CN105225710B - The reactor core analogue body and steam generator analogue body method for designing of circulation loop system - Google Patents

Abstract

The invention discloses a method for designing a reactor core simulation body and a steam generator simulation body of a circulation loop system, including design requirements, structural design, similarity ratio analysis and design of the reactor core simulation body, and design requirements of the steam generator simulation body , structural design and design results, this method determines the design requirements of the core simulation body and the steam generator simulation body of the experimental loop system according to the design parameters and functional requirements of the natural circulation experimental loop, and then respectively determines the core simulation body and the steam generator simulation body The simulation body is designed and analyzed. The invention improves the reliability of the measures for accident setting beyond the design basis and the diversification of the safety system of the nuclear power plant, and has high engineering value.

Description

Design Method of Core Simulator and Steam Generator Simulator for Circulation Loop System

technical field

The invention belongs to the field of reactor thermal water conservancy, and in particular relates to a design method for a core simulation body and a steam generator simulation body of a circulation loop system.

Background technique

The reactor can use the ability of natural circulation to export heat without relying on external power to realize the operation of the passive safety facilities of the reactor under accidents, thereby improving the safety of the reactor.

Since the Fukushima incident in Japan, the international and domestic communities have put forward higher requirements for nuclear energy safety, and more and more attention has been paid to the reliability of mitigation measures for beyond-design basis accidents such as power outages and complete loss of cooling chains. . In the "General Technical Requirements for Nuclear Power Plant Improvement Actions after the Fukushima Nuclear Accident (Trial)" issued by the National Nuclear Safety Administration in June 2012, it has repeatedly proposed that some or all of the safety system functions of nuclear power units in operation and under construction in nuclear power plants In the case of loss, such as the flood event beyond the design basis, more measures should be taken to bring out the residual heat. The newly released "Safety Requirements and Review Principles for New Nuclear Power Plants During the Twelfth Five-Year Plan Period" clearly requires that new nuclear power plants during the Twelfth Five-Year Plan period must increase the consideration of waste heat discharge from the reactor core, emergency cooling and final heat sink. Set up a diverse final heat sink.

Although the current technical scheme of the ACPR1000 project has set up some mitigation measures for beyond design basis accidents, there is still a big gap in the diversification design of the safety system of the nuclear power plant. According to the results of the current deterministic safety analysis and PSA analysis, the accidents related to the secondary side of the steam generator have a significant contribution. Therefore, it is necessary to set up a diversified mitigation system with higher reliability for accidents beyond the design basis such as complete loss of feed water, rupture of main steam pipe, rupture of main feed water pipe combined with loss of auxiliary feed water, power outage of the whole plant, complete loss of cooling chain, etc. The side passive waste heat removal system meets this requirement. The present invention is designed at the above-mentioned problem just.

Contents of the invention

The purpose of the embodiments of the present invention is to provide a design method for the core simulation body and the steam generator simulation body of the circulation loop system, aiming at solving the problem that the reliability of the measures set for accidents beyond the design basis is not high enough, and the safety systems of nuclear power plants are diversified. The problem of major deficiencies.

The present invention is achieved in this way, a method for designing a core simulation body and a steam generator simulation body of a circulation loop system, including the design requirements, structural design, similarity ratio analysis and design of the reactor core simulation body, and the steam generator simulation body According to the design requirements, structural design and design results of the natural circulation experimental circuit, this method determines the design requirements of the core simulation body and the steam generator simulation body of the experimental loop system, and then respectively determines the core simulation body and the steam generator simulation body. The steam generator simulation body is designed and analyzed.

Furthermore, the design of the core simulation body is based on ACPR1000 as the prototype. The ACPR1000 core has 157 boxes of fuel assemblies. The core simulation body simulates one of the fuel assemblies. The surface heat flux ratio of the heating element is 2:1;

The core simulation body includes copper rods, flat covers, cylinder ends, inlet and outlet joints, inlet and outlet flanges, cylinders, hanging baskets, ceramics, fuel assembly simulation parts, lower heads, hanging rings, inlet and outlet anti-flanges ;

The fuel assembly simulation part is suspended on the hanging ring through the hanging basket. Two copper rods are installed on the flat cover. One end of the two copper rods is connected to the positive and negative poles of the power supply, and the other end is connected to the fuel assembly simulation part;

The space between the component mock-up and the metal hanging basket is filled with ceramics.

