Method for estimating the activity concentration of steam supplied externally to a nuclear heat supply device

Abstract

The application discloses an estimation method for the radioactivity concentration of steam supplied by a nuclear energy heating device. The method comprises the following steps: firstly, determining the arrangement sequence, quantity and the phase state of the heating fluid in the heat exchanger according to the process flow of the nuclear energy heating device; then, determining the parameters of the heat exchanger according to the arrangement sequence, quantity and the phase state of the heating fluid in the heat exchanger; then, constructing a calculation model to estimate the radioactivity concentration of the steam supplied by the nuclear energy heating device according to the operation condition of the nuclear energy heating device and the parameters of the heat exchanger; finally, comparing the radioactivity concentration of the steam supplied by the nuclear energy heating device with the radioactivity control index to determine whether the radioactivity concentration of the steam supplied by the nuclear energy heating device meets the requirements of the relevant regulations and standards. The method is used for determining whether the radioactivity concentration of the steam supplied by the nuclear energy heating device meets the control index of the relevant regulations and standards. If the radioactivity concentration of the steam supplied by the nuclear energy heating device does not meet the control index, an optimization scheme is proposed according to the process design.

Description

Technical Field

[0001] This invention relates to nuclear power technology, and more specifically to a method for estimating the radioactivity concentration of externally supplied steam in a nuclear heating device. Background Technology

[0002] Nuclear energy, as a safe, clean, and carbon-free energy source, can significantly reduce pollutant emissions, and its important role in energy conservation and emission reduction is becoming increasingly prominent. Nuclear heating can not only meet the ever-growing energy demands of economic and social development, effectively improve my country's energy structure, alleviate the increasingly severe energy supply shortage, and achieve coordinated development of energy, economy, and ecological environment, but also enhance comprehensive economic strength and industrial technology level. It is of great significance in protecting the environment and achieving China's "dual carbon" goals. The industrial utilization of nuclear heating and steam supply can open up new avenues for the comprehensive utilization of nuclear energy. It can not only solve the problem of insufficient clean heat sources in regions and support the development of chemical industrial parks, but also help to tap the capacity of nuclear power units and improve the economic efficiency of power plants. According to the direction and goals of national energy structure reform, using clean nuclear energy to provide regional heat sources is a more effective way to improve my country's energy structure, reduce coal resource consumption, and has significant strategic importance for improving air pollution.

[0003] Nuclear heating systems typically use the main steam from the secondary loop of the nuclear power plant as the heating source for external steam supply. To ensure the safe operation of the nuclear power plant and steam supply system, and to provide clean and reliable energy, nuclear safety is the primary consideration. Therefore, it is necessary to study and analyze the radioactivity level of the external steam produced by the nuclear heating system. The radioactivity level is reflected in the radioactivity concentration. Only after knowing the radioactivity concentration can we assess whether the external steam meets the control indicators required by relevant regulations and standards, or whether the steam supply system control needs to be optimized. However, currently, there is no method in existing technology to estimate the radioactivity concentration of the external steam supplied by a nuclear heating system. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for estimating the radioactivity concentration of external steam supplied by a nuclear heating device, which addresses the above-mentioned deficiencies of the prior art. This method can estimate the radioactivity concentration of external steam supplied by the nuclear heating device to assess whether the external steam meets the control indicators of relevant regulations and standards, and to propose an optimization scheme based on the process design after determining that the radioactivity concentration of external steam supplied by the nuclear heating device does not meet the control indicators.

[0005] This invention provides a method for estimating the radioactivity concentration of externally supplied steam in a nuclear heating device, the method comprising the following steps:

[0006] Step S1: Determine the heat exchanger arrangement sequence, number of heat exchangers, and phase state of the heating fluid in the heat exchangers according to the process flow of the nuclear heating device.

[0007] Step S2: Determine the parameters of the heat exchangers based on the arrangement sequence of the heat exchangers, the number of heat exchangers, and the phase state of the heated fluid in the heat exchangers; the heat exchangers consist of N stages, where N is a natural number greater than or equal to 1.

[0008] Step S3: Based on the operating conditions of the nuclear heating device and the parameters of the heat exchanger, construct a calculation model to estimate the radioactivity concentration of the external steam supplied by the nuclear heating device.

[0009] Step S4: Compare the radioactivity concentration of the external steam supplied by the nuclear heating device with the radioactivity control index to determine whether the radioactivity concentration of the external steam supplied by the nuclear heating device meets the requirements of relevant regulations and standards.

[0010] Further, in step S3, based on the operating conditions of the nuclear heating device and the parameters of the heat exchanger, the radioactivity concentration of the external steam supplied by the nuclear heating device is estimated, specifically including:

[0011] Based on the operating conditions of the nuclear heating device and the parameters of the heat exchanger, the specific activity of the radioactive fluid on the shell side of the Nth stage heat exchanger is calculated, and the specific activity of the radioactive fluid on the shell side of the Nth stage heat exchanger is converted into the radioactive activity concentration of each nuclide in the external steam and its condensate, thereby estimating the radioactive activity concentration of the external steam of the nuclear heating device.

[0012] The specific activity of the radioactivity of the shell-side fluid of the Nth stage heat exchanger is calculated based on the specific activity of the shell-side fluid of the (N-1)th stage heat exchanger, and so on. The specific activity of the radioactivity of the shell-side fluid of the next stage heat exchanger in the flow direction is calculated based on the specific activity of the shell-side fluid of the previous stage heat exchanger in the flow direction. When N equals 1, the background of the specific activity of the radioactivity of the shell-side fluid of the Nth stage heat exchanger is 0.

[0013] In step S4, the radioactivity concentration of the external steam supplied by the nuclear heating device is compared with radioactivity control indicators to determine whether the radioactivity concentration of the external steam supplied by the nuclear heating device meets the requirements of relevant regulations and standards. Specifically, this includes:

[0014] The radioactivity concentration of the external steam supplied by the nuclear heating device is compared with the radioactivity control index. When the radioactivity concentration of the external steam supplied by the nuclear heating device is less than or equal to the radioactivity control index, it is determined that the radioactivity concentration of the external steam supplied by the nuclear heating device meets the requirements of relevant regulations and standards; when the radioactivity concentration of the external steam supplied by the nuclear heating device is greater than the radioactivity control index, it is determined that the radioactivity concentration of the external steam supplied by the nuclear heating device does not meet the requirements of relevant regulations and standards.

[0015] Further, in step S3, based on the operating conditions of the nuclear heating device and the parameters of the heat exchanger, the specific activity of the radioactive fluid on the shell side of the Nth stage heat exchanger is calculated, including:

[0016] Based on the normal operating conditions of the nuclear heating plant and the parameters of the heat exchanger, the specific activity of tritium radioactivity in the shell-side fluid of the Nth stage heat exchanger under normal operating conditions is calculated.

