Sodium-cooled fast reactor heat balance measurement and error analysis method

Abstract

The invention belongs to the technical field of nuclear power station heat balance measurement, and particularly relates to a sodium-cooled fast reactor heat balance measurement and error analysis method. Comprising the following steps: step 01, when it is checked that the unit power reaches a target power platform + / -1% Pn range, starting to execute a heat balance measurement test; 02, waiting for 8 hours of operation of the unit, and monitoring operation parameters of a main loop; and 03, performing heat balance test result calculation and error analysis on the exported test data. The method has the beneficial effects that a calculation technical means of two times of standard deviation of test data and parameter error transmission is adopted, so that the effect that a heat balance measurement result has the confidence coefficient of more than 95.5% is realized, and the test result and error analysis are ensured to be accurate and reliable; not only is the accuracy of the test result of the heat balance measurement of the large-scale sodium-cooled fast reactor under low power improved, but also unnecessary operation is reduced while the accuracy of the test result under high power is ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of thermal balance measurement of nuclear power plants, and in particular relates to a thermal balance measurement and error analysis method for a sodium-cooled fast reactor. Background Art

[0002] The core power of a nuclear power plant reactor must be strictly controlled within the design allowable range to prevent nuclear safety incidents such as core fuel meltdown. The real-time nuclear power of the core of a sodium-cooled fast reactor unit is obtained through the neutron signal measured by the external nuclear measurement system. This measurement method is easily affected by factors such as changes in the core coolant temperature and the accumulation of core component burnup, and it is impossible to estimate the error range of the measurement results, which brings great risks to the operation of the unit. Therefore, it is a very critical link to obtain accurate core thermal power calculation results and error ranges through thermal balance measurement tests, and the nuclear power measured by the external nuclear measurement system can be regularly calibrated.

[0003] Previously, in a certain experimental sodium-cooled fast reactor, a thermal balance measurement and commissioning test was carried out. The heat transfer of coolant sodium was calculated by specific heat capacity, and no error analysis was conducted on the thermal balance measurement results themselves. Error analysis is essential for the thermal balance measurement test results of large commercial nuclear power units, but thermal balance measurement calculation and error analysis of sodium-cooled fast reactor units are not easy. The main reasons are:

[0004] 1. The heat transfer system of the sodium-cooled fast reactor unit consists of three circuits: sodium + sodium + water. Unlike the pressurized water reactor, the coolant of the sodium-cooled fast reactor is in a high-temperature state under any operating condition. Even when the reactor is shut down for refueling, there is a temperature difference of at least 200°C between the coolant and the air around the equipment. Although the system equipment and the outer surface of the pipeline are equipped with an insulation layer, the volume of sodium in the main circuit is very large. Therefore, the heat dissipation through the surface of the main circuit system is very large and changes with temperature. Due to the large change, the real-time heat loss must be accurately calculated.

[0005] Second, the operation of the accident residual heat removal system, the primary sodium purification system, the secondary sodium purification system, the primary main circulation pump distilled water cooling system, the secondary main circulation pump distilled water cooling system, the pit ventilation system, the third-circuit steam generator feed water and other system equipment will also cause the main circuit heat transfer to change. The main circuit heat transfer system is much more complicated than that of the pressurized water reactor, involving many types of media (liquid sodium, air, water, steam, etc.), many systems, many coolant circuits, and many parameter measurement points, which makes the heat balance measurement calculation and error analysis difficult. Usually, for simplicity and accuracy, the engineering thermal calculation formula uses enthalpy instead of specific heat capacity. For example, the pressurized water reactor unit uses the IAPWS-IF97 formula to calculate the enthalpy of water and steam. The operation requirements of large-scale commercial sodium-cooled fast reactor units are more stringent. Therefore, it is necessary to introduce the sodium enthalpy formula in the sodium-cooled fast reactor unit for heat balance measurement and calculation, and establish an error analysis method on this basis. Summary of the invention

[0006] The purpose of the present invention is to provide a sodium-cooled fast reactor heat balance measurement and error analysis method, which can solve the problem of heat balance measurement and error analysis of sodium-cooled fast reactor units and is suitable for heat balance measurement of sodium-cooled fast reactor units.

[0007] The technical solution of the present invention is as follows: A method for measuring and calculating the thermal balance of a sodium-cooled fast reactor and analyzing the error, comprising the following steps:

[0008] Step 01: Check that the unit power reaches the target power platform within ±1% Pn, and start the thermal balance measurement test;

[0009] Step 02: Wait for the unit to run for 8 hours and monitor the main circuit operating parameters;

[0010] Step 03: Calculate the thermal balance test results and perform error analysis on the exported test data.

