A method for analyzing the minimum temperature of a hydrostatic test of a nuclear power plant

Abstract

This invention relates to a method for analyzing the minimum temperature during hydrostatic testing of a nuclear power plant, comprising the following steps: S100, performing a drop hammer test and neutron flux measurement to calculate the ductile-brittle transition temperature of the pressure vessel; S200, determining whether the ductile-brittle transition temperature obtained in step S100 is greater than or equal to the set temperature for pre-service testing of the pressure vessel; S300, increasing the ductile-brittle transition temperature obtained in step S200 by a certain value based on the test pressure to obtain an initial value for the minimum test temperature; S400, determining whether the initial value for the minimum test temperature obtained in step S300 is greater than or equal to 60°C; S500, if the pressure vessel has defects, adjusting the initial value for the minimum test temperature obtained in step S400 based on the actual condition of the defects to obtain the minimum temperature for the hydrostatic test. This invention improves the accuracy of the minimum temperature for primary loop hydrostatic testing.

Description

Technical Field

[0001] This invention relates to the field of nuclear power plant hydrostatic testing technology, and in particular to a method for analyzing the lowest temperature during nuclear power plant hydrostatic testing. Background Technology

[0002] Currently, according to RSE-M specifications, each nuclear power plant must apply to the Safety Bureau for the minimum temperature for each primary circuit hydrostatic test, as required by the in-service inspection outline. This is due to the risk of brittle fracture of the pressure vessel, the influence of carbon segregation in the main equipment, and the ductile-brittle transition temperature (RT) of the pressure vessel material. NDT Due to issues such as uncertainties in the values ​​(measured / predicted / design required values), the effectiveness of irradiation monitoring tube test data coverage, and inconsistent application standards, existing temperature analysis methods often fail to accurately determine the minimum temperature for primary circuit hydrostatic testing. Therefore, developing a standard analytical method for the minimum temperature of primary circuit hydrostatic testing is an urgent problem to be solved. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for analyzing the lowest temperature in a nuclear power plant hydrostatic test.

[0004] The technical solution adopted by this invention to solve its technical problem is: a method for analyzing the lowest temperature during a hydrostatic test in a nuclear power plant, comprising the following steps:

[0005] S100, conduct drop hammer tests and neutron flux measurements to calculate the ductile-brittle transition temperature of the pressure vessel;

[0006] S200: Determine whether the ductile-brittle transition temperature in step S100 is greater than or equal to the set temperature of the pre-service test of the pressure vessel. If so, proceed to the next step.

[0007] S300: Based on the test pressure, increase the ductile-brittle transition temperature of step S200 by a certain value to obtain the initial value of the minimum test temperature, and then proceed to the next step.

[0008] S400. Determine whether the initial value of the minimum test temperature in step S300 is greater than or equal to 60°C. If so, proceed to the next step.

[0009] S500. If the pressure vessel has a defect, adjust the initial value of the minimum test temperature in step S400 according to the actual situation of the defect to obtain the minimum temperature for the hydrostatic test.

[0010] Preferably, step S100 includes the following sub-steps:

[0011] S101. Conduct a drop hammer test to obtain the experimental value of the initial ductile-brittle transition temperature of the core shell material of the pressure vessel; the core shell material of the pressure vessel includes the core shell section material and the core shell section weld material.

[0012] S102. Conduct a drop hammer test to obtain the experimental value of the ductile-brittle transition temperature deviation of the core cylinder material; conduct a neutron flux measurement to obtain the neutron flux value, and obtain the composition data of the core cylinder material to calculate the design value of the ductile-brittle transition temperature deviation of the pressure vessel.

[0013] S103. Calculate the ductile-brittle transition temperature of the pressure vessel based on the data obtained in steps S101-S102.

[0014] Preferably, step S102 includes the following sub-steps:

[0015] S102-1. Conduct a drop hammer test to obtain the experimental value of the ductile-brittle transition temperature deviation between the core tube section material and the weld material of the core tube section.

[0016] S102-2. Perform neutron flux measurement to obtain the experimental value and the design value of neutron flux, and take the maximum value of the two as the neutron flux value.

[0017] S102-3. Obtain the mass percentages of phosphorus, copper, and nickel in the core cylinder section material;

[0018] S102-4. Calculate the design value ΔRT of the ductile-brittle transition temperature deviation of the core cylinder section material using formula (1). NDT1 :

[0019]

[0020] Where P1 is the mass percentage of phosphorus in the core tube material, Cu1 is the mass percentage of copper in the core tube material, Ni1 is the mass percentage of nickel in the core tube material, and f is the neutron flux value.

[0021] S102-5. Obtain the mass percentages of phosphorus, copper, and nickel in the weld material of the core cylinder section;

[0022] S102-6. Calculate the design value ΔRT of the ductile-brittle transition temperature deviation of the weld material in the core cylinder section using formula (2). NDT2 :

[0023]

[0024] Wherein, P2 is the mass percentage of phosphorus in the weld material of the core tube section, Cu2 is the mass percentage of copper in the weld material of the core tube section, Ni2 is the mass percentage of nickel in the weld material of the core tube section, and f is the neutron flux value.

[0025] Preferably, step S103 includes the following sub-steps:

[0026] S103-1. Based on the data obtained in steps S101-S102, calculate the ductile-brittle transition temperature RT of the core shell material of the pressure vessel using equation (3). NDT :

[0027] RT NDT =Initial RT NDT +△RT NDT +D value (3)

[0028] Wherein, the initial RT NDT The initial ductile-brittle transition temperature, ΔRT, is the experimental value of the pressure vessel. NDT The maximum value between the experimental value and the design value of the ductile-brittle transition temperature deviation of the core shell material is denoted as D. The value of D is the difference between the experimental value and the design value of the ductile-brittle transition temperature deviation of the core shell material. If the experimental value of the ductile-brittle transition temperature deviation is less than the design value of the ductile-brittle transition temperature deviation, then the difference is 0.

