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Journal Articles

Experimental evaluation of wall shear stress in a double contraction nozzle using a water mock-up of a liquid Li target for an intense fusion neutron source

Kondo, Hiroo*; Kanemura, Takuji*; Park, C. H.*; Oyaizu, Makoto*; Hirakawa, Yasushi; Furukawa, Tomohiro

Fusion Engineering and Design, 146(Part A), p.285 - 288, 2019/09

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

Herein, the wall shear stress in a double contraction nozzle has been evaluated experimentally to produce a liquid lithium (Li) target as a beam target for intense fusion neutron sources such as the International Fusion Materials Irradiation Facility (IFMIF), the Advanced Fusion Neutron Source (A-FNS), and the DEMO Oriented Neutron Source (DONES). The boundary layer thickness and wall shear stress are essential physical parameters to understand erosion-corrosion by the high-speed liquid Li flow in the nozzle, which is the key component in producing a stable Li target. Therefore, these parameters were experimentally evaluated using an acrylic mock-up of the target assembly. The velocity distribution in the nozzle was measured by a laser-doppler velocimeter and the momentum thickness along the nozzle wall was calculated using an empirical prediction method. The resulting momentum thickness was used to estimate the variation of the wall shear stress along the nozzle wall. Consequently, the wall shear stress was at the maximum in the second convergent section in front of the nozzle exit.

Journal Articles

Study on analysis method for inert gas behavior in liquid metal flow with considering dissolution and entrainment at free surface

Matsushita, Kentaro; Ito, Kei*; Ezure, Toshiki; Tanaka, Masaaki

Dai-24-Kai Doryoku, Enerugi Gijutsu Shimpojiumu Koen Rombunshu (USB Flash Drive), 5 Pages, 2019/06

In the design study on a sodium-cooled fast reactor (SFR), a numerical simulation code named SYRENA has been developed in Japan Atomic Energy Agency to analyze the behavior of gas bubbles and/or dissolved gas in the primary coolant system. In the present study, the effect of the non-condensable gas entrainment at the free surface on the bubble and the dissolved gas behavior in the primary coolant system were investigated for a typical pool type reactor, and also effect of a dipped-plate (D/P) installed below the free surface in the reactor vessel to suppress the gas bubble entrainment into the primary coolant system was especially investigated. It was clarified that the D/P was influential to the non-condensable gas behavior and the molar flow rate of gas bubbles in the primary coolant system varies depending on the relationship between the gas entrainment rate at the free surface and the exchange flow rate through the D/P.

Journal Articles

Parametric analysis of bubble and dissolved gas behavior in primary coolant system of sodium-cooled fast reactors

Matsushita, Kentaro; Ito, Kei*; Ezure, Toshiki; Tanaka, Masaaki

Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 9 Pages, 2019/05

A numerical simulation code named SYRENA has been developed in JAEA to analyze the behavior of entrained bubbles and dissolved gas in the primary coolant of sodium-cooled fast reactor (SFR). In the present study, a flow network model of SYRENA to a hypothetical pool type reactor was developed and the non-condensable gas behavior was investigated through the comparison with that in the loop type reactor. The effect of the dipped-plate (D/P) tentatively introduced into the pool-type reactor on the gas behavior was investigated through the parametric analyses about the sodium exchange flow rate through the D/P and the gas entrainment rate at the free surface. It was suggested that the increase in the exchange flow rate through the D/P doesn't always work to decrease the bubble volume in the primary coolant system.

Journal Articles

Conceptual design and verification of long-distance laser-probe system for Li target diagnostics of intense fusion neutron source

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

Fusion Engineering and Design, 136(Part A), p.24 - 28, 2018/11

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

In the IFMIF-EVEDA project, we designed and constructed the IFMIF-EVEDA Li Test Loop (ELTL), and we performed experiments to validate the stability of the Li target. This project required a diagnostic tool to be developed in order to examine the Li target; as such, we developed a unique laser-based method that we call the laser-probe method; this method combines a high-precision laser distance meter with a statistical data analysis method. Following the successful development of the laser-probe method, we proposes a long-distance-measurement of the laser probe method (long-distance LP method) as a diagnostics tool in off-beam conditions for IFMIF or the relevant neutron sources. In this study, the measurement uncertainty resulting from coherency of the laser in a long-distance-measurement has been verified by using stationary objects and a water jet simulating the liquid Li target.

