight gain was observed under certain reheating-after-quenching conditions. Nevertheless, it seemed that the temperature transients including quenching-and-reheating process did not significantly affect the embrittlement of cladding. It was found that the embrittlement behavior of cladding during the temperature transients including quenching-and-reheating process could be dealt with on the basis of the ECR based on Baker-Just correlation.

The Welded joint strength reduction factors of modified 9Cr-1Mo Steel for the advanced loop-type sodium cooled fast reactor

Yamashita, Takuya; Wakai, Takashi; Onizawa, Takashi; Sato, Kenichiro*; Yamamoto, Kenji*

Journal of Pressure Vessel Technology, 138(6), p.061407_1 - 061407_6, 2016/12

https://doi.org/10.1115/1.4034017

Development of inspection and repair techniques in reactor vessel of experimental fast reactor "Joyo"; Retrieval of the bent test subassembly

Ashida, Takashi; Ito, Hideaki; Miyamoto, Kazuyuki*; Nakamura, Toshiyuki; Koga, Kazuhiro*; Ohara, Norikazu*; Ino, Hiroichi*

Nihon Genshiryoku Gakkai Wabun Rombunshi, 15(4), p.210 - 222, 2016/12

https://doi.org/10.3327/taesj.J15.032

In the experimental fast reactor Joyo, it was confirmed that the top of the irradiation test sub-assembly of material testing rig named "MARICO-2" had been broken and bent onto the in-vessel storage rack as an obstacle and had damaged the upper core structure (UCS). As the result, for Joyo restart, it was necessary to replace the damaged UCS and to retrieve the bent sub-assembly. This paper describes in-vessel repair techniques performed in the retrieval work of the obstacle inside of the reactor vessel. The devices which were prepared for this work demonstrated expected performance under the environmental conditions of an SFR such as high temperature and radiation dose, and the work was completed in 2014. The successful operation of this retrieval work of the damaged component inside of a reactor vessel will contribute to the development of in-service inspections and repair technics in an SFR.

Creep-fatigue evaluation method for weld joint of Mod.9Cr-1Mo steel, 2; Plate bending test and proposal of a simplified evaluation method

Ando, Masanori; Takaya, Shigeru

Nuclear Engineering and Design, 310, p.217 - 230, 2016/12

AA2016-0318.pdf:2.62MB

https://doi.org/10.1016/j.nucengdes.2016.10.025

In the present study, to develop an evaluation procedure and design rules for Mod.9Cr-1Mo steel weld joints, a method for creep-fatigue life evaluation of Mod.9Cr-1Mo steel weld joints was proposed based on the finite element analysis (FEA) results with a series of cyclic plate bending tests of the longitudinal and horizontal seamed plates. The strain concentration and redistribution behaviors were evaluated and failure cycles were estimated using FEA by considering the test conditions and metallurgical discontinuities in the weld joints. The elastic follow-up factors calculated from a comparison of the elastic and inelastic FEA results were determined to be less than 1.5. Based on the estimated elastic follow-up factors obtained via inelastic FEA, a simplified technique using elastic FEA was proposed for evaluating the creep-fatigue life in Mod.9Cr-1Mo steel weld joints.

Dissolution behavior of lithium compounds in ethanol

Furukawa, Tomohiro; Hirakawa, Yasushi; Kondo, Hiroo; Kanemura, Takuji

Nuclear Materials and Energy (Internet), 9, p.286 - 291, 2016/12

BB2015-1402.pdf:3.16MB

https://doi.org/10.1016/j.nme.2016.05.005

In order to exchange the components which received irradiation damage during the operation at the International Fusion Materials Irradiation Facility, the adhered lithium, which is partially converted to lithium compounds such as lithium oxide and lithium hydroxide, should be removed from the components. In this study, the dissolution experiments of lithium compounds (lithium nitride, lithium hydroxide, and lithium oxide) were performed in a candidate solvent, allowing the clarification of time and temperature dependence. Based on the results, a cleaning procedure for adhered lithium on the inner surface of the components was proposed.