[0029] S103-2. Select the maximum value of the ductile-brittle transition temperature of the core cylinder material as the ductile-brittle transition temperature of the pressure vessel.

[0030] Preferably, in step S300, if the test pressure is 1.2 times the design pressure, the ductile-brittle transition temperature of step S200 is increased by 12°C to obtain the initial value of the minimum test temperature; if the test pressure is 1.33 times the design pressure, the ductile-brittle transition temperature of step S200 is increased by 18°C ​​to obtain the initial value of the minimum test temperature.

[0031] Preferably, in step S500, the minimum temperature of the hydrostatic test is increased by a margin of 1-3°C to be the final minimum temperature of the hydrostatic test.

[0032] Preferably, the minimum temperature analysis method for nuclear power plant hydrostatic testing further includes step S600:

[0033] S600 specifies that the maximum temperature for the hydrostatic test is 150℃.

[0034] Preferably, the minimum temperature analysis method for nuclear power plant hydrostatic testing further includes step S600:

[0035] S600. If the test pressure is 1.2 times the design pressure, the maximum temperature of the hydrostatic test is specified as 180℃; if the test pressure is 1.33 times the design pressure, the maximum temperature of the hydrostatic test is specified as 160℃.

[0036] Preferably, the minimum temperature analysis method for nuclear power plant hydrostatic testing further includes step S700:

[0037] S700. Substituting the design pressure and the ductile-brittle transition temperature from step S100 into equation (4), we obtain the relationship between the test pressure and the test temperature for the hydrostatic test of the pressure vessel:

[0038]

[0039] Where P is the test pressure, P C The design pressure is T, the test temperature is RT. NDT It is the ductile-brittle transition temperature.

[0040] Preferably, the test pressure corresponding to the test temperature between the lowest and highest temperatures is obtained according to the relationship equation between the test pressure and the test temperature of the hydrostatic test, that is, the range of test temperature and test pressure allowed for the hydrostatic test.

[0041] The implementation of this invention has the following beneficial effects: This invention proposes a method for analyzing the minimum temperature of a nuclear power plant hydrostatic test. Based on the ductile-brittle transition temperature of the pressure vessel, the temperature is normalized according to the judgment criteria to obtain the minimum temperature of the hydrostatic test. This method can prevent the risk of non-plastic failure and excessive deformation of the pressure vessel, and overcomes problems such as carbon segregation of the pressure vessel, uncertainty in the calculation of the ductile-brittle transition temperature, and the effectiveness of test data coverage, thereby improving the accuracy of the minimum temperature of the primary circuit hydrostatic test. Attached Figure Description

[0042] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0043] Figure 1 This is a graph showing the relationship between test pressure and test temperature during a hydrostatic test at a certain design pressure according to the present invention.

[0044] Figure 2 This is another test pressure-test temperature relationship diagram when a hydrostatic test is conducted under a certain design pressure according to the present invention;

[0045] Figure 3 This is a graph showing the relationship between test pressure and test temperature during a hydrostatic test according to an embodiment of the present invention. Detailed Implementation

[0046] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0047] This invention proposes a method for analyzing the minimum temperature during a hydrostatic test in a nuclear power plant, comprising the following steps:

[0048] S100, drop weight test and neutron flux measurement are performed to calculate the ductile-brittle transition temperature of the pressure vessel.

[0049] Pressure vessels (whose materials may become embrittled under irradiation) are at risk of non-plastic failure if the hydrostatic test temperature exceeds the ductile-brittle transition temperature (RT) of the pressure vessel material. NDT Low-alloy ferritic steels, which can form the reactor core, can withstand bulging deformation without brittle fracture even with defects. Therefore, the temperature of the hydrostatic test must exceed the pressure vessel's RT. NDT The minimum value of the function temperature is a prerequisite.

[0050] The ductile-brittle transition temperature of the pressure vessel refers to the ductile-brittle transition temperature of the core shell material of the pressure vessel. The core shell material includes the core shell section material and the core shell section weld material. The core shell includes two butt-welded shell sections, with the weld located between the two shell sections.

[0051] Furthermore, step S100 includes the following sub-steps:

[0052] S101. Conduct a drop hammer test to obtain the experimental value of the initial ductile-brittle transition temperature of the core shell material of the pressure vessel. The core shell material includes the core shell section material and the core shell section weld material.

[0053] S102. Conduct a drop hammer test to obtain the experimental value of the ductile-brittle transition temperature deviation of the core shell material; conduct a neutron flux measurement to obtain the neutron flux value, and obtain the composition data of the core shell material to calculate the design value of the ductile-brittle transition temperature deviation of the pressure vessel. The composition data refers to the elemental mass percentages of the core shell section material and the core shell section weld material, respectively.

[0054] Furthermore, step S102 includes the following sub-steps:

[0055] S102-1. Conduct a drop hammer test to obtain the experimental values ​​of the ductile-brittle transition temperature deviation of the core tube section material and the core tube section weld material.

[0056] S102-2. Perform neutron flux measurement to obtain the experimental value and the design value of neutron flux, and take the maximum value of the two as the neutron flux value.

