In order to solve the problem that the traditional"horizontal and vertical"nodal grid is difficult to deal with the deformation of nodal grid caused by the bowing of PWR fuel assembly,this paper studies the neutron diffusion solution method based on arbitrary quadrilateral mesh and conformal mapping according to the nonlinear iterative neutron diffusion solution idea.Arbitrary quadrilateral mesh is used to characterize the deformation of nodal grid caused by fuel assembly bowing,and the global coarse mesh difference finite equation based on arbitrary quadrilateral mesh is established.The arbitrary quadrilateral is transformed into rectangle by conformal mapping,and a local two-node expansion equation based on conformal mapping is established.The numerical results of bowing cases based on two-dimensional mini-core and HPR1000 core indicate that,the core effective multiplication factor(keff)and power distribution calculated by the proposed method are in good agreement with the reference NECP-MCX.Therefore,the method proposed in this paper could accurately characterize and simulate the fuel-assembly bowing.
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