Tensile properties and hardness of two types of 11Cr-ferritic/martensitic steel after aging up to 45,000 h

Yano, Yasuhide; Tanno, Takashi; Sekio, Yoshihiro; Oka, Hiroshi; Otsuka, Satoshi; Uwaba, Tomoyuki; Kaito, Takeji

Nuclear Materials and Energy (Internet), 9, p.324 - 330, 2016/12

BB2015-1728.pdf:1.04MB

https://doi.org/10.1016/j.nme.2016.08.007

Overview and outcomes of the OECD/NEA benchmark study of the accident at the Fukushima Daiichi Nuclear Power Station

Nagase, Fumihisa; Gauntt, R. O.*; Naito, Masanori*

Nuclear Technology, 196(3), p.499 - 510, 2016/12

https://doi.org/10.13182/NT16-10

The OECD/NEA Benchmark Study of the Accident at the Fukushima Daiichi Nuclear Power Station (BSAF) project was established in November 2012. The primary objectives of this benchmark study are to estimate accident progression and status inside the nuclear reactors, including fuel debris distribution, and consequently to contribute to the decommissioning activity at the Fukushima Daiichi Nuclear Power Plant. Fifteen organizations of eight countries calculated thermo-hydraulic behavior inside the three reactors for the time span of about six days from the occurrence of the earthquake with their severe accident integral codes. The submitted results were compared on coolant level change, hydrogen generation, initiation and progression of melt in fuel bundle and control blade, failure of reactor pressure vessel, distribution and composition of molten and solidified materials, and progression of molten core concrete interaction. This issue summarizes the results of the comparison and discussion with still remaining uncertainties and data needs as the output from the project.

Superconductivity in repulsively interacting fermions on a diamond chain; Flat-band-induced pairing

Kobayashi, Keita*; Okumura, Masahiko; Yamada, Susumu; Machida, Masahiko; Aoki, Hideo*

Physical Review B, 94(21), p.214501_1 - 214501_7, 2016/12

https://doi.org/10.1103/PhysRevB.94.214501

no abstracts in English

Measurements of double-helicity asymmetries in inclusive production in longitudinally polarized collisions at GeV

Adare, A.*; Imai, Kenichi; Hasegawa, Shoichi; Nagamiya, Shoji; Sako, Hiroyuki; Sato, Susumu; Tanida, Kiyoshi; PHENIX Collaboration*; 328 of others*

Physical Review D, 94(11), p.112008_1 - 112008_10, 2016/12

AA2016-0475.pdf:0.51MB

https://doi.org/10.1103/PhysRevD.94.112008

Flow-sheet study of MA recovery by extraction chromatography for SmART cycle project

Watanabe, So; Nomura, Kazunori; Kitawaki, Shinichi; Shibata, Atsuhiro; Kofuji, Hirohide; Sano, Yuichi; Takeuchi, Masayuki

Procedia Chemistry, 21, p.101 - 108, 2016/12

BB2015-3215.pdf:0.34MB

https://doi.org/10.1016/j.proche.2016.10.015

Uranium and plutonium extraction by -dialkylamides using multistage mixer-settler extractors

Ban, Yasutoshi; Hotoku, Shinobu; Tsutsui, Nao; Suzuki, Asuka; Tsubata, Yasuhiro; Matsumura, Tatsuro

Procedia Chemistry, 21, p.156 - 161, 2016/12

https://doi.org/10.1016/j.proche.2016.10.022

A continuous counter-current experiment was carried out to demonstrate the validity of a process using -dialkylamides for recovering U and Pu. This process consisted of two cycles, and the 1st cycle and the 2nd cycle employed -di(2-ethylhexyl)-2,2-dimethylpropanamide and -di(2-ethylhexyl)butanamide as extractants, respectively. The feed solution for the 1st cycle was 5.1 mol/dm (M) nitric acid containing 0.92 M U, 1.6 mM Pu, and 0.6 mM Np. The raffinate collected in the 1st cycle was used as the feed for the 2nd cycle. The ratios of U recovered in the U fraction and U-Pu fraction were 99.1% and 0.8%, respectively. The ratio of Pu recovered in the U-Pu fraction was 99.7%. The concentration ratio of U with respect to Pu in the U-Pu fraction was 9, and this indicated that Pu was not isolated. The decontamination factor of U with respect to Pu in the U fraction was obtained as 4.510. These results supported the validity of the proposed process.