[0057] The neutron fluence measurement, in accordance with relevant ASTM standards, involves weighing the detector sample, measuring and processing its activity, correcting the neutron fluence rate spectrum based on transport calculations, calculating the fast neutron fluence rate of the detector, and calculating the weighted average fast neutron rate and fluence to obtain the average fast neutron fluence of the irradiation monitoring tube, i.e., the experimental neutron fluence value. Additionally, the design neutron fluence value is calculated based on the radiation effects monitoring outline. Understandably, neutron fluence measurement and calculation are existing technologies and will not be elaborated upon further here.

[0058] S102-3. Obtain the mass percentages of phosphorus, copper, and nickel in the core shell section material.

[0059] S102-4. Calculate the design value ΔRT of the ductile-brittle transition temperature deviation of the core section material using formula (1). NDT1 :

[0060]

[0061] Where P1 is the mass percentage of phosphorus in the core tube material, %; Cu1 is the mass percentage of copper in the core tube material, %; Ni1 is the mass percentage of nickel in the core tube material, %; and f is the neutron flux value, n / cm². 2 For the core cylinder material forged from solid ingots, P1 is 1.14 times the mass percentage of phosphorus. If P1 < 0.008%, then (P1 - 0.008) = 0 in equation (1). For the core cylinder material forged from solid ingots, Cu1 is 1.08 times the mass percentage of copper. If Cu1 < 0.08%, then (Cu1 - 0.08) = 0 in equation (1).

[0062] S102-5. Obtain the mass percentages of phosphorus, copper, and nickel in the weld material of the core cylinder section.

[0063] S102-6. Calculate the design value ΔRT of the ductile-brittle transition temperature deviation of the weld material in the core section using formula (2). NDT2 :

[0064]

[0065] Wherein, P2 is the mass percentage of phosphorus in the weld material of the core cylinder section, %; Cu2 is the mass percentage of copper in the weld material of the core cylinder section, %; Ni2 is the mass percentage of nickel in the weld material of the core cylinder section, %; and f is the neutron flux value, n / cm. 2 If P2 < 0.008%, then (P2 - 0.008) = 0 in equation (2); if Cu2 < 0.08%, then (Cu2 - 0.08) = 0 in equation (2).

[0066] In some embodiments of the present invention, before step S102, step S100 further includes step S102':

[0067] S102', Verification experiment on the ductile-brittle transition temperature deviation of the core cylinder material of the pressure vessel.

[0068] This verification experiment was used to obtain the variation trend of the ductile-brittle transition temperature of the core shell material over different years, and to compare the experimental value and the design value of the ductile-brittle transition temperature deviation.

[0069] Under normal circumstances, the design value of the ductile-brittle transition temperature deviation should be greater than the experimental value; otherwise, the hydrostatic test cannot be carried out. Therefore, if the design value of the ductile-brittle transition temperature deviation for different years is greater than the experimental value, then the trend of the change of the design value of the ductile-brittle transition temperature deviation of the core tube material is correct. In this case, the design value of the ductile-brittle transition temperature deviation of the core tube material obtained in step S102 is also greater than the experimental value.

[0070] Furthermore, step S102' includes the following sub-steps:

[0071] S102'-1. Conduct a drop hammer test to obtain the experimental value of the ductile-brittle transition temperature deviation of the core cylinder material.

[0072] The core cylinder material refers to the core cylinder section material sample and the core cylinder section weld material sample installed in the irradiation monitoring tube. The irradiation monitoring tube is removed from the pressure vessel at different ages to obtain core cylinder materials of different ages, and then subjected to drop hammer tests.

[0073] S102'-2. Perform neutron flux measurement to obtain experimental neutron flux values ​​and design neutron flux values ​​for different years, and take the maximum value of the two as the neutron flux value.

[0074] S102'-3, Obtain the mass percentages of phosphorus, copper, and nickel in the core shell section material. This step is identical to obtaining the composition data (i.e., mass percentages) of the core shell section material in step S102-3.

[0075] S102'-4. Calculate the design value ΔRT of the ductile-brittle transition temperature deviation of the core shell section material for different ages using formula (1'). NDT1 ':

[0076]

[0077] Where P1 is the mass percentage of phosphorus in the core tube material, %; Cu1 is the mass percentage of copper in the core tube material, %; Ni1 is the mass percentage of nickel in the core tube material, %; and f' is the neutron flux value for different aging periods, n / cm². 2For the core cylinder material forged from solid ingots, P1 is 1.14 times the mass percentage of phosphorus. If P1 < 0.008%, then (P1 - 0.008) = 0 in formula (1'). For the core cylinder material forged from solid ingots, Cu1 is 1.08 times the mass percentage of copper. If Cu1 < 0.08%, then (Cu1 - 0.08) = 0 in formula (1').

[0078] S102'-5, Obtain the mass percentages of phosphorus, copper, and nickel in the weld material of the core section. This step is identical to the composition data (i.e., element mass percentages) of the weld material in the core section obtained in step S102-5.

[0079] S102'-6. Calculate the design value ΔRT of the ductile-brittle transition temperature deviation of the weld material in the core tube section for different ages using formula (2'). NDT2 ':

[0080]

[0081] Wherein, P2 is the mass percentage of phosphorus in the weld material of the core cylinder section, %; Cu2 is the mass percentage of copper in the weld material of the core cylinder section, %; Ni2 is the mass percentage of nickel in the weld material of the core cylinder section, %; and f' is the neutron flux value for different ages, n / cm. 2 If P2 < 0.008%, then (P2 - 0.008) = 0 in equation (2'); if Cu2 < 0.08%, then (Cu2 - 0.08) = 0 in equation (2').

