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A general theory is developed for the time dependent transient electrophoretic mobility of spherical colloidal particles in a salt-free liquid medium containing only counterions when a step external electric field is suddenly applied to the colloidal suspension. It is found that as in the case of the steady electrophoretic mobility in a salt-free medium, there is a certain critical value of the particle surface charge separating two cases, that is, the low-surface-charge case and the high-surface-charge case. In the latter case the counterion condensation takes place near the particle surface. For the low-surface charge case, the transient electrophoretic mobility agrees with that of a sphere in an electrolyte solution in the limit of very low electrolyte concentrations. For the high-surface-charge case, however, the transient mobility becomes independent of the particle surface charge because of the counterion condensation effects. A simple expression is derived for the ratio of the transient electrophoretic mobility to the steady electrophoretic mobility, which is found to take the same form irrespective of the magnitude of the particle surface charge. Using this equation, it is now possible to predict how the system will approach its final steady state.

A theoretical framework is established for the gel diffusiophoresis of a spherical colloidal particle moving through an uncharged dilute porous polymer gel medium when an electrolyte concentration gradient field is applied. The network of cross-linked polymer segments is treated as a porous skeleton containing an electrolyte solution using the Brinkman–Debye–Bueche model. We derive a general expression for the gel-diffusiophoretic mobility of a charged spherical colloidal particle. Based on this general mobility expression, we farther derive a closed-form approximate expression for the gel-diffusiophoretic mobility of a weakly charged spherical particle correct to the second order of the particle’s zeta potential. The obtained mobility expression depends on the Debye–Hückel parameter and the Brinkmann parameter.

Deep placement of coated urea, lime nitrogen (Lime N), or urea with a nitrification inhibitor, 3,4-dimethylpyrazole phosphate (DMPP-U) did not inhibit N fixation activity, and it promoted soybean growth and seed yield. However, the effect of deep placement on the N budget including N leaching has not been evaluated. In this research, soybean plants were cultivated with a basal deep placement of urea, Lime N, or DMPP-U, and the control without deep placement of N fertilizer in lysimeters filled with Andosols. The nitrate was the principal N leachate and most of them leached until the flowering stage. The total amount of leached nitrate was the highest in urea deep placement, and it was reduced by the deep placement of Lime N or DMPP-U. In 2020, the total amount of nitrate in the leachate during the cultivation was 0.95, 1.83, and 2.78 ​g ​N m−2 in control, Lime N, and urea, respectively. The seed yield was higher in Lime N (424 ​g ​m−2) and urea (399 ​g ​m−2) than in the control (267 ​g ​m−2). The total amount of N accumulated in the shoots was higher in Lime N (32.1 ​g ​N m−2) than in the control (26.5 ​g ​N m−2) and urea (24.2 ​g ​N m−2) treatments. These results indicated that soybean plants with Lime N might assimilate more N both from N fertilizer and N2 fixation compared with control plants. Soil incubation test confirmed that the Lime N or DMPP-U retarded nitrification than urea.

A simple relationship between the Hamaker constant and the Hansen solubility parameters for non-polar liquids is derived by combining a Hamaker constant/surface tension relationship derived by Israelachvili and a Hansen solubility parameters/surface tension relationship derived by Abbott. With this relationship, one can easily estimate the Hamaker constant of non-polar liquids on the basis of the database of the Hansen solubility parameters. This is an entirely new method for calculating the Hamaker constant without recourse to data on the frequency-dependent dielectric permittivity of those substances (which are required for the rigorous Lifshitz theory) and laborious numerical calculations.