Journal Articles

Development on high-power spallation neutron sources with liquid metals

Futakawa, Masatoshi

Proceedings of 13th International Symposium on Advanced Science and Technology in Experimental Mechanics (13th ISEM'18) (USB Flash Drive), 6 Pages, 2018/10

Issues on the engineering technologies relating to high-power spallation neutron sources with liquid metals are introduced. The present status on research activities and results was reviewed.

Journal Articles

Oxidation characteristics of lead-alloy coolants in air ingress accident

Kondo, Masatoshi*; Okubo, Nariaki; Irisawa, Eriko; Komatsu, Atsushi; Ishikawa, Norito; Tanaka, Teruya*

Energy Procedia, 131, p.386 - 394, 2017/12

 Times Cited Count:3 Percentile:5.9

The chemical behaviors of lead (Pb) based coolants in the air ingress accident of fast reactors were investigated by means of the thermodynamic considerations and the static oxidation experiments for Pb alloys at various chemical compositions. The results of the static oxidation tests for lead-bismuth (Pb-Bi) alloys indicated that Pb was depleted from the alloy due to the preferential formation of PbO in air at 773K. Pb-Bi oxide and Bi$$_{2}$$O$$_{3}$$ were formed after the enrichment of Bi in the alloys due to the Pb depletion. The oxidation rates of the alloys were much larger than that of the steels, and became larger with higher Pb concentration in the alloys. The compatibility of Pb-Bi alloys with stainless steel was worse when the Pb concentration in the alloys became low, since the dissolution type corrosion was promoted by the Bi composition in the alloy. The Pb-Li alloys were oxidized as they formed Li$$_{2}$$PbO$$_{3}$$ and Li$$_{2}$$CO$$_{3}$$. Then, Li was depleted from the alloy.

Journal Articles

Effect of oxidizing metallic ions on corrosion of stainless steel during concentration process simulating High-level Activity Liquid Waste (HALW) concentrator

Irisawa, Eriko; Kato, Chiaki; Kamoshida, Michio*; Hakamatsuka, Yasuyuki*; Ueno, Fumiyoshi; Yamamoto, Masahiro

Proceedings of European Corrosion Congress 2017 (EUROCORR 2017) and 20th ICC & Process Safety Congress 2017 (USB Flash Drive), 9 Pages, 2017/09

JAEA Reports

Proceedings of the first topical meeting on Asian network for accelerator-driven systems and nuclear transmutation technology

Sasa, Toshinobu

JAEA-Review 2015-042, 213 Pages, 2016/03

JAEA-Review-2015-042.pdf:166.0MB

The first topical meeting on Asian Network for Accelerator-driven System (ADS) and Nuclear Transmutation Technology (NTT) was held on 26-27 October 2015 at the J-PARC Center, Japan Atomic Energy Agency, Japan. The meeting was an optional one in-between the regular meeting, which will be held in every second year. Instead of the regular meeting, which covers all research fields for ADS and NTT, such as accelerator, spallation target, subcritical reactor, fuel, and material, this topical meeting is focused on the specific topic to make technical discussions more deeply. In this meeting, the technology for lead-bismuth eutectic alloy was selected as one of the hot issues in the world and had deep discussions with specialists in Asian countries. Through the discussion, the importance of cooperation in Again region is recognized to solve the issues for application of LBE. This report summarizes all presentation materials discussed in the meeting.

Journal Articles

Liquid divertor

Shimada, Michiya; Miyazawa, Junichi*

Purazuma, Kaku Yugo Gakkai-Shi, 92(2), p.119 - 124, 2016/02

AA2015-0751.pdf:0.61MB

Actively convected liquid metal divertor is promising for providing a solution for issues of DEMO reactors including heat removal and disruptions. This chapter gives an overview of the motivation, research history, recent development, future perspective and issues to be resolved.

