CN115099172B - Method for analyzing characteristics of melt chip bed forming process - Google Patents
Method for analyzing characteristics of melt chip bed forming process Download PDFInfo
- Publication number
- CN115099172B CN115099172B CN202210800225.XA CN202210800225A CN115099172B CN 115099172 B CN115099172 B CN 115099172B CN 202210800225 A CN202210800225 A CN 202210800225A CN 115099172 B CN115099172 B CN 115099172B
- Authority
- CN
- China
- Prior art keywords
- fluid
- melt
- fragments
- model
- chip
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 238000000034 method Methods 0.000 title claims abstract description 58
- 230000008569 process Effects 0.000 title claims abstract description 44
- 239000012634 fragment Substances 0.000 claims abstract description 113
- 239000012530 fluid Substances 0.000 claims abstract description 56
- 239000000155 melt Substances 0.000 claims abstract description 49
- 238000012546 transfer Methods 0.000 claims abstract description 34
- 238000004364 calculation method Methods 0.000 claims abstract description 31
- 239000007787 solid Substances 0.000 claims abstract description 23
- 239000007788 liquid Substances 0.000 claims abstract description 20
- 239000000463 material Substances 0.000 claims abstract description 19
- 102100021807 ER degradation-enhancing alpha-mannosidase-like protein 1 Human genes 0.000 claims abstract description 18
- 230000008878 coupling Effects 0.000 claims abstract description 16
- 238000010168 coupling process Methods 0.000 claims abstract description 16
- 238000005859 coupling reaction Methods 0.000 claims abstract description 16
- 230000003993 interaction Effects 0.000 claims abstract description 16
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 15
- 239000002245 particle Substances 0.000 claims description 88
- 239000012071 phase Substances 0.000 claims description 28
- 239000007791 liquid phase Substances 0.000 claims description 18
- 230000016507 interphase Effects 0.000 claims description 14
- 230000004927 fusion Effects 0.000 claims description 13
- 230000008859 change Effects 0.000 claims description 11
- 238000009833 condensation Methods 0.000 claims description 9
- 230000005494 condensation Effects 0.000 claims description 9
- 230000008020 evaporation Effects 0.000 claims description 9
- 238000001704 evaporation Methods 0.000 claims description 9
- 238000002474 experimental method Methods 0.000 claims description 9
- 238000004088 simulation Methods 0.000 claims description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 9
- 238000001816 cooling Methods 0.000 claims description 8
- 238000009825 accumulation Methods 0.000 claims description 7
- 238000013016 damping Methods 0.000 claims description 6
- 239000007790 solid phase Substances 0.000 claims description 6
- 230000036962 time dependent Effects 0.000 claims description 6
- 239000012808 vapor phase Substances 0.000 claims description 6
- NAWXUBYGYWOOIX-SFHVURJKSA-N (2s)-2-[[4-[2-(2,4-diaminoquinazolin-6-yl)ethyl]benzoyl]amino]-4-methylidenepentanedioic acid Chemical compound C1=CC2=NC(N)=NC(N)=C2C=C1CCC1=CC=C(C(=O)N[C@@H](CC(=C)C(O)=O)C(O)=O)C=C1 NAWXUBYGYWOOIX-SFHVURJKSA-N 0.000 claims description 3
- 230000001133 acceleration Effects 0.000 claims description 3
- 238000009835 boiling Methods 0.000 claims description 3
- 238000013500 data storage Methods 0.000 claims description 3
- 239000008187 granular material Substances 0.000 claims description 3
- 238000013064 process characterization Methods 0.000 claims description 3
- 238000011084 recovery Methods 0.000 claims description 3
- 238000004458 analytical method Methods 0.000 abstract description 10
- 239000002826 coolant Substances 0.000 abstract description 6
- 238000011160 research Methods 0.000 description 9
- 239000012768 molten material Substances 0.000 description 5
- 238000011439 discrete element method Methods 0.000 description 3
- 230000014759 maintenance of location Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 238000004880 explosion Methods 0.000 description 2
- 239000000446 fuel Substances 0.000 description 2
- 230000001788 irregular Effects 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 229910052770 Uranium Inorganic materials 0.000 description 1
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 238000005253 cladding Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 238000007726 management method Methods 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000000941 radioactive substance Substances 0.000 description 1
- 230000005514 two-phase flow Effects 0.000 description 1
- JFALSRSLKYAFGM-UHFFFAOYSA-N uranium(0) Chemical compound [U] JFALSRSLKYAFGM-UHFFFAOYSA-N 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
Classifications
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/20—Design optimisation, verification or simulation
- G06F30/28—Design optimisation, verification or simulation using fluid dynamics, e.g. using Navier-Stokes equations or computational fluid dynamics [CFD]
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/20—Design optimisation, verification or simulation
- G06F30/23—Design optimisation, verification or simulation using finite element methods [FEM] or finite difference methods [FDM]
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F2113/00—Details relating to the application field
- G06F2113/08—Fluids
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
- G06F2119/14—Force analysis or force optimisation, e.g. static or dynamic forces
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Theoretical Computer Science (AREA)
- General Physics & Mathematics (AREA)
- Computer Hardware Design (AREA)
- General Engineering & Computer Science (AREA)
- Geometry (AREA)
- Evolutionary Computation (AREA)
- Fluid Mechanics (AREA)
- Pure & Applied Mathematics (AREA)
- Mathematical Physics (AREA)
- Mathematical Optimization (AREA)
- Mathematical Analysis (AREA)
- Computing Systems (AREA)
- Algebra (AREA)
- Management, Administration, Business Operations System, And Electronic Commerce (AREA)
Abstract
