CN-122021402-A - Neutron calculation modeling method for multidimensional non-uniform cavitation share of spiral petal-shaped fuel assembly

CN122021402ACN 122021402 ACN122021402 ACN 122021402ACN-122021402-A

Abstract

The invention provides a neutron computation modeling method for multidimensional non-uniform cavitation share of a spiral petal-shaped fuel assembly. The method comprises the steps of firstly constructing a geometric model of a fuel rod and a gas-liquid two-phase flow coolant area, then carrying out shaft-radial self-adaptive unlimited partition on the coolant area, adjusting the scale according to cavitation share distribution characteristics, setting axial reference cavitation rate and radial correction coefficient of each subarea, establishing a unified partition numbering rule, then constructing a cavitation share exponential decay coupling model by combining a gas-liquid two-phase flow theory and a spiral structure secondary flow effect, coupling the density of the coolant and the boron concentration to obtain the mixed density, storing geometric and physical information in an HDF5 format, completing geometric consistency verification, and finally outputting partition modeling results and coupling analysis reports through a gas-liquid two-phase flow numerical simulation verification method. The method provides a scientific, efficient and accurate modeling solution for the multi-physical field coupling analysis of the pressurized water reactor core by adopting the spiral petal-shaped fuel assemblies.

Inventors

CAI WEIHUA
WANG JINCHENG
LI SHUNQI
SUN JIANCHUANG
ZHANG WENCHAO
LI QIAN
CHE XUNJIAN
DU LIPENG

Assignees

东北电力大学

Dates

Publication Date: 20260512
Application Date: 20251230

Claims (10)

1. A method of neutron computational modeling of a multi-dimensional non-uniform cavitation fraction of a helical petaline fuel assembly, the method comprising: Constructing discrete partition of spiral geometry, namely performing axial and radial space discrete treatment on a coolant area to construct a calculation partition suitable for the spiral petal-shaped geometric configuration; establishing a partitioning index mechanism of a coolant, and defining a reference cavitation share distribution trend of an axial level and a transverse correction rule of a radial subarea; Constructing a coupling modified cavitation-density model, namely calculating the local cavitation share and the corresponding mixed density parameter of each discrete partition based on the secondary flow effect and the phase distribution characteristic induced by the spiral structure and combining the preset gas-liquid two-phase flow constitutive relation; And (3) carrying out adaptation solution, namely mapping the mixed density parameters into target neutron calculation codes, and carrying out physical calculation solution on the multi-petal spiral fuel assembly.
2. The method of claim 1, wherein the spiral-petaline fuel assembly comprises a fuel rod having a spiral character with a cross-section formed by alternating connection of a plurality of outer arcs and inner arcs, and wherein the cross-sectional geometry of the spiral-petaline fuel assembly comprises any one of 2 lobes to 8 lobes or a combination thereof.
3. The method of claim 2, wherein in the discretized zoning construction process of the spiral geometry, in a radial dimension, the coolant area is adaptively divided into N annular or irregular geometric subregions according to the radial gradient distribution characteristics of void fractions, wherein N is more than or equal to 2; In the axial dimension, the coolant region is divided into M level sub-regions, wherein M is equal to or greater than 2, and the level height is set in association with the spiral pitch of the fuel rod so as to capture the axial periodic fluctuation or overall transportation trend of the cavitation share.
4. A method according to claim 3, wherein the parameterized partition hierarchy is established during the establishment of the partition parameterized index and correction rules, in particular: axial reference distribution-dividing the region into multiple levels in the axial dimension-defining reference void fractions for each level The reference cavitation share is monotonically increased or distributed in a specific function along the flow direction; Radial correction distribution, dividing the region into a plurality of characteristic groups in the radial dimension, defining correction coefficients of each group relative to a reference cavitation fraction 。
5. The method of claim 4, wherein the coolant partition indexing mechanism assigns a unique material identifier to each discrete sub-volume unit in a hierarchical coding format, the identifier comprising a combination of an axial hierarchical code and a radial group code to enable automated mapping of material properties and geometric space.
6. The method of claim 5, wherein constructing the coupling-corrected cavitation-density model is based on calculating local cavitation shares based on the following relationship : Wherein, the method comprises the steps of, Representing the radial coordinate from the center of the assembly, For the outer radius of the fuel rod cladding, Is cavitation share peak value, dynamically adjusts along with the working condition of gas-liquid two-phase flow, The damping coefficient is obtained by fitting gas-liquid two-phase flow test data or reference calculation results, Is a helix angle For reflecting the influence of the axial helical structure on the bubble distribution.
7. The method of claim 6, wherein the calculating of the mixing density parameters for each discrete partition Following the steps of dependent on the local cavitation fraction Combined with liquid phase density Density with gas phase Calculated as follows: and simultaneously, introducing a boron concentration correction term into the calculation, and performing the calculation on the mixed density parameter And (3) correcting the boron concentration, wherein the correction term adjusts the liquid density according to the product of the preset boron dilution coefficient and the boron concentration.
8. The method of claim 7, wherein in the process of adaptive solving, geometric and physical information is stored in an HDF5 format, geometric consistency verification is completed, finally, a partition modeling result and a coupling analysis report are output through a gas-liquid two-phase flow numerical simulation verification method, specifically, according to the coding format and a cavitation-density model, geometric boundaries, cavitation share, mixed density parameters and working condition parameters of each coolant sub-area are written into an HDF5 file in the form of a data set, consistency of a partition topological structure and the geometric model is verified by summing all partition volumes and comparing the total volume with the total volume of the coolant given by the geometric model, then, the HDF5 file is read through a gas-liquid two-phase flow numerical simulation program, steady state or transient calculation is carried out on a representative spiral petal component or sub-channel, and accuracy verification is carried out on the modeling method through cavitation share and pressure drop distribution of a comparison numerical result and a test reference or an upper fine calculation result.
9. An electronic device comprising a memory and a processor, the memory storing a computer program, characterized in that the processor implements the steps of the method of any of claims 1-8 when the computer program is executed.
10. A computer readable storage medium storing computer instructions which, when executed by a processor, implement the steps of the method of any one of claims 1-8.