Journal Articles

The Promising features of new nano liquid metals; Liquid sodium containing titanium nanoparticles (LSnanop)

Itami, Toshio*; Saito, Junichi; Ara, Kuniaki

Metals, 5(3), p.1212 - 1240, 2015/09

 Times Cited Count:2 Percentile:92.86(Materials Science, Multidisciplinary)

A new kind of suspension liquid was developed by dispersing Ti nanoparticles (10 nm) in liquid Na, which was then determined by TEM (transmission electron microscopy) analysis. The volume fraction was estimated to be 0.0088 from the analyzed Ti concentration (2 at.%) and the densities of Ti and Na. This suspension liquid, Liquid Sodium containing nanoparticles of titanium (LSnanop), shows, despite only a small addition of Ti nanoparticles, many striking features, namely a negative deviation of 3.9% from the ideal solution for the atomic volume, an increase of 17% in surface tension, a decrease of 11% for the reaction heat to water, and the suppression of chemical reactivity to water and oxygen. The decrease in reaction heat to water seems to be derived from the existence of excess cohesive energy of LSnanop. The excess cohesive energy was discussed based on simple theoretical analyses, with particular emphasis on the screening effect. The suppression of reactivity is discussed with the relation to the decrease of heat of reaction to water or the excess cohesive energy, surface tension, the action as a plug of Ti oxide, negative adsorption on the surface of LSnanop, and percolation.

Journal Articles

Actively convected liquid metal divertor

Shimada, Michiya; Hirooka, Yoshihiko*

Nuclear Fusion, 54(12), p.122002_1 - 122002_7, 2014/12

 Times Cited Count:27 Percentile:13.47(Physics, Fluids & Plasmas)

Tungsten is considered to be the most promising material for divertor in a fusion reactor. Tungsten divertor can withstand the heat loads of ITER, but the heat loads of DEMO divertor is a challenge. Pulsive heat loads as those associated with disruption could melt tungsten targets. The surface would not be flat after subsequent resolidification, which would significantly deteriorate its heat handling capability. Furthermore, DBTT of tungsten is rather high: $$sim$$ 400$$^{circ}$$C, which would become even higher after neutron irradiation, possibly resulting in cracks in tungsten. Our proposal is to use liquid metal for the divertor target material and actively circulate it with $$j$$ $$times$$ $$B$$ force. A simplified analysis of mhd equation in a cylindrical geometry suggests that the engineering requirement is modest. This analysis suggests that this new divertor concept merits further investigation.

JAEA Reports

Study on numerical simulation of bubble and dissolved gas behavior in liquid metal flow

Ito, Kei; Tanaka, Masaaki; Ohno, Shuji; Ohshima, Hiroyuki

JAEA-Research 2014-023, 34 Pages, 2014/11

JAEA-Research-2014-023.pdf:4.48MB

In a sodium-cooled fast reactor, inert gas (bubbles or dissolved gas) exists in the primary coolant system. Such inert gas may cause disturbance in reactivity and/or degradation of IHX performance, and therefore, the inert gas behaviors have to be investigated to ensure the stable operation of a fast reactor. The authors have developed a plant dynamics code SYRENA to simulate the concentration distributions of the dissolved gas and the bubbles in a fast reactor. In this study, the models in SYRENA code are improved to achieve accurate simulations. Moreover, new models are introduced to simulate the various bubble behaviors in liquid metal flows. To validate the improved models and the newly developed models, the inert gas behaviors in the large-scale sodium-cooled reactor are simulated. As a result, it is confirmed that the complicated bubble dynamics in each component can be simulated appropriately by SYRENA code.