A method for analysis of characteristics of a melt chip bed formation process, comprising the steps of: 1. performing geometric modeling and grid division; 2. modeling the molten fragment morphology, selecting fragment materials and coolant materials, and setting initial parameters; 3. coupling EDEM software and Fluent software, and setting a calculation model and boundary conditions; 4. calculating a fluid mass, energy and momentum conservation equation to obtain gas-liquid share, fluid state and temperature distribution; 5. calculating a solid-liquid interaction force and a heat transfer model to obtain the drag force and the heat transfer quantity of the fluid to fragments; 6. calculating a solid collision mechanical model and a heat conduction model of the molten fragments; 7. calculating the position, speed and temperature distribution of the molten fragments at the next moment by combining the drag force and heat transfer quantity information transmitted by Fluent; 8. judging whether the ending time is reached, if not, advancing according to the time step, and if so, outputting a calculation result. Based on the method of the present invention, the morphology of the final melt chip bed can be predicted.
Description
Technical Field
The invention relates to the technical field of fluid-solid coupling mechanical action and heat transfer phase change research of molten fragments and coolant of a severe accident reactor core of a nuclear power plant, in particular to a method for analyzing the characteristics of a molten fragment bed forming process.
Background
In the three-mile island nuclear accident in 1979, the reactor core is destroyed to melt part of the nuclear uranium fuel of the zirconium cladding of the fuel rod, so that radioactive substances are leaked. This accident is a high concern for serious accidents of nuclear reactors by students in the international nuclear field, and a serious accident management strategy is proposed for the accident: in-pile Retention (IVR) strategy. In-stack retention refers to the containment of core melt within a pressure vessel after a severe accident in a nuclear power plant by employing a series of strategies or means to maintain the integrity of the pressure vessel, thereby limiting the consequences of the severe accident within a circuit boundary.
Extensive and intensive research into this melt in-pile retention strategy is underway internationally, and the behavior after severe accident of core fusion can be divided into the following aspects: the melt reacts with the water (steam-containing explosion stage, jet break-up), the melt fragments settle and accumulate to form a fragment bed, the cooling of the fragment bed, the remelting of the fragment bed and the dynamic behaviour of the bath. Earlier studies were mainly directed to the steam explosion process, the cooling process of the chip bed, whereas the study of the chip bed formation process and the remelting of the chip bed was relatively blank, the present invention was developed as a calculation method for the analysis of the characteristics of the melt chip bed formation process.
The research of the formation process of the chip bed in the initial stage mainly utilizes experimental research, and a large number of experiments of injecting the melt into a water tank are carried out internationally, and a series of mechanism models, semi-empirical formulas and empirical formulas are provided according to the experimental research. Based on the experiment and the model, a large number of integrated serious accident analysis programs are developed, and a series of processes after the melt jet enters the water tank can be simulated. Nevertheless, due to the complexity of the various processes themselves and the limited experimental conditions (e.g., using simulated materials and non-prototype dimensions), there is still a great deal of uncertainty in the current understanding and prediction of certain phenomena of serious accidents. The late stage of melting of the in-pile melt is a field of great need for further investigation, since it not only affects the prediction of the whole serious accident by the power plant, but also relates to the dynamic evolution of the in-pile melt to the pressure vessel, closely related to the safety of the nuclear reactor.
The molten material disintegrates after contacting with coolant water to form molten material fragments of variable size and shape, and the molten material fragments are settled under the drive of gravity and accumulated in the reactor core support structure or the lower chamber of the reactor vessel to form a fragment bed, which is called a fragment bed forming process. The process of forming the chip bed plays a decisive role in determining the final form of the chip bed, and research on the process has great significance in improving the cooling performance of the chip bed, reducing the remelting risk of the chip bed and keeping the integrity of the containment of the pressure vessel, but the research on a calculation model of the process of forming the chip bed is relatively less, and the process belongs to an imperfect research field at home and abroad.
Part of students use a mechanical analysis method and a computational fluid Dynamics (Computational Fluid Dynamics, CFD) method to simulate the formation process of a fragment bed in the severe accident field of a nuclear reactor, such as two-dimensional and three-dimensional numerical simulation of the formation process of the fragment bed in the severe accident by adopting a discrete element method (Discrete Element Method, DEM), research on collapse and accumulation of core melt fragments by adopting a Contact Dynamics (CD) method, and analysis of the porosity of the accumulation form of the fragment bed. However, the discrete medium mechanical analysis method can only complete collision simulation among particles and cannot meet the requirement of solid-liquid two-phase flow simulation. Some scholars consider the melt fragments as continuous media for simulation, such as using CFD methods to study the melt interaction with water, but the calculations do not agree well with small scale mixing experiments.