Further, the length, hydraulic equivalent diameter, and flow cross-sectional area of the core simulation body piping of the core simulation body reflect its flow velocity and flow resistance.

Furthermore, the dimensionless momentum equation in the design of the core simulation volume is:

The dimensionless energy equation is:

The definitions of the dimensionless parameters in the momentum and energy equations are respectively: Richardson number Characterizes the relationship between buoyancy and inertial forces; drag coefficient Characterize the friction and shape resistance of the circuit; the heat source number is also called the phase change number Characterize the effect of fuel element heat release on loop enthalpy rise; heat capacity numbers Characterize the heat capacity of a structure as a function of loop enthalpy rise.

Furthermore, the dimensionless phase transition number in the design of the core simulation volume is:

The dimensionless degree of supercooling is:

Furthermore, the steam generator simulation body models the steam generator, the heat exchange tube height ratio is 1:4, the heat exchange tube diameter and grid pitch of the prototype are adopted, the temperature and pressure of the primary side and the secondary side of the steam generator are both Consistent with the prototype, according to the heat transfer capacity and heat transfer area of the steam generator in the prototype, the heat transfer area of the steam generator in the experimental circuit and the structural size of the heat transfer tube are obtained by modeling;

The steam generator simulation body includes an upper head, an end shell, a heat exchange tube, a lower end shell, and a lower end head. The heat exchange tube is fixed on the lower end shell through a fixed tube sheet, and sufficient quantities of The supporting plate and the baffle, and the lower head is separated by a partition.

Further, the core simulation body adopts a stainless steel tube with a length of 1050 mm and an outer diameter of 9.5 mm as a heating element, and the electric heating element is fixed by a positioning grid, and the positioning grid is planned to adopt the positioning grid in the prototype, and the upper and lower ends of the electric heating element and the copper plate The copper plates are respectively connected to the positive and negative poles of the power supply. The inlet and outlet pipes of the core simulation body are stainless steel pipes with an inner diameter of 105mm. The positions are arranged according to the prototype, and the space between the electric heating element and the pressure vessel is filled with ceramics.

The invention improves the reliability of the measures for accident setting beyond the design basis and the diversification of the safety system of the nuclear power plant, and has high engineering value.

Description of drawings

Fig. 1 is the front view of the core simulation body provided by the embodiment of the present invention;

Fig. 2 is a view of the inlet and outlet pipes of the core simulation body provided by the embodiment of the present invention;

Fig. 3 is a top view of the base of the core simulation body provided by the embodiment of the present invention;

Fig. 4 is a schematic diagram of the heat exchange tube layout provided by the embodiment of the present invention;

Fig. 5 is a B-B cross-sectional view of the heat exchange tube layout provided by the embodiment of the present invention;

In the figure: 1, copper rod; 2, flat cover; 3, cylinder end; 4, inlet and outlet joints; 5, inlet and outlet flanges; 6, cylinder; 7, hanging basket; 8, ceramics; 9, fuel Component simulation part; 10. Lower head; 11. Hanging ring; 12. Inlet and outlet anti-flange; 13. Steam outlet connection; 14. Upper head; 15. Upper shell; 16. Heat exchange tube; 17. Lower end Shell; 18, fixed tube plate; 19, lower head; 20, partition; 21, deionized water inlet and outlet connection; 22, tap water inlet connection; 23, deionized water inlet; 24, deionized water outlet; 25 , Tap water import; 26, Steam outlet.

detailed description

In order to make the object, technical solution and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with the examples. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

1. Design requirements for core simulation body

The core simulation body is one of the key equipment for the experimental research of passive waste heat removal in the natural circulation experimental circuit. Taking ACPR1000 as the prototype, the core of ACPR1000 has 157 boxes of fuel assemblies, and this core simulator simulates one box of fuel assemblies. The height ratio is 1:4, the speed ratio is 1:2, the surface heat flux density ratio of the electric heating element is 2:1, and the axial and lateral resistance characteristics are reasonably designed.