[0017] The formula for calculating the tritium radioactivity specific activity of the shell-side fluid of the Nth stage heat exchanger under normal operating conditions is as follows:

[0018]

[0019] In formula (1):

[0020] This represents the specific activity of tritium radioactivity in the shell-side fluid of the Nth stage heat exchanger under normal operating conditions.

[0021] The specific activity of tritium radioactivity in the shell-side fluid of the N-1 stage heat exchanger under normal operating conditions.

[0022] C SH This refers to the specific activity of the main steam in the secondary loop of a nuclear power plant.

[0023] The tritium permeability in the Nth stage heat exchanger.

[0024] The leakage rate under normal operating conditions in the Nth stage heat exchanger.

[0025] This represents the tube-side flow rate in the Nth stage heat exchanger.

[0026] This represents the shell-side flow rate in the Nth stage heat exchanger.

[0027] in, The background is Under normal operating conditions, the specific activity of tritium radioactivity in the shell-side fluid of the Nth stage heat exchanger is calculated based on the background of the specific activity of tritium radioactivity in the shell-side fluid of the (N-1)th stage heat exchanger, and so on. The specific activity of tritium radioactivity in the shell-side fluid of the next stage heat exchanger in the flow direction is calculated based on the background of the specific activity of tritium radioactivity in the shell-side fluid of the previous stage heat exchanger in the flow direction. When N equals 1, the specific activity of tritium radioactivity in the shell-side fluid of the Nth stage heat exchanger is... The background is 0.

[0028] Furthermore, in step S3, calculating the specific activity of the radioactive fluid on the shell side of the Nth stage heat exchanger based on the operating conditions of the nuclear heating device and the parameters of the heat exchanger also includes:

[0029] If the analysis pertains to extreme accident conditions, then based on the analysis of the flow rates of each stage of the heat exchanger, the tube-side flow rate, and the shell-side flow rate, the location of the single-tube rupture when the impact on the radioactivity concentration of industrial steam is greatest is determined to be the Nth stage heat exchanger. Under extreme accident conditions, the tritium radioactivity specific activity of the shell-side fluid of the Nth stage heat exchanger is calculated using the leakage rate of the Nth stage heat exchanger as the single-tube rupture leakage rate. Leakage rate under normal operating conditions

[0030] For heat exchangers without single-tube rupture, the calculation method for the tritium radioactivity specific activity of the shell-side fluid is the same as under normal operating conditions.

[0031] The formula for calculating the tritium radioactivity specific activity of the shell-side fluid of the Nth stage heat exchanger under extreme accident conditions is as follows:

[0032]

[0033] In formula (2):

[0034] This represents the specific activity of tritium radioactivity in the shell-side fluid of the Nth stage heat exchanger under extreme accident conditions.

[0035] The specific activity of tritium radioactivity in the shell-side fluid of the N-1 stage heat exchanger under extreme accident conditions;

[0036] The single-tube rupture leakage rate in the Nth stage heat exchanger.

[0037] in, The background is Under extreme accident conditions, the specific activity of tritium radioactivity in the shell-side fluid of the Nth stage heat exchanger is calculated based on the background specific activity of tritium radioactivity in the shell-side fluid of the (N-1)th stage heat exchanger, and so on. The specific activity of tritium radioactivity in the shell-side fluid of the next stage heat exchanger in the flow direction is calculated based on the background specific activity of tritium radioactivity in the shell-side fluid of the previous stage heat exchanger in the flow direction. When N equals 1, the specific activity of tritium radioactivity in the shell-side fluid of the Nth stage heat exchanger under extreme accident conditions is... The background is 0.

[0038] Furthermore, step S4 specifically includes:

[0039] The radioactivity concentration of tritium in the externally supplied steam and its condensate is compared with the first radioactivity control index to determine whether the radioactivity concentration of tritium meets the requirements of relevant regulations and standards under normal operating conditions or extreme accident conditions. When the radioactivity concentration of tritium in the externally supplied steam and its condensate is less than or equal to the first radioactivity control index under normal operating conditions or extreme accident conditions, it is determined that the radioactivity concentration of tritium meets the requirements of relevant regulations and standards. When the radioactivity concentration of tritium in the externally supplied steam and its condensate is greater than the first radioactivity control index under normal operating conditions or extreme accident conditions, it is determined that the radioactivity concentration of tritium does not meet the requirements of relevant regulations and standards.

[0040] Furthermore, in step S3, calculating the specific activity of the radioactive fluid on the shell side of the Nth stage heat exchanger based on the operating conditions of the nuclear heating device and the parameters of the heat exchanger also includes:

[0041] Based on the normal operating conditions of the nuclear heating plant and the parameters of the heat exchanger, calculate the specific activity of all radioactive source terms (excluding tritium) in the shell-side fluid of the Nth stage heat exchanger under normal operating conditions, specifically including any one of the following conditions: A1, A2, or A3.

[0042] A1: When the phase states of the fluid before and after heating by the Nth stage heat exchanger are liquid and liquid respectively, the formula for calculating the specific activity of all radioactive source terms except tritium in the shell-side fluid of the Nth stage heat exchanger under normal operating conditions is as follows:

[0043]

[0044] In formula (3):

[0045] This represents the specific activity of all radioactive source terms, excluding tritium, in the shell-side fluid of the Nth stage heat exchanger under normal operating conditions.

[0046] This represents the specific activity of all radioactive source terms, excluding tritium, in the shell-side fluid of the N-1 stage heat exchanger under normal operating conditions.

[0047] C SH This refers to the specific activity of the main steam in the secondary loop of a nuclear power plant.

[0048] The leakage rate under normal operating conditions in the Nth stage heat exchanger.

[0049] This represents the shell-side flow rate in the Nth stage heat exchanger.

[0050] A2: When the phase states of the material before and after heating by the Nth stage heat exchanger are liquid and gas, respectively, the formula for calculating the specific activity of all radioactive source terms (excluding tritium) of the shell-side fluid of the Nth stage heat exchanger under normal operating conditions is as follows:

[0051]

[0052] In formula (4):

[0053] The steam-water distribution factor in the Nth stage heat exchanger;

[0054] A3: When the phase states of the material before and after heating by the Nth stage heat exchanger are gas and gas respectively, the formula for calculating the specific activity of all radioactive source terms (excluding tritium) of the shell-side fluid of the Nth stage heat exchanger under normal operating conditions is as follows:

[0055]

[0056] In formula (5):

[0057] The flash evaporation fraction in the Nth stage heat exchanger;

[0058] in, The background is Under normal operating conditions, the specific activity of all radioactive source terms (excluding tritium) in the shell-side fluid of the Nth stage heat exchanger is calculated based on the specific activity of all radioactive source terms (excluding tritium) in the shell-side fluid of the (N-1)th stage heat exchanger, and so on. The specific activity of the specific activity of the shell-side fluid of the next stage heat exchanger in the flow direction is calculated based on the specific activity of the shell-side fluid of the previous stage heat exchanger in the flow direction. When N equals 1, the background of the specific activity of all radioactive source terms (excluding tritium) in the shell-side fluid of the Nth stage heat exchanger is 0.