Thus, the present study combines discrete media mechanics analysis methods with computational fluid dynamics to provide a method for melt chip bed formation process characterization.
Disclosure of Invention
In order to study the interaction process of fragments and coolant and obtain the movement characteristics of the molten fragments and the morphology of the final fragment bed in the fragment bed forming process, the invention provides a method for analyzing the characteristics of the molten fragments in the forming process of the molten fragments bed on the basis of the simulation of the accident of nuclear power plant reactor core melting and the simulation of the interaction experiment of the molten fragments and water in the prior art.
In order to achieve the above purpose, the invention adopts the following technical scheme:
a method for melt chip bed formation process characterization comprising the steps of:
step 1: based on calculation objects in a nuclear power plant reactor core fusion accident simulation or a fusion and water interaction experiment, obtaining fusion fragment characteristic information and nuclear reactor core structure or experimental equipment information, performing geometric modeling on a calculation domain of the core structure or experimental equipment, fusion fragments and fluid, and performing grid division on a geometric body;
step 2: modeling the shape and the size of the molten fragments in EDEM software, setting basic information of the material type, the material thermophysical property, the material mechanical property, the mass or the volume, the initial speed and the initial temperature of the molten fragments, setting information of the material type, the material thermophysical property and the mechanical property of a nuclear reactor core structure or an experimental container, and setting contact mechanical parameters among the molten fragments and between the molten fragments and a wall surface; selecting a fluid name in Fluent software and setting the morphology, thermophysical property, initial temperature, initial speed and distribution of the fluid in a calculation domain;
step 3: the coupling of the Fluent software and an adapter interface Adaptor Interface provided by the EDEM software is realized through the UDF function of the Fluent software, so that the movement of the molten fragments and the flow field information of the two software can be mutually transmitted; selecting a contact mechanical model and a particle heat transfer model of the molten fragments in the EDEM software, and setting boundary conditions, calculation time step, calculation time and data storage frequency of the release of the molten fragments; selecting a multiphase flow model, a turbulence model, a gas-liquid evaporation and condensation model, a fluid-solid coupling drag model and corresponding boundary conditions of fluid in Fluent software;
step 4: combining initial melt fragment particle information transmitted by EDEM software, regarding the melt fragments as solid phase fragments injected by a DPM model in Fluent software, and calculating a mass equation, a momentum equation and an energy equation by using a multiphase flow model in Fluent software to obtain the gas-liquid share and distribution, the fluid flow state and the temperature distribution of a fluid domain at the next moment; the gas-liquid share is calculated by using an evaporation condensation model-Lee model, and the mass exchange between gas and liquid phases can be calculated as shown in the formulas (1), (2) and (3):
wherein:
v-represents the vapor phase;
l-represents a liquid phase;
α v -steam volume fraction;
ρ v steam density/kg.m -3 ；
Vapor phase velocity/m.s -1 ；
Evaporation mass rate/kg.s -1 ·m -3 ；
Condensation mass rate/kg.s -1 ·m -3 ；
α l -liquid phase volume fraction;
ρ l density of liquid phase/kg.m -3 ；
T l -liquid phase temperature/K;
T sat -liquid phase saturation temperature/K;
c-adjustment of the coefficient, similar to the relaxation time;
step 5: calculating the drag force and interphase heat transfer quantity of fluid on the molten fragment particles by using a fluid-solid coupling mechanical model and a fluid-solid phase-to-phase heat transfer model, and transmitting the drag force and interphase heat transfer quantity to all the molten fragment particles in the EDEM software; the fluid-solid coupling mechanical model is shown as the following formula (4), and the fluid-solid phase heat transfer model is shown as the following formula (5):
wherein:
-stress/N representing the melt chip particles;
s-represents the melt chip particulate phase;
f-represents the fluid phase;
m s -particle mass/kg;
τ r -particle relaxation time;
fluid phase velocity/m.s -1 ；
-melt chip particle phase velocity/m.s -1 ；