Abstract Background Thyroid stimulating hormone (TSH) receptor and local infiltrate lymphocytes have been considered as major pathological factors for developing thyroid-related ophthalmopathy. Overexpression of insulin-like growth factor-I (IGF-I) receptor has emerged as a promising therapeutic target for refractory patients. However, the relationship between activation of growth hormone (GH)/IGF-I receptor signaling and development or exacerbation of thyroid ophthalmopathy has not been elucidated. Herein we describe a case that provides further clarification into the association between thyroid-related ophthalmopathy and GH/IGF-I receptor signaling. Case presentation A 62-year-old Japanese female diagnosed with thyroid-related ophthalmopathy was admitted to Kurume University Hospital. She had received daily administration of GH subcutaneously for severe GH deficiency; however, serum IGF-I levels were greater than + 2 standard deviation based on her age and sex. She exhibited mild thyrotoxicosis and elevation in levels of TSH-stimulating antibody. Discontinuation of GH administration attenuated the clinical activity scores of her thyroid-related ophthalmopathy. Additionally, concomitant use of glucocorticoid and radiation therapies resulted in further improvement of thyroid-related ophthalmopathy. The glucocorticoid administration was reduced sequentially, followed by successful termination. Thereafter, the patient did not undergo recurrence of thyroid-related ophthalmopathy and maintained serum IGF-I levels within normal physiological levels. Conclusions We describe here a case in which development of thyroid-related ophthalmopathy occurred upon initiation of GH administration. GH/IGF-I signaling was highlighted as a risk factor of developing thyroid-related ophthalmopathy. Additionally, aberrant TSH receptor expression was suggested to be a primary pathophysiological mechanism within the development of thyroid-related ophthalmopathy. Physicians should be aware of the risks incurred via GH administration, especially for patients of advanced age, for induction of thyroid-related ophthalmopathy.

The general theory is developed for the time-dependent transient electrophoresis of a weakly charged spherical colloidal particle with an electrical double layer of arbitrary thickness in an uncharged or charged polymer gel medium. The Laplace transform of the transient electrophoretic mobility of the particle with respect to time is derived by considering the long-range hydrodynamic interaction between the particle and the polymer gel medium on the basis of the Brinkman–Debye–Bueche model. According to the obtained Laplace transform of the particle’s transient electrophoretic mobility, the transient gel electrophoretic mobility approaches the steady gel electrophoretic mobility as time approaches infinity. The present theory of the transient gel electrophoresis also covers the transient free-solution electrophoresis as its limiting case. It is shown that the relaxation time for the transient gel electrophoretic mobility to reach its steady value is shorter than that of the transient free-solution electrophoretic mobility and becomes shorter as the Brinkman screening length decreases. Some limiting or approximate expressions are derived for the Laplace transform of the transient gel electrophoretic mobility.

We develop the theory of transient electrophoresis of a weakly charged, infinitely long cylindrical colloidal particle under an application of a transverse or tangential step electric field. Transient electrophoretic mobility approaches steady electrophoretic mobility with time. We derive closed-form expressions for the transient electrophoretic mobility of a cylinder without involving numerical inverse Laplace transformations and the corresponding time-dependent transient Henry functions. The transient electrophoretic mobility of an arbitrarily oriented cylinder is also derived. It is shown that in contrast to the case of steady electrophoresis, the transient Henry function of an arbitrarily oriented cylinder at a finite time is significantly smaller than that of a sphere with the same radius and mass density as the cylinder so that a cylinder requires a much longer time to reach its steady mobility than the corresponding sphere.

The general expression is derived for the Laplace transform of the time-dependent transient electrophoretic mobility (with respect to time) of a spherical colloidal particle when a step electric field is applied. The transient electrophoretic mobility can be obtained by the numerical inverse Laplace transformation method. The obtained expression is applicable for arbitrary particle zeta potential and arbitrary thickness of the electrical double layer around the particle. For the low potential case, this expression gives the result obtained by Huang and Keh. On the basis of the obtained general expression for the Laplace transform of the transient electrophoretic mobility, we present an approximation method to avoid the numerical inverse Laplace transformation and derive a simple approximate analytic mobility expression for a weakly charged particle without involving numerical inverse Laplace transformations. The transient electrophoretic mobility can be obtained directly from this approximate mobility expression without recourse to the numerical inverse Laplace transformation. The results are found to be in excellent agreement with the exact numerical results obtained by Huang and Keh.