[0059] Furthermore, in step S3, calculating the specific activity of the radioactive fluid on the shell side of the Nth stage heat exchanger based on the operating conditions of the nuclear heating device and the parameters of the heat exchanger also includes:

[0060] If the analysis pertains to extreme accident conditions, then based on the analysis of the flow rates of each stage of the heat exchanger, the tube-side flow rate, and the shell-side flow rate, the location of the single-tube rupture when the impact on the radioactivity concentration of industrial steam is greatest is determined to be the Nth stage heat exchanger. Under extreme accident conditions, the specific activity of all radioactive source terms (excluding tritium) in the shell-side fluid of the Nth stage heat exchanger is calculated using the leakage rate of the Nth stage heat exchanger as a single-tube rupture leakage rate. Leakage rate under normal operating conditions

[0061] For heat exchangers without single-tube rupture, the calculation method for the specific activity of all radioactive source terms (excluding tritium) in the shell-side fluid is the same as under normal operating conditions.

[0062] The formula for the specific activity of all radioactive source terms except tritium in the shell-side fluid of the Nth stage heat exchanger under extreme accident conditions, specifically including any one of the following cases B1, B2, or B3.

[0063] B1: When the phase states before and after heating by the Nth stage heat exchanger are liquid and liquid respectively, the formula for calculating the specific activity of all radioactive source terms (excluding tritium) of the shell-side fluid of the Nth stage heat exchanger under extreme accident conditions is as follows:

[0064]

[0065] In formula (6):

[0066] This represents the specific activity of all radioactive source terms, excluding tritium, in the shell-side fluid of the Nth stage heat exchanger under extreme accident conditions.

[0067] This represents the specific activity of all radioactive source terms, excluding tritium, in the shell-side fluid of the N-1 stage heat exchanger under normal operating conditions.

[0068] C SH This refers to the specific activity of the main steam in the secondary loop of a nuclear power plant.

[0069] The single-tube rupture leakage rate in the Nth stage heat exchanger.

[0070] This represents the shell-side flow rate in the Nth stage heat exchanger.

[0071] B2: When the phase states before and after heating by the Nth stage heat exchanger are liquid and gas, respectively, the formula for calculating the specific activity of all radioactive source terms (excluding tritium) of the shell-side fluid of the Nth stage heat exchanger under extreme accident conditions is as follows:

[0072]

[0073] In formula (7):

[0074] The steam-water distribution factor in the Nth stage heat exchanger;

[0075] B3: When the phase states of the material before and after heating by the Nth stage heat exchanger are gas and gas respectively, the formula for calculating the specific activity of all radioactive source terms of the shell-side fluid of the Nth stage heat exchanger, excluding tritium, under extreme accident conditions is as follows:

[0076]

[0077] In formula (8):

[0078] The flash evaporation fraction in the Nth stage heat exchanger;

[0079] in, The background is Under extreme accident conditions, the specific activity of all radioactive source terms (excluding tritium) in the shell-side fluid of the Nth stage heat exchanger is calculated based on the specific activity of all radioactive source terms (excluding tritium) in the shell-side fluid of the (N-1)th stage heat exchanger, and so on. The specific activity of the specific activity of the shell-side fluid of the next stage heat exchanger in the flow direction is calculated based on the specific activity of the shell-side fluid of the previous stage heat exchanger in the flow direction. When N equals 1, the background of the specific activity of all radioactive source terms (excluding tritium) in the shell-side fluid of the Nth stage heat exchanger is 0.

[0080] Step S4 specifically includes:

[0081] The radioactivity concentrations of all radioactive source items other than tritium in the externally supplied steam and its condensate are compared with the second radioactivity control index to determine whether the radioactivity concentrations of all radioactive source items other than tritium meet the requirements of relevant regulations and standards under normal operating conditions or extreme accident conditions.

[0082] When the radioactivity concentration of all radioactive source items other than tritium in the externally supplied steam and its condensate is less than or equal to the second radioactivity control index under normal operating conditions or extreme accident conditions, the radioactivity concentration of all radioactive source items other than tritium meets the requirements of relevant regulations and standards; when the radioactivity concentration of all radioactive source items other than tritium in the externally supplied steam and its condensate is greater than the second radioactivity control index under normal operating conditions or extreme accident conditions, the radioactivity concentration of all radioactive source items other than tritium does not meet the requirements of relevant regulations and standards, and the second radioactivity control index is the control index for all radioactive source items other than tritium.

[0083] Furthermore, step S4 is followed by step S5.

[0084] S5: If it is determined that the radioactivity concentration of the external steam supplied by the nuclear heating device does not meet the control indicators, an optimization plan should be proposed based on the process design.

[0085] The beneficial effects of this invention are:

[0086] This invention can estimate the radioactivity concentration of external steam supplied by a nuclear heating device under both normal operating conditions and extreme accident conditions. The radioactivity concentration includes the specific activity concentration of tritium and the specific activity concentrations of all radioactive source terms other than tritium. Then, the radioactivity concentration of external steam supplied by the nuclear heating device is compared with radioactivity control indicators to determine whether the radioactivity concentration of external steam supplied by the nuclear heating device meets the requirements of relevant regulations and standards. If it does not meet the control indicators, an optimization scheme needs to be proposed based on the process design. Attached Figure Description

[0087] Figure 1 This is a flowchart illustrating the estimation of radioactivity concentration of externally supplied steam in a nuclear heating device according to an embodiment of the present invention.

[0088] Figure 2 This diagram illustrates a method for estimating the radioactivity concentration of externally supplied steam in a nuclear heating device according to an embodiment of the present invention. Detailed Implementation

[0089] To enable those skilled in the art to better understand the technical solution of the present invention, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0090] It is understood that the specific embodiments and accompanying drawings described herein are merely for explaining the invention and are not intended to limit the invention.

[0091] It is understood that, without conflict, the various embodiments and features in the embodiments of the present invention can be combined with each other.

[0092] It is understood that, for ease of description, only the parts related to the present invention are shown in the accompanying drawings, while the parts unrelated to the present invention are not shown in the drawings.

[0093] It is understood that each unit or module involved in the embodiments of the present invention may correspond to only one entity structure, or may be composed of multiple entity structures, or multiple units or modules may be integrated into one entity structure.

[0094] It is understood that, without conflict, the functions and steps marked in the flowcharts and block diagrams of this invention may occur in a different order than that marked in the accompanying drawings.

[0095] It is understood that the flowcharts and block diagrams of this invention illustrate the possible architecture, functions, and operations of systems, apparatuses, devices, and methods according to various embodiments of this invention. Each block in the flowchart or block diagram may represent a unit, module, program segment, or code, containing executable instructions for implementing the specified function. Furthermore, each block or combination of blocks in the block diagram and flowchart can be implemented using a hardware-based system to achieve the specified function, or using a combination of hardware and computer instructions.