2. Structural design of core simulation body

The general structure diagram of the core simulation body is shown in Fig. 1-Fig. 3. The core simulation body includes copper rod 1, flat cover 2, cylinder end 3, inlet and outlet joints 4, inlet and outlet flanges 5, cylinder 6, hanging basket 7, ceramics 8, fuel assembly simulation parts 9, and lower head 10, hanging ring 11, import and export anti-flange 12.

The fuel assembly simulation part 9 uses a stainless steel tube with a length of 1050 mm (1/4 of the height of the fuel assembly) and an outer diameter of 9.5 mm (the outer diameter of the fuel assembly) as a heating element. In order to simulate the spacer grid of the fuel assembly, the electric heating element is also fixed by the spacer grid, and the spacer grid is proposed to adopt the spacer grid in the prototype. The fuel assembly simulation part 9 is suspended on the hanging ring 11 through the hanging basket 7 to realize fixing. Two copper rods 1 are installed on the flat cover 2, and one end of the two copper rods 1 is respectively connected with the positive and negative poles of the power supply, and the other end is connected with the fuel assembly simulation part 9 to realize the purpose of electric heating.

In order to reduce the heat capacity of the metal, ceramics 8 are used to fill the space between the component simulation part 9 and the metal hanging basket 7 . The inlet and outlet joint 4 adopts a stainless steel pipe (about 1/7 of the prototype size) with an internal diameter of 105mm, and the position is arranged according to the prototype.

3. Similar proportion analysis of core simulation body

The structure of the reactor primary loop system is complex, and both the core and the steam generator need to be simplified through certain assumptions. The equipment of the reactor primary loop system can be simply divided into two types, that is, with heat transfer and without heat transfer; three types of equipment: piping, steam generator, and core. Wherein, the steam generator here refers to the part where the inlet and outlet temperature or density changes, that is, the steam generator tube bundle. The reactor core is the part of the core that undergoes temperature or density changes, that is, the heated part, and the rest is considered the pipe. If the influence of the two-phase flow pattern is considered, strictly speaking, the density of the fluid in the pipeline can also change. Pipes are characterized by no heat transfer, only the fluid's position changes and contributes to resistance. In reactor tube bundles, such as cold pipes and heat pipes, there is no major problem in conforming to the one-dimensional assumption, while some components with local mutations can reflect their role in the natural circulation process through resistance. Therefore, the length, hydraulic equivalent diameter, and flow cross-sectional area of the pipeline can reflect its flow velocity and flow resistance; the contribution of its position change to the gravity can be reflected through the projection in the direction of gravity. Regardless of the number of pipes, they can be converted into one-dimensional components with the above features.

3.1 Fundamental equations

The first is the one-dimensional assumption, which means that the flow is carried out along the axial direction of the equipment or pipeline, while the heat transfer is carried out in the radial direction of the one-dimensional boundary; secondly, by using characteristic parameters, such as thermal hydraulic diameter, etc. The role of directional influence is evaluated and simulated; in addition, heat loss, axial heat transfer, and higher-order terms in the equation need to be ignored, and the governing equation is:

(1) Continuity equation

In the above formula, ρ is the fluid density, and u is the fluid velocity.

(2) Momentum equation

In the above formula, P is the pressure, f is the resistance coefficient, and _De is the hydraulic equivalent diameter.

(3) Energy equation

In the above formula, h is the enthalpy of the fluid, ζ is the perimeter, A is the cross-sectional area, T _w and T _f are the wall temperature and fluid temperature, respectively.