ρ s -melt chip particle phase density/kg·m -3 ；
ρ f -fluid phase density/kg.m -3 ；
-gravitational acceleration/m.s -2 ；C vm -a virtual quality factor; c p,s Specific heat capacity of the granules/J.kg -1 ·K -1 ；
h-convection heat transfer coefficient/W.m -2 ·K -1 ；
T s -melt chip particle phase temperature/K;
A s particle surface area/m 2 ；
T ∞ -continuous phase local temperature/K; epsilon s Particle emissivity (dimensionless);
sigma-Stefin-Boltzmann constant/W.m -2 ·K -4 ；
θ R -radiation temperature/K;
step 6: calculating the mutual collision among the melt chip particles by using Hertz-Mindlin contact mechanical models expressed by a formula (6), a formula (7) and a formula (8), and calculating the heat transfer quantity among the melt chip particles by using a solid chip particle heat conduction model expressed by a formula (9) and a formula (10);
wherein:
-stress/N of the melt chip particles;
-represents normal force/N;
-represents tangential force/N;
-represents normal elastic force/N;
-represents the normal damping force/N;
E * equivalent Young's modulus/Pa;
R * -equivalent radius/m;
δ n -normal overlap vector/m of the melt chip particles;
beta-equivalent recovery coefficient;
m * -equivalent mass/kg;
S n -normal stiffness/pa·m;
normal relative velocity/m.s -1 ；
F t e -represents tangential elastic force/N;
F t d -represents tangential damping force/N;
S t -tangential stiffness/pa·m;
δ t -tangential overlap of the melt chip particles/m;
tangential relative velocity/m.s -1 ；
m-mass/kg;
C p specific heat capacity/J.kg -1 ·K -1 ；
T-temperature/K;
q-heat exchange between melt chip particles/J.s -1 ；
Q p1p2 Heat exchange between the melt chip particles p1 and p 2/J.s -1 ；
h c Heat exchange coefficient/W.m -2 ·K -1 ；
ΔT p1p2 Melt chip particles p1 and temperature differences/K between particles p2
k p1 ,k p2 -thermal conductivity/w.m of melt chip particles p1 and particles p2 -2 ·K -1 ；
Step 7: combining the drag force and interphase heat transfer quantity information of the melt chip particles transmitted by the UDF in Fluent software, calculating the positions and the speeds of the melt chip particles at the next moment by using Newton's second law, and calculating the temperature distribution of the melt chip particles by using a basic heat conduction model;
step 8: and (3) repeating the steps 4-7 within the set calculation time to obtain the time-dependent change process of the position, speed, temperature and resultant force of fragments in the settling process of the fragments of the molten mass at different moments, obtain the time-dependent change of the gas-liquid volume fraction, the fluid distribution, the speed, the pressure and the temperature of the fluid domain, obtain the interaction force and the interphase heat transfer quantity between the fragments of the molten mass particles and the fluid, and obtain the accumulation form, the porosity and the temperature distribution of the final fragments of the molten mass bed. The above data can be used to analyze and predict the final melt chip bed morphology during the melt chip bed formation process, melt chip motion process, melt chip collision process, melt chip and fluid interaction process, gas-liquid boiling phenomenon, fluid and melt solid chip temperature change process to improve chip bed cooling performance, reduce chip bed remelting risk and maintain pressure vessel containment integrity.
Compared with the prior art, the invention has the following advantages:
the analysis method can accurately solve the collision between the molten fragments and the wall surface, and simultaneously considers the interaction force and inter-phase heat exchange between the molten fragments and the fluid; aiming at irregular melt fragments, the invention can combine regular particles to form irregular melt fragments with different sizes and shapes, so that the fragment motion characteristics of the fragment bed forming process are more real. And the coupling of the EDEM software and the Fluent software is extremely convenient, the advantages of high calculation speed and calculation setting exist, a large number of complicated pretreatment and post-treatment are avoided, and large-scale calculation can be performed, so that the safety of the reactor is more efficiently and accurately evaluated.
Drawings
FIG. 1 is a flow chart of the method of the present invention.
Fig. 2 is a schematic diagram of a chip bed formation experiment.
Fig. 3a and 3b are schematic views of the morphology of the elongated fragments and the elongated curved fragments, respectively.
FIG. 4 is a schematic view of the morphology of a chip bed of accumulated melt chips.
Detailed Description
The invention is described in further detail below with reference to the drawings and the detailed description.