[0011] The step 1 includes stopping the operation that may destroy the thermal equilibrium state:

[0012] 1) Maintain the speed of the primary and secondary circuit pumps stable;

[0013] 2) The damper of the accident residual heat discharge system remains closed or remains at a certain opening;

[0014] 3) The primary and secondary circuit sodium purification systems remain isolated or maintain a certain stable flow rate;

[0015] 4) The opening of the ventilation air volume regulating valve of the stack pit remains unchanged, and the air supply temperature of the air conditioner remains unchanged;

[0016] 5) The secondary circuit electric heating is in the DCS remote automatic control state, the local electrical cabinet is set to the constant voltage mode, and the target temperature has been globally set to a certain value and remains unchanged;

[0017] 6) The three-circuit SG water supply flow and temperature remain stable.

[0018] The main loop operating parameters in step 2 include the main loop sodium circulation pump speed, the core inlet and outlet sodium temperature, the intermediate heat exchanger inlet and outlet sodium temperature, the main container busbar wall temperature, the steam generator inlet and outlet sodium temperature, and the three-loop feed water temperature, pressure, and flow rate. Monitor whether the above parameters meet the requirements. If they meet the requirements, derive the main loop sodium circulation pump speed, the core inlet and outlet sodium temperature, the intermediate heat exchanger inlet and outlet sodium temperature, the reactor unit supply air temperature, the reactor pit exhaust air temperature, the accident waste heat removal system intermediate loop inlet and outlet sodium temperature and flow rate, the main loop sodium purification system inlet and outlet sodium temperature and flow rate, the steam generator inlet and outlet sodium temperature and flow rate, and the three-loop feed water temperature, pressure, and flow rate.

[0019] The step 3 comprises:

[0020] 1) If the current unit power is less than 7% Pn, the power of the electric heater in the secondary circuit system is taken into account as the heat source for calculation; if the current unit power is ≥ 7% Pn, the power of the electric heater in the secondary circuit system does not need to be taken into account as the heat source for calculation; when the power of the electric heater in the secondary circuit system is taken into account as the heat source for calculation, check and record the operating status of all electric heaters in the secondary circuit system, and add up the power of the electric heaters in operation to obtain the total power of the electric heater in the secondary circuit system, P 总电加热功率 =∑ 处于投用状态的电加热器功率 ;

[0021] 2) The heat removed from the sodium-air heat exchanger of the accident residual heat removal system is calculated by the patch thermometers at the inlet and outlet of the sodium-air heat exchanger. The average of the 72 temperature measuring points at the inlet and 28 temperature measuring points at the outlet of each loop sodium-air heat exchanger is taken as the input of thermal calculation, P = (H 入口焓值 -H 出口焓值 )*F 流量 *ρ 密度 ,in:

[0022] a)H=40.25707*(t / 1000+0.27315)-28.23849*(t / 1000+

[0023] 0.27315) 2 / 2+20.69402*(t / 1000+0.27315) 3 / 3-3.641872*

[0024] (t / 1000+0.27315) 4 / 4+0.079874 / (t / 1000+0.27315)-

[0025] -11.188301, t is temperature;

[0026] b)ρ=952-0.24*t, t is temperature.

[0027] The beneficial effects of the present invention are as follows: the calculation technology means of twice the standard deviation of the test data and the parameter error transmission are adopted, so that the heat balance measurement result has an effect of more than 95.5% confidence level, ensuring that the test result and the error analysis are accurate and reliable; the technical means of considering the power of the electric heater of the secondary circuit system in different power intervals are adopted, for example, the power of the electric heater of the secondary circuit system is considered in the power interval of 1% Pn and other power intervals below 7% Pn, and the power of the electric heater of the secondary circuit system is not considered in the power interval above 7% Pn, so as to achieve the following effects: the accuracy of the test results of the heat balance measurement of a large sodium-cooled fast reactor at low power is improved, and unnecessary operations are reduced while ensuring the accuracy of the test results at high power; the technical means of calculating the heat conduction of the accident residual heat removal system by the inlet and outlet temperatures of the sodium-air heat exchanger is adopted, so as to achieve the effect of improving the accuracy of the heat conduction calculation of the accident residual heat removal system, and avoid the disadvantages that the inlet and outlet temperatures of the secondary side of the independent heat exchanger have large system errors due to the small number of measuring points and are easily affected by the pipeline electric heater. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a heat balance flow chart;

