Hybrid Monte Carlo and Deterministic Particle Transport Method Based on Transition Area

Abstract

A hybrid Mote Carlo and deterministic particle transport method based on the transition area is provided. Firstly, the geometric complexity is analyzed based on the CAD model. Based on the geometric complexity and the physical characteristics, an area having complex geometry is divided as a Monte Carlo particle transport calculation area, an area having simple geometry is divided as a deterministic particle transport calculation area, and a transition area with a determined thickness is created between the two areas. In the particle transport calculation, the Monte Carlo particle transport calculation is performed in the Monte Carlo particle transport area and the transition area, and the deterministic calculation is performed in the deterministic area and the transition area. Basically consistent results of the transition area under the two calculations can be achieved through multiple iterations, thereby realizing seamless coupling of the two calculations.

Claims

1. A hybrid Mote Carlo and deterministic particle transport method based on a transition area, comprising: (1) performing preliminary automatic dividing to obtain a deterministic particle transport area and a Monte Carlo particle transport area, comprising: (11) generating a CAD mode based on a calculation model required for particle transport calculation; and (12) automatically analyzing the CAD model obtained in step (11) to obtain geometric complexity of the calculation model, automatically analyzing a physical characteristic of the calculation model, and dividing a calculation area into two calculation areas: the Monte Carlo particle transport area and the deterministic particle transport area, on which particle transport simulation is performed respectively with a Monte Carlo method and a deterministic method; (2) creating a transition area and determining a final deterministic transport area, comprising: (21) determining an interface of the two calculation areas obtained in step (1) as a surface of the transition area in the calculation model required for the particle transport calculation; (22) automatically analyzing a physical characteristic of each cell at the surface of the transition area obtained in step (21), calculating a maximum neutron transport mean free path at a surface of a bounding box, and creating the transition area in the deterministic particle transport area obtained in step (1) using N times the maximum neutron transport mean free path as a thickness of the transition area; and (23) subtracting the transition area obtained in (22) from the deterministic particle transport area obtained in step (1), to obtain the final deterministic particle transport area; and (3) performing a seamless coupling calculation, comprising: (31) simulating the Monte Carlo particle transport in the Monte Carlo particle transport area and the transition area, to obtain flux of particles and a surface current of each cell at the interface between the Monte Carlo particle transport area and the transition area; (32) performing the deterministic particle transport calculation in the deterministic particle transport area and the transition area by taking the surface current at the interface between the Monte Carlo particle transport area and the transition area obtained in step (31) as a source, to obtain flux of the particles and surface current at the interface between the deterministic particle transport area and the transition area; (33) comparing fluxes of the transition area obtained through the two calculations in steps (31) and (32); turning to step (34) if the maximum relative deviation between flux calculation results of the two calculations is smaller than a given deviation threshold dlt0, which indicates substantially consistent calculation results of the two calculations and seamless coupling of the two calculations; and turning to step (31) by taking the surface current at the interface between the deterministic particle transport area and the transition area as a new interface reflecting source if the maximum relative deviation is not less than dlt0; and (34) combining flux calculation results of the Monte Carlo particle transport area and the transition area obtained in (31) with flux calculation results of the deterministic particle transport area obtained in (32), to obtain particle flux of the whole space.

2. The hybrid Mote Carlo and deterministic particle transport method based on a transition area, according to claim 1, wherein the (12) of step (1) comprising: a) creating a series of bounding boxes based on the CAD model, and counting complex faces in the bounding boxes to obtain distribution of geometric complexity of the model; b) calculating a distance from a surface of the bounding box having complexity of x to the source, and obtaining a maximum attenuation coefficient w of particle transport on the surface of the bounding box based on an average free path of the particle transport in a material; and c) comparing the maximum attenuation coefficient w with a given attenuation coefficient limit w0; if w>w0, selecting the surface of the bounding box having the complexity x as an interface between the Monte Carlo particle transport calculation and the deterministic particle transport calculation, performing the Monte Carlo particle transport calculation in an area having complexity greater than x, and performing the deterministic particle transport calculation in an area having complexity less than x; if w<w0, increasing x by y % and repeating step (b), where y is set by a user or is set to be 0.1 to 0.5 by a program; if w<w0 after x is increased for a specified number of times M where M ranges from 10 to 20, stopping the increase, selecting the surface of the bounding box having the complexity x as the interface between the Monte Carlo particle transport calculation and the deterministic particle transport calculation, performing the Monte Carlo particle transport calculation in the area having the complexity greater than x, and performing the deterministic particle transport calculation in the area having the complexity less than x.

