Modeling of permanent magnet flowmeter for voltage signal estimation and its experimental verification

Prototype Fast Breeder Reactor (PFBR) is a 500 MWe, sodium cooled, pool type, mixed oxide (MOX) fueled reactor. Sodium flow measurement in various loops of the reactor is of prime importance from the operational and safety aspects. To measure the flow of electrically conducting liquid sodium in secondary circuits, permanent magnet flowmeters (PMFMs) made up of ALNICO-5 are used in Fast Breeder Test Reactor (FBTR), PFBR and existing sodium loops in Indira Gandhi Centre for Atomic Research (IGCAR). PMFM made up of ALNICO-5 are bulky and heavy, hence to reduce size of flowmeter a PMFM made up of Samarium Cobalt (SmCo) is designed and calibrated in existing sodium loop. Calibration of flowmeter requires dedicated sodium rig with pipe sizes of same dimension as flowmeter pipe, which needs modification in existing system. As an alternate method of sodium calibration, three dimensional Finite Element Modeling of SmCo PMFM is done for its voltage signal prediction. In simulation magnetic field distribution across the flowmeter pipe and effect of sodium flow on magnetic field are analyzed. Effect of sodium temperature on flowmeter voltage signal and its change with change in sodium flow rate is predicted with modeling and compared with experimental tests conducted for use of PMFM.

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► Permanent magnet flowmeter made up of SmCo is designed and calibrated in existing sodium loop.
► Finite element modeling of SmCo flowmeter is done for its voltage signal estimation.
► Magnetic fields in pipe, effect of end currents and effect of electrically conducting SS walls were analyzed.
► Modeling predicts the flowmeter output within 2% of experimental values obtained for flowmeter calibration.