[0096] It is understood that the units and modules involved in the embodiments of the present invention can be implemented by software or by hardware. For example, the units and modules can be located in a processor.

[0097] Example:

[0098] like Figure 1 and Figure 2 As shown in the figure, this embodiment provides a method for estimating the radioactivity concentration of externally supplied steam in a nuclear heating device. The method includes the following steps:

[0099] The heat exchanger arrangement sequence, number of heat exchangers, and phase state of the heating fluid in the heat exchangers are determined based on the process flow of the nuclear heating plant.

[0100] The parameters of the heat exchangers are determined based on the arrangement sequence of the heat exchangers, the number of heat exchangers, and the phase state of the heated fluid in the heat exchangers; the heat exchangers consist of N stages, where N is a natural number greater than or equal to 1.

[0101] Based on the operating conditions of the nuclear heating device and the parameters of the heat exchanger, a calculation model is constructed to calculate the specific activity of the radioactive fluid on the shell side of the Nth stage heat exchanger, and the specific activity of the radioactive fluid on the shell side of the Nth stage heat exchanger is converted into the radioactive activity concentration of each nuclide in the external steam and its condensate, thereby estimating the radioactive activity concentration of the external steam of the nuclear heating device.

[0102] The specific activity of the radioactive fluid on the shell side of the Nth stage heat exchanger was calculated, including:

[0103] (1) Based on the normal operating conditions of the nuclear heating plant and the parameters of the heat exchanger, calculate the tritium radioactivity specific activity of the shell-side fluid of the Nth stage heat exchanger under normal operating conditions.

[0104] The formula for calculating the tritium radioactivity specific activity of the shell-side fluid of the Nth stage heat exchanger under normal operating conditions is as follows:

[0105]

[0106] In formula (1):

[0107] This represents the specific activity of tritium radioactivity in the shell-side fluid of the Nth stage heat exchanger under normal operating conditions.

[0108] The specific activity of tritium radioactivity in the shell-side fluid of the N-1 stage heat exchanger under normal operating conditions.

[0109] The tritium permeability in the Nth stage heat exchanger.

[0110] The leakage rate under normal operating conditions in the Nth stage heat exchanger.

[0111] This represents the tube-side flow rate in the Nth stage heat exchanger.

[0112] This represents the shell-side flow rate in the Nth stage heat exchanger.

[0113] in, The background is Under normal operating conditions, the tritium radioactivity specific activity of the shell-side fluid of the Nth stage heat exchanger is calculated based on the tritium radioactivity specific activity of the shell-side fluid of the (N-1)th stage heat exchanger, and so on. The tritium radioactivity specific activity of the shell-side fluid of the previous stage heat exchanger is calculated based on the tritium radioactivity specific activity of the shell-side fluid of the next stage heat exchanger. When N equals 1, the background of the tritium radioactivity specific activity of the shell-side fluid of the Nth stage heat exchanger is 0.

[0114] (2) Based on (1), if the analysis is of the extreme accident condition, then the location of the single tube rupture when the impact on the radioactivity concentration of industrial steam is greatest is determined by analyzing the flow rates of each stage of heat exchanger, tube side flow rate, and shell side flow rate. This location is the Nth stage heat exchanger. The tritium radioactivity specific activity of the shell side fluid of the Nth stage heat exchanger under the extreme accident condition is calculated using the leakage rate of the Nth stage heat exchanger as the single tube rupture leakage rate. Leakage rate under normal operating conditions

[0115] For heat exchangers without single-tube rupture, the calculation method for the tritium radioactivity specific activity of the shell-side fluid is the same as under normal operating conditions.

[0116] The formula for calculating the tritium radioactivity specific activity of the shell-side fluid of the Nth stage heat exchanger under extreme accident conditions is as follows:

[0117]

[0118] In formula (2):

[0119] This represents the specific activity of tritium radioactivity in the shell-side fluid of the Nth stage heat exchanger under extreme accident conditions.

[0120] The specific activity of tritium radioactivity in the shell-side fluid of the N-1 stage heat exchanger under extreme accident conditions;

[0121] The single-tube rupture leakage rate in the Nth stage heat exchanger.

[0122] in, The background is Under extreme accident conditions, the specific activity of tritium radioactivity in the shell-side fluid of the Nth stage heat exchanger is calculated based on the background specific activity of tritium radioactivity in the shell-side fluid of the (N-1)th stage heat exchanger, and so on. The specific activity of tritium radioactivity in the shell-side fluid of the next stage heat exchanger in the flow direction is calculated based on the background specific activity of tritium radioactivity in the shell-side fluid of the previous stage heat exchanger in the flow direction. When N equals 1, the specific activity of tritium radioactivity in the shell-side fluid of the Nth stage heat exchanger under extreme accident conditions is... The background is 0.

[0123] (3) Based on the normal operating conditions of the nuclear heating plant and the parameters of the heat exchanger, calculate the specific activity of all radioactive source terms except tritium in the shell-side fluid of the Nth stage heat exchanger under normal operating conditions, specifically including any one of the following conditions A1, A2 or A3.

[0124] A1: When the phase states of the fluid before and after heating by the Nth stage heat exchanger are liquid and liquid respectively, the formula for calculating the specific activity of all radioactive source terms except tritium in the shell-side fluid of the Nth stage heat exchanger under normal operating conditions is as follows:

[0125]

[0126] In formula (3):

[0127] This represents the specific activity of all radioactive source terms, excluding tritium, in the shell-side fluid of the Nth stage heat exchanger under normal operating conditions.

[0128] This represents the specific activity of all radioactive source terms, excluding tritium, in the shell-side fluid of the N-1 stage heat exchanger under normal operating conditions.

[0129] C SH This refers to the specific activity of the main steam in the secondary loop of a nuclear power plant.

[0130] The leakage rate under normal operating conditions in the Nth stage heat exchanger.

[0131] This represents the shell-side flow rate in the Nth stage heat exchanger.

[0132] A2: When the phase states of the material before and after heating by the Nth stage heat exchanger are liquid and gas, respectively, the formula for calculating the specific activity of all radioactive source terms (excluding tritium) of the shell-side fluid of the Nth stage heat exchanger under normal operating conditions is as follows:

[0133]

[0134] In formula (4):

[0135] The steam-water distribution factor in the Nth stage heat exchanger;

[0136] A3: When the phase states of the material before and after heating by the Nth stage heat exchanger are gas and gas respectively, the formula for calculating the specific activity of all radioactive source terms (excluding tritium) of the shell-side fluid of the Nth stage heat exchanger under normal operating conditions is as follows:

[0137]

[0138] In formula (5):

[0139] The flash evaporation fraction in the Nth stage heat exchanger;

[0140] in, The background is Under normal operating conditions, the specific activity of all radioactive source terms (excluding tritium) in the shell-side fluid of the Nth stage heat exchanger is calculated based on the specific activity of all radioactive source terms (excluding tritium) in the shell-side fluid of the (N-1)th stage heat exchanger, and so on. The specific activity of the specific activity of the shell-side fluid of the next stage heat exchanger in the flow direction is calculated based on the specific activity of the shell-side fluid of the previous stage heat exchanger in the flow direction. When N equals 1, the background of the specific activity of all radioactive source terms (excluding tritium) in the shell-side fluid of the Nth stage heat exchanger is 0.