We derive the general expression for the diffusiophoretic mobility of a soft particle (i.e., polyelectrolyte-coated hard particle) in a concentration gradient of electrolytes for the case in which the particle’s core size is large enough compared with the Debye length. Therefore, the particle surface can be regarded as planar, and the electrolyte concentration gradient is parallel to the core surface. The obtained expression can be applied for arbitrary values of the fixed charge density of the polyelectrolyte layer and the surface charge density of the particle core. We derive approximate analytic mobility expressions for soft particles of three types, i.e., (i) weakly charged soft particles, (ii) soft particles with a thick polyelectrolyte layer, in which the equilibrium electric potential deep inside the polyelectrolyte layer is equal to the Donnan potential, and (iii) soft particles with an uncharged polymer layer of finite thickness.

Sodium fire is one of key issues in sodium-cooled fast reactor (SFR) plants. JAEA has developed sodium fire analysis codes, a zone model code SPHINCS and a field model code AQUA-SF, to evaluate the consequence of sodium fire events. This paper describes a PIRT (Phenomena Identification and Ranking Table) process for sodium fire events. Ranking table for important phenomena and an assessment matrix are completed. Because a sodium fire event in an SFR plant involves complex phenomena, the ranking table has been established through both element- and sequence-based phenomena analyses in addition to the engineering judgement. The assessment matrix confirms sufficiency of experimental data for validation of models corresponding to the identified important phenomena in the sodium fire analysis codes. As a part of comprehensive validation based on the assessment matrix, an experimental analysis for a large-scale sodium spray fire experiment Run-E1 is conducted by using the SPHINCS and AQUA-SF codes. The analytical results of the both codes show good agreements with the experimental data of gas pressure transient. Difference from the experimental result of the maximum pressure are about 5% smaller in the SPHINCS code and about 10% larger in the AQUA-SF code. General validity for the codes would be confirmed through the comprehensive validation based on the assessment matrix.

The authors are developing the design concept of the pool-type sodium-cooled fast reactor (SFR) that addresses Japan’s specific siting conditions such as earthquakes and meets safety design criteria (SDC) and safety design guidelines (SDG) for Generation IV SFRs. The development of this concept will broaden not only options for reactor types in Japan but also the range and depth of international cooperation. A design concept of 1,500 MWt (650 MWe) class pool-type SFR was thought up by applying design technology obtained from the design of advanced loop-type SFR, named JSFR, equipped with safety measures that reflect results from the feasibility study on commercialized fast reactor cycle systems and fast reactor cycle technology development, improved maintainability and repairability, and lessons learned from the Fukushima Daiichi Nuclear Power Plants accident. The design concepts of a reactor vessel (RV) and its internal structures have been investigated whether they could withstand severe seismic conditions in Japan and thermal loads. The design adopted enhanced RV support structure, enhanced conical-shaped core support structure, a thickened knuckle part of the RV, and a flat plenum separator with ribs. A three-dimensional steady-state thermal hydraulic analysis of the RV revealed that the temperature difference of the upper and lower surfaces of the flat plenum separator could be effectively reduced by installing layers of thermal insulation plates. The authors have also conducted a transient analysis of loss of flow type anticipated transients without scram events to evaluate the feasibility of a self-actuated shutdown system. Moreover, the configuration of the decay heat removal system has been investigated considering sufficient utilization of natural circulation capability of sodium coolant, heat removal capacity of each cooling system, conformance with design requirements, and recommendations of SDC and SDG such as diversity and redundancy of components.

In case pressurized water or vapor leaks from a failed heat transfer tube in a steam generator of a sodium-cooled fast reactor, a high-velocity, high-temperature, and corrosive jet with sodium-water chemical reaction may cause tube failure propagation. In this study, a numerical analysis method to predict the occurrence of tube failure propagation by overheating rupture was developed to expand an application range of an existing computer code. This method consists of the elemental analysis models for a sodium-side temperature distribution formed by a reacting jet, water-side thermal hydraulics, heat transfer of a tube, and tube failure by internal pressure. To evaluate event progress at a shortest computation time, the elemental analysis models of this code were constructed from the experimental data, semi-theoretical correlations, or one-dimensional equations. Applicability of the method was investigated through the computation of an experiment on water vapor discharging in liquid sodium. In this experiment, one tube for water vapor discharging and the 91 target tubes were placed in a liquid sodium pool. Temperature of the target tubes increased by the effect of the reacting jet in this computation. Some of the target tubes near the initial water leak resulted in overheating rupture as with the experimental result. This computation demonstrated that the proposed method could predict the occurrence of overheating rupture and provide conservative results.