Dynamics in condensed matter by 4SEASONS

Kajimoto, Ryoichi

Radioisotopes, 65(12), p.523 - 534, 2016/12

https://doi.org/10.3769/radioisotopes.65.523

no abstracts in English

Forest type effects on the retention of radiocesium in organic layers of forest ecosystems affected by the Fukushima nuclear accident

Koarashi, Jun; Atarashi-Andoh, Mariko; Matsunaga, Takeshi; Sanada, Yukihisa

Scientific Reports (Internet), 6, p.38591_1 - 38591_11, 2016/12

https://doi.org/10.1038/srep38591

Forest-floor organic layers play a key role in controlling the overall bioavailability of Cs in forest ecosystems; however, there is still an insufficient understanding of how forest types influence the retention capability of Cs in organic layers in Japanese forest ecosystems. Here we conducted plot-scale investigations on the retention of Cs in organic layers at two contrasting forest sites in Fukushima. In a deciduous broad-leaved forest, approximately 80% of the deposited Cs migrated to mineral soil located below the organic layers within two years after the accident, with an ecological half-life of approximately one year. Conversely, in an evergreen coniferous forest, more than half of the deposited Cs remained in the organic layers, with an ecological half-life of 2.1 years. The observed retention behavior can be well explained by the tree phenology and accumulation of Cs associated with litter materials with different degrees of degradation in the organic layers.

Efforts in the "Fugen"; The History of up to termination of operation and Efforts of decommissioning measures

Morishita, Yoshitsugu

Denki Hyoron, 101(11), p.24 - 29, 2016/11

no abstracts in English

Impact of mesoscale recirculation of the Kuroshio on asymmetric oceanic structure around Okinawa Island

Uchiyama, Yusuke*; Odani, Sachika*; Yamanishi, Takafumi*; Kamidaira, Yuki; Mitarai, Satoshi*

Doboku Gakkai Rombunshu, B2 (Kaigan Kogaku) (Internet), 72(2), p.I_481 - I_486, 2016/11

http://doi.org/10.2208/kaigan.72.I_481

no abstracts in English

Synthesis and characteristics of ternary Be-Ti-V beryllide pebbles as advanced neutron multipliers

Kim, Jae-Hwan; Nakamichi, Masaru

Fusion Engineering and Design, 109-111(Part B), p.1764 - 1768, 2016/11

https://doi.org/10.1016/j.fusengdes.2015.09.015

Novel neutron scattering techniques using neutron transmission spectra

Oba, Yojiro*; Morooka, Satoshi; Sato, Hirotaka*; Sato, Nobuhiro*; Inoue, Rintaro*; Sugiyama, Masaaki*

Hamon, 26(4), p.170 - 173, 2016/11

https://doi.org/10.5611/hamon.26.4_170

Evaluation of DNA damage induced by Auger electrons from Cs

Watanabe, Ritsuko; Hattori, Yuya; Kai, Takeshi

International Journal of Radiation Biology, 92(11), p.660 - 664, 2016/11

https://doi.org/10.3109/09553002.2015.1136853

To understand the effect of internal exposure of Cs, we focus on estimation of microscopic energy deposition pattern and DNA damage induced by directly emitted electrons (beta-rays, internal conversion electrons, Auger electrons) from Cs. Monte Carlo track simulation method was used to calculate the microscopic energy deposition pattern. To simulate the energy deposition by directly emitted electrons, we considered the multiple ejections of electrons after internal conversion. Induction process of DNA strand breaks and base lesions was modeled and simulated using Monte Carlo methods for cell mimetic condition. The yield and spatial distribution of simple and complex DNA damage were calculated for the cases of -rays and electrons from Cs. The simulation showed that significant difference of DNA damage spectrum was not caused by the difference between secondary electron spectrum by -rays and directly ejected electron spectrum. The result support that the existing evaluation that internal exposure and external exposure are almost equivalent.