[0029] Figure 2 This is the relationship diagram between the sodium temperature and power at the outlet of the secondary circuit SG;

[0030] Figure 3 This is an example diagram of error analysis. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] The heat transfer system of the sodium-cooled fast reactor unit consists of three loops: sodium + sodium + water. The heat balance flow chart is shown in Figure 1 The calculation principle is as follows:

[0033] W 堆芯 =Q 堆本体散热 +Q 二回路系统散热 +Q JNB +Q 一回路钠净化系统排热

[0034] +Q 二回路钠净化系统排热 +Q 一泵蒸馏水 +Q 二泵蒸馏水 +Q SG -W 一泵

[0035] -W 二泵 -Q 二回路电加热

[0036] Where: W 堆芯 Refers to the core thermal power; Q 堆本体散热 Refers to the heat dissipation of the stack body; Q 二回路系统散热Refers to the heat dissipation of the secondary circuit pipeline; Q JNB Refers to the heat dissipation of the accident residual heat discharge system; Q 一回路钠净化系统排热 It refers to the heat discharged from the primary circuit by the primary circuit sodium purification system; Q 二回路钠净化系统排热 Refers to the heat discharged from the secondary circuit by the secondary circuit sodium purification system; Q SG Refers to the heat transferred from the steam generator to the three circuits; Q 一泵蒸馏水 It refers to the heat extracted from the primary circuit by the distilled water cooling system of the primary circuit sodium circulation pump; Q 二泵蒸馏水 It refers to the heat extracted from the secondary circuit by the distilled water cooling system of the secondary circuit sodium circulation pump; W 一泵 It refers to the heat introduced into the primary circuit by the primary sodium circulation pump; W 二泵 It refers to the heat introduced into the secondary circuit by the secondary circuit sodium circulation pump; Q 二回路电加热 It refers to the heat introduced into the secondary circuit by the electric heating of the secondary circuit system.

[0037] According to the relationship between SG outlet sodium temperature and power, see Figure 2 When the unit is operating at a power between 0% Pn and 7% Pn, the sodium temperature of the cold section of the secondary circuit is in the range of 220℃-280℃, and the target temperature for automatic electric heating of the secondary circuit system is generally in the range of 200-250℃, which are relatively close. Therefore, the electric heating power of the secondary circuit system needs to be included in the calculation; when the unit is operating at a power of 7% Pn and above, the sodium temperature of the cold section of the secondary circuit is in the range of 280℃ and above, which is much higher than the heating target temperature of the electric heater, so the electric heating of the secondary circuit system is basically not used, and the electric heating power of the secondary circuit is regarded as 0 at this time.

[0038] The accident waste heat removal system JNB mainly relies on the passive sodium natural circulation to remove heat due to the temperature difference and density difference of the hot and cold sodium caused by the air heat dissipation on the surface of the sodium-air heat exchanger. The temperature measurement points at the inlet and outlet of the sodium-air heat exchanger are used to calculate the heat removed from the accident waste heat removal system JNB. The sodium physical property formula adopts the enthalpy formula, which is as follows:

[0039] H=40.25707*(t / 1000+0.27315)-28.23849*(t / 1000+

[0040] 0.27315) 2 / 2+20.69402*(t / 1000+0.27315) 3 / 3-3.641872*

[0041] (t / 1000+0.27315) 4 / 4+0.079874 / (t / 1000+0.27315)-

[0042] -11.188301, Note: t is temperature, °C;

[0043] Regarding error analysis, the measured values ​​of each parameter are calculated according to 2 times the standard deviation and the error transfer function, with a confidence level of about 95.5%. See the error analysis example diagram Figure 3 , as follows:

[0044] (1) According to the program, collect data for 30 minutes, assuming that m1, m2, ..., m n is n measured values ​​of a parameter, then the average value m0 of these values ​​is:

[0045]

[0046] Then the standard deviation s of this parameter is:

[0047]

[0048] (2) For each parameter, the deviation Δ is calculated based on 2 times the standard deviation and the transfer function Y, as follows:

[0049] Y=F(X1,X2,……,X m )

[0050]

[0051] A method for measuring and calculating the thermal balance of a sodium-cooled fast reactor and analyzing the error thereof comprises the following steps:

[0052] Step 01: Check that the unit power reaches the target power platform within ±1% Pn, and start the thermal balance measurement test;