(4) Heat transfer equation

The present invention does not simulate the convective heat transfer coefficient, the main reasons are: 1. the structure of the metal member is complex, and the one-dimensional method simulation in this model cannot be accurately described; Value; ③The fuel element basically conducts heat with a constant heat flux and is not affected by the heat transfer coefficient, while the wall temperature of the fuel rod itself is related to the material and structure, so it is not necessary to simulate in detail, and its research can be carried out in other situations. In this way, the energy equation and the heat transfer equation in the basic equation are combined, and the new energy equation is:

Vapor content by mass express

3.2 Equation dimensionless

It can be seen from the energy equation (6) that the density of the loop fluid is mainly controlled by the boundary heat transfer. When the core heat transfer changes, the local density changes at this time, but the density change does not immediately have a great impact on the flow rate. It is only this density change that substantially affects the density difference in the circuit as the fluid flow propagates throughout the circuit, resulting in a change in flow rate. Therefore, it can be considered that the partial differential term of the circuit fluid density with respect to time is an item that can be ignored. Therefore, the continuity equation changes to:

ρuA = ρ _in u _in A _in = const (7)

In the above formula, ρ _in , u _in and A _in are the density, flow velocity and flow cross-sectional area at the inlet of the core, respectively.

The conservation equation is dimensionless, and its dimensionless parameters are: velocity length density density difference circulation area time temperature etc., the subscript 0 represents the initial value of the parameter.

The continuity equation is dimensionless:

That is, the dimensionless velocity is

The momentum equation is dimensionless:

(1) Gravity pressure drop term Δρgl _hc

(2) Inertia term

Depend on Available

(3) Friction item

(4) Migration item

The momentum equation after dimensionless is

The energy equation after dimensionless is (the derivation method is similar to the momentum equation)

The definitions of the dimensionless parameters in the momentum and energy equations are respectively: Richardson number Characterizes the relationship between buoyancy and inertial forces; drag coefficient Characterize the friction and shape resistance of the circuit; the heat source number is also called the phase change number Characterize the effect of fuel element heat release on loop enthalpy rise; heat capacity numbers Characterize the heat capacity of a structure as a function of loop enthalpy rise.

3.3 Similarity criterion

First make sure the height ratio is similar

In order to satisfy the similarity between the prototype and the model, the ratios of the model and the prototype in (14) and (15) are both equal to 1, so we have

In order to satisfy the similarity of the continuity equation, we have

For the flow resistance, it is more appropriate to adopt the same rod bundle arrangement structure as the prototype because of the requirement of the gas-liquid two-phase flow simulation characteristics. In the same medium (water-water simulation) and isobaric simulation, first, the flow area of the prototype and the model is similar, that is

Depend on and Available

According to formula (23), we have

which is This criterion number characterizes the pressure ratio of the prototype and the model as a constant:

According to the above formula, it can be obtained that the core inlet and outlet density has the following relationship

According to formula (17), formula (24) and formula (26), we can get

The above formula expresses the relationship between the height ratio and the natural circulation speed ratio under the same physical properties.

(Π _Fi ) _R can be simplified according to formula (21):

Since the pressure ratio of the model and the prototype is constant, so established.

Similarly, [(Π _H ) _i ] _R can be written as:

This formula is the dimensionless phase change number In the same way, the definition of inlet air content can be deduced to the dimensionless subcooling degree

It is known from the energy equation that the mass gas content in the core changes the same, if the gas content at the core outlet is guaranteed to be equal (X _e ) _R ＝1, then (X _in ) _R ＝1, we have

(Π _sub ) _R ＝1 (30)

For heat capacity numbers there are:

When the thermophysical properties of the fluid and the metal material are the same, the above formula has:

This formula represents the mass relationship between the metal component and the circuit fluid in each local area.

