System and method for evaluating background of pipe deposition source term under power operation condition of nuclear power plant

Abstract

The application discloses a kind of nuclear power plant power operation mode pipeline deposition source item background evaluation system and method, this method includes: S1.the activity ratio ε of activated corrosion product nuclide i is measured i , pipe surface dose rate D and the activity concentration C of nuclide i in primary coolant i ;S2.modeling and calculating the effective dose rate D of pipe surface by activated corrosion product in deposition contribution d ;S3.modeling and calculating the surface activity of activated corrosion product nuclide i in deposition source item;S4.modeling and calculating the total count rate CPS or total absorbed dose rate Gy / h of pipeline deposition source item to detector.The nuclear power plant power operation mode pipeline deposition source item background evaluation system and method of the application, the activity ratio of activated corrosion product nuclide i, pipe surface dose rate, the activity concentration of nuclide i in primary coolant are measured, modeling and calculating the total count rate CPS or total absorbed dose rate Gy / h of pipeline deposition source item to detector, realize the evaluation of deposition source item background under the power operation mode of unit.

Description

Technical Field

[0001] This invention relates to the field of radioactivity measurement, and in particular to a system and method for assessing the background of pipeline deposition source terms under the power operation conditions of a nuclear power plant. Background Technology

[0002] Currently, all nuclear power plants are equipped with radiation monitoring systems to monitor the plant's processes, radioactive process fluid systems, and equipment. This allows them to assess the effectiveness and normal operation of these systems and equipment by monitoring changes in radiation levels. The most important aspect is monitoring the integrity and effectiveness of the first and second safety barriers (fuel cladding and primary circuit pressure boundaries) to ensure the safe operation of the nuclear power plant.

[0003] Currently, the main methods for monitoring fuel cladding damage in domestic nuclear power plants include: periodic manual sampling and analysis, online gamma dose rate monitoring, and offline aspiration. The periodic manual sampling and analysis method involves manually obtaining primary coolant samples periodically through the plant's nuclear sampling system during operation. After sample pretreatment, a gamma spectroscopy device is used to analyze the radioactivity concentration of key characteristic nuclides in the primary coolant. The radioactivity concentration of these nuclides is compared with the nuclear power plant's radiochemical technical specifications to determine if the fuel cladding is damaged. The online gamma spectroscopy method involves installing fixed gamma dose rate or gamma activity concentration monitoring equipment near the pipelines of the nuclear power plant's chemical and volume control system or nuclear sampling system. The radiation dose rate level or characteristic nuclide activity concentration of the primary coolant within the pipelines reflects whether the fuel cladding is damaged. When the radioactivity level or nuclide activity concentration exceeds the limit, an alarm is triggered, automatically activating the isolation of the relevant discharge pipelines from the primary coolant to the containment. Offline sipping method: This refers to the process where, during a nuclear power plant shutdown, fuel assemblies are placed in a sipping chamber with a water loop. The water in the loop is heated by an electric heater, which in turn heats the fuel assemblies. If a fuel assembly is damaged, radioactive fission products from the fuel cladding are released into the sipping chamber through the breach. The inert gas in the fission products enters the gas loop for circulation. A gamma spectrometer is set up on the gas loop to measure the activity of the inert gas in the gas, and the gas activity is used to determine whether the fuel cladding is damaged.

[0004] Non-radioactive metals in pipelines or equipment within nuclear power plant systems can enter the primary coolant through corrosion or abrasion products. After activation by neutrons in the reactor core, radioactive nuclides are generated and deposited on the inner walls of the pipelines and equipment through a series of physical processes and chemical reactions, forming deposition source terms. The total gamma monitoring method involves placing monitoring equipment near the pipelines of the chemical and volume control system or nuclear sampling system. The detector measures both the radioactive primary coolant within the pipeline and the deposition source terms on the pipeline's inner walls. The background of these deposition source terms adds extra counts to the detector, potentially causing the total gamma monitoring equipment to overestimate the readings. This could lead to false alarms and malfunctions, misjudging fuel cladding damage, and affecting the safe and stable operation of the nuclear power plant. Because the primary coolant and deposition source terms coexist within the pipeline and contain the same nuclides, direct measurement methods cannot obtain relevant information about the deposition source terms. In summary, a method is needed to assess the impact of pipeline deposition on detector measurement results when both primary coolant source terms and pipeline deposition source terms exist simultaneously in the pipe being measured by the detector during power operation of a nuclear power plant. This method would subtract the background and obtain the true radioactivity level of the primary coolant, and would also enable rapid troubleshooting of false alarms.

[0005] In existing technologies, the deduction of background values ​​(generated by deposition source terms within the pipe walls) from detectors in domestic power plant radiation monitoring systems is primarily performed during unit shutdown. There is no unified method for assessing the background of pipe deposition source terms during power operation. The background deduction method during shutdown is as follows:

[0006] 1) Ensure that there is no radioactive fluid inside the pipe being tested;

[0007] 2) Record the detector counts over a period of time and calculate the average count.

[0008] 3) It is assumed that the contribution of the deposition source term to the detector count in the next fuel cycle is this average value, and this value is written into the back-end processing equipment of the detector as the background value of the detector.

