Rie Aizawa

Electromagnetic Pumps for Main Cooling Systems of Commercialized Sodium-Cooled Fast Reactor

An electromagnetic pump (EMP) has superior potential to improve the economic performance and ease of maintenance of sodium-cooled fast reactors. This study investigates the adequateness of a modular-type EMP system for large-sized (1,500MWe class) sodium-cooled fast reactors. A flow rate of over 500 m3/min is required for the main circulating pump of such reactors. There is concern that such a large EMP will cause flow instability. A modular-type EMP system can solve this issue since smaller EMPs are arranged in parallel and the flow rate of each EMP is reduced. Parallel-module EMP systems have been investigated as the primary and secondary circulating pumps. The results of the design study and electromagnetic analysis of the primary main pump confirmed that flow instability does not occur under all operational conditions. From a safety viewpoint, a reliable flow-coast-down system has been proposed, comprising an electric supply system with a permanent magnet synchronous motor and a reliable circuit breaker system. The modular-type EMP system is also effective for the secondary system, drastically simplifying the piping arrangement. The results of this study show that the modular-type EMP system is highly compatible with the main circulating pumps of large-sized sodium-cooled fast reactors, as well as the advantages gained from adopting this system.

Development of a three-dimensional magnetohydrodynamics code for electromagnetic pumps

Annular linear induction pumps (ALIPs) are one of the electromagnetic (EM) pumps, which drive liquid metal using EM force, for fast reactors and have been developed in many countries. An ALIP mainly consists of multiple coils, iron cores and an annular flow channel. We have calculated the developed pressure of ALIPs using a two-dimensional magnetohydrodynamics (MHD) code. There are some reports in which pressure drop and fluctuation were observed in EM pump operations near the top of the pressure and flow rate relation (P–Q) curve. For fear of this phenomenon, the EM pump design is sometimes too conservative. To simulate the pressure drop and fluctuation occurrence conditions, we have developed a new three-dimensional (3D) MHD code. Clarification of this condition and its phenomena in the sodium flow will enable design of a new structure or determination of operation conditions that preclude this pressure drop and fluctuation and, thereby, achieve high efficiency. In this paper, the model of our new 3D MHD code, the accuracy of the code, simulation results focusing on pressure drop and fluctuation by radial and circumferential vortices are reported.

X-ray Visualization of Carbon-Particle Oxidation Process in Supercritical Water

A real-time X-ray visualization system for low X-ray absorption materials has been developed. The system is mainly composed of a multi-color scintillator based image intensifier and a real-time image-processing unit. The color image intensifier has such advantages as the high sensitivity, the wide dynamic range and the long lifetime over the conventional one. The dynamic imaging of low X-ray absorption materials was realized by the video-rate image subtraction function of the image processor. The system has been successfully applied for an observation of a carbon-particle oxidation process in supercritical water. The low X-ray absorption difference between carbon and supercritical water, surrounded by high X-ray absorption metal wall, is one of the most difficult objects to get good image. In our system, the carbon-particle image was taken at a 30 frame/sec video-rate by continuously subtracting the background image until at the instance of the carbon-particle disappearance by oxidation.

Large Electro-Magnetic Pump Design for Application in the ASTRID Sodium-Cooled Fast Reactor

Within the framework of the French Sodium Fast Reactor (SFR) prototype called ASTRID (Advance Sodium Technological Reactor for Industrial Demonstration), an application of Large capacity Electro-Magnetic Pumps (LEMP) is considered as a main concept of the circulating pump on intermediate sodium circuits. The use of LEMP has several merits in the design of reactor, operation, and maintenance. Furthermore, high efficiency is acquired when heat-resistant coil insulation is used for this LEMP. Nevertheless, some theoretical and technological developments have to be carried out in order to validate the design tools by taking into account Magneto Hydro Dynamic (MHD) phenomena and the applicability of the LEMP to ASTRID steady state and transient operating conditions. In this aim, a collaboration agreement between the CEA and TOSHIBA Corporation came into force in April 2012 to carry out a joint work program on the ASTRID EMP design and development. This paper describes the dedicated design studies and experimental activities for the LEMP development within the framework of the CEA-TOSHIBA collaboration.© 2014 ASME

Pressure Drop of Annular Flow Channel Electromagnetic Pump Examined Using Divided Flow Channel Model

Abstract It has been reported that operating an annular flow channel electromagnetic pump (EMP) near the peak of the head pressure and flow rate curve sometimes suffers a drop of head pressure. This phenomenon was attributed to nonuniform distribution of inlet flow or magnetic field, but its mechanism has not been clarified. For fear of this undesired head pressure drop, current EMP design is sometimes too conservative in that the rated efficiency is set low compared with experimentally achieved values. Understanding this phenomenon clearly, therefore, will prospectively make possible more proper design. We modeled the annular channel with parallel divided channels to examine the response of the EMP for distributed inlet flow. For each of the divided channels, the equation of fluid motion is numerically solved including the pressure from the external flow loop. Since the time constant of the pressure from the external loop is slow compared with that of the divided channels, decreased flow in some divided channels can undergo reversed pressure and become unstable in certain cases. Transient behaviors, such as the total head pressure and the flow rate of the EMP, were examined, and conditions of this pressure drop occurrence were clarified, making possible more proper EMP design.

