Effect Of Laser Welding Quality Of Nuclear Reactor Coolant Pump Can On Eddy Current Losses

In 1950s, canned pump was applied on pressurized water reactor power plant. In order to improve plant's efficiency, large aspect ratio of rotor was adopted that has a short inertia time when the power failure happens. Moreover, the operation environment of cans was complicated that increases failure rate with the rise of plant's power. Due to these disadvantages, large-scale shaft seal pump was used by the second generation reactor power plant. To meet the demand for larger power and higher reliable security, one kind of canned pump with great inertia, higher reliability, convenient maintenance was applied on the third generation reactor power plant. The increase of pump's inertia moment leads to inertia time expand as well as pump's efficiency. However, its structure made the air gap in the pump larger and decline the power coefficient. The emergence of losses further decease the efficiency of canned pump. So, the research about power losses of canned pump becomes one of the most key programs.At the initial design of canned motor, the empirical formula was used for the calculation of eddy current losses of cans. And the losses curve gained from experiments was used to revise the losses parameters. Though the analytic method calculating the eddy current losses of cans can describe the its formation mechanism, due to the restriction of mathematical tools, it has to ignore the magnetic field and eddy current distribution, basing on some suppositions or postulations.Then, the finite element method was used to study the vary canned motor models. And it provides the mathematic models to calculate the eddy current losses of cans. However, all of the previous works based on the perfect situation of cans and haven't discussed the effect of processing technic on the eddy current losses of cans. Works in this paper are as follows:(1) based on Maxwell electromagnetic field theory, the finite element software ANSYS was applied to simulate the 2-D eddy current field of canned motor, building the 2-D mathematic model and setting the boundary condition, calculating the eddy current losses of cans. Then, the result was verified by the emprical formula;(2) surface topography and micro-structure of weld joint of laser welding Hastelloy C-276 were investigated by means of Optics microscope and X-ray diffraction. Then, the weld reinforcement and variation trend of electrical resistivity were studied and discussed. Furthermore, the double bridge method was used to test the value of electrical resistance of laser welding samples;(3) finite element method software ANSYS was applied to simulate the eddy current losses of can with weld reinforcement and to study the effect of weld reinforcement on the losses. The increase of eddy current losses induced by the weld reinforcement was analysed to make further understanding of effect of can with weld reinforcement on electromagnetic field;(4) concerning the variation of electrical resistivity of laser welding samples, ANSYS was used to simulate the effect of variation of electrical properties on the eddy current losses of can by means of changing the model of cans and resetting the value of electrical resistivity of cans. When the electrical resistivity of cans increased, the eddy current losses of can would decline as well as the eddy current in the can.