[0082] S102'-7. Using the RCC-M standard ZG 3430 calculation formula, i.e., formula (3'), calculate the design value ΔRT of the ductile-brittle transition temperature deviation of the core tube material and the core tube weld material for different ages. NDT ':

[0083]

[0084] Wherein, Cu is the mass percentage of copper in the core section material or the weld material of the core section, %; P is the mass percentage of phosphorus in the core section material or the weld material of the core section, %; and f' is the neutron flux value for different ages, n / cm. 2 If Cu < 0.08%, then Cu in equation (3') is 0.08; if P < 0.008%, then P in equation (3') is 0.008.

[0085] S102'-8. Calculate the difference between the experimental and design values ​​of the ductile-brittle transition temperature deviation of the core tube material and the core tube weld material for different years. If the experimental value of the ductile-brittle transition temperature deviation for the same year is less than the design value of the ductile-brittle transition temperature deviation, then the difference for that year is 0.

[0086] S103. Calculate the ductile-brittle transition temperature of the pressure vessel based on the data obtained in steps S101-S102.

[0087] Furthermore, step S103 includes the following sub-steps:

[0088] S103-1. Based on the data obtained in steps S101-S102, the ductile-brittle transition temperature RT of the core shell material of the pressure vessel is calculated using equation (3). NDT :

[0089] RT NDT =Initial RT NDT +△RT NDT +D value (3)

[0090] Wherein, the initial RT NDT The initial ductile-brittle transition temperature of the pressure vessel is the experimental value, in °C; ΔRT NDT denoted as , where is the maximum value between the experimental and design values ​​of the ductile-brittle transition temperature deviation of the core shell material, in °C; and denoted as D, the difference between the experimental and design values ​​of the ductile-brittle transition temperature deviation of the core shell material, in °C. If the experimental value of the ductile-brittle transition temperature deviation is less than the design value, the difference is 0.

[0091] Since the core shell material includes the core shell section material and the core shell section weld material, the ductile-brittle transition temperature of the core shell section material and the core shell section weld material should be calculated separately using equation (3), with an initial RT. NDT , △RT NDT The D value and the core tube section material correspond to the core tube section weld material, respectively.

[0092] Furthermore, if the design values ​​of the ductile-brittle transition temperature deviation for different years in step S102' are all greater than the experimental values ​​of the ductile-brittle transition temperature deviation, then ΔRT in equation (3) NDT If the design value for the ductile-brittle transition temperature deviation is 0, then step S102-1 in step S102 can be omitted. Furthermore, this design value for the ductile-brittle transition temperature deviation can also be calculated using relevant standard calculation formulas based on the design values ​​for the ductile-brittle transition temperature deviation for different years in step S102'.

[0093] S103-2. The maximum value of the ductile-brittle transition temperature of the core shell material is selected as the ductile-brittle transition temperature of the pressure vessel. Specifically, the maximum integer value of the ductile-brittle transition temperature of the shell section material and the shell section weld material is selected as the ductile-brittle transition temperature of the pressure vessel.

[0094] S200. Determine whether the ductile-brittle transition temperature in step S100 is greater than or equal to the set temperature of the pre-service test of the pressure vessel. According to the pre-service inspection specifications, the set temperature for the pre-service inspection is 35°C. Therefore, determine whether the ductile-brittle transition temperature is greater than or equal to 35°C. If so, proceed to the next step.

[0095] Further, if not, the ductile-brittle transition temperature is set as the pre-service test temperature for the pressure vessel, and then the next step is performed.

[0096] S300: Based on the test pressure, increase the ductile-brittle transition temperature of step S200 by a certain value to obtain the initial value of the lowest test temperature, and then proceed to the next step.

[0097] Specifically, if the test pressure is 1.2 times the design pressure, the ductile-brittle transition temperature of step S200 is increased by 12°C to obtain the initial value of the minimum test temperature; if the test pressure is 1.33 times the design pressure, the ductile-brittle transition temperature of step S200 is increased by 18°C ​​to obtain the initial value of the minimum test temperature.

[0098] S400: Determine whether the initial value of the minimum test temperature in step S300 is greater than or equal to 60℃. If so, proceed to the next step.

[0099] Furthermore, to protect the pressure vessel, the hydrostatic test temperature should be greater than or equal to 60°C. Therefore, if the initial value of the minimum test temperature is less than 60°C, the initial value of the minimum test temperature should be set to 60°C, and then the next step should be performed.

[0100] S500 If the pressure vessel has defects, adjust the initial value of the minimum test temperature in step S400 according to the actual situation of the defects to obtain the minimum temperature for the hydrostatic test.

[0101] If a pressure vessel has defects, a materials science analysis is performed based on the size, type, and impact of the defects, and the initial minimum test temperature is appropriately increased. It is understood that defect analysis of pressure vessels is existing technology and will not be elaborated upon here.

[0102] Furthermore, in step S500, the minimum temperature of the hydrostatic test is increased by a margin of 1-3°C, which is then used as the final minimum temperature for the hydrostatic test.

[0103] S600 specifies that the maximum temperature for the hydrostatic test is 150℃; or...

[0104] S600. If the test pressure is 1.2 times the design pressure, the maximum temperature of the hydrostatic test is specified as 180℃; if the test pressure is 1.33 times the design pressure, the maximum temperature of the hydrostatic test is specified as 160℃.