Electromagnetic Pump Flow Simulation by 3D MHD Code

Electromagnetic (EM) pumps, which drive liquid metal by electromagnetic force in Fast Reactors, have been developed [1] [2]. Annular Linear Induction Pump (ALIP) is one of EM pumps. There have been some reports in which developed pressure’s drop and fluctuation were described near the top of the relation curve between developed pressure and flow rate (P-Q curve). These phenomena were reported by Gailitis, Kirillov and Araseki. Araseki simulated this phenomenon by two-dimensional (2D) code and reported that it is characterized by vortexes, which were initiated by azimuthal non-uniformity of sodium flow velocity and/or magnetic field, in the sodium flow.We calculated the developed pressure of an EM pump by 2D magnetohydrodynamics (MHD) code and designed the EM pump. The code simulated the developed pressure with high accuracy in normal operations. When the flow rate was lower than the one at the top of P-Q curve, the developed pressure’s drop and fluctuation occurred. The fluctuation could disturb the stable operation of the pump. For fear of this phenomenon, the design of EM pump is sometimes too conservative. To simulate this phenomenon and examine its occurring conditions, we have developed a new three-dimensional (3D) MHD code. Clarification of these conditions for the occurrence of this phenomenon will enable to design a new structure or determine its operation conditions reasonably.This paper describes the simulation results focusing on the occurrence of developed pressure’s drop and fluctuation. We use initial conditions which have azimuthal non-uniformity of sodium velocity to simulate the initiation of vortexes in sodium. The 3D MHD code simulates the developed pressure’s drop and fluctuation by vortexes and provides more clear illustration of their occurrence.© 2014 ASME

Development of a Large Diameter Electromagnetic Pump for 4S

Toshiba has been developing the Super-Safe, Small and Simple sodium-cooled fast reactor, named as the 4S. This reactor has features of passive safety, long refueling interval up to 30 years and low maintenance requirement.[1] To approach the features, the 4S adopts a high temperature sodium-immersed electromagnetic pump (EM pump) as the primary circulation pump. The rated flow rate and head are 10.6m3 /min and 50kPa respectively. EM pump is static equipment with no moving parts, and then it enables the long-term maintenance to be unnecessary. However, there are some technical issues to apply an EM pump to the 4S. The outer diameter of the 4S EM pump is 1.8 times larger than that of 160m3 /min EM pump which Toshiba has already developed. [2] Aspect ratio of the 4S EM pump defined by stator diameter to the length is much larger than our EM pump experiences, which may concern generation of flow instability. In order to confirm the design and fabrication procedure, the prototype full-scale EM pump for the 4S was manufactured. This EM pump characteristics were evaluated using electromagnetic flow code named as EAGLE developed by Toshiba, which combined with Maxwell’s equations and Navier-Stokes equation. To confirm characteristic of the completed EM pump, magnetic field in the annuals flow gap was measured in the air along the axial directional in condition of 250V-18Hz. The data were confirmed to agree with the analytical results of EAGLE. In order to demonstrate applicability of EM pump for the 4S, sodium test facility was constructed. The facility consists of one electromagnetic flow meter (EM flow meter), 14 sodium pressure sensors, EM flow meter calibration tank, 600kW cooler and sodium impurity control system. The pump characteristic tests were performed in sodium, it was demonstrated that the EM pump could apply to the 4S as the performance was satisfied with the design rated.Copyright

Investigation of the voltage life of mica-alumina composite insulation at high temperatures

Experiments and investigations were carried out on the voltage life of a bar-coil model with a nickel-plated copper conductor covered with mica-alumina composite insulation at a temperature range of 550–850 °C. Diffusion of copper into the insulation layer was observed on the specimens aged for a long period. Insulation with mica paper gave faster diffusion speed and shorter voltage life than insulation with mica flake. The diffusion speed became higher with an increase in temperature. The ac current gradually increased with aging time and increased rapidly just before breakdown. There was the relationship I = aEn (a, n: constants) between ac current I and applied stress E, and n was approximately equal to 1 in the region where thermal unbalance did not occur. Arrheniuss law held in the relationship between ac current and aging time. Therefore, the breakdown mechanism might be that the effective insulation thickness decreased due to copper diffusion into the insulation layer and the ac current increased gradually until thermal breakdown in the last stage. If copper diffuses into the insulation layer, even with no voltage application, the aging time required to decrease the breakdown voltage to a certain level (the voltage life) obeys Arrheniuss law. If the voltage life is dominated by diffusion into the insulation layer, the activation energy for voltage life in the aging test becomes twice that for diffusion, both with and without voltage application.