When pressurized water or vapor leaks from a failed heat transfer tube in a steam generator of sodium-cooled fast reactors, a high-velocity and high-temperature jet with sodium-water chemical reaction may cause wastage on the adjacent tubes. To evaluate the effect of the reacting jet to the adjacent tubes, a computational fluid dynamics code SERAPHIM, in which a compressible multicomponent multiphase flow with sodium-water chemical reaction is computed, has been developed. The multiphase flow under the tube failure accident is calculated by the multi-fluid model considering compressibility. The chemical reaction between liquid sodium and water vapor is considered under the assumption of an infinite reaction rate. The original SERAPHIM code is based on the finite difference method. In this study, unstructured mesh-based numerical method was developed and introduced into the SERAPHIM code to advance a numerical accuracy for a complex-shaped domain including multiple heat transfer tubes. Validity of the unstructured mesh-based SERAPHIM code was investigated through the analysis of an under-expanded jet experiment, which is a key phenomenon in the tube failure accident. The calculated pressure profile showed good agreement with the experimental data. Numerical analysis of water vapor discharging into liquid sodium was also performed. The calculated temperature field agreed with the existing experimental knowledge. It was demonstrated that the proposed numerical method could be applicable to evaluation of the sodium-water reaction phenomenon.

Sodium-cooled fast breeder reactors use liquid sodium as a moderator and coolant to transfer heat from the reactor core. The main hazard associated with sodium is its rapid reaction with water. Sodium–water reaction (SWR) takes place when water or vapor leak into the sodium side through a crack on a heat-transfer tube in a steam generator. If the SWR continues for some time, the SWR will damage the surface of the defective area, causing it to enlarge. This self-enlargement of the crack is called “self-wastage phenomena.” A stepwise numerical evaluation model of the self-wastage phenomena was devised using a computational code of multicomponent multiphase flow involving a sodium–water chemical reaction: sodiumwater reaction analysis physics of interdisciplinary multiphase flow (SERAPHIM). The temperature of gas mixture and the concentration of NaOH at the surface of the tube wall are obtained by a numerical calculation using SERAPHIM. Averaged thermophysical properties are used to assess the local wastage depth at the tube surface. By reflecting the wastage depth to the computational grid, the self-wastage phenomena are evaluated. A two-dimensional benchmark analysis of an SWAT (Sodium-Water reAction Test rig) experiment is carried out to evaluate the feasibility of the numerical model. Numerical results show that the geometry and scale of enlarged cracks show good agreement with the experimental result. Enlarged cracks appear to taper inward to a significantly smaller opening on the inside of the tube wall. The enlarged outer diameter of the crack is 4.72 mm, which shows good agreement with the experimental data (4.96 mm).

In the original licensing application for the prototype fast-breeder reactor, MONJU, the event progression during an unprotected loss of flow (ULOF), which is one of the technically inconceivable events postulated beyond design basis, was evaluated. Through this evaluation, it was confirmed that radiological consequences could be suitably limited even if mechanical energy was released. Following the Fukushima-Daiichi accident, a new nuclear safety regulation has become effective in Japan. The conformity of MONJU to this new regulation should hence be investigated. The objectives of the present study are to conduct a preliminary evaluation of ULOF for MONJU, reflecting the knowledge obtained after the original licensing application through CABRI experiments and EAGLE projects, and to gain the prospect of in-vessel retention for the conformity of MONJU to the new regulation. The preliminary evaluation in the present study showed that no significant mechanical energy release would take place, and that thermal failure of the reactor vessel could be avoided by the stable cooling of disrupted-core materials. This result suggests that the prospect of in-vessel retention against ULOF, which lies within the bounds of the original licensing evaluation and conforms to the new nuclear safety regulation, will be gained.