[0105] To avoid the risk of excessive deformation in the steam generator tube bundle, the test temperature is limited to a maximum value, which varies depending on the acceptance specifications of the steam generator tube bundle material. The test pressure for the hydrostatic test is typically 1.2 or 1.33 times the design pressure. According to the relevant specifications of the American Society of Mechanical Engineers (ASME), the maximum temperature for the hydrostatic test is uniformly set at 150°C. However, according to the design and manufacturing guidelines for pressurized water reactor nuclear island mechanical components, the maximum temperature for the hydrostatic test should be set at 180°C or 160°C, depending on whether the test pressure is 1.2 or 1.33 times the design pressure.

[0106] S700, Substituting the design pressure and the ductile-brittle transition temperature of step S100 into equation (4), we obtain the relationship equation between the test pressure and the test temperature for the hydrostatic test of the pressure vessel, as shown in equation (4):

[0107]

[0108] Where P is the test pressure, in bar; P C Design pressure (bar); T is test temperature (°C); RT NDT The temperature at which the ductile-brittle transition occurs is ℃.

[0109] Furthermore, based on the relationship equation between the test pressure and test temperature in the above-mentioned hydrostatic test, the test pressure corresponding to the test temperature between the minimum and maximum temperatures is obtained, i.e., the allowable range of test temperature and test pressure for the hydrostatic test. Among these, relevant specifications require that the test pressure for the hydrostatic test should be greater than 30 bar.

[0110] Understandably, the lowest temperature under a certain pressure condition corresponds to the temperature that the inner wall of the pressure vessel must reach in order to avoid the pressure vessel rupture; the highest temperature under a certain pressure condition refers to the temperature that cannot be exceeded in order to avoid damage to the tube bundle of the steam generator.

[0111] Given a design pressure Pc = 171.3 bar, substituting it into equation (4), we obtain equation (5):

[0112] P=103.81+9.44exp[0.035×(55.5+T-RT NDT )](5)

[0113] Figure 1 Equation (5) is shown in RT NDT When the temperature is +12 or +18℃ or greater than or equal to 60℃, which meets the requirements of step S400, curve ① is obtained. In the figure, T1 is the set temperature for pre-service inspection, and T2 is the RT. NDTThe temperature value is +12 or +18℃, T3 is the maximum test temperature, P1 is the maximum test pressure, P2 is the set pressure of the safety valve (as overpressure protection, i.e. the actual maximum test pressure), and the shaded part indicates the prohibited test temperature and test pressure range.

[0114] Figure 2 Equation (5) is shown in RT NDT When the temperature is +12 or +18℃ less than 60℃, i.e., the requirements of step S400 are not met, curve ② is obtained. In the figure, T1' is the set temperature for pre-service inspection, and T2' is RT. NDT The temperature value is +12 or +18℃, T3' is the maximum test temperature, P1' is the maximum test pressure, P2' is the set pressure of the safety valve (as overpressure protection, i.e. the actual maximum test pressure), and the shaded part is the prohibited test temperature and test pressure range.

[0115] It is evident that if the temperature after increasing the ductile-brittle transition temperature by 12 or 18°C ​​is still less than 60°C, the actual minimum test temperature should be 60°C, and the temperature range for the hydrostatic test can be selected as 60-160°C. However, if the temperature after increasing the ductile-brittle transition temperature by 12 or 18°C ​​is greater than 60°C (taking 70°C as an example), the selectable temperature range becomes 70-160°C. This selection range is smaller, and since raising the temperature for the primary hydrostatic test is relatively difficult, the smaller temperature selection range increases the difficulty of the hydrostatic test.

[0116] To make the objectives, technical solutions, and technical effects of the present invention clearer, the following examples and accompanying drawings will be used to further describe the embodiments of the present invention in detail.

[0117] The minimum temperature analysis method for nuclear power plant hydrostatic testing of the present invention specifies the design pressure P. C =171.3 bar, and the test pressure P = 1.33P C The method includes the following steps:

[0118] S100, drop weight test and neutron flux measurement are performed to calculate the ductile-brittle transition temperature of the pressure vessel.

[0119] S101. Conduct a drop hammer test to obtain the experimental value of the initial ductile-brittle transition temperature of the core shell material of the pressure vessel. The core shell includes two core shell sections and the weld between the core shell sections.

[0120] S102', Verification experiment on the ductile-brittle transition temperature deviation of the core cylinder material of the pressure vessel.

[0121] S102'-1. Conduct a drop hammer test to obtain the experimental value of the ductile-brittle transition temperature deviation of the core cylinder material.

[0122] The core shell material includes metallic materials (i.e., core shell section material samples) and weld materials (i.e., core shell section weld material samples).

[0123] S102'-2. Perform neutron flux measurement to obtain experimental neutron flux values ​​and design neutron flux values ​​for different years, and take the maximum value of the two as the neutron flux value.

[0124] S102'-3. Obtain the mass percentages of phosphorus, copper, and nickel in the core shell section material. The core shell section comprises two segments, and the material composition data for these two segments may be different or the same.

[0125] S102'-4. Calculate the design value ΔRT of the ductile-brittle transition temperature deviation of the core shell section material for different ages using formula (1'). NDT1 Equation (1) is expressed as follows:

[0126]

[0127] Where P1 is the mass percentage of phosphorus in the core tube material, %; Cu1 is the mass percentage of copper in the core tube material, %; Ni1 is the mass percentage of nickel in the core tube material, %; and f' is the neutron flux value for different aging periods, n / cm². 2 .

[0128] S102'-5. Obtain the mass percentages of phosphorus, copper, and nickel in the weld material of the core cylinder section.