Description

Neutron calculation modeling method for multidimensional non-uniform cavitation share of spiral petal-shaped fuel assembly Technical Field The invention relates to the technical field of neutron physics and thermal hydraulic coupling analysis of nuclear reactors, relates to a two-phase flow modeling method suitable for a fuel assembly with special-shaped geometric features, and particularly relates to a neutron calculation modeling method for multidimensional non-uniform cavitation share of a spiral petal-shaped fuel assembly. Background The prior experimental study shows that under the working conditions of undersaturation boiling and subsequent flow boiling, the proportion of coolant cavitation bubbles in the sub-channels is obviously unevenly distributed in the radial direction. When the total cavity share is low, the cavity is mainly concentrated in the near wall area of the shell, and gradually drifts towards the center of the sub-channel along with the increase of the cavity share and the development of flow boiling, and under the actions of vortex, cavity drift, turbulent mixing and the like, the cavity distribution on the whole section presents complex non-uniform characteristics. The data presented by the existing pressurized water reactor sub-track and component test benchmarks (e.g., pressurized water reactor sub-track and component test international benchmarks PSBT) indicate that it is difficult to accurately reproduce this feature using simple uniform or linear distribution assumptions. For the above phenomena, there has been proposed a cavitation distribution model using an exponential decay form, that is, assuming that cavitation share decays exponentially from the outer surface of the envelope to the center of the sub-channel, the volume average cavitation share is made to coincide with the test or reference calculation result by adjusting the peak value and the decay coefficient. The model essentially assumes that the diffusion and condensation process of bubbles generated by the wall surface to the volume liquid can be approximated as diffusion-drift behavior, and the model is simple in form and convenient to apply in engineering analysis. However, conventional models are mostly built for cylindrical fuel rod channels, do not fully take into account the effect of fuel rod cross-sectional shape and channel geometry on cavitation distribution, and are typically modeled in only one radial dimension, with inadequate consideration of axial and circumferential non-uniformities. On the other hand, the existing pressurized water reactor coolant cavitation modeling method adopts a fixed number of partitions with regular sizes on the space discrete basis, the partition scale cannot be adjusted in a self-adaptive mode according to the actual gradient of the cavitation share, and encryption description of a region with a larger cavitation gradient is difficult while the calculated amount is kept controllable. In addition, the existing method has insufficient quantitative coupling consideration between cavitation share, coolant density and boron concentration, and lacks a set of system modeling flow which can directly generate standardized data files and can be conveniently coupled with gas-liquid two-phase flow numerical simulation and neutron programming. For the reasons mentioned above, it is very necessary to propose a neutron computation modeling method for multidimensional non-uniform cavitation share aiming at a spiral petal-shaped fuel assembly, which performs adaptive partitioning on a coolant area in the axial and radial directions, introduces an exponential decay cavitation model considering the influence of a spiral structure, and couples with the coolant density and the boron concentration to form a standardized data interface that can be directly invoked in numerical simulation. Disclosure of Invention The invention aims to solve the problems of insufficient description dimension, limited spatial resolution, incomplete coupling of cavitation share, coolant density and boron concentration and lack of standardized data interfaces of a petal-shaped spiral fuel assembly coolant two-phase flow in the prior art, and provides a neutron calculation modeling method for a multidimensional non-uniform cavitation share of a spiral petal-shaped fuel assembly. According to the invention, on the basis of the geometry of a spiral petal-shaped fuel rod (such as FPF, TPF and the like), the coolant area is subjected to unlimited partition of axial and radial multidimensional, the non-uniform distribution of cavitation share is described by adopting an exponential decay coupling model, the coolant density of each partition is calculated on the basis, a standard data file (such as HDF 5) is finally generated, and the modeling result is subjected to comprehensive verification in terms of neutron and thermal hydraulic power through gas-liquid two-phase flow numerical simulation. The invention is realized by th