3. The hybrid Mote Carlo and deterministic particle transport method based on a transition area according to claim 1, wherein the N in step (22) ranges from 1 to 3.

4. The hybrid Mote Carlo and deterministic particle transport method based on a transition area according to claim 1, wherein the dlt0 in step (33) ranges from 0.0001 to 0.01.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1 is a flow chart of a method according to the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] The fusion shielding benchmark are published by Alamos National Laboratory in the United States in 1991. The seventh device in that model is selected as an application example of the present disclosure. The entire model is within a rectangular box of 899.16 cm690.85 cm678.18 cm, includes a shield layer with a thickness of 55.88 cm, and is mainly made of iron and borated polyethylene. The cement shield structure of the model includes a deuterium tritium fusion neutron source with energy of 14 MeV and coordinates (356.87,232.02,157.40). The volume fluxes of all the cells of the space are to be calculated.

[0029] The automatic preliminary dividing for a deterministic particle transport area and a Monte Carlo particle transport area is performed as follows.

[0030] Based on the geometrical characteristics of the fusion shielding benchmark, a cubic bounding box is selected, and the position of the neutron source is taken as the center of the bounding box. A series of nested cubic bounding boxes are set up with an initial side length of 100 cm and a side length step of 100 cm, and the geometric complexity of the bounding boxes are analyzed, to obtain a distribution map of the geometric complexity.

[0031] According to the given geometric complexity limit, a cubic bounding box with a side length of 300 cm is selected. The surface of the bounding box is made of concrete and water, and the average transport free path of the neutron with energy of 14 MeV is calculated. The maximum attenuation coefficient w of the neutron transport is calculated based on the distance from the source to the surface of the bounding box. Since the maximum attenuation coefficient w is less than a given attenuation coefficient limit w0, the surface of the bounding box with a center at the position of the neutron source and a side length of 300 cm is taken as the interface between the Monte Carlo particle transport calculation and the deterministic particle transport calculation. The inside of the bounding box is the Monte Carlo particle transport area, and the outside of the bounding box is the deterministic particle transport area.

[0032] A transition area is created as follows.

[0033] The surface of the cubic bounding box with a center at the position of the neutron source and a side length of 300 cm is taken as the surface of the transition area.

[0034] Based on the calculated maximum particle transport mean free path (about 1.5 cm in the material of water), a cubic bounding box with a side length of 301.5 cm is created, and the area between the two bounding boxes is the transition area, which has a thickness of one maximum particle transport mean free path.

[0035] The outside of the cubic bounding box with the side length of 301.5 cm is taken as the final deterministic particle transport area.

[0036] The seamless coupling calculation is performed as follows.

[0037] The Monte Carlo particle transport calculation is performed in the inside of the cubic bounding box (Monte Carlo particle transport area and transition area) with the side length of 301.5 cm, to count the volume flux of all cells in the area and the surface current at the surface of the cubic bounding box with the side length of 3500 cm.

[0038] With the surface current at the surface of the cubic bounding box with the side length of 300 cm as the source, the deterministic particle transport calculation is performed on the outside (the deterministic particle transport area and the transition area) of the cubic bounding box with the side length of 300 cm, to count the volume flux of all cells in the area and the surface current at the surface of the cubic bounding box with the side length of 301.5 cm.

[0039] The volume fluxes of the transition area obtained through the two calculations are compared. If the maximum deviation dlt of the two results is greater than a given deviation threshold dlt0, the surface current at the surface of the cubic bounding box with the side length of 301.5 cm is taken as a new reflection source for the Monte Carlo particle transport calculation, and the above-mentioned steps of the Monte Carlo and deterministic particle transport calculations are re-performed. If dlt is less than dlt0, the calculation results of the Monte Carlo particle transport area, the transition area and the deterministic particle transport area are combined, to obtain the particle flux of the whole space.

[0040] The dividing for the Monte Carlo transport calculation area and deterministic transport calculation area is automatically performed based on the geometric and physical characteristics of the model, avoiding the manual division which is dependent on the user experience and is error-prone. Further, the seamless coupling of Monte Carlo transport calculation and deterministic transport calculation is achieved through the setting of the transition layer and multiple iterations, ensuring the correctness of the final results. Therefore, an effective particle transport calculation method for large-scale reactor shield analysis is provided.

[0041] The above-mentioned embodiments are provided for the purpose of describing the present disclosure and are not intended to limit the scope of the present disclosure. The scope of the present disclosure is defined by the appended claims. Various equivalent substitutions and modifications not departing from the spirit and principles of the present disclosure fall within the scope of the present disclosure.