[0129] S102'-6. Calculate the design value ΔRT of the ductile-brittle transition temperature deviation of the weld material in the core tube section for different ages using formula (2'). NDT2 Equation (2) is expressed as follows:

[0130]

[0131] Wherein, P2 is the mass percentage of phosphorus in the weld material of the core cylinder section, %; Cu2 is the mass percentage of copper in the weld material of the core cylinder section, %; Ni2 is the mass percentage of nickel in the weld material of the core cylinder section, %; and f' is the neutron flux value for different ages, n / cm. 2 .

[0132] S102'-7. Using formula (3'), calculate the design value ΔRT of the ductile-brittle transition temperature deviation for core tube section materials and core tube section weld materials at different ages. NDT Equation (3) is expressed as follows:

[0133]

[0134] Wherein, Cu is the mass percentage of copper in the core section material or the weld material of the core section, %; P is the mass percentage of phosphorus in the core section material or the weld material of the core section, %; and f' is the neutron flux value for different ages, n / cm. 2 .

[0135] S102'-8. Calculate the difference between the experimental and design values ​​of the ductile-brittle transition temperature deviation of the core tube material and the core tube weld material for different years. If the experimental value of the ductile-brittle transition temperature deviation for the same year is less than the design value of the ductile-brittle transition temperature deviation, then the difference for that year is 0.

[0136] The experimental results are shown in Table 1, where U, V, Z, and Y represent 10, 20, 30, and 40 years, respectively, meaning the irradiation monitoring tube was proposed in 10, 20, 30, and 40 years. △RT NDT0 ' represents the design value of the deviation of the ductile-brittle transition temperature obtained from steps S102'-4 and S102'-6, ΔRT NDT ' represents the design value of the ductile-brittle transition temperature deviation obtained in step S102'-7.

[0137] Table 1. Test results of ductile-brittle transition temperature deviation of metallic materials and weld materials

[0138]

[0139]

[0140] As shown in Table 1, the design values ​​of the ductile-brittle transition temperature deviations for the corresponding years are all greater than the experimental values, so the difference between the experimental values ​​and the design values ​​is 0.

[0141] S102. Conduct a drop hammer test to obtain the experimental value of the ductile-brittle transition temperature deviation of the core cylinder material; conduct a neutron flux measurement to obtain the neutron flux value, and obtain the composition data of the core cylinder material to calculate the design value of the ductile-brittle transition temperature deviation of the pressure vessel.

[0142] S102-1. Conduct a drop hammer test to obtain the experimental values ​​of the ductile-brittle transition temperature deviation of the core cylinder material and the weld material of the core cylinder. According to the verification experiment in step S102', the design value of the ductile-brittle transition temperature deviation of the pressure vessel's core cylinder material at different ages is greater than the experimental value. Therefore, the design value of the ductile-brittle transition temperature deviation obtained on the test day in step S102 will also be greater than the experimental value. Thus, the difference between the experimental value and the design value of the ductile-brittle transition temperature deviation is 0, and step S102-1 can be omitted.

[0143] S102-2. Perform neutron flux measurements to obtain the experimental and design neutron flux values, and take the maximum value as the neutron flux value. The neutron flux measurement results are shown in Table 2.

[0144] Table 2 Neutron Flux Measurement Results

[0145] <![CDATA[Neutron fluence experimental value (n / cm 2 )]]> <![CDATA[f 实验 =3.170×10 19 ]]> <![CDATA[Design value of neutron fluence (n / cm 2 )]]> <![CDATA[f 设计 =3.253×10 19 ]]> <![CDATA[Neutron fluence value (n / cm 2 )]]> <![CDATA[f=3.253×10 19 ]]>

[0146] According to Table 2, the neutron fluence value is 3.253 × 10⁻⁶. 19 n / cm 2 .

[0147] S102-3, Obtain the mass percentages of phosphorus, copper, and nickel in the core shell section material. Since the relevant composition data of the core shell section material has already been obtained in step S102'-3, this step can be omitted.

[0148] S102-4. Calculate the design value ΔRT of the ductile-brittle transition temperature deviation of the core section material using formula (1). NDT1 Equation (1) is expressed as follows:

[0149]

[0150] Where P1 is the mass percentage of phosphorus in the core tube material, %; Cu1 is the mass percentage of copper in the core tube material, %; Ni1 is the mass percentage of nickel in the core tube material, %; and f is the neutron flux value, n / cm². 2 .

[0151] S102-5, Obtain the mass percentages of phosphorus, copper, and nickel in the weld material of the core section. Since the relevant composition data of the core section material has already been obtained in step S102'-5, this step can be omitted.

[0152] S102-6. Calculate the design value ΔRT of the ductile-brittle transition temperature deviation of the weld material in the core section using formula (2). NDT2 Equation (2) is expressed as follows:

[0153]

[0154] Wherein, P2 is the mass percentage of phosphorus in the weld material of the core cylinder section, %; Cu2 is the mass percentage of copper in the weld material of the core cylinder section, %; Ni2 is the mass percentage of nickel in the weld material of the core cylinder section, %; and f is the neutron flux value, n / cm. 2 .

[0155] S103. Calculate the ductile-brittle transition temperature of the pressure vessel based on the data obtained in steps S101-S102.

[0156] S103-1. Based on the data obtained in steps S101-S102, the ductile-brittle transition temperature RT of the core shell material of the pressure vessel is calculated using equation (3). NDT Equation (3) is expressed as follows:

[0157] RT NDT =Initial RT NDT +△RT NDT +D value (3)

[0158] Wherein, the initial RT NDT The initial ductile-brittle transition temperature of the pressure vessel is the experimental value, in °C; ΔRT NDT denoted as , and denoted as D, is the maximum value between the experimental and design values ​​of the ductile-brittle transition temperature deviation of the core shell material, in °C; denoted as D is the difference between the experimental and design values ​​of the ductile-brittle transition temperature deviation of the core shell material, in °C.