Journal Articles

Actively circulated liquid metal divertor (ACLMD)

Shimada, Michiya; Hirooka, Yoshihiko*; Zhou, H.*

Europhysics Conference Abstracts (Internet), 38F, p.O2.110_1 - O2.110_4, 2014/00

Tungsten is considered to be most promising candidate for divertor target material for fusion reactor. Although tungsten target can withstand the heat loads of ITER, the heat exhaust requirement for DEMO is much more demanding. Pulsive heat loads associated with disurption would melt the tungsten divertor target. Melting and subsequent resolidification will roughen the tungsten surface, significantly deteriorating the heat handling capability. Further, tungsten has a rather high DBTT (Ductile-Brittle-Transition temperature) of 400$$^{circ}$$C. Neutron irradiation would further increase the DBTT, which could result in cracks. In view of these issues, liquid metal divertor is proposed, which is actively circulated with the Lorentz force introduced through the electrodes in the liquid metal. A modest flow speed of 0.3 m/s seems to be adequate for the heat load exhaust of DEMO. A simple treatment of MHD equation in a cylindrical geometry suggests that the requirements on the current and voltage are modest if the ramp-up of current is made slowly (e.g. in a minute), implying that the this concept is worth further study.

JAEA Reports

Compatibility of reduced activation ferritic/martensitic steel specimens with liquid Na and NaK in irradiation rig of IFMIF

Yutani, Toshiaki*; Nakamura, Hiroo; Sugimoto, Masayoshi

JAERI-Tech 2005-036, 10 Pages, 2005/06

JAERI-Tech-2005-036.pdf:2.06MB

In the high flux region of the International Fusion Materials Irradiation Facility (IFMIF), the neutron irradiation damage for iron-based alloys will exceed 20 dpa/ year. An accurate specimen temperature measurement under a large amount of nuclear heating is a key issue but the change of heat transfer of gap between irradiation specimens and specimen holder during irradiation test is inevitable, if gap is filled with an inert gas and temperature is monitored by a thermocouple buried in the specimen holder. A solution to make heat transfer predictable is to fill the gap with a liquid metal (sodium or sodium-potassium alloy). An issue of compatibility between Reduced Activation Ferritic/Martensitic steels and the liquid metalsis addressed in this paper, and some recommendations for designing irradiation rig are presented, such as a purification control before filling liquid metals, or a careful selection of material of rig to avoid carbon mass transfer.

JAEA Reports

Corrosion behavior of austenitic and ferritic/martensitic steels in oxygen-saturated liquid Pb-Bi eutectic at 450$$^{circ}$$C and 550$$^{circ}$$C

Kurata, Yuji; Futakawa, Masatoshi; Saito, Shigeru

JAERI-Research 2005-002, 37 Pages, 2005/02

JAERI-Research-2005-002.pdf:20.04MB

Static corrosion tests of various austenitic and ferritic/martensitic steels were conducted in oxygen-saturated liquid Pb-Bi at 450$$^{circ}$$C and 550$$^{circ}$$C for 3000h to study the effects of temperature and alloying elements on corrosion behavior. Oxidation, grain boundary corrosion, dissolution and penetration were observed. The corrosion depth decreases at 450$$^{circ}$$C with increasing Cr content in steels regardless of ferritic/martensitic or austenitic steels. Appreciable dissolution of Ni and Cr does not occur in the three austenitic steels at 450$$^{circ}$$C. The corrosion depth of ferritic/martensitic steels also decreases at 550$$^{circ}$$C with increasing Cr content whereas the corrosion depth of austenitic steels, JPCA and 316ss becomes larger due to ferritization caused by dissolution of Ni at 550$$^{circ}$$C than that of ferritic/martensitic steels. An austenitic stainless steel containing about 5%Si exhibits fine corrosion resistance at 550$$^{circ}$$C because the protective Si oxide film is formed and prevents dissolution of Ni and Cr.