In summary, the isobaric water-water simulation criterion relationship is shown in Table 1:

Table 1 Criteria for isobaric water-water simulation

3.4 Core Simulator

This experiment intends to simulate a box of fuel assemblies, and there are 157 boxes of fuel assemblies in the prototype, and the flow cross-sectional area of the core inlet in the prototype is From (22) can get

That is, the core inlet pipe diameter in the model is about 105mm. In this experiment, the diameter ratio is 1:7.23, the area ratio is 1:52, and the height ratio is 1:4, that is, the speed ratio is 1:2, and the surface heat flux ratio of the electric heating element is 2:1. The design results of the core simulation body are as follows:

a) Core height 1:4 design;

b) The flow area is designed according to 1:52, and the core flow rate ratio is 1:2;

c) Direct heating is adopted, and the surface heat flux density ratio of the rod is 2:1;

d) adopt the rod diameter of the prototype, and the grid pitch;

e) Reasonable design of axial and lateral resistance characteristics (simulation positioning grid);

f) Appropriate modeling of lateral flow characteristics.

4. Design requirements of steam generator

Similar to the core simulation body, the steam generator is modeled, the heat exchange tube height ratio is 1:4, and the heat exchange tube diameter and grid pitch of the prototype are adopted. It can be seen from the modeling that the thermal parameters of the steam generator should be consistent with the prototype, that is, the temperature and pressure of the primary side and the secondary side of the steam generator should be consistent with the prototype. According to the heat transfer capacity and heat transfer area of the steam generator in the prototype, the heat transfer area of the steam generator in the experimental circuit and the structural size of the heat transfer tube can be obtained by modeling.

5. Structural design of steam generator

Figures 4 and 5 show the structural design of the steam generator. The steam generator includes an upper head 14 , an end shell 15 , a heat exchange tube 16 , a lower end shell 17 , and a lower head 19 . The deionized water enters the heat exchange tube 16 from the deionized water inlet and outlet 23, exchanges heat with the condensate, and flows out from the deionized water outlet 24. The heat exchange tube 16 is fixed on the lower shell 17 through the fixed tube plate 18, Different positions of the heat exchange tubes 16 should be equipped with a sufficient number of support plates and baffles, and the lower heads 19 are separated by partitions 20 . The cold fluid tap water flows in through the tap water inlet 25, and after flowing in, deposits in the cavity of the lower shell 17 to exchange heat with the hot fluid in the heat exchange tube 16, then vaporizes into steam, and is discharged through the steam outlet 26 for circulation.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. within range.

Claims (6)

1. a kind of reactor core analogue body of circulation loop system and steam generator analogue body method for designing, it is characterised in that described Circulation loop system reactor core analogue body and steam generator analogue body method for designing including reactor core analogue body design requirement, Structure design, similar proportion analysis and design, and the design requirement of steam generator analogue body, structure design and design knot Really, the method determines experimental loop system heap core analogue body according to the design parameter and functional requirement of Natural Circulation experimental loop With the design requirement of steam generator analogue body, then reactor core analogue body and steam generator analogue body be designed and divided respectively Analysis is calculated；

With ACPR1000 as prototype, ACPR1000 reactor cores have 157 box fuel assemblies for the design of reactor core analogue body, the reactor core analogue body Box fuel assembly therein is simulated, highly than taking 1:4, speed ratio is 1:2, the surface heat flux ratio of electrical heating elements is 2: 1；

Reactor core analogue body includes copper rod, flat cover, barrel end, inlet-outlet connector, import and export flange, cylinder, hanging basket, ceramics, combustion Material component simulating piece, low head, link, the anti-flange of import and export；

Fuel assembly simulating piece, on link, is equipped with 2 copper rods, two copper rod one end in copper rod by hanging basket suspension on flat cover It is connected with the both positive and negative polarity of power supply respectively, the other end is connected with fuel assembly simulating piece；

Ceramic filler is used between component simulating piece and metal hanging basket.

2. the reactor core analogue body of circulation loop system as claimed in claim 1 and steam generator analogue body method for designing, its Be characterised by, reactor core analogue body reactor core analogue body pipeline length, hydraulics equivalent diameter and actual internal area embody its flow velocity, Flow resistance.

