The flow field model solves the conservation equations of mass, energy, and axial momentum. The time-dependent TH model comprises core analysis for all fuel channels, particularly, by coupling fuel heating, heat transfer from the heated clad surface to the coolant, and single-phase flow field.
In this paper, we perform 3-D transient and thermal-hydraulic (TH) coupled neutronic simulations of PAFO in ATOM. The previous feasibility study was performed using a lumped PWR model. Instead, the transients are entirely achieved by the passive response of the SBF core to the core inlet coolant temperature variation. In PAFO, the control rods and soluble-boron are not utilized to vary the core power. In previous works, we introduced a new operational scheme named the passively autonomous frequency control operation (PAFO) to be applied in ATOM which is a soluble-boron-free (SBF) 450 MWth PWR. The pellet dimension affects the highest temperature mostly. In addition, the size effect of pellet, helium gap and zircaloy cladding on the highest temperature in NFRs is also studied using HBM. The numerical results of NFRs are carried out both in steady-state and transient-state cases. In order to further validate the practical applicability of HBM, nonlinear heat conduction problems of nuclear fuel rods (NFRs) are solved by HBM. Besides, the computation time ratio of HBM to FVM decreases as the element numbers increase, and it is only 0.16% when 1000 elements are involved. HBM shows a comparable accuracy to the analytical solutions, and a higher accuracy than finite volume method (FVM) especially with fewer elements in the discretized model. They are steady-state and transient-state problems with linear and nonlinear material properties.
The accuracy and efficiency of HBM are first tested by solving three one-dimensional radial conduction problems in cylindrical coordinates. Half-boundary method (HBM) is extended to solve one-dimensional radial conduction problems in nuclear fuel rods.
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