[0159] S103-2. The maximum value of the ductile-brittle transition temperature of the core shell material is selected as the ductile-brittle transition temperature of the pressure vessel. The calculation results are shown in Table 3, where the initial RT... NDT The initial ductile-brittle transition temperature (ΔRT) of the core shell material (including the materials of the two core shell sections and the weld material of the core shell sections) obtained in step S101 is given by experimental value. NDT The design value of the deviation of the ductile-brittle transition temperature obtained in steps S102-4 and S102-6 is D. The value of D is the difference between the initial experimental value of the ductile-brittle transition temperature and the design value of the deviation of the ductile-brittle transition temperature, and the value of D is 0 in both cases.

[0160] Table 3 Calculation results of the ductile-brittle transition temperature of pressure vessels

[0161]

[0162] According to Table 3, the maximum integer value of the ductile-brittle transition temperature of the reactor core shell material is 47℃. Therefore, the ductile-brittle transition temperature RT of the pressure vessel is... NDT The temperature is 47℃.

[0163] S200, Determine whether the ductile-brittle transition temperature in step S100 is greater than or equal to the set temperature of the pre-service test of the pressure vessel, wherein the aforementioned ductile-brittle transition temperature RT NDT =47℃>35℃, therefore proceed to the next step.

[0164] S300: Based on the test pressure, increase the ductile-brittle transition temperature of step S200 by a certain value to obtain the initial value of the lowest test temperature, and then proceed to the next step.

[0165] In this embodiment, since the test pressure is 1.33 times the design pressure, the ductile-brittle transition temperature RT is... NDT=47℃, increased by 18℃, to obtain the lowest initial test temperature T0 = 65℃.

[0166] S400. Determine whether the initial value of the minimum test temperature in step S300 is greater than or equal to 60°C. In this embodiment, the initial value of the minimum test temperature T0 = 65°C > 60°C, so proceed to the next step.

[0167] S500. If the pressure vessel has defects, adjust the initial value of the minimum test temperature in step S400 according to the actual situation of the defects to obtain the minimum temperature T for the hydrostatic test. mini .

[0168] In this embodiment, since the pressure vessel is defect-free, there is no need to adjust the initial value of the minimum test temperature. Furthermore, the minimum temperature T for the hydrostatic test is set... mini Adding a 2°C margin yields the lowest possible temperature T for the final hydrostatic test. mini =67℃.

[0169] According to the design and manufacturing guidelines for mechanical components of a pressurized water reactor nuclear island, since the test pressure is 1.33 times the design pressure, the maximum temperature of the hydrostatic test is 160°C.

[0170] S700, the ductile-brittle transition temperature RT of step S100. NDT =47℃ and design pressure P C Substituting 171.3 bar into equation (4), equation (4) is expressed as follows:

[0171]

[0172] Where P is the test pressure, in bar; P C Design pressure (bar); T is test temperature (°C); RT NDT The temperature at which the ductile-brittle transition occurs is ℃.

[0173] The equation relating the test pressure and test temperature in the hydrostatic test is obtained as follows:

[0174] P=103.81+9.44exp[0.035×(55.5+T-47)](6).

[0175] The relational equation of equation (6) is as follows: Figure 3 As shown in curve ③, in the figure, Ta is RT. NDT =47℃, Tb is RT NDT+18 = 65℃, Tc is 67℃ obtained by adding 2℃ margin to Tb, Pa is the maximum test pressure, i.e. 1.33Pc = 228 bar, Pb is the set pressure of the safety valve (as overpressure protection, i.e. the actual maximum test pressure), the shaded part represents the allowable test temperature and test pressure range when performing hydrostatic testing, where the test pressure of hydrostatic testing is greater than 30 bar and less than 228 bar (the actual maximum test pressure is the set pressure of the safety valve), and the test temperature is greater than 67℃ and less than 160℃.

[0176] In summary, this invention proposes a method for analyzing the minimum temperature of a nuclear power plant's hydrostatic test. Based on the ductile-brittle transition temperature of the pressure vessel, the method normalizes this temperature according to a judgment criterion to obtain the minimum temperature of the hydrostatic test. This method can prevent the risk of non-plastic failure and excessive deformation of the pressure vessel, and overcomes problems such as carbon segregation in the pressure vessel, uncertainty in the calculation of the ductile-brittle transition temperature, and the effectiveness of test data coverage, thereby improving the accuracy of the minimum temperature of the primary circuit hydrostatic test.