Review of the microdosimetric studies for high-energy charged particle beams using a tissue-equivalent proportional counter

Tsuda, Shuichi; Sato, Tatsuhiko; Ogawa, Tatsuhiko; Sasaki, Shinichi*

JPS Conference Proceedings (Internet), 11, p.060004_1 - 060004_6, 2016/11

https://doi.org/10.7566/JPSCP.11.060004

Track structure and energy deposition around charged particle beams in microscopic site of a living cell is important information for understanding of biological effects of energetic heavy ion beams. In this work, measurements of lineal energy () distributions for various kinds of ion beams have been performed for the verification of the microdosimetric function that incorporated in the PHITS code. In the international symposium focused on radiation detectors, the wall-less tissue equivalent proportional counter that developed in this study to measure distributions will be introduced, together with a series of data.

Performance of Panasonic ZP-1460 electronic personal dosemeter under exposure conditions likely to be found at Fukushima Daiichi Nuclear Power Plant

Tsujimura, Norio; Yoshida, Tadayoshi; Hoshi, Katsuya; Momose, Takumaro

JPS Conference Proceedings (Internet), 11, p.070008_1 - 070008_6, 2016/11

https://doi.org/10.7566/JPSCP.11.070008

The Evaluation of the 0.07 mm and 3 mm dose equivalent with a portable beta spectrometer

Hoshi, Katsuya; Yoshida, Tadayoshi; Tsujimura, Norio; Okada, Kazuhiko

JPS Conference Proceedings (Internet), 11, p.070009_1 - 070009_6, 2016/11

https://doi.org/10.7566/JPSCP.11.070009

Beta spectra of various nuclide species were measured by commercially available compact spectrometer. The shape of spectra obtained from the spectrometer approximately agreed with that of theoretical spectra. The beta dose equivalent at any depths has been able to be obtained as a product of measured pulse height spectra and appropriate conversion coefficients of ICRP Publ. 74. The dose rates evaluated from the spectra were comparable to the reference dose rates of standard beta calibration sources. And, we were able to determine the dose equivalent with relative error of indication of 10% without the complicated correction.

Influence of temperature histories during reactor startup periods on microstructural evolution and mechanical properties of austenitic stainless steel irradiated with neutrons

Kasahara, Shigeki; Kitsunai, Yuji*; Chimi, Yasuhiro; Chatani, Kazuhiro*; Koshiishi, Masato*; Nishiyama, Yutaka

Journal of Nuclear Materials, 480, p.386 - 392, 2016/11

https://doi.org/10.1016/j.jnucmat.2016.06.017

This paper addresses influence of two different temperature profiles during startup periods in the Japan Materials Testing Reactor and a boiling water reactor upon microstructural evolution and mechanical properties of austenitic stainless steel irradiated with neutrons to about 1 dpa and 3 dpa. Tensile tests at 290C and Vickers hardness tests at room temperature were carried out, and their microstructures were observed by FEG-TEM. Influence of difference in the temperature profiles was observed obviously in interstitial cluster formation, in particular, growth of Frank loops. The influence was also found certainly in loss of strain hardening capacity and ductility, although the influence on the yield strength and the Vickers hardness was not clearly observed. As a result, Frank loops, which were observed in austenitic stainless steel irradiated at doses of 1 dpa or more, were considered to contribute to deformation of the austenitic stainless steel.

Nanoscopic structural investigation of physically cross-linked nanogels formed from self-associating polymers

Sekine, Yurina; Endo, Hitoshi*; Iwase, Hiroki*; Takeda, Shigeo*; Mukai, Sadaatsu*; Fukazawa, Hiroshi; Littrell, K. C.*; Sasaki, Yoshihiro*; Akiyoshi, Kazunari*

Journal of Physical Chemistry B, 120(46), p.11996 - 12002, 2016/11

https://doi.org/10.1021/acs.jpcb.6b06795

The detailed structure of a nanogel formed by self-association of cholesterol-bearing pullulans (CHP) was determined by contrast variation small-angle neutron scattering. The decomposition of scattering intensities into partial scattering functions of each CHP nanogel component, i.e., pullulan, cholesterol, and the cross-term between the pullulan and the cholesterol allows us to investigate the internal structure of the nanogel. The effective spherical radius of the skeleton formed by pullulan chains was found to be about 8.1 nm. In the CHP nanogel, there are about 19 cross-linking points where a cross-linking point is formed by aggregation of trimer cholesterol molecules with the spatially inhomogeneous distribution of the mass fractal dimension of 2.6. The average radius of the partial chains can also be determined to be 1.7 nm. As the result, the complex structure of the nanogels is coherently revealed at the nanoscopical level.

