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 (1,500 MWe class) sodium-cooled fast reactors. A flow rate of over 500 m 3 /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.

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Electromagnetic (EM) pumps, which drive liquid metals by electromagnetic force for Fast Reactor, had been developed. Annular Linear Induction Pumps (ALIPs) are one of EM pumps. There are some reports in which a drop and a fluctuation of the developed pressure occurred near the top of the developed pressure and flow rate relation curve (P-Q curve). This phenomenon was reported by Gailitis, Kirillov and Araseki. They simulated it using two-dimensional (2D) code and reported that it was characterized by vortices, which were initiated by azimuthal non-uniformity of sodium flow velocity and/or magnetic field, in the liquid sodium flow. We have calculated the developed pressure of EM pump by 2D magnetohydrodynamics (MHD) code and designed an EM pump. It was found that the code simulated the developed pressure with high accuracy in normal operations. When the flow rate was lower than one in the top of P-Q curve, the developed pressure's drop and fluctuation occurred. The fluctuation would disturb the stable operation of the pump. For avoiding this phenomenon, the EM pump's design becomes sometimes too conservative. To evaluate the quantitative effect of this phenomenon and occurred conditions, we have developed a new three-dimensional(3D) MHD code. Clarification of these conditions and its phenomena will enable us to design a new structure or determine operation conditions. This paper presents the simulation results in terms of the generation of a developed pressure's drop and fluctuation occurrence. We used initial conditions which had azimuthal non-uniformity of sodium velocity to simulate vortices in the liquid sodium. Our 3D MHD code simulated the developed pressure's drop and fluctuation by vortices in radial and circumferential direction. It was confirmed that the vortices developed in the radial direction and then the vortices in circumferential direction developed.

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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.