[0177] It is understood that the above embodiments only illustrate preferred embodiments of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can freely combine the above technical features without departing from the concept of the present invention, and can also make several modifications and improvements, all of which fall within the protection scope of the present invention. Therefore, all equivalent transformations and modifications made with respect to the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. A method of minimum temperature analysis for a hydrotest of a nuclear power plant, characterized by, Includes the following steps: S100, conduct drop hammer tests and neutron flux measurements to calculate the ductile-brittle transition temperature of the pressure vessel; S200: Determine whether the ductile-brittle transition temperature in step S100 is greater than or equal to the set temperature of the pre-service test of the pressure vessel. If yes, proceed to the next step; if no, set the ductile-brittle transition temperature to the set temperature of the pre-service test of the pressure vessel, and then proceed to the next step. S300: Based on the test pressure, increase the ductile-brittle transition temperature of step S200 by a certain value to obtain the initial value of the minimum test temperature, and then proceed to the next step. S400. Determine whether the initial value of the minimum test temperature in step S300 is greater than or equal to 60°C. If yes, proceed to the next step; if no, set the initial value of the minimum test temperature to 60°C and then proceed to the next step. S500. If the pressure vessel has a defect, adjust the initial value of the minimum test temperature in step S400 according to the actual situation of the defect to obtain the minimum temperature for the hydrostatic test. Step S100 includes the following sub-steps: S101. Conduct a drop hammer test to obtain the experimental value of the initial ductile-brittle transition temperature of the core shell material of the pressure vessel; the core shell material of the pressure vessel includes the core shell section material and the core shell section weld material. S102. Conduct a drop hammer test to obtain the experimental value of the ductile-brittle transition temperature deviation of the core cylinder material; conduct a neutron flux measurement to obtain the neutron flux value, and obtain the composition data of the core cylinder material to calculate the design value of the ductile-brittle transition temperature deviation of the pressure vessel. S103. Calculate the ductile-brittle transition temperature of the pressure vessel based on the data obtained in steps S101-S102. Step S103 includes the following sub-steps: S103-1. Based on the data obtained in steps S101-S102, calculate the ductile-brittle transition temperature RT of the core shell material of the pressure vessel using equation (3). NDT Since the core shell material of the pressure vessel includes the core shell section material and the core shell section weld material, the ductile-brittle transition temperature of the core shell section material and the core shell section weld material are calculated separately using equation (3), with an initial RT. NDT , △RT NDT The D value and the core tube section material correspond to the core tube section weld material, respectively. RT NDT = Initial RT NDT +△RT NDT +D value (3) Wherein, the initial RT NDT The initial ductile-brittle transition temperature, ΔRT, is the experimental value of the pressure vessel. NDT The maximum value between the experimental value and the design value of the ductile-brittle transition temperature deviation of the core shell material is denoted as D. The value of D is the difference between the experimental value and the design value of the ductile-brittle transition temperature deviation of the core shell material. If the experimental value of the ductile-brittle transition temperature deviation is less than the design value of the ductile-brittle transition temperature deviation, then the difference is 0. S103-2. Select the maximum value of the ductile-brittle transition temperature of the core cylinder material as the ductile-brittle transition temperature of the pressure vessel.

2. The minimum temperature analysis method for a water test of a nuclear power plant according to claim 1, characterized by, Step S102 includes the following sub-steps: S102-1. Conduct a drop hammer test to obtain the experimental value of the ductile-brittle transition temperature deviation between the core tube section material and the weld material of the core tube section. S102-2. Perform neutron flux measurement to obtain the experimental value and the design value of neutron flux, and take the maximum value of the two as the neutron flux value. S102-3. Obtain the mass percentages of phosphorus, copper, and nickel in the core cylinder section material; S102-4, calculate the ductile-brittle transition temperature deviation design value ΔRT of the core barrel section material by using formula (1) NDT1 : （1） Where P1 is the mass percentage of phosphorus in the core tube material, Cu1 is the mass percentage of copper in the core tube material, Ni1 is the mass percentage of nickel in the core tube material, and f is the neutron flux value. S102-5. Obtain the mass percentages of phosphorus, copper, and nickel in the weld material of the core cylinder section; S102-6. Calculate the design value ΔRT of the ductile-brittle transition temperature deviation of the weld material in the core section using formula (2). NDT2 : （2） Wherein, P2 is the mass percentage of phosphorus in the weld material of the core tube section, Cu2 is the mass percentage of copper in the weld material of the core tube section, Ni2 is the mass percentage of nickel in the weld material of the core tube section, and f is the neutron flux value.

3. The method for analyzing the lowest temperature during a hydrostatic test at a nuclear power plant according to claim 1, characterized in that, In step S300, if the test pressure is 1.2 times the design pressure, the ductile-brittle transition temperature of step S200 is increased by 12°C to obtain the initial value of the minimum test temperature; if the test pressure is 1.33 times the design pressure, the ductile-brittle transition temperature of step S200 is increased by 18°C ​​to obtain the initial value of the minimum test temperature.

4. The minimum temperature analysis method for a water test of a nuclear power plant according to claim 1, characterized by, In step S500, the minimum temperature of the hydrostatic test is increased by a margin of 1-3°C to be used as the final minimum temperature of the hydrostatic test.

5. The method of claim 1, wherein the minimum temperature analysis of the water test of the nuclear power plant is characterized by, It also includes the S600 step: S600 specifies that the maximum temperature for the hydrostatic test is 150℃.

6. The method for analyzing the lowest temperature during a hydrostatic test at a nuclear power plant according to claim 1, characterized in that, It also includes the S600 step: S600. If the test pressure is 1.2 times the design pressure, the maximum temperature of the hydrostatic test is specified as 180℃; if the test pressure is 1.33 times the design pressure, the maximum temperature of the hydrostatic test is specified as 160℃.

7. The method for analyzing the lowest temperature during a hydrostatic test at a nuclear power plant according to claim 5 or 6, characterized in that, It also includes the S700 steps: S700. Substituting the design pressure and the ductile-brittle transition temperature from step S100 into equation (4), we obtain the relationship between the test pressure and the test temperature for the hydrostatic test of the pressure vessel: （4） where P is the test pressure, P C is the design pressure, T is the test temperature, RT NDT is the ductile-to-brittle transition temperature.

8. The minimum temperature analysis method for a water test of a nuclear power plant according to claim 7, characterized by, Based on the relationship equation between the test pressure and the test temperature in the hydrostatic test, the test pressure corresponding to the test temperature between the minimum temperature and the maximum temperature is obtained, which is the range of the allowable test temperature and test pressure for the hydrostatic test.

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