Texture measurement of A1050 aluminum alloy using neutron diffraction

Xu, P. G.; Harjo, S.; Onuki, Yusuke*

Kako To Netsushori Niyoru Yusen Hoi Seigyo, p.1 - 6, 2016/11

no abstracts in English

Survey and countermeasures on radiocesium inflow into a laboratory building for radioactivity analysis

Kurita, Yoshiyuki; Saegusa, Jun; Maeda, Satoshi

Nihon Hoshasen Anzen Kanri Gakkai-Shi, 15(2), p.180 - 185, 2016/11

http://doi.org/10.11269/jjrsm.15.180

In 2012, JAEA has established a laboratory in Fukushima-city to implement radioactivity analysis of environmental samples. Key nuclides measured in this laboratory are Cs and Cs (radiocesium). For the purpose, situation of radiocesium inflow into the laboratory building and its effects were investigated based on high-resolution gamma-spectrometry with germanium detectors. As a result, the surface density of radiocesium in the laboratory was found to be far below the minimum detectable activities of survey instruments routinely used for radiation control purposes.

Spin transport in half-metallic ferromagnets

Onuma, Yuichi; Matsuo, Mamoru; Maekawa, Sadamichi

Physical Review B, 94(18), p.184405_1 - 184405_5, 2016/11

https://doi.org/10.1103/PhysRevB.94.184405

We theoretically investigate spin transport in half-metallic ferromagnets at finite temperatures. The side-jump and skew-scattering contributions to spin Hall conductivity are derived using the Kubo formula. The electron-magnon interaction causes a finite density of states in the energy gap of the minority-spin band and induces spin Hall conductivity. We show that spin Hall conductivity is proportional to , with being temperature and is sensitive to . We propose that spin Hall conductivity may be a tool to study the minority-spin state.

Nitrogen hot trap design and manufactures for lithium test loop in IFMIF/EVEDA project

Wakai, Eiichi; Watanabe, Kazuyoshi*; Ito, Yuzuru*; Suzuki, Akihiro*; Terai, Takayuki*; Yagi, Juro*; Kondo, Hiroo; Kanemura, Takuji; Furukawa, Tomohiro; Hirakawa, Yasushi; et al.

Plasma and Fusion Research (Internet), 11, p.2405112_1 - 2405112_4, 2016/11

BB2015-1982.pdf:2.03MB

http://doi.org/10.1585/pfr.11.2405112

CFD simulation of a CIGMA experiment CC-PL-04 on the containment thermal hydraulics affected by the outer surface cooling

Ishigaki, Masahiro; Abe, Satoshi; Shibamoto, Yasuteru; Yonomoto, Taisuke

Proceedings of 10th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-10) (USB Flash Drive), 10 Pages, 2016/11

no abstracts in English

Analysis with CFD code for THAI test on thermal-hydraulics during PAR activation

Sato, Masatoshi; Matsumoto, Toshinori; Sugiyama, Tomoyuki; Maruyama, Yu

Proceedings of 10th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-10) (USB Flash Drive), 10 Pages, 2016/11

Event sequence analyses of a forest fire heat effect on a sodium-cooled fast reactor for an external hazard PRA methodology development

Okano, Yasushi; Yamano, Hidemasa

Proceedings of 10th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-10) (USB Flash Drive), 9 Pages, 2016/11

This paper deals with an event sequence by forest fire heat effect on a decay heat removal function of a sodium-cooled fast reactor. Related to the potential vulnerability, an event scenario was developed using conservative assumptions. An event tree was developed with an initiating event of the loss of off-site power, and the headings are related to "external diesel fuel tanks", "emergency diesel generator and its auxiliary system", "alternative cooling system and its power source", and "decay heat air cooler". A failure probability on each heading was given from a fragility curve as a function of reaction intensity or by assumptions based on conservative models. A core damage frequency, under the conditional of the loss of off-site power, was conservatively evaluated around 10/year. A key heading in the event tree with large effect on the frequency is the intactness of the external diesel fuel tanks.