[0141] (4) Based on (3), if the analysis is of the extreme accident condition, then the location of the single tube rupture when the impact on the radioactivity concentration of industrial steam is the Nth stage heat exchanger is determined by analyzing the flow rates of each stage heat exchanger, tube side flow rate, and shell side flow rate. The specific activity of all radioactive source terms except tritium in the shell side fluid of the Nth stage heat exchanger under the extreme accident condition is calculated as the leakage rate of the Nth stage heat exchanger using the single tube rupture leakage rate. Leakage rate under normal operating conditions

[0142] For heat exchangers without single-tube rupture, the calculation method for the specific activity of all radioactive source terms (excluding tritium) in the shell-side fluid is the same as under normal operating conditions.

[0143] The formula for the specific activity of all radioactive source terms except tritium in the shell-side fluid of the Nth stage heat exchanger under extreme accident conditions, specifically including any one of the following cases B1, B2, or B3.

[0144] B1: When the phase states before and after heating by the Nth stage heat exchanger are liquid and liquid respectively, the formula for calculating the specific activity of all radioactive source terms (excluding tritium) of the shell-side fluid of the Nth stage heat exchanger under extreme accident conditions is as follows:

[0145]

[0146] In formula (6):

[0147] This represents the specific activity of all radioactive source terms, excluding tritium, in the shell-side fluid of the Nth stage heat exchanger under extreme accident conditions.

[0148] This represents the specific activity of all radioactive source terms, excluding tritium, in the shell-side fluid of the N-1 stage heat exchanger under normal operating conditions.

[0149] C SH This refers to the specific activity of the main steam in the secondary loop of a nuclear power plant.

[0150] The single-tube rupture leakage rate in the Nth stage heat exchanger.

[0151] This represents the shell-side flow rate in the Nth stage heat exchanger.

[0152] B2: When the phase states before and after heating by the Nth stage heat exchanger are liquid and gas, respectively, the formula for calculating the specific activity of all radioactive source terms (excluding tritium) of the shell-side fluid of the Nth stage heat exchanger under extreme accident conditions is as follows:

[0153]

[0154] In formula (7):

[0155] The steam-water distribution factor in the Nth stage heat exchanger;

[0156] B3: When the phase states of the material before and after heating by the Nth stage heat exchanger are gas and gas respectively, the formula for calculating the specific activity of all radioactive source terms of the shell-side fluid of the Nth stage heat exchanger, excluding tritium, under extreme accident conditions is as follows:

[0157]

[0158] In formula (8):

[0159] The flash evaporation fraction in the Nth stage heat exchanger;

[0160] in, The background is Under extreme accident conditions, the specific activity of all radioactive source terms (excluding tritium) in the shell-side fluid of the Nth stage heat exchanger is calculated based on the specific activity of all radioactive source terms (excluding tritium) in the shell-side fluid of the (N-1)th stage heat exchanger, and so on. The specific activity of the specific activity of the shell-side fluid of the next stage heat exchanger in the flow direction is calculated based on the specific activity of the shell-side fluid of the previous stage heat exchanger in the flow direction. When N equals 1, the background of the specific activity of all radioactive source terms (excluding tritium) in the shell-side fluid of the Nth stage heat exchanger is 0.

[0161] Next, the radioactivity concentration of tritium in the externally supplied steam and its condensate is compared with the first radioactivity control index to determine whether the radioactivity concentration of tritium meets the requirements of relevant regulations and standards under normal operating conditions or extreme accident conditions:

[0162] When the radioactivity concentration of tritium in the externally supplied steam and its condensate is less than or equal to the first radioactivity control index under normal operating conditions or extreme accident conditions, it is determined that the radioactivity concentration of tritium meets the requirements of relevant regulations and standards; when the radioactivity concentration of tritium in the externally supplied steam and its condensate is greater than the first radioactivity control index under normal operating conditions or extreme accident conditions, it is determined that the radioactivity concentration of tritium does not meet the requirements of relevant regulations and standards.

[0163] or,

[0164] The radioactivity concentrations of all radioactive source items other than tritium in the externally supplied steam and its condensate are compared with the second radioactivity control index to determine whether the radioactivity concentrations of all radioactive source items other than tritium meet the requirements of relevant regulations and standards under normal operating conditions or extreme accident conditions.

[0165] When the radioactivity concentration of all radioactive source items other than tritium in the externally supplied steam and its condensate is less than or equal to the second radioactivity control index under normal operating conditions or extreme accident conditions, the radioactivity concentration of all radioactive source items other than tritium meets the requirements of relevant regulations and standards; when the radioactivity concentration of all radioactive source items other than tritium in the externally supplied steam and its condensate is greater than the second radioactivity control index under normal operating conditions or extreme accident conditions, the radioactivity concentration of all radioactive source items other than tritium does not meet the requirements of relevant regulations and standards, and the second radioactivity control index is the control index for all radioactive source items other than tritium.

[0166] Once it is determined that the concentration of radioactive activity in the external steam supplied by the nuclear heating unit does not meet the control targets, an optimization plan needs to be proposed based on the process design.

[0167] To more clearly illustrate the implementation process, taking the industrial steam produced under normal operating conditions of a nuclear power plant's nuclear heating unit as an example, the calculation steps of this method are given:

[0168] The first step involves analyzing the process flow of the heating unit. The demineralized water is heated by the feedwater preheater to become saturated demineralized water, heated by the evaporator to become saturated steam, and heated by the superheater to become superheated steam that meets the external supply standards. The heat exchangers at each stage are numbered as follows: the feedwater preheater is the first-stage heat exchanger, the evaporator is the second-stage heat exchanger, and the superheater is the third-stage heat exchanger.

[0169] Furthermore, the analysis condition was determined to be the normal operating condition, and the specific activity of radioactivity in the main steam of the secondary loop of the nuclear power plant was analyzed, taking I-132 as an example. SH The C of H-3 is 100 Bq / kg. SH The flow rate F on the tube side of the first-stage heat exchanger is 3000 Bq / kg. S1 =250t / h, shell-side flow rate F P1 =200t / h, tritium permeability P S1 =0.2%, conventional leakage rate L S1 = 1 kg / h; Secondary heat exchanger tube-side flow rate F S2 =250t / h, shell-side flow rate F P2 =200t / h, tritium permeability P S2 =0.2%, conventional leakage rate L S2 = 1 kg / h; Three-stage heat exchanger tube-side flow rate F S3 =250t / h, shell-side flow rate F P3 =200t / h, tritium permeability P S3 =0.2%, conventional leakage rate L S3 = 1 kg / h; Evaporator steam-water distribution factor F HS The fraction of superheater flash evaporation is 1 for inert gases, 0.01 for iodine, and 0.005 for other nuclides; F HC The density of industrial steam is P1 = 1.0E-02 kg / L; the density of condensate is P2 = 1 kg / L.