Step 1: based on calculation objects in a nuclear power plant reactor core fusion accident simulation or a fusion and water interaction experiment, obtaining fusion fragment characteristic information and nuclear reactor core structure or experimental equipment information, performing geometric modeling on a calculation domain of the core structure or experimental equipment, fusion fragments and fluid, and performing grid division on a geometric body;
step 2: modeling the shape and the size of the molten fragments in EDEM software, setting basic information of the material type, the material thermophysical property, the material mechanical property, the mass or the volume, the initial speed and the initial temperature of the molten fragments, setting information of the material type, the material thermophysical property and the mechanical property of a nuclear reactor core structure or an experimental container, and setting contact mechanical parameters among the molten fragments and between the molten fragments and a wall surface; selecting a fluid name in Fluent software and setting the morphology, thermophysical property, initial temperature, initial speed and distribution of the fluid in a calculation domain;
step 3: the coupling of the Fluent software and an adapter interface Adaptor Interface provided by the EDEM software is realized through the UDF function of the Fluent software, so that the movement of the molten fragments and the flow field information of the two software can be mutually transmitted; selecting a contact mechanical model and a particle heat transfer model of the molten fragments in the EDEM software, and setting boundary conditions, calculation time step, calculation time and data storage frequency of the release of the molten fragments; selecting a multiphase flow model, a turbulence model, a gas-liquid evaporation and condensation model, a fluid-solid coupling drag model and corresponding boundary conditions of fluid in Fluent software;
step 4: combining initial melt fragment particle information transmitted by EDEM software, regarding the melt fragments as solid phase fragments injected by a DPM model in Fluent software, and calculating a mass equation, a momentum equation and an energy equation by using a multiphase flow model in Fluent software to obtain the gas-liquid share and distribution, the fluid flow state and the temperature distribution of a fluid domain at the next moment; the gas-liquid share is calculated by using an evaporation condensation model-Lee model, and the mass exchange between gas and liquid phases can be calculated as shown in the formulas (1), (2) and (3):
wherein:
v-represents the vapor phase;
l-represents a liquid phase;
α v -steam volume fraction;
ρ v steam density/kg.m -3 ；
Vapor phase velocity/m.s -1 ；
Evaporation mass rate/kg.s -1 ·m -3 ；
Condensation mass rate/kg.s -1 ·m -3 ；
α l -liquid phase volume fraction;
ρ l density of liquid phase/kg.m -3 ；
T l -liquid phase temperature/K;
T sat -liquid phase saturation temperature/K;
c-adjustment of the coefficient, similar to the relaxation time;
step 5: calculating the drag force and interphase heat transfer quantity of fluid on the molten fragment particles by using a fluid-solid coupling mechanical model and a fluid-solid phase-to-phase heat transfer model, and transmitting the drag force and interphase heat transfer quantity to all the molten fragment particles in the EDEM software; the fluid-solid coupling mechanical model is shown as the following formula (4), and the fluid-solid phase heat transfer model is shown as the following formula (5):
wherein:
-stress/N representing the melt chip particles;
s-represents the melt chip particulate phase;
f-represents the fluid phase;
m s -particle mass/kg;
τ r -particle relaxation time;
fluid phase velocity/m.s -1 ；
-melt chip particle phase velocity/m.s -1 ；
ρ s -melt chip particle phase density/kg·m -3 ；
ρ f -fluid phase density/kg.m -3 ；
-gravitational acceleration/m.s -2 ；C vm -a virtual quality factor; c p,s Specific heat capacity of the granules/J.kg -1 ·K -1 ；
h-convection heat transfer coefficient/W.m -2 ·K -1 ；
T s -melt chip particle phase temperature/K;
A s particle surface area/m 2 ；
T ∞ -continuous phase local temperature/K; epsilon s Particle emissivity (dimensionless);
sigma-Stefin-Boltzmann constant/W.m -2 ·K -4 ；
θ R -radiation temperature/K;
step 6: calculating the mutual collision among the melt chip particles by using Hertz-Mindlin contact mechanical models expressed by a formula (6), a formula (7) and a formula (8), and calculating the heat transfer quantity among the melt chip particles by using a solid chip particle heat conduction model expressed by a formula (9) and a formula (10);
wherein:
-stress/N of the melt chip particles;
-represents normal force/N;
-represents tangential force/N;
-represents normal elastic force/N;
-represents the normal damping force/N;
E * equivalent Young's modulus/Pa;
R * -equivalent radius/m;
δ n -normal overlap vector/m of the melt chip particles;
beta-equivalent recovery coefficient;
m * -equivalent mass/kg;
S n -normal stiffness/pa·m;
normal relative velocity/m.s -1 ；
F t e -represents tangential elastic force/N;
F t d -represents tangential damping force/N;
S t -tangential stiffness/pa·m;
δ t -tangential overlap of the melt chip particles/m;
tangential relative velocity/m.s -1 ；
m-mass/kg;
C p specific heat capacity/J.kg -1 ·K -1 ；
T-temperature/K;
q-heat exchange between melt chip particles/J.s -1 ；
Q p1p2 Heat exchange between the melt chip particles p1 and p 2/J.s -1 ；
h c Heat exchange coefficient/W.m -2 ·K -1 ；
ΔT p1p2 Melt chip particles p1 and temperature differences/K between particles p2
k p1 ,k p2 -thermal conductivity/w.m of melt chip particles p1 and particles p2 -2 ·K -1 ；
Step 7: combining the drag force and interphase heat transfer quantity information of the melt chip particles transmitted by the UDF in Fluent software, calculating the positions and the speeds of the melt chip particles at the next moment by using Newton's second law, and calculating the temperature distribution of the melt chip particles by using a basic heat conduction model;
step 8: and (3) repeating the steps 4-7 within the set calculation time to obtain the time-dependent change process of the position, speed, temperature and resultant force of fragments in the settling process of the fragments of the molten mass at different moments, obtain the time-dependent change of the gas-liquid volume fraction, the fluid distribution, the speed, the pressure and the temperature of the fluid domain, obtain the interaction force and the interphase heat transfer quantity between the fragments of the molten mass particles and the fluid, and obtain the accumulation form, the porosity and the temperature distribution of the final fragments of the molten mass bed. The above data can be used to analyze and predict the final melt chip bed morphology during the melt chip bed formation process, melt chip motion process, melt chip collision process, melt chip and fluid interaction process, gas-liquid boiling phenomenon, fluid and melt solid chip temperature change process to improve chip bed cooling performance, reduce chip bed remelting risk and maintain pressure vessel containment integrity.