3. the reactor core analogue body of circulation loop system as claimed in claim 1 and steam generator analogue body method for designing, its It is characterised by, the dimensionless momentum equation in the design of reactor core analogue body is：

${\mathrm{\Π}}_R{\mathrm{\Δ\ρ}}^{+}{l}_{hc}^{+}=\underset{i}{\mathrm{\Σ}}\frac{l_i^{+}}{A_i^{+}}\frac{\∂u_{in}^{+}}{\∂\mathrm{\τ}}+\frac{1}{2}{\left(u_{in}^{+}\right)}^2{\mathrm{\Π}}_F+{\left(u_{in}^{+}\right)}^2\underset{i}{\mathrm{\Σ}}{\left(\frac{A_{in}}{A_i}\right)}^2\left(\frac{{\mathrm{\ρ}}_{in}^{+}}{{\mathrm{\ρ}}_i^{+}}\right)$

Dimensionless energy equation is：

$\left(\frac{{\mathrm{\ρ}}^{+}}{{\mathrm{\ρ}}_{in}^{+}}\right)\frac{\∂x}{\∂\mathrm{\τ}}+\frac{\∂x}{\∂s}={\mathrm{\Π}}_{pch}{q}^{+}-{\mathrm{\Π}}_C\frac{\∂\mathrm{\θ}}{\∂\mathrm{\τ}}$

The definition of dimensionless group is respectively in momentum and energy equation：Richardson numbersCharacterize buoyance lift Relation between power and inertia force；Resistance coefficientCharacterize friction and the shape in loop Resistance；Thermal source number is also referred to as phase parameterCharacterize the influence that fuel element heat release rises to loop enthalpy；Thermal capacitance numberCharacterize the relation that the thermal capacity of structure rises with loop enthalpy.

4. the reactor core analogue body of circulation loop system as claimed in claim 1 and steam generator analogue body method for designing, its It is characterised by, the dimensionless phase parameter in the design of reactor core analogue body is：

${\mathrm{\Π}}_{pch}=\frac{q_0{l}_{hc0}{\mathrm{\ξ}}_i}{{\mathrm{\ρ}}_0{u}_0{A}_0{\mathrm{\Δh}}_{fg}}\left(\frac{{\mathrm{\Δ\ρ}}_{fg}}{{\mathrm{\ρ}}_g}\right)$

Dimensionless is subcooled the number of degrees：

${\mathrm{\Π}}_{sub}=\frac{{\mathrm{\Δh}}_{sub}}{h_{fg}}\left(\frac{{\mathrm{\Δ\ρ}}_{fg}}{{\mathrm{\ρ}}_g}\right).$

5. the reactor core analogue body of circulation loop system as claimed in claim 1 and steam generator analogue body method for designing, its It is characterised by, steam generator analogue body carries out modelling to steam generator, tube height ratio takes 1:4, using changing for prototype The temperature and pressure of heat pipe footpath and pitch, primary side of steam generator and secondary side is all consistent with prototype, is steamed according in prototype The exchange capability of heat and heat exchange area of vapour generator, modelling obtains the heat exchange area and heat exchanger tube of steam generator in experimental loop Physical dimension；

Steam generator analogue body includes upper cover, end housing, heat exchanger tube, lower end housing, low head, and heat exchanger tube passes through fixing pipe Plate is fixed in lower end housing, and the diverse location of heat exchanger tube is sufficiently loaded with the supporting plate and baffle plate of quantity, low head by dividing plate every Open and separate.

6. the reactor core analogue body of circulation loop system as claimed in claim 1 and steam generator analogue body method for designing, its It is characterised by, reactor core analogue body uses 1050mm long, and the stainless steel tube of external diameter 9.5mm used as heating element heater, adopt by electrical heating elements Fixed with grid spacer, grid spacer is intended using the grid spacer in prototype, and the upper and lower side of electrical heating elements is connected with copper coin, copper Plate is connected with the both positive and negative polarity of power supply respectively, and the import and export pipeline internal diameter of reactor core analogue body is the stainless steel tube of 105mm, and position is pressed Prototype arrangement, uses ceramic filler between electrical heating elements and pressure vessel.