[0170] Furthermore, a computational model is established for the shell-side fluid of the heat exchanger at each stage:

[0171] Specific activity of radioactivity in the shell-side fluid of the primary heat exchanger:

[0172] tritium:

[0173]

[0174] Other nuclides:

[0175]

[0176] A H1 - Specific activity of tritium in water after passing through the primary heat exchanger, Bq / kg;

[0177] A O1 - Specific activity of other nuclides in the water after passing through the primary heat exchanger, Bq / kg;

[0178] C SH - Specific activity of the main steam in the secondary loop of a nuclear power plant, Bq / kg;

[0179] P S1 - The permeability of tritium;

[0180] L S1 - Leakage rate of the primary heat exchanger, t / h;

[0181] F P1 - Shell-side flow rate of the primary heat exchanger, t / h;

[0182] F S1 - Tube-side flow rate of the first-stage heat exchanger, t / h.

[0183] Specific activity of radioactivity in the shell-side fluid after heating in the secondary heat exchanger:

[0184] tritium:

[0185]

[0186] Other nuclides:

[0187]

[0188] A H2 - Specific activity of tritium in the steam after the secondary heat exchanger, Bq / kg;

[0189] A O2 - Specific activity of other nuclides in the steam after the secondary heat exchanger, Bq / kg;

[0190] A H1 -Specific activity of tritium in water after passing through the primary heat exchanger, Bq / kg;

[0191] A O1 - Specific activity of other nuclides in the water after passing through the primary heat exchanger, Bq / kg;

[0192] C SH - Specific activity of the main steam in the secondary loop of a nuclear power plant, Bq / kg;

[0193] P S2 - The permeability of tritium;

[0194] L S2 - Leakage rate of the secondary heat exchanger, t / h;

[0195] F P2 - Shell-side flow rate of the secondary heat exchanger, t / h;

[0196] F S2 - The tube-side flow rate of the secondary heat exchanger, t / h.

[0197] F Hs - The steam-water distribution factor of the secondary heat exchanger.

[0198] Specific activity of radioactivity in the shell-side fluid after heating in a three-stage heat exchanger:

[0199] tritium:

[0200]

[0201] Other nuclides:

[0202]

[0203] A H3 - Specific activity of tritium in the steam after passing through the heat exchanger, Bq / kg;

[0204] A O3 - Specific activity of other nuclides in the steam after passing through the heat exchanger, Bq / kg;

[0205] A H2 -Specific activity of tritium in the steam after the secondary heat exchanger, Bq / kg;

[0206] A O2 - Specific activity of other nuclides in the steam after the secondary heat exchanger, Bq / kg;

[0207] C SH - Specific activity of the main steam in the secondary loop of a nuclear power plant, Bq / kg;

[0208] P S3 - The permeability of tritium;

[0209] L S3 - Leakage rate of the tertiary heat exchanger, t / h;

[0210] F P3 - Shell-side flow rate of the three-stage heat exchanger, t / h;

[0211] F S3 - Tube-side flow rate of the three-stage heat exchanger, t / h;

[0212] FHC -Flash evaporation fraction of the three-stage heat exchanger;

[0213] Furthermore, since the analysis focuses on normal operating conditions, it is not necessary to analyze the location of a single pipe rupture.

[0214] Furthermore, based on the above calculation model and parameters, the specific activity of tritium in the shell-side fluid of the first-stage heat exchanger was calculated to be A. H1 =7.52 Bq / kg, the specific activity of other nuclides is A O1 =5.00E-04Bq / kg; the specific activity of tritium radioactivity in the shell-side fluid of the secondary heat exchanger is A. H2 =15.0 Bq / kg, the specific activity of other nuclides is

[0215] A O2 =1.00E-05Bq / kg; the specific activity of tritium radioactivity in the shell-side fluid of the three-stage heat exchanger is A. H3 =22.5 Bq / kg, the specific activity of other nuclides is A O3 =2.10E-04Bq / kg. After unit conversion, the radioactivity concentrations of tritium in industrial steam are C1 = 2.25E-01Bq / L, and the radioactivity concentrations of I-132 are C1 = 2.10E-06Bq / L. The corresponding radioactivity concentrations of tritium in condensate are C2 = 22.5Bq / L, and the radioactivity concentrations of I-132 are C2 = 2.10E-04Bq / L.

[0216] Finally, referring to the French Public Health Law, which sets the reference value for tritium activity concentration in drinking water at 100 Bq / L, and the National Food Safety Standard for Drinking Natural Mineral Water (GB 8537-2018), which gives a total β radioactivity limit of 1.5 Bq / L, it can be seen from the calculation results of the radioactivity concentration in the condensate in the previous step that, under normal operating conditions, the externally supplied steam tritium and other nuclides all meet the radioactivity control requirements of relevant regulations and standards.

[0217] This embodiment can estimate the radioactivity concentration of the external steam supplied by the nuclear heating device for both normal operation and extreme accident conditions. The radioactivity concentration includes the specific activity concentration of tritium and the specific activity concentrations of all radioactive source terms except tritium. Then, the radioactivity concentration of the external steam supplied by the nuclear heating device is compared with the radioactivity control indicators to determine whether the radioactivity concentration of the external steam supplied by the nuclear heating device meets the requirements of relevant regulations and standards. If it does not meet the control indicators, an optimization scheme needs to be proposed based on the process design.

[0218] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method for estimating the radioactivity concentration of externally supplied steam in a nuclear heating device, characterized in that, The method includes the following steps: Step S1: Determine the heat exchanger arrangement sequence, number of heat exchangers, and phase state of the heating fluid in the heat exchangers according to the process flow of the nuclear heating device. Step S2: Determine the parameters of the heat exchangers based on the arrangement sequence of the heat exchangers, the number of heat exchangers, and the phase state of the heated fluid in the heat exchangers; the heat exchangers consist of N stages, where N is a natural number greater than or equal to 1. Step S3: Based on the operating conditions of the nuclear heating device and the parameters of the heat exchanger, construct a calculation model to estimate the radioactivity concentration of the external steam supplied by the nuclear heating device. Step S3 specifically includes: Based on the operating conditions of the nuclear heating device and the parameters of the heat exchanger, the specific activity of the radioactive fluid on the shell side of the Nth stage heat exchanger is calculated, and the specific activity of the radioactive fluid on the shell side of the Nth stage heat exchanger is converted into the radioactive activity concentration of each nuclide in the external steam and its condensate, thereby estimating the radioactive activity concentration of the external steam of the nuclear heating device. The specific activity of the radioactivity of the shell-side fluid of the Nth stage heat exchanger is calculated based on the specific activity of the shell-side fluid of the (N-1)th stage heat exchanger, and so on. The specific activity of the radioactivity of the shell-side fluid of the next stage heat exchanger in the flow direction is calculated based on the specific activity of the shell-side fluid of the previous stage heat exchanger in the flow direction. When N equals 1, the background of the specific activity of the radioactivity of the shell-side fluid of the Nth stage heat exchanger is 0. Step S4: Compare the radioactivity concentration of the external steam supplied by the nuclear heating device with the radioactivity control index to determine whether the radioactivity concentration of the external steam supplied by the nuclear heating device meets the requirements of relevant regulations and standards.