In summary, the geometric modeling and grid division of the calculation object are completed through the steps 1 to 3, and the calculation of a conservation equation, a fluid-solid coupling interaction force model and an inter-phase heat transfer model is completed through the steps 4 to 5, so that the gas-liquid share, the fluid state and the temperature distribution of the fluid domain, the drag force and the heat transfer quantity of the fluid domain on the molten fragments are obtained; and (3) completing the calculation of the contact mechanical model, the solid fragment particle heat conduction model and the Newton second law through the steps 6 to 7 to obtain the position, the speed and the temperature distribution of the melt fragment particles. By combining the steps, the characteristics of the formation process of the molten material fragment bed are simulated and analyzed, so that the accumulation form, the porosity and the temperature distribution of the final molten material fragment bed are obtained, the cooling performance analysis of the fragment bed is facilitated, the remelting risk of the fragment bed is reduced, and the integrity of the containment vessel of the pressure vessel is maintained.
The effects of the present invention will be described below with reference to specific calculation objects, taking the experiment of the formation of a chip bed shown in fig. 2 as an example. Firstly, obtaining the characteristic information of the molten fragments and the structural or experimental information of the nuclear reactor core, such as the equipment size, the conventional morphology of the molten fragments, the mass of the fragments, the volume of the fragments, the materials, the fragments and the temperature of the coolant, wherein the experimental schematic diagram is shown in fig. 2, and the conventional morphology of the molten fragments of the long-strip fragments and the long-strip-shaped bent fragments is shown in fig. 3a and 3 b. And finishing geometric modeling, meshing and initial parameter setting based on the information. In EDEM software, a collision mechanics model selects a Hertz-Mindlin model; in Fluent software, the multiphase flow model is set as a mixing model, and the turbulence model is set as a reallizable K-epsilon model. After the calculation is started, the molten fragments are released from the bottom of the funnel, and according to the steps 4 to 7, the mechanical and heat transfer interactions among the molten fragments, between the molten fragments and the wall surface and between the molten fragments and the coolant can be calculated, so that the change of the molten fragments movement characteristic, the fluid movement characteristic and the solid-liquid temperature distribution with time in the step 8 can be obtained. And finally outputting the result, and obtaining the accumulation form, the porosity and the temperature distribution of the molten fragment bed shown in fig. 4, which is helpful for the cooling performance analysis of the fragment bed, reduces the remelting risk of the fragment bed and maintains the integrity of the containment of the pressure vessel.
Claims (1)
1. A method for melt chip bed formation process characterization, characterized by: the method comprises the following steps:
step 1: based on calculation objects in a nuclear power plant reactor core fusion accident simulation or a fusion and water interaction experiment, obtaining fusion fragment characteristic information and nuclear reactor core structure or experimental equipment information, performing geometric modeling on a calculation domain of the core structure or experimental equipment, fusion fragments and fluid, and performing grid division on a geometric body;
step 2: modeling the shape and the size of the molten fragments in EDEM software, setting basic information of the material type, the material thermophysical property, the material mechanical property, the mass or the volume, the initial speed and the initial temperature of the molten fragments, setting information of the material type, the material thermophysical property and the mechanical property of a nuclear reactor core structure or an experimental container, and setting contact mechanical parameters among the molten fragments and between the molten fragments and a wall surface; selecting a fluid name in Fluent software and setting the morphology, thermophysical property, initial temperature, initial speed and distribution of the fluid in a calculation domain;
step 3: the coupling of the Fluent software and an adapter interface Adaptor Interface provided by the EDEM software is realized through the UDF function of the Fluent software, so that the movement of the molten fragments and the flow field information of the two software can be mutually transmitted; selecting a contact mechanical model and a particle heat transfer model of the molten fragments in the EDEM software, and setting boundary conditions, calculation time step, calculation time and data storage frequency of the release of the molten fragments; selecting a multiphase flow model, a turbulence model, a gas-liquid evaporation and condensation model, a fluid-solid coupling drag model and corresponding boundary conditions of fluid in Fluent software;