JAEA Reports

Structural integrity of heavy liquid-metal target installed in spallation neutron facility, 4; Consideration by fracture mechanics of target container window

Ishikura, Shuichi*; Kogawa, Hiroyuki; Futakawa, Masatoshi; Kikuchi, Kenji; Haga, Katsuhiro; Kaminaga, Masanori; Hino, Ryutaro

JAERI-Tech 2003-093, 55 Pages, 2004/01

JAERI-Tech-2003-093.pdf:5.41MB

To estimate the structural integrity of the heavy liquid-metal (Hg) target used in a MW-class neutron scattering facility, static and dynamic stress behaviors due to the incident of a 1MW-pulsed proton beam were analyzed. In the analyses, two-type target containers with semi-cylindrical type and flat type window were used as analytical models of the structural analysis codes LS-DYNA. As a result, it is confirmed that the stress generated by dynamic thermal shock becomes the largest at the center of window, and the flat type window is more advantageous from the structural viewpoint than the semi-cylindrical type window. It was confirmed to erosion damage the target container by mercury's becoming negative pressure in the window and generating the cavitation by the experiment. Therefore, it has been understood that the point top of the window was in the compression stress field by the steady state thermal stress because of the evaluation from destroying the dynamic viewpoint for the crack in the generated pit and the pit point, and the crack did not progress.

Journal Articles

X-ray structural studies on elemental liquids under high pressures

Katayama, Yoshinori; Tsuji, Kazuhiko*

Journal of Physics; Condensed Matter, 15(36), p.6085 - 6103, 2003/09

 Times Cited Count:78 Percentile:7.03(Physics, Condensed Matter)

X-ray structural studies on several elemental liquids under high pressure are reviewed. Combination of synchrotron radiation sources and large volume presses enables us to carry out in-situ structural measurements on liquids at high pressures up to several GPa. The measurements have revealed that compressions of liquid alkali metals are almost uniform, whereas those of liquids that have covalent components in bonding are mostly anisotropic. In some elements, different types of volume dependence of the nearest neighbour distances are observed in different pressure ranges. This behaviour suggests that the liquid phase can be divided in regions. Although most of the observed structural changes are continuous, a discovery of an abrupt structural change in liquid phosphorus, which is completed over a pressure range of less than 0.05 GPa around 1GPa and 1050 $$^{circ}$$C, supports existence of a first-order liquid-liquid phase transition.

Journal Articles

Erosion damage on solid boundaries in contact with liquid metals by impulsive pressure injection

Futakawa, Masatoshi; Kogawa, Hiroyuki; Hino, Ryutaro; Date, Hidefumi*; Takeishi, Hiromasa*

International Journal of Impact Engineering, 28(2), p.123 - 135, 2003/02

JAERI is carrying out research & development to construct the a of spallation neutron source facility, which may bring us innovative science fields. A high power proton beam will be injected into a liquid mercury target to produce neutrons. The mercury vessel will consequently be subjected to the pressure waves generated by rapid thermal expansion. The pressure waves will propagate from the liquid mercury into the vessel solid metal, and back again. The pressure waves may induce erosion at the interface between the solid metal vessel and the liquid mercury under certain loading conditions, e.g. impact. In order to investigate the impact erosion damage due to the pressure wave, we have carried out impact experiments using a modified conventional split Hopkinson pressure bar apparatus on mercury filling a small chamber. Surface degradation in the form of many pits was observed and the ranking order of damage was found to be A6061$$>$$316SS@Inconel600$$>$$Maraging steel, which is the same as that of hardness.

Journal Articles

Thermal shock analysis of liquid-mercury spallation target

Ishikura, Shuichi*; Kogawa, Hiroyuki; Futakawa, Masatoshi; Hino, Ryutaro; Date, Hidefumi*

Koon Gakkai-Shi, 28(6), p.329 - 335, 2002/11

The developments of the neutron scattering facilities are carried out under the high-intensity proton accelerator project promoted by JAERI and KEK. To estimate the structural integrity of the heavy liquid-metal (Hg) target used as a spallation neutron source in a MW-class neutron scattering facility, dynamic stress behavior due to the incident of a 1MW-pulsed proton beam were analyzed by using FEM code. Two-type target containers with semi-cylindrical type and flat-plate type window were used as models for analyses. As a result, it is confirmed that the stress (pressure wave) generated by dynamic thermal shock becomes the largest at the center of window, and the flat-plate type window is more advantageous from the structural viewpoint than the semi-cylindrical type window. It has been understood that the stress generated in the window by the pressure wave can be treated as the secondary stress.

63 (Records 1-20 displayed on this page)