A plant dynamics analysis code named Super-COPD is being developed in Japan Atomic Energy Agency (JAEA) to offer a methodology for the design and safety assessments of future commercialized sodium-cooled fast reactors (SFRs). In this study, the friction loss coefficients in the whole core thermal-hydraulic model, which is based on flow network modeling, was modified to improve the prediction accuracy of the sodium temperature distribution in a fuel subassembly under the natural circulation conditions. Super-COPD with the modified whole core model was applied to analyses of experiments, that were performed by using JAEA's test facility PLANDTL and were simulated natural circulation decay heat removal operations in SFRs, as a part of the code validation study. The obtained numerical results of sodium temperature distributions in the core showed good agreement with the measured data. It implies that the modified whole core model can properly reproduce dominant thermal-hydraulic phenomena in the core region under natural circulation conditions, i.e., flow redistribution among fuel subassemblies as well as in a fuel subassembly and inter-subassembly heat transfer.

In the last two decades, CFD codes have been widely used for the design studies of NPPs. Recently high-precision simulation models have been developed to evaluate complicated phenomena, e.g. fuel melting in severe accident. The authors also are developing a high-precision CFD code with an interface tracking method to simulate the gas entrainment (GE) phenomena in sodium-cooled fast reactors (SFRs), which might be caused by a highly-intensified free surface vortex. The GE in SFRs is characterized by an elongated interfacial dent along the vortex core and the bubble pinch-off at the tip of the dent. To simulate this complicated phenomenon, the authors’ CFD code has physics-basis algorithms which model accurately the interfacial dynamic behavior, the pressure jump condition at an interface and the surface tension. Several verification problems, e.g. the slotted-disk problem, have been already solved and the accuracy of each individual algorithm is confirmed. In this paper, a basic experiment of the GE is simulated to validate the developed CFD code. In the experiment, the entrained gas flow rate is measured by image processing with a high-speed video camera. The simulation result of the entrained flow rate shows comparable value to the experimental data, that is, our CFD code is considered applicable to the evaluation of the GE in SFRs.

When pressurized water or vapor leaks from a failed heat transfer tube in a steam generator of sodium-cooled fast reactors, a high-velocity, high-temperature jet with sodium-water chemical reaction may cause wastage on the adjacent tubes. For assessment of the wastage environment, a mechanistic computer code called SERAPHIM calculating compressible multicomponent multiphase flow with sodium-water chemical reaction has been developed. In this study, applicability of the SERAPHIM code was investigated through the analysis of the experiment on water vapor discharging in liquid sodium under actual condition of the steam generator. The computational domain consists of the cylindrical vessel and the simulated two horizontal heat transfer tubes. The cylindrical vessel was initially filled with liquid sodium. Pressurized water vapor goes into the sodium pool vertically upward from the discharging nozzle located at the center of one of the two tubes. The numerical result showed that the underexpanded jet appeared and impinged on the target tube located above the discharging tube. The calculated temperature distribution agreed with the measurement result well. The liquid droplet entrainment and its transport were considered in this analysis. The region with higher impingement velocity of the liquid droplet was close to the wastage region confirmed in the experiment.

In order to clarify the adsorption behavior of cationic surfactants on the air/aqueous electrolyte solution surface, we derived the theoretical equation for the surface tension. The equation includes the electrical work required for charging the air/water surface and the work attributable to the configurational entropy in the adsorbed film. By fitting the equation to the experimental data, we determined the binding constant between adsorbed surfactant ion and counterion, and found that the bromide ions, rather than the chloride ions, are preferentially adsorbed by the air/water surface. Furthermore, it was suggested that the contribution of configurational entropy to the surface tension is predominant in the presence of electrolytes because of the increase in the surface density of surfactant molecules associated with decreasing the repulsive interaction between their hydrophilic groups.

This paper introduces our own hierarchical data visualization technique, HeiankyoView, and discusses its potential for fluid science. HeiankyoView represents hierarchy as nested rectangles, and displays thousands of data elements in one display space. The paper briefly introduces the algorithm and various applications of HeiankyoView, and discusses our attempts for visualization of computational fluid dynamics data. Finally, the paper introduces our work on visualization of atomic plant data using HeiankyoView.