2. The method for estimating the radioactivity concentration of externally supplied steam in a nuclear heating device according to claim 1, characterized in that, In step S4, the radioactivity concentration of the external steam supplied by the nuclear heating device is compared with radioactivity control indicators to determine whether the radioactivity concentration of the external steam supplied by the nuclear heating device meets the requirements of relevant regulations and standards. Specifically, this includes: The radioactivity concentration of the external steam supplied by the nuclear heating device is compared with the radioactivity control index. When the radioactivity concentration of the external steam supplied by the nuclear heating device is less than or equal to the radioactivity control index, it is determined that the radioactivity concentration of the external steam supplied by the nuclear heating device meets the requirements of relevant regulations and standards; when the radioactivity concentration of the external steam supplied by the nuclear heating device is greater than the radioactivity control index, it is determined that the radioactivity concentration of the external steam supplied by the nuclear heating device does not meet the requirements of relevant regulations and standards.

3. The method for estimating the radioactivity concentration of externally supplied steam in a nuclear heating device according to claim 1, characterized in that, In step S3, the specific activity of the radioactive fluid on the shell side of the Nth stage heat exchanger is calculated based on the operating conditions of the nuclear heating device and the parameters of the heat exchanger, including: Based on the normal operating conditions of the nuclear heating plant and the parameters of the heat exchanger, the specific activity of tritium radioactivity in the shell-side fluid of the Nth stage heat exchanger under normal operating conditions is calculated. The formula for calculating the tritium radioactivity specific activity of the shell-side fluid of the Nth stage heat exchanger under normal operating conditions is as follows: （1） In formula (1): This represents the specific activity of tritium radioactivity in the shell-side fluid of the Nth stage heat exchanger under normal operating conditions. The specific activity of tritium radioactivity in the shell-side fluid of the N-1 stage heat exchanger under normal operating conditions. CSH is the specific activity of the main steam in the secondary loop of a nuclear power plant. The tritium permeability in the Nth stage heat exchanger. The leakage rate under normal operating conditions in the Nth stage heat exchanger. This represents the tube-side flow rate in the Nth stage heat exchanger. This represents the shell-side flow rate in the Nth stage heat exchanger. in, The background is Under normal operating conditions, the specific activity of tritium radioactivity in the shell-side fluid of the Nth stage heat exchanger is calculated based on the background of the specific activity of tritium radioactivity in the shell-side fluid of the (N-1)th stage heat exchanger, and so on. The specific activity of tritium radioactivity in the shell-side fluid of the next stage heat exchanger in the flow direction is calculated based on the background of the specific activity of tritium radioactivity in the shell-side fluid of the previous stage heat exchanger in the flow direction. When N equals 1, the specific activity of tritium radioactivity in the shell-side fluid of the Nth stage heat exchanger is... The background is 0.

4. The method for estimating the radioactivity concentration of externally supplied steam in a nuclear heating device according to claim 3, characterized in that, In step S3, the specific activity of the radioactive fluid on the shell side of the Nth stage heat exchanger is calculated based on the operating conditions of the nuclear heating device and the parameters of the heat exchanger. This step also includes: If the analysis pertains to extreme accident conditions, then based on the analysis of the flow rates of each stage of the heat exchanger, the tube-side flow rate, and the shell-side flow rate, the location of the single-tube rupture when the impact on the radioactivity concentration of industrial steam is greatest is determined to be the Nth stage heat exchanger. Under extreme accident conditions, the tritium radioactivity specific activity of the shell-side fluid of the Nth stage heat exchanger is calculated using the leakage rate of the Nth stage heat exchanger as the single-tube rupture leakage rate. Leakage rate under normal operating conditions , For heat exchangers without single-tube rupture, the calculation method for the tritium radioactivity specific activity of the shell-side fluid is the same as under normal operating conditions. The formula for calculating the tritium radioactivity specific activity of the shell-side fluid of the Nth stage heat exchanger under extreme accident conditions is as follows: （2） In formula (2): This represents the specific activity of tritium radioactivity in the shell-side fluid of the Nth stage heat exchanger under extreme accident conditions. The specific activity of tritium radioactivity in the shell-side fluid of the N-1 stage heat exchanger under extreme accident conditions; The single-tube rupture leakage rate in the Nth stage heat exchanger. in, The background is Under extreme accident conditions, the specific activity of tritium radioactivity in the shell-side fluid of the Nth stage heat exchanger is calculated based on the background specific activity of tritium radioactivity in the shell-side fluid of the (N-1)th stage heat exchanger, and so on. The specific activity of tritium radioactivity in the shell-side fluid of the next stage heat exchanger in the flow direction is calculated based on the background specific activity of tritium radioactivity in the shell-side fluid of the previous stage heat exchanger in the flow direction. When N equals 1, the specific activity of tritium radioactivity in the shell-side fluid of the Nth stage heat exchanger under extreme accident conditions is... The background is 0.

5. The method for estimating the radioactivity concentration of externally supplied steam in a nuclear heating device according to claim 4, characterized in that, Step S4 specifically includes: The radioactivity concentration of tritium in externally supplied steam and its condensate is compared with the first radioactivity control index to determine whether the radioactivity concentration of tritium meets the requirements of relevant regulations and standards under normal operating conditions or extreme accident conditions. When the radioactivity concentration of tritium in the externally supplied steam and its condensate is less than or equal to the first radioactivity control index under normal operating conditions or extreme accident conditions, it is determined that the radioactivity concentration of tritium meets the requirements of relevant regulations and standards; when the radioactivity concentration of tritium in the externally supplied steam and its condensate is greater than the first radioactivity control index under normal operating conditions or extreme accident conditions, it is determined that the radioactivity concentration of tritium does not meet the requirements of relevant regulations and standards.