step 4: combining initial melt fragment particle information transmitted by EDEM software, regarding the melt fragments as solid phase fragments injected by a DPM model in Fluent software, and calculating a mass equation, a momentum equation and an energy equation by using a multiphase flow model in Fluent software to obtain the gas-liquid share and distribution, the fluid flow state and the temperature distribution of a fluid domain at the next moment; the gas-liquid share is calculated by using an evaporation condensation model-Lee model, and the mass exchange between gas and liquid phases can be calculated as shown in the formulas (1), (2) and (3):
wherein:
v-represents the vapor phase;
l-represents a liquid phase;
α v -steam volume fraction;
ρ v steam density/kg.m -3 ；
Vapor phase velocity/m.s -1 ；
Evaporation mass rate/kg.s -1 ·m -3 ；
Condensation mass rate/kg.s -1 ·m -3 ；
α l -liquid phase volume fraction;
ρ l density of liquid phase/kg.m -3 ；
T l -liquid phase temperature/K;
T sat -liquid phase saturation temperature/K;
c-adjustment of the coefficient, similar to the relaxation time;
step 5: calculating the drag force and interphase heat transfer quantity of fluid on the molten fragment particles by using a fluid-solid coupling mechanical model and a fluid-solid phase-to-phase heat transfer model, and transmitting the drag force and interphase heat transfer quantity to all the molten fragment particles in the EDEM software; the fluid-solid coupling mechanical model is shown as the following formula (4), and the fluid-solid phase heat transfer model is shown as the following formula (5):
wherein:
-stress/N representing the melt chip particles;
s-represents the melt chip particulate phase;
f-represents the fluid phase;
m s -particle mass/kg;
τ r -particle relaxation time;
fluid phase velocity/m.s -1 ；
-melt chip particle phase velocity/m.s -1 ；
ρ s -melt chip particle phase density/kg·m -3 ；
ρ f -fluid phase density/kg.m -3 ；
-gravitational acceleration/m.s -2 ；C vm -a virtual quality factor; c p,s Specific heat capacity of the granules/J.kg -1 ·K -1 ；
h-convection heat transfer coefficient/W.m -2 ·K -1 ；
T s -melt chip particle phase temperature/K;
A s particle surface area/m 2 ；
T ∞ -continuous phase local temperature/K; epsilon s Particle emissivity (dimensionless);
sigma-Stefin-Boltzmann constant/W.m -2 ·K -4 ；
θ R -radiation temperature/K;
step 6: calculating the mutual collision among the melt chip particles by using Hertz-Mindlin contact mechanical models expressed by a formula (6), a formula (7) and a formula (8), and calculating the heat transfer quantity among the melt chip particles by using a solid chip particle heat conduction model expressed by a formula (9) and a formula (10);
wherein:
-stress/N of the melt chip particles;
-represents normal force/N;
-represents tangential force/N;
-represents normal elastic force/N;
-represents the normal damping force/N;
E * equivalent Young's modulus/Pa;
R * -equivalent radius/m;
δ n -normal overlap vector/m of the melt chip particles;
beta-equivalent recovery coefficient;
m * -equivalent mass/kg;
S n -normal stiffness/pa·m;
-normal relative speed-m·s -1 ；
F t e -represents tangential elastic force/N;
F t d -represents tangential damping force/N;
S t -tangential stiffness/pa·m;
δ t -tangential overlap of the melt chip particles/m;
tangential relative velocity/m.s -1 ；
m-mass/kg;
C p specific heat capacity/J.kg -1 ·K -1 ；
T-temperature/K;
q-heat exchange between melt chip particles/J.s -1 ；
Q p1p2 Heat exchange between the melt chip particles p1 and p 2/J.s -1 ；
h c Heat exchange coefficient/W.m -2 ·K -1 ；
ΔT p1p2 Melt chip particles p1 and temperature differences/K between particles p2
k p1 ,k p2 -thermal conductivity/w.m of melt chip particles p1 and particles p2 -2 ·K -1 ；
Step 7: combining the drag force and interphase heat transfer quantity information of the melt chip particles transmitted by the UDF in Fluent software, calculating the positions and the speeds of the melt chip particles at the next moment by using Newton's second law, and calculating the temperature distribution of the melt chip particles by using a basic heat conduction model;
step 8: repeating the steps 4-7 within the set calculation time to obtain the time-dependent change process of the position, speed, temperature and resultant force of fragments in the settling process of the fragments of the molten fragments at different moments, obtain the time-dependent change of the gas-liquid volume fraction, fluid distribution, speed, pressure and temperature of the fluid domain, obtain the interaction force and interphase heat transfer quantity between the particles of the solid molten fragments and the fluid, and obtain the accumulation form, porosity and temperature distribution of the final molten fragment bed; the above data can be used to analyze and predict the final melt chip bed morphology during the melt chip bed formation process, melt chip motion process, melt chip collision process, melt chip and fluid interaction process, gas-liquid boiling phenomenon, fluid and melt solid chip temperature change process to improve chip bed cooling performance, reduce chip bed remelting risk and maintain pressure vessel containment integrity.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210800225.XA CN115099172B (en) | 2022-07-08 | 2022-07-08 | Method for analyzing characteristics of melt chip bed forming process |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210800225.XA CN115099172B (en) | 2022-07-08 | 2022-07-08 | Method for analyzing characteristics of melt chip bed forming process |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN115099172A CN115099172A (en) | 2022-09-23 |