Event sequence analysis of core disruptive accident in a metal-fueled sodium-cooled fast reactor

Yamano, Hidemasa; Tobita, Yoshiharu; Kubo, Shigenobu; Ueda, Nobuyuki*

Proceedings of 10th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-10) (USB Flash Drive), 10 Pages, 2016/11

In this study, the event sequence analysis of CDA in a large metal-fueled SFR has been performed in order to investigate reactivity progression and molten fuel relocation behavior in the metal-fueled SFR. The initiating phase analysis during the CDA initiated by unprotected loss-of-flow accidents has been conducted using the CANIS code, which showed a small power peak. Using the initial conditions based on the initiating phase analysis, the SIMMER-III code was applied to a whole-core scale analyses to clarify the event sequence including the reactivity progression and molten fuel relocation. As a result, recriticality in the whole core analysis resulted in a very mild energy release. The mild energy release in the metal-fueled core can be attributed to the small specific heat of metal fuel and the large prompt negative reactivity feedback mechanism.

In-vessel retention of unprotected accident in a fast reactor; Assessment of material-relocation and heat-removal behavior in ULOF

Sogabe, Joji; Suzuki, Toru; Wada, Yusaku; Tobita, Yoshiharu

Proceedings of 10th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-10) (USB Flash Drive), 7 Pages, 2016/11

Experimental database for bed formation behaviors of solid particles

Sheikh, M. A. R.*; Son, E.*; Kamiyama, Motoki*; Morioka, Toru*; Matsumoto, Tatsuya*; Morita, Koji*; Matsuba, Kenichi; Kamiyama, Kenji; Suzuki, Toru

Proceedings of 10th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-10) (USB Flash Drive), 10 Pages, 2016/11

During the material relocation phase of core disruptive accidents in sodium-cooled fast reactors, the sedimentation behavior of fragmented debris leading to the formation of debris beds is crucial for in-vessel retention by debris bed cooling. In this study, a series of experiments using simulant materials was performed to develop an experimental database of bed formation behavior by gravity driven discharge of solid particles from a nozzle into a quiescent cylindrical water pool. The bed height as well as the bed shape was measured. Three types of spherical and non-spherical particles, namely AlO, ZrO and stainless steel with different size were employed to study the effect of key experimental parameter on debris bed mound shape. Based on the experimental results, an empirical correlation as experimental database was proposed to predict the particle bed height. The proposed correlation reasonably reproduces the experimental trend of the bed height variation on the crucial factors. This result demonstrates a wide applicability of the proposed empirical model to predict the bed height in terms of all crucial factors with reasonable accuracy.

Production of droplets during liquid jet impingement onto a flat plate

Yi, Z.*; Oya, Naoki*; Enoki, Koji*; Okawa, Tomio*; Ohno, Shuji; Aoyagi, Mitsuhiro; Takata, Takashi

Proceedings of 10th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-10) (USB Flash Drive), 7 Pages, 2016/11

It is important to set the amount of sodium droplet mechanistically for appropriate numerical evaluations of sodium leak and fire behavior in a sodium-cooled fast reactor plant. In the present work, fundamental experiments were performed to measure the splash ratio during the vertical water jet impact onto a horizontal wall. It was shown that the splash ratio can be correlated well as a function of the impact Weber number, the Strouhal number and the Ohnesorge number of the droplets impinging the liquid film.

Development of air cooling performance evaluation method for fuel debris on retrieval of Fukushima Daiichi NPS by dry method, 1; Outline of research project

Yoshida, Hiroyuki; Uesawa, Shinichiro; Yamashita, Susumu; Nagase, Fumihisa

Proceedings of 10th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-10) (USB Flash Drive), 7 Pages, 2016/11

Development of evaluation method for hydraulic behavior in venturi scrubber for filtered venting

Horiguchi, Naoki; Yoshida, Hiroyuki; Nakao, Yasuhiro*; Kaneko, Akiko*; Abe, Yutaka*

Proceedings of 10th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-10) (USB Flash Drive), 7 Pages, 2016/11