Methods for simulating the flow of a fluid in a vessel of a nuclear reactor and for calculating the mechanical deformation of assemblies of a nuclear reactor core, and associated computer program products

Patent metadata

Field	Value
Publication number	US-10354767-B2
Application number	US-201414782770-A
Country	US
Kind code	B2
Filing date	Apr 4, 2014
Priority date	Apr 10, 2013
Publication date	Jul 16, 2019
Grant date	Jul 16, 2019

Abstract

A method for simulating the flow of a fluid in a vessel of a nuclear reactor is provided. The nuclear reactor includes the vessel and a core inside the vessel, the core including nuclear fuel assemblies, each one extending in an axial direction, including nuclear fuel rods and a grid for maintaining the rods, and being spaced apart from another by a clearance between the grids in a transverse direction.
This method for simulating a fluid flow in the vessel of a nuclear reactor includes determining of head loss coefficients in the core, and computing the fluid pressure and speed component(s) in the core using the equation: ∇P=−K×V where P is the component of the fluid pressure, K is a matrix including the determined head loss coefficients, and V is a vector including the fluid speed component(s).
A transverse head loss coefficient in the assemblies is determined from a transverse Reynolds number, and an axial head loss coefficient in the clearance is from the dimension of the clearance in the transverse direction.

First claim

What is claimed is:

1. A method for simulating the flow of a fluid inside a vessel of a nuclear reactor, the nuclear reactor comprising the vessel and a core positioned inside the vessel, the core including nuclear fuel assemblies, each assembly extending in an axial direction and including nuclear fuel rods and at least one grid for maintaining the rods, each assembly being spaced apart from another assembly by a clearance between the grids in a transverse direction perpendicular to the axial direction, the fluid being able to flow inside the core,
the method comprising, implementing by a computer including a processor and a memory associated with the processor, the following steps:
i) determining head loss coefficients in the core by determining a transverse head loss coefficient in the assemblies as a function of a transverse Reynolds number in the transverse direction, and determining an axial head loss coefficient in the clearance as a function of the dimension of the clearance in the transverse direction;
ii) computing the pressure of the fluid and component(s) of a speed of the fluid in the core, using the following equation:
∇ P=−K×V

where ∇ is the order one spatial derivation nabla operator,
P is the component of the pressure of the fluid,
K is a matrix including the head loss coefficients determined during step i), and
V is a vector including the component(s) of the speed of the fluid; and
generating a simulation of the flow of the fluid inside the core such that the fluid is simulated to flow inside the core in accordance with values of the pressure of the fluid and the component(s) of the speed computed in step ii).

2. The method as recited in claim 1 , wherein, during step i), the transverse head loss coefficient is determined, for a value of the transverse Reynolds number, by comparison with a variable computed for a part of the assembly using a first model, with the variable computed for the part of the assembly using a second model, separate from the first model.

3. The method as recited in claim 2 , wherein the relationship of the transverse head loss coefficient as a function of the transverse Reynolds number is computed by interpolation of several values of the transverse head loss coefficient determined for a plurality of comparisons performed.

4. The method as recited in claim 2 , wherein at least one first grid among the grids- further comprises additional mixers able to generate a flow having at least one transverse speed in the transverse direction, and at least one second grid among the grids does not include additional mixers, and
wherein a first relationship of the transverse head loss coefficient as a function of the transverse Reynolds number is computed for a first part of the assembly including the first grid, and a second relationship of the transverse head loss coefficient as a function of the transverse Reynolds number is computed for a second part of the assembly including the second grid.

5. The method as recited in claim 1 , wherein, during step i), the axial head loss coefficient in the clearance is determined, for a value of the dimension of the clearance, by comparison with a variable computed for a part of the assembly using a first model, with the variable computed for the part of the assembly using a second model, different from the first model.

6. The method as recited in claim 5 , wherein the relationship of the axial head loss coefficient in the clearance as a function of the dimension of the clearance is computed by interpolation of several values of the axial head loss coefficient in the clearance between the grids, determined for a plurality of comparisons performed.

7. The method as recited in claim 1 , wherein during step i), the head loss coefficients other than the transverse head loss coefficient in the assemblies and the axial head loss coefficient in the clearance between the grids each have a predetermined value.

8. The method as recited in claim 1 , wherein the vessel includes a fluid inlet orifice and a fluid outlet orifice, the core including a lower plate and an upper plate, the assemblies extending between the lower and upper plates, the core having a volume delimited by first and second interfaces in the axial direction, the first and second interfaces respectively corresponding to the lower and upper plates,
the method further comprising:
determining at least one additional volume inside the vessel, the additional volume being outside the core volume and situated at one end thereof in the axial direction, the additional volume being delimited by two interfaces in the axial direction, one of the two interfaces of the additional volume being the first interface or the second interface,
computing, for the additional volume and using the mass balance, movement quantity balance and energy balance equations of the fluid, the pressure of the fluid and the component(s) of the speed of the fluid, from an initial value of the speed or pressure in one of the interfaces of the additional volume and an initial value of the speed or the pressure in the other of the interfaces of the additional volume,
computing, for the core volume, the pressure of the fluid and the component(s) of the speed of the fluid, from an initial value of the speed or pressure of the fluid in the first interface and an initial value of the speed or pressure of the fluid in the second interface and according to step ii), and
the computation of the pressure of the fluid and of the component(s) of the speed of the fluid is first done for a first volume among the additional volume and the core volume, in the interface among the first and second interfaces that is shared by the additional volume and the core volume,
then the pressure of the fluid and of the component(s) of the speed of the fluid is computed for the second volume among the additional volume and the core volume, the initial value of the speed or pressure at the interface shared by the additional volume and the core volume and for that computation step associated with the second volume then being the value of the corresponding variable among the speed and the pressure previously computed at the interface for the first volume.

9. The method as recited in claim 8 , wherein the mass balance, movement quantity balance and energy balance equations are respectively as follows:

⁢

∂
ρ

∂
t

+

∇

(

ρ
⁢

⁢
V

)

=

S
m

⁢

⁢

⁢

Assignees

• Areva Np

Inventors

• Goreaud Nicolas
• Chazot Benjamin
• Galpin Jérémy
• Salaün Hubert
• Mery De Montigny Elodie

Classifications

• G06F17/18

  for evaluating statistical data {, e.g. average values, frequency distributions, probability functions, regression analysis (forecasting specially adapted for a specific administrative, business or logistic context G06Q10/04)} · CPC title

• G21D3/001 Primary

  Computer implemented control · CPC title

• Y02E30/40

  Cross-Sectional Technologies · mapped topic

• G21D3/005

  Thermo-hydraulic simulations · CPC title

• Y02E30/00

  Energy generation of nuclear origin · CPC title