6. The method for estimating the radioactivity concentration of externally supplied steam in a nuclear heating device according to claim 3, characterized in that, In step S3, the specific activity of the radioactive fluid on the shell side of the Nth stage heat exchanger is calculated based on the operating conditions of the nuclear heating device and the parameters of the heat exchanger. This step also includes: Based on the normal operating conditions of the nuclear heating plant and the parameters of the heat exchanger, calculate the specific activity of all radioactive source terms (excluding tritium) in the shell-side fluid of the Nth stage heat exchanger under normal operating conditions, specifically including any one of the following conditions: A1, A2, or A3. A1: When the phase states of the fluid before and after heating by the Nth stage heat exchanger are liquid and liquid respectively, the formula for calculating the specific activity of all radioactive source terms except tritium in the shell-side fluid of the Nth stage heat exchanger under normal operating conditions is as follows: （3） In formula (3): This represents the specific activity of all radioactive source terms, excluding tritium, in the shell-side fluid of the Nth stage heat exchanger under normal operating conditions. This represents the specific activity of all radioactive source terms, excluding tritium, in the shell-side fluid of the N-1 stage heat exchanger under normal operating conditions. CSH is the specific activity of the main steam in the secondary loop of a nuclear power plant. The leakage rate under normal operating conditions in the Nth stage heat exchanger. This represents the shell-side flow rate in the Nth stage heat exchanger. A2: When the phase states of the material before and after heating by the Nth stage heat exchanger are liquid and gas, respectively, the formula for calculating the specific activity of all radioactive source terms (excluding tritium) of the shell-side fluid of the Nth stage heat exchanger under normal operating conditions is as follows: （4） In formula (4): The steam-water distribution factor in the Nth stage heat exchanger; A3: When the phase states of the material before and after heating by the Nth stage heat exchanger are gas and gas respectively, the formula for calculating the specific activity of all radioactive source terms (excluding tritium) of the shell-side fluid of the Nth stage heat exchanger under normal operating conditions is as follows: （5） In formula (5): The flash evaporation fraction in the Nth stage heat exchanger; in, The background is Under normal operating conditions, the specific activity of all radioactive source terms (excluding tritium) in the shell-side fluid of the Nth stage heat exchanger is calculated based on the specific activity of all radioactive source terms (excluding tritium) in the shell-side fluid of the (N-1)th stage heat exchanger, and so on. The specific activity of the specific activity of the shell-side fluid of the next stage heat exchanger in the flow direction is calculated based on the specific activity of the shell-side fluid of the previous stage heat exchanger in the flow direction. When N equals 1, the background of the specific activity of all radioactive source terms (excluding tritium) in the shell-side fluid of the Nth stage heat exchanger is 0.

7. The method for estimating the radioactivity concentration of externally supplied steam in a nuclear heating device according to claim 6, characterized in that, In step S3, the specific activity of the radioactive fluid on the shell side of the Nth stage heat exchanger is calculated based on the operating conditions of the nuclear heating device and the parameters of the heat exchanger. This step also includes: If the analysis pertains to extreme accident conditions, then based on the analysis of the flow rates of each stage of the heat exchanger, the tube-side flow rate, and the shell-side flow rate, the location of the single-tube rupture when the impact on the radioactivity concentration of industrial steam is greatest is determined to be the Nth stage heat exchanger. Under extreme accident conditions, the specific activity of all radioactive source terms (excluding tritium) in the shell-side fluid of the Nth stage heat exchanger is calculated using the leakage rate of the Nth stage heat exchanger as a single-tube rupture leakage rate. Leakage rate under normal operating conditions , For heat exchangers without single-tube rupture, the calculation method for the specific activity of all radioactive source terms (excluding tritium) in the shell-side fluid is the same as under normal operating conditions. The formula for the specific activity of all radioactive source terms except tritium in the shell-side fluid of the Nth stage heat exchanger under extreme accident conditions, specifically including any one of the following cases B1, B2, or B3. B1: When the phase states before and after heating by the Nth stage heat exchanger are liquid and liquid respectively, the formula for calculating the specific activity of all radioactive source terms (excluding tritium) of the shell-side fluid of the Nth stage heat exchanger under extreme accident conditions is as follows: （6） In formula (6): This represents the specific activity of all radioactive source terms, excluding tritium, in the shell-side fluid of the Nth stage heat exchanger under extreme accident conditions. This represents the specific activity of all radioactive source terms, excluding tritium, in the shell-side fluid of the N-1 stage heat exchanger under normal operating conditions. CSH is the specific activity of the main steam in the secondary loop of a nuclear power plant. The single-tube rupture leakage rate in the Nth stage heat exchanger. This represents the shell-side flow rate in the Nth stage heat exchanger. B2: When the phase states before and after heating by the Nth stage heat exchanger are liquid and gas, respectively, the formula for calculating the specific activity of all radioactive source terms (excluding tritium) of the shell-side fluid of the Nth stage heat exchanger under extreme accident conditions is as follows: （7） In formula (7): The steam-water distribution factor in the Nth stage heat exchanger; B3: When the phase states of the material before and after heating by the Nth stage heat exchanger are gas and gas respectively, the formula for calculating the specific activity of all radioactive source terms of the shell-side fluid of the Nth stage heat exchanger, excluding tritium, under extreme accident conditions is as follows: （8） In formula (8): The flash evaporation fraction in the Nth stage heat exchanger; in, The background is Under extreme accident conditions, the specific activity of all radioactive source terms (excluding tritium) in the shell-side fluid of the Nth stage heat exchanger is calculated based on the specific activity of all radioactive source terms (excluding tritium) in the shell-side fluid of the (N-1)th stage heat exchanger, and so on. The specific activity of the specific activity of the shell-side fluid of the next stage heat exchanger in the flow direction is calculated based on the specific activity of the shell-side fluid of the previous stage heat exchanger in the flow direction. When N equals 1, the background of the specific activity of all radioactive source terms (excluding tritium) in the shell-side fluid of the Nth stage heat exchanger is 0.

8. The method for estimating the radioactivity concentration of externally supplied steam in a nuclear heating device according to claim 7, characterized in that, Step S4 specifically includes: The radioactivity concentrations of all radioactive source items other than tritium in the externally supplied steam and its condensate are compared with the second radioactivity control index to determine whether the radioactivity concentrations of all radioactive source items other than tritium meet the requirements of relevant regulations and standards under normal operating conditions or extreme accident conditions. When the radioactivity concentration of all radioactive source items other than tritium in the externally supplied steam and its condensate is less than or equal to the second radioactivity control index under normal operating conditions or extreme accident conditions, the radioactivity concentration of all radioactive source items other than tritium meets the requirements of relevant regulations and standards; when the radioactivity concentration of all radioactive source items other than tritium in the externally supplied steam and its condensate is greater than the second radioactivity control index under normal operating conditions or extreme accident conditions, the radioactivity concentration of all radioactive source items other than tritium does not meet the requirements of relevant regulations and standards, and the second radioactivity control index is the control index for all radioactive source items other than tritium.

9. The method for estimating the radioactivity concentration of externally supplied steam from a nuclear heating device according to any one of claims 1 to 8, characterized in that, Step S4 is followed by step S5. S5: If it is determined that the radioactivity concentration of the external steam supplied by the nuclear heating device does not meet the control indicators, an optimization plan should be proposed based on the process design.

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