[0053] Reference Figure 1 , the operator is required to stop the operations that may destroy the thermal balance state in principle: 1) Maintain the rotation speed of the first and second circuit pumps stable; 2) The damper of the accident residual heat discharge system remains closed or maintains a certain opening; 3) The first and second circuit sodium purification systems remain isolated or maintain a certain stable flow; 4) The valve opening of the pit ventilation air volume regulating valve remains unchanged, and the air conditioning supply air temperature remains unchanged; 5) The second circuit electric heating is in the DCS remote automatic control state, the local electrical cabinet is set to the constant voltage mode (recommended rated voltage / power), and the target temperature has been globally set to a certain value (200-250℃) and remains unchanged; 6) The third circuit SG water supply flow and temperature remain stable.

[0054] Step 02: Wait for the unit to run for 8 hours, and monitor the main loop operating parameters according to the heat balance measurement test procedure. The main loop operating parameters include the sodium circulation pump speed, the core inlet and outlet sodium temperature, the intermediate heat exchanger inlet and outlet sodium temperature, the main container busbar wall temperature, the steam generator inlet and outlet sodium temperature, and the three-circuit feed water temperature, pressure, flow and other parameters. If the requirements are met, derive the main loop sodium circulation pump speed, core inlet and outlet sodium temperature, intermediate heat exchanger inlet and outlet sodium temperature, reactor unit supply air temperature, reactor pit exhaust air temperature, accident residual heat removal system intermediate loop inlet and outlet sodium temperature and flow, main loop sodium purification system inlet and outlet sodium temperature and flow, steam generator inlet and outlet sodium temperature and flow, and three-circuit feed water temperature, pressure, flow and other parameters and other test data;

[0055] Step 03: According to Figure 1 Based on the first law of thermodynamics, the thermal balance test results and error analysis are performed on the derived test data. The calculation process refers to the thermal balance flow chart (see Figure 1 ) and the above principle formula, the error analysis process refers to the example diagram ( Figure 3 ) and the above error analysis formula, other matters needing attention are as follows:

[0056] 1) If the current unit power is less than 7% Pn, the power of the secondary circuit system electric heater must be considered as a heat source for calculation; if the current unit power is ≥ 7% Pn, the power of the secondary circuit system electric heater does not need to be considered as a heat source for calculation. Figure 2 When the power of the electric heater in the secondary circuit system is taken into account as the heat source for calculation, check and record the operating status of all electric heaters in the secondary circuit system, and add up the power of the electric heaters in operation to obtain the total power of the electric heaters in the secondary circuit system, P 总电加热功率 =∑ 处于 The power of the electric heater in use.

[0057] 2) The heat removed from the sodium-air heat exchanger of the accident residual heat removal system is calculated by the patch thermometers at the inlet and outlet of the sodium-air heat exchanger. The average of the 72 temperature measurement points at the inlet and 28 temperature measurement points at the outlet of each loop sodium-air heat exchanger is used as the input for thermal calculation. P = (H 入口焓值 -H 出口焓值 )*F 流量 *ρ 密度 ,in:

[0058] a)H=40.25707*(t / 1000+0.27315)-28.23849*(t / 1000+

[0059] 0.27315) 2 / 2+20.69402*(t / 1000+0.27315)3 / 3-3.641872*

[0060] (t / 1000+0.27315) 4 / 4+0.079874 / (t / 1000+0.27315)-

[0061] -11.188301, Note: t is temperature, °C;

[0062] b)ρ=952-0.24*t, Note: t is temperature, °C.

[0063] Reference Figure 3 The error analysis of the test results is carried out, taking the calculation of the heat output from the sodium-air heat exchanger as an example:

[0064] a) According to the standard deviation formula in the technical solution, calculate the standard deviation s of each temperature and flow measurement point respectively, and further obtain the standard deviation of the inlet and outlet temperature by averaging;

[0065] b) According to the error transfer formula in the technical solution; substitute the inlet and outlet temperatures + 2*s into the enthalpy formula to obtain the enthalpy value considering 2 times the standard deviation, subtract the enthalpy value without considering the standard deviation, and obtain the inlet and outlet enthalpy value error; derive the density formula and multiply it by 2 times the standard deviation to obtain the density error;

[0066] c) Substitute the error into the power calculation formula, and the power obtained is the power under 2 times the standard deviation:

[0067] P1=(H 2倍标准差下入口焓值 -H 2倍标准差下出口焓值 )*F 2倍标准差下流量 *ρ 2倍标准差下密度

[0068] d) Subtract the power under 2 times the standard deviation from the power without considering the standard deviation to obtain the power error of the measured data under 2 times the standard deviation.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that modifying the technical solutions described in the aforementioned embodiments, or replacing some or all of the technical features therein by equivalents, does not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for measuring and calculating the thermal balance of a sodium-cooled fast reactor and analyzing the error, characterized in that: The steps include: Step 01: Check that the unit power reaches the target power platform within ±1% Pn, and start the thermal balance measurement test; Step 02: Wait for the unit to run for 8 hours and monitor the main circuit operating parameters; Step 03: Calculate the thermal balance test results and perform error analysis on the exported test data.

2. A sodium-cooled fast reactor thermal balance measurement, calculation and error analysis method as claimed in claim 1, characterized in that: The step 1 includes stopping the operation that may destroy the thermal equilibrium state: 1) Maintain the speed of the primary and secondary circuit pumps stable; 2) The damper of the accident residual heat discharge system remains closed or remains at a certain opening; 3) The primary and secondary circuit sodium purification systems remain isolated or maintain a certain stable flow rate; 4) The opening of the ventilation air volume regulating valve of the stack pit remains unchanged, and the air supply temperature of the air conditioner remains unchanged; 5) The secondary circuit electric heating is in the DCS remote automatic control state, the local electrical cabinet is set to the constant voltage mode, and the target temperature has been globally set to a certain value and remains unchanged; 6) The three-circuit SG water supply flow and temperature remain stable.

3. A sodium-cooled fast reactor thermal balance measurement, calculation and error analysis method as claimed in claim 1, characterized in that: The main loop operating parameters in step 2 include the main loop sodium circulation pump speed, the core inlet and outlet sodium temperature, the intermediate heat exchanger inlet and outlet sodium temperature, the main container busbar wall temperature, the steam generator inlet and outlet sodium temperature, and the three-loop feed water temperature, pressure, and flow rate. Monitor whether the above parameters meet the requirements. If they meet the requirements, derive the main loop sodium circulation pump speed, the core inlet and outlet sodium temperature, the intermediate heat exchanger inlet and outlet sodium temperature, the reactor unit supply air temperature, the reactor pit exhaust air temperature, the accident waste heat removal system intermediate loop inlet and outlet sodium temperature and flow rate, the main loop sodium purification system inlet and outlet sodium temperature and flow rate, the steam generator inlet and outlet sodium temperature and flow rate, and the three-loop feed water temperature, pressure, and flow rate.

4. A sodium-cooled fast reactor thermal balance measurement, calculation and error analysis method as claimed in claim 1, characterized in that: The step 3 comprises: 1) If the current unit power is less than 7% Pn, the power of the secondary circuit system electric heater is considered as the heat source for calculation.

5. A sodium-cooled fast reactor thermal balance measurement, calculation and error analysis method as claimed in claim 4, characterized in that: The step 3 comprises: If the current unit power is ≥7% Pn, there is no need to consider the power of the secondary circuit system electric heater as a heat source for calculation.

6. A sodium-cooled fast reactor thermal balance measurement, calculation and error analysis method as claimed in claim 5, characterized in that: The step 3 comprises: When the power of the electric heater in the secondary circuit system is taken into account as the heat source for calculation, check and record the operating status of all electric heaters in the secondary circuit system, and add up the power of the electric heaters in operation to obtain the total power of the electric heaters in the secondary circuit system, P 总电加热功率 =∑ 处于投用状态的电加热器功率 .

7. A sodium-cooled fast reactor thermal balance measurement, calculation and error analysis method as claimed in claim 4, characterized in that: The step 3 comprises: 2) The heat removed from the sodium-air heat exchanger of the accident residual heat removal system is calculated by the patch thermometers at the inlet and outlet of the sodium-air heat exchanger. The average of the 72 temperature measuring points at the inlet and 28 temperature measuring points at the outlet of each loop sodium-air heat exchanger is taken as the input of thermal calculation, P = (H 入口焓值 -H 出口焓值 )*F 流量 * 密度 ,in: a)H=40.25707*(t / 1000+0.27315)-28.23849*(t / 1000+ 0.27315) 2 / 2+20.69402*(t / 1000+0.27315) 3 / 3-3.641872* (t / 1000+0.27315) 4 / 4+0.079874 / (t / 1000+0.27315)- -11.188301, t is temperature; b)ρ=952-0.24*t, t is temperature.

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