In a sodium-cooled fast reactor (SFR), liquid sodium is used as a heat transfer fluid because of its excellent heat transport capability. On the other hand, it has strong chemical reactivity with water vapor. One of the design basis accidents of the SFR is the water leakage into the liquid sodium flow by a breach of heat transfer tubes. This process ends up damages on the heat transport equipment in the SFR. Therefore, the study on sodium-water chemical reactions is of paramount importance for security reasons. This study aims to clarify the sodium-water reaction mechanisms using an elementary reaction analysis. A quasi one-dimensional flame model is applied to a sodium-water counter-flow reaction field. The analysis contains 25 elementary reactions, which consist of 17 H2-O2 and 8 Na-H2O reactions. Temperature and species concentrations in the counter-flow reaction field were measured using laser diagnostics such as LIF and CARS. The main reaction in the experimental conditions is Na+H2O→NaOH+H and OH is produced by H2O+H→H2+OH. It is demonstrated that the reaction model in this study well explains the structure of the sodium-water counter-flow diffusion flame.

A vortex is considered as one of significant phenomena which may cause gas entrainment (GE) and/or vortex cavitation in sodium-cooled fast reactors. In our past studies, the vortex is assumed to be approximated by the well-known Burgers vortex model. However, the Burgers vortex model has a simple but unreal assumption that the axial velocity component is horizontally constant, while in real the free surface vortex has the axial velocity distribution which shows large gradient in radial direction near the vortex center. In this study, a new vortex model with realistic axial velocity distribution is proposed. This model is derived from the steady axisymmetric Navier-Stokes equation as well as the Burgers vortex model, but the realistic axial velocity distribution in radial direction is considered, which is defined to be zero at the vortex center and to approach asymptotically to zero at infinity. As the verification, the new vortex model is applied to the evaluation of a simple vortex experiment, and shows good agreements with the experimental data in terms of the circumferential velocity distribution and the free surface shape. In addition, it is confirmed that the Burgers vortex model fails to calculate accurate velocity distribution with the assumption of uniform axial velocity. However, the calculation accuracy of the Burgers vortex model can be enhanced close to that of the new vortex model in consideration of the effective axial velocity which is calculated as the average value only in the vicinity of the vortex center.

We investigate theoretically the electrostatics and electrokinetics of a soft particle, i.e. a hard particle covered with an ion-penetrable surface layer of polyelectrolytes. The electric properties of soft particles in an electrolyte solution, which differ from those of hard particles, are essentially determined by the Donnan potential in the surface layer. In particular, the Donnan potential plays an essential role in the electrostatics and electrokinetics of soft particles. Furthermore, the concept of zeta potential, which is important in the electrokinetics of hard particles, loses its physical meaning in the electrokinetics of soft particles. In this review, we discuss the potential distribution around a soft particle, the electrostatic interaction between two soft particles, and the motion of a soft particle in an electric field.

A new apparatus for in situ continuous measurements of atmospheric CO_2 concentration at Syowa Station, Antarctica was developed using a non-dispersive infrared CO_2 analyzer with a precision better than ±0.01ppm. Standard gases employed were CO_2 in air mixtures and their concentrations were determined against special gases with absolute accuracies around ±0.1ppm, which were prepared gravimetrically using an extremely precise balance.

In the study of safety enhancements on advanced sodium-cooled fast reactors (SFRs) by the Japan Atomic Energy Agency (JAEA), it has been essential to clarify the thermal hydraulics under various operating conditions at high and low flow rate conditions in a fuel assembly (FA) with wire-wrapped fuel pins to assess the structural integrity of the fuel pin that achieves a high-performance core with high burnup ratio and high power density. A finite element thermal-hydraulic analysis code named SPIRAL has been developed by JAEA to analyze the detailed thermal-hydraulic phenomena in the FA of a SFR. In this study, numerical simulations of 37-pin bundle sodium experiments at different Reynolds (Re) number conditions, including a transitional condition between laminar and turbulent flows and turbulent flow conditions, were performed to validate the developed hybrid k-ε/kθ-εθ turbulence model equipped in SPIRAL to consider the low Re number effect near the wall in the flow and temperature fields. The temperature distributions predicted by SPIRAL were consistent with those measured in the sodium experiments at the Re number conditions. Through the validation study, the applicability of the hybrid turbulence model in SPIRAL to the thermal-hydraulic evaluation of sodium-cooled FAs in a wide range of Re numbers was confirmed. [ABSTRACT FROM AUTHOR]