| CN115099172B true CN115099172B (en) | 2024-03-12 |
Family
ID=83296121
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202210800225.XA Active CN115099172B (en) | 2022-07-08 | 2022-07-08 | Method for analyzing characteristics of melt chip bed forming process |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN115099172B (en) |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2016001164A (en) * | 2014-06-12 | 2016-01-07 | 一般財団法人電力中央研究所 | Reactor core molten material dispersion structure |
| WO2019190367A1 (en) * | 2018-03-28 | 2019-10-03 | Bechta Sevostian | A safety system of a nuclear reactor for stabilization of ex-vessel core melt during a severe accident |
| CN111785402A (en) * | 2020-07-02 | 2020-10-16 | 西安交通大学 | Experimental device and method for researching migration behavior of melt in fragment bed |
| CN111832214A (en) * | 2020-06-29 | 2020-10-27 | 西安交通大学 | Method for simulating melting process of nuclear reactor severe accident scrap bed based on particle method |
| CN113192567A (en) * | 2021-04-30 | 2021-07-30 | 西安交通大学 | Nuclear reactor plate fuel melt fluid-solid coupling grid-free analysis method |
-
2022
- 2022-07-08 CN CN202210800225.XA patent/CN115099172B/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2016001164A (en) * | 2014-06-12 | 2016-01-07 | 一般財団法人電力中央研究所 | Reactor core molten material dispersion structure |
| WO2019190367A1 (en) * | 2018-03-28 | 2019-10-03 | Bechta Sevostian | A safety system of a nuclear reactor for stabilization of ex-vessel core melt during a severe accident |
| CN111832214A (en) * | 2020-06-29 | 2020-10-27 | 西安交通大学 | Method for simulating melting process of nuclear reactor severe accident scrap bed based on particle method |
| CN111785402A (en) * | 2020-07-02 | 2020-10-16 | 西安交通大学 | Experimental device and method for researching migration behavior of melt in fragment bed |
| CN113192567A (en) * | 2021-04-30 | 2021-07-30 | 西安交通大学 | Nuclear reactor plate fuel melt fluid-solid coupling grid-free analysis method |
Non-Patent Citations (2)
| Title |
|---|
| LOCA事故后堆芯瞬态传热及熔融过程数值研究;刘逸群;张小英;王彪;徐俊英;张雷;张会勇;展德奎;;核动力工程(01);全文 * |
| 下封头熔融物碎片床冷却模型研究;余红星;卢庆;何晓强;苏光辉;;核动力工程(02);全文 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN115099172A (en) | 2022-09-23 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Beckermann et al. | Multiphase/-scale modeling of alloy solidification | |
| Koshizuka | Current achievements and future perspectives on particle simulation technologies for fluid dynamics and heat transfer | |
| Ikeda et al. | Numerical analysis of jet injection behavior for fuel-coolant interaction using particle method | |
| Shukla et al. | CFD simulation of steam condensation in a subcooled water pool | |
| CN115099172B (en) | Method for analyzing characteristics of melt chip bed forming process | |
| Moriyama et al. | Analytical tool development for coarse break-up of a molten jet in a deep water pool | |
| Yakush et al. | Three-phase VOF modeling of water jet–molten metal interaction | |
| Yakush et al. | Modeling of two-phase natural convection flows in a water pool with a decay-heated debris bed | |
| Gou et al. | Simulation of isothermal multi-phase fuel-coolant interaction using MPS method with GPU acceleration | |
| Xu et al. | Numerical study of debris bed formation behavior for severe accident in sodium-cooled fast reactor by using least square MPS-DEM method | |
| Fukuda et al. | Analysis of the localized metallic phase solidification in VULCANO VF-U1 with MPS method | |
| Park et al. | Three-dimensional modeling of debris mixing and sedimentation in severe accidents using the moving particle semi-implicit method coupled with rigid body dynamics | |
| Morgan et al. | Thermal stratification modeling for sodium-cooled fast reactors: a status update | |
| Colombo et al. | CFD model development for two-phase flows | |
| Cheng et al. | Study on the effect of jet cross section shape on molten fuel fragmentation behavior with simulant experiments | |
| Guo et al. | Numerical simulation on the impact of a liquid square on rigid plate and liquid layer | |
| Jo¹ et al. | On Using SPH to Study Nuclear Severe Accidents | |
| Wang et al. | Numerical Investigation of Melt Fragmentation in Sodium-Cooled Fast Reactor Based on Moving Particle Method | |
| Matsuo et al. | Study on application of artificial neural network to debris bed coolability calculations for sodium-cooled fast reactors | |
| Yamano et al. | Experimental analyses by SIMMER-III on debris-bed coolability and metallic fuel freezing behavior | |
| Eom et al. | Evaluation of jet breakup length with a CFD code under steam generation condition in a pre-flooded cavity | |
| Li et al. | Preliminary evaluation on the relocation phase of ex-vessel debris of fukushima daiichi nuclear power plant unit-3 | |
| Kren et al. | Bubble Breakup Sensitivity on Local Surface Tension Modification in LES of Turbulent Slug Flow | |
| Kashcheev et al. | Simulating the retention of molten fuel in a fast-neutron reactor during a severe accident | |
| Xu et al. | Numerical simulation of melt jet breakup under non solidification conditions |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |