Reactor primary loop average temperature correction method

Abstract

The invention relates to the field of nuclear reactors, in particular to a method for correcting the loop average temperature of a primary loop of a reactor. The method comprises the following steps: performing numerical simulation on typical working conditions according to actual operation parameters of a nuclear power plant to obtain fluid mechanics simulation data; on the basis of streamline distribution and flow distribution conditions in the fluid mechanics simulation data, dividing a reactor core into regions, enabling the regions to correspond to a hot section outlet, and determining a flow distribution coefficient according to the flow of a cold section inlet coolant flowing into the regions respectively; quantizing the inlet coolant flow, the initial temperature, the area temperature, the area inlet specific enthalpy and the power of each area based on the area division result and the flow distribution coefficient; performing heat balance calculation on each area to obtain the specific enthalpy increasing amount of the coolant flowing through each area and the coolant temperature at the outlet of each area; and averaging the coolant temperature at the inlet and the outlet of each area to obtain the average temperature of the coolant of each loop. The measurement accuracy is improved, and the calculation deviation of the primary loop heat balance power is improved.

Description

Technical Field

[0001] This invention relates to the field of nuclear reactors, and more particularly to a method for correcting the average temperature of the primary loop of a reactor. Background Technology

[0002] The average temperature of the primary circuit in a reactor is a key parameter for reactor power control and safety protection, directly reflecting nuclear power and heat transfer. Therefore, it is of great significance to the safety and economic efficiency of reactor operation.

[0003] The original Generation II nuclear power plants used bypass temperature measurement to measure the primary loop temperature: a bypass temperature measurement line was introduced into the main pipeline, and insertion thermometers were placed on the bypass temperature measurement line to obtain the coolant temperature. The average loop temperature was then calculated by adding the temperatures of the cold and hot sections of each loop. Because of the mixing effect of the pumps, only one sampling pipe was needed for the cold pipe section of the primary loop. For the hot pipe section, three sampling nozzles at 120° intervals were inserted into the coolant flow channel of the main pipeline at the same cross-section. The sampled water from the three nozzles was mixed and flowed into the temperature measurement bypass to represent the water temperature of the hot pipe section. However, in actual operation, the average temperature of the primary loop often deviated from the theoretical value, leading to a mismatch between calculated and actual power, affecting reactor operation control and power boosting. The root cause was the uneven temperature distribution of the coolant in the primary loop's hot pipe section, resulting in inaccurate measurement of the average temperature of the hot pipe section. In other words, the bypass sampling temperature measurement method could not completely eliminate the effect of temperature stratification. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a method for correcting the average temperature of the primary loop of a reactor, thereby improving measurement accuracy and reducing the deviation in the calculation of the primary loop thermal balance power.

[0005] This invention provides a method for correcting the average temperature of the primary loop in a reactor, comprising the following steps:

[0006] Step 1: Perform numerical simulations of typical operating conditions based on actual operating parameters of the nuclear power plant to obtain fluid dynamics simulation data;

[0007] Step 2: Based on the streamline distribution and flow distribution in the fluid dynamics simulation data, divide the core into regions and correspond them with the hot section outlet. Determine the flow distribution coefficient according to the flow rate of the coolant flowing into the cold section inlet of each region.

[0008] Step 3: Based on the results of the region division and the flow distribution coefficient, quantify the inlet coolant flow rate, initial temperature, region temperature, region inlet specific enthalpy, and power of each region;

[0009] Step 4: Perform heat balance calculations for each region to obtain the increase in specific enthalpy of the coolant as it flows through each region, as well as the coolant temperature at the outlet of each region.

[0010] Step 5: Average the coolant temperature at the inlet and outlet of each area to obtain the average temperature of the coolant in each loop.

[0011] In a specific embodiment of the present invention, the operating parameters in step 1 include: coolant inlet temperature, flow rate, radial power distribution of fuel assembly, axial power distribution of fuel assembly, and coolant outlet pressure.

[0012] In a specific embodiment of the present invention, in step 1, when performing numerical simulation, different inlet coolants are set as components with the same physical properties, and the flow distribution results of the simulated core region are averaged to obtain the flow distribution results and streamline distribution results.

[0013] In a specific embodiment of the present invention, in step 2, the stack type is divided into a main region, a transition region and a central component region according to the coolant flow path and outlet location, with each region corresponding to a hot leg outlet.

[0014] In one specific embodiment of the present invention, in step 3, Qin j Let T be the coolant flow rate at the inlet of the j-th reactor. inj Given the coolant temperature at the j-th inlet, the inlet flow rate of the i-th region is calculated using the following formula:

[0015]

[0016] j=1, 2, 3; i=1, 2, 3;

[0017] The inlet temperature of the i-th region is calculated using the following formula:

[0018]

[0019] Specific enthalpy at the inlet of the i-th region: Calculated from the inlet temperature based on the specific enthalpy-temperature relationship curve of the coolant.

[0020] h i，in =f(T) i，in )

[0021] Let P be the total heat power borne by the i-th region. i Considering the average power distribution between the transition region and the central component region, P i Calculated using the following formula:

[0022]

[0023] in:

[0024] P area，i The main region's own power;

[0025] P trans，i，k The power allocated to the adjacent region in the transition region;

[0026] P center Total power of the central component.

[0027] In a specific embodiment of the present invention, in step 4, the increase in specific enthalpy Δh of the coolant flowing through the i-th region i :

[0028]

[0029] The export enthalpy h of region i i，out :h i，out =h i，in +Δh i ;

[0030] h i，in Let enthalpy be the input ratio of the i-th region;

[0031] Based on the specific enthalpy-temperature relationship curve of the coolant, from h i，out Back-calculation of the outlet temperature T of region i i，out T i，out =f -1 (h i，out ).

[0032] In a specific embodiment of the present invention, in step 5, the average temperature of the coolant in each loop is obtained by means of arithmetic mean, enthalpy integral mean, or flow rate weighted mean.

[0033] In one specific embodiment of the present invention, the entire loop is considered as a single uniform pipe, and the average temperature of the coolant in each loop is obtained by using an arithmetic mean method.

[0034]

[0035] T i，ave T represents the average temperature of the loop coolant. i，out Let T be the outlet temperature of region i. i，in Let be the inlet temperature of the i-th region.

[0036] Compared with the prior art, the reactor primary loop average temperature correction method of the present invention has the following advantages:

[0037] Beneficial effects:

[0038] (1) Based on simulated flow field data, a partitioned heat balance calculation model is constructed to effectively avoid the interference of temperature stratification on the results in traditional measurement methods, making the average temperature measurement of the primary loop closer to the actual working conditions.

[0039] (2) By regionalizing the core and coupling flow-power distribution, the calculation deviation of the primary loop thermal balance power is improved, providing more accurate parameter support for reactor power enhancement and operation control;

[0040] (3) Abstract the multi-condition simulation data into a general flow distribution coefficient to avoid separate modeling for different core loading schemes, reduce the complexity of engineering applications, and ensure the correction effect.

[0041] (4) By quantitatively correcting temperature deviations and optimizing unit operation monitoring parameters, technical support is provided for reactor thermal-hydraulic characteristic management, thereby helping to improve operational safety and economy.

[0042] (5) Through systematic regional division rules and thermal balance calculation logic, a reusable temperature deviation correction methodology is formed, providing a reference paradigm for parameter optimization of similar pressurized water reactor units.

[0043] In summary, this invention quantifies the non-uniformity of flow and heat transfer inside the reactor core through high-resolution fluid dynamics simulation, and establishes a partitioned thermal balance model based on this, reconstructs the partitioned thermal balance, calculates the true average temperature, and corrects the inherent bias. Attached Figure Description

[0044] Figure 1 This is a flowchart illustrating the reactor primary loop average temperature correction method. Detailed Implementation

[0045] To further understand the present invention, embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the present invention.

[0046] An embodiment of the present invention discloses a method for correcting the average temperature of the primary loop of a reactor, comprising the following steps:

[0047] Step 1: Perform numerical simulations of typical operating conditions based on actual operating parameters of the nuclear power plant to obtain fluid dynamics simulation data;

[0048] The operating parameters include: coolant inlet temperature, flow rate, radial power distribution of fuel assembly, axial power distribution of fuel assembly, and coolant outlet pressure.

[0049] The typical operating conditions refer to the typical operating conditions of different core loading schemes when the reactor is operating at rated power;

[0050] When performing numerical simulations, different inlet coolants are set to have the same physical properties, and the flow distribution results of the simulated core region are averaged to obtain the flow distribution results and streamline distribution results.

[0051] Step 2: Based on the streamline distribution and flow distribution in the fluid dynamics simulation data, divide the core into regions and correspond them with the hot section outlet. Determine the flow distribution coefficient according to the flow rate of the coolant flowing into the cold section inlet of each region.

[0052] Numerical simulations under different core loading schemes show that the mixing process of coolant within the pressure vessel is far from complete. The coolant exiting from a particular outlet primarily originates from nearby fuel assemblies. Although some mixing occurs as it flows around various in-core components, overall, most of the coolant is not fully mixed. Based on the coolant flow path and outlet location, the system is divided into three regions. Within each region, most of the coolant tends to flow directly to its corresponding outlet channel, while effective mixing with adjacent regions is relatively limited.

[0053] Although there are slight differences under different working conditions, they all conform to the above characteristics. In order to improve the versatility of the method, the partitioning principle is as follows: each region corresponds to a hot leg outlet and consists of a main region, a transition region, and a central component region.

[0054] All streamlines flowing from the fuel assembly outlets in the main region converge at the same hot leg outlet. The core region, independently belonging to a specific hot leg outlet, primarily receives coolant flow towards that outlet and serves as the basic unit for temperature correction in each loop. Power is directly assigned to this region and is not shared with other regions. In the transition region, all streamlines flowing from the fuel assembly outlets flow into the two adjacent hot leg outlets. The overlapping area at the boundary of the two main regions requires its power to be evenly distributed among the adjacent main regions. The central assembly region, located at the geometric center of the core, receives its power evenly distributed among the three main regions. After this division, the average deviation of the coolant mass fraction between the three outlets and their corresponding regions should be less than 3%.

[0055] The flow distribution coefficient refers to the mass fraction of coolant flowing into the three zones from each inlet. It is obtained by statistical numerical simulation results of the coolant flow rate at different inlets in each zone. α i，j Let be the flow distribution coefficient from the j-th inlet to the i-th region;

[0056] satisfy

[0057] The partitioning results and flow allocation coefficients obtained in this step are used as general parameters for the calculation of new operating conditions.

[0058] Step 3: Based on the results of the region division and the flow distribution coefficient, quantify the inlet coolant flow rate, initial temperature, region temperature, region inlet specific enthalpy, and power of each region;

[0059] Q inj Let T be the coolant flow rate at the inlet of the j-th reactor. inj Given the coolant temperature at the j-th inlet, the inlet flow rate of the i-th region is calculated using the following formula:

[0060]

[0061] j=1, 2, 3; i=1, 2, 3;

[0062] The inlet temperature of the i-th region is calculated using the following formula:

[0063]

[0064] Specific enthalpy at the inlet of the i-th region: Calculated from the inlet temperature based on the specific enthalpy-temperature relationship curve of the coolant.

[0065] h i，in =f(T) i，in )

[0066] Let P be the total heat power borne by the i-th region. i Considering the average power distribution between the transition region and the central component region, P i Calculated using the following formula:

[0067]

[0068] in:

[0069] P area，i The main region's own power;

[0070] P trans，i，k The power allocated to the adjacent region in the transition region;

[0071] P center Total power of the central component;

[0072] The total power of the central component is evenly distributed among the three regions.

[0073] The specific enthalpy-temperature relationship curve of the coolant was obtained from a physical property database.

[0074] Step 4: Perform heat balance calculations for each region to obtain the increase in specific enthalpy of the coolant as it flows through each region, as well as the coolant temperature at the outlet of each region.

[0075] The increase in specific enthalpy Δh of the coolant flowing through the i-th region i:

[0076]

[0077] Export enthalpy of region i: h i，out =h i，in +Δh i ;

[0078] The outlet temperature of region i: based on the specific enthalpy-temperature relationship curve of the coolant, from h i，out Back-calculation of the corresponding temperature T i，out That is: T i，out =f -1 (h i，out ).

[0079] Step 5: Average the coolant temperature at the inlet and outlet of each area to obtain the average temperature of the coolant in each loop;

[0080] The average temperature of the coolant in each loop is obtained by using the arithmetic mean, enthalpy integral average, or flow rate weighted average method.

[0081] Preferably, the entire loop is considered as a single uniform pipe, and the average temperature of the coolant in each loop is obtained using an arithmetic mean method.

[0082]

[0083] T i，ave T represents the average temperature of the loop coolant. i，out Let T be the outlet temperature of region i. i，in Let be the inlet temperature of the i-th region.

[0084] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0085] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for correcting the average temperature of a reactor primary loop, characterized in that, Includes the following steps: Step 1: Perform numerical simulations of typical operating conditions based on actual operating parameters of the nuclear power plant to obtain fluid dynamics simulation data; Step 2: Based on the streamline distribution and flow distribution in the fluid dynamics simulation data, divide the core into regions and correspond them with the hot section outlet. Determine the flow distribution coefficient according to the flow rate of the coolant flowing into the cold section inlet of each region. Step 3: Based on the results of the region division and the flow distribution coefficient, quantify the inlet coolant flow rate, initial temperature, region temperature, region inlet specific enthalpy, and power of each region; Step 4: Perform heat balance calculations for each region to obtain the increase in specific enthalpy of the coolant as it flows through each region, as well as the coolant temperature at the outlet of each region. Step 5: Average the coolant temperature at the inlet and outlet of each area to obtain the average temperature of the coolant in each loop.

2. The reactor primary loop average temperature correction method according to claim 1, characterized in that, In step 1, the operating parameters include: coolant inlet temperature, flow rate, radial power distribution of fuel assembly, axial power distribution of fuel assembly, and coolant outlet pressure.

3. The reactor primary loop average temperature correction method according to claim 1, characterized in that, In step 1, during numerical simulation, different inlet coolants are set to have the same physical properties, and the flow distribution results of the simulated core region are averaged to obtain the flow distribution results and streamline distribution results.

4. The reactor primary loop average temperature correction method according to claim 1, characterized in that, In step 2, the stack is divided into a main region, a transition region, and a central component region according to the coolant flow path and outlet location, with each region corresponding to a hot leg outlet.

5. The reactor primary loop average temperature correction method according to claim 4, characterized in that, In step 3, Q inj Let T be the coolant flow rate at the inlet of the j-th reactor. inj Given the coolant temperature at the j-th inlet, the inlet flow rate of the i-th region is calculated using the following formula: j=1, 2, 3; i=1, 2, 3; The inlet temperature of the i-th region is calculated using the following formula: Specific enthalpy at the inlet of the i-th region: Calculated from the inlet temperature based on the specific enthalpy-temperature relationship curve of the coolant. h i，in =f(T i，in ) Let Pi be the total heat power borne by the i-th region. Considering the average power distribution between the transition region and the central component region, Pi is calculated using the following formula: in: P area，i The main region's own power; P trans，i，k The power allocated to the adjacent region in the transition region; P center Total power of the central component.

6. The reactor primary loop average temperature correction method according to claim 5, characterized in that, In step 4, the increase in specific enthalpy Δh of the coolant flowing through the i-th region i : The export enthalpy h of region i i，out :h i，out =h i，in +Δh i ; h i，in Let enthalpy be the input ratio of the i-th region; Based on the specific enthalpy-temperature relationship curve of the coolant, from h i，out Back-calculation of the outlet temperature T of region i i，out T i，out =f -1 (h i，out ).

7. The reactor primary loop average temperature correction method according to claim 1, characterized in that, In step 5, the average temperature of the coolant in each loop is obtained by using the arithmetic mean, enthalpy integral average, or flow rate weighted average method.

8. The reactor primary loop average temperature correction method according to claim 7, characterized in that, Treating the entire loop as a single uniform pipe, the average temperature of the coolant in each loop is obtained using the arithmetic mean method. T i，ave T represents the average temperature of the loop coolant. i，out Let T be the outlet temperature of region i. i，in Let be the inlet temperature of the i-th region.

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