[0009] Existing technologies often have many technical shortcomings. After the oxidation and purification process before the reactor shutdown in the previous fuel cycle, most of the deposited source terms detach from the inner wall of the pipes and are removed by the purification system. Therefore, the background of the pipe deposited source terms measured after shutdown is low. As the next fuel cycle unit operates at power, due to changes in unit operating conditions (changes in primary loop flow rate, temperature, pressure, primary loop coolant pH, etc.), the pipe deposited source terms will slowly increase, resulting in the average contribution of the deposited source terms measured at shutdown to the detector count being lower than the true value. Therefore, this background subtraction method cannot completely eliminate the influence of deposited source terms on the total gamma online monitoring equipment measurements. Summary of the Invention

[0010] The technical problem this invention aims to solve is to provide an improved pipeline deposition source term background assessment system and method under nuclear power plant power operation conditions, addressing the issue that background measurements of deposition source terms during reactor shutdown cannot accurately reflect the true situation of deposition source terms in the next fuel cycle. This system is used to assess the contribution of pipeline deposition source terms to detector measurement results when there is a significant difference between the sampling measurement results from the nuclear power plant radiochemical laboratory and the detector measurement results, and when both primary coolant source terms and pipeline deposition source terms exist simultaneously in the measured pipeline.

[0011] The technical solution adopted by this invention to solve its technical problem is: to provide a method for assessing the background of pipeline deposition source terms under the power operation conditions of a nuclear power plant, including...

[0012] S1. Measure the activity ratio ε of the activated corrosion product nuclide i. i The surface dose rate D of the pipeline and the activity concentration C of nuclide i in the primary coolant. i ;

[0013] S2. Establish a first model, and calculate the contribution D of nuclide i per unit activity in the primary coolant based on the first model. c,i and the total volume of fluid in the pipe V pipe ;

[0014] The effective dose rate D on the pipe surface contributed by the corrosion products in the deposition was calculated according to formulas (1) and (2). d ;

[0015] D d =DD coolant (1)

[0016]

[0017] in:

[0018] D coolant The effective dose rate at the pipe surface contributed by the radionuclides in the primary coolant;

[0019] S3. Establish a second model, and calculate the contribution D of the activated corrosion product per unit activity nuclide i based on the second model. d,i and the total internal surface area S of the pipeline pipe ;

[0020] The surface activity A of the activated corrosion product nuclide i in the sediment source term is calculated according to formulas (3), (4) and (5). s,i :

[0021]

[0022]

[0023]

[0024] In the formula:

[0025] A represents the total activity of the activated corrosion products of the sediment source term;

[0026] A i The activity of nuclide i, an activated corrosion product in the sediment source term;

[0027] S4. Establish a third model and calculate the total internal surface area S of the pipeline based on the third model. pipe and the count rate (cps) of nuclide i with unit activity in the sediment source term in the detector. Bq,i ;

[0028] The total count rate (CPS) of the pipe deposition source term to the detector was calculated according to formula (6):

[0029]

[0030] Preferably, step S2 further includes:

[0031] S21. Establish the first model, and calculate the contribution D of nuclide i per unit activity in the primary coolant based on the first model. c,i and the total volume of fluid in the pipe V pipe ;

[0032] S22. The effective dose rate D of the pipe surface contributed by the activated corrosion products in the deposition is calculated according to the formulas (1) and (2). d The effective dose rate D on the pipe surface contributed by the activated corrosion products in the deposition d The unit is mSv / h.

[0033] Preferably, the first model is a Monte Carlo model, and the calculation method in step S21 is the Monte Carlo method; or, the first model is a point kernel integral model.

[0034] Preferably, step S3 further includes:

[0035] S31. Establish the second model, and calculate the contribution D of the activated corrosion product per unit activity nuclide i based on the second model. d,i and the total internal surface area S of the pipeline pipe ;;

[0036] S32. The surface activity A of the activated corrosion product nuclide i in the sediment source term is calculated according to formulas (3), (4) and (5). s,i The surface activity A of the activated corrosion product nuclide i in the deposition source term s,i The unit is Bq / cm2 .

[0037] Preferably, the second model is a Monte Carlo model, and the calculation method in step S31 is the Monte Carlo method; or, the second model is a point kernel integral model.

[0038] Preferably, step S4 further includes:

[0039] S41. Establish the third model and calculate the total inner surface area S of the pipeline based on the third model. pipe and the count rate (cps) of nuclide i with unit activity in the sediment source term in the detector. Bq,i ;

[0040] S42. The total count rate (CPS) of the pipeline deposition source term to the detector is calculated according to formula (6), wherein the unit of the total count rate (CPS) of the pipeline deposition source term to the detector is c / s.

[0041] Preferably, the third model is a Monte Carlo model, and the calculation method in step S41 is the Monte Carlo method.

[0042] A system for assessing the background of pipeline deposition source terms under nuclear power plant power operation conditions is also provided, comprising a measuring device, a first modeling and calculation device, a second modeling and calculation device, and a third modeling and calculation device, wherein:

[0043] The measuring device is used to measure the activity ratio ε of the activated corrosion product nuclide i. i The surface dose rate D of the pipeline and the activity concentration C of nuclide i in the primary coolant. i ;

[0044] The first modeling and computing device is used to establish a first model and calculate the contribution D of nuclide i per unit activity in the primary coolant based on the first model. c,i and the total volume of fluid in the pipe V pipe The effective dose rate D on the pipe surface contributed by the activated corrosion products in the deposition was calculated according to formulas (1) and (2). d ;

[0045] D d =DD coolant (1)

[0046]

[0047] in:

[0048] D coolant The effective dose rate at the pipe surface contributed by the radionuclides in the primary coolant;

[0049] The second modeling and computing device is used to establish a second model, and calculate the contribution D of the activated corrosion product per unit activity nuclide i based on the second model. d,i and the total internal surface area S of the pipeline pipe The surface activity A of the activated corrosion product nuclide i in the sediment source term is calculated according to formulas (3), (4) and (5). s,i :

[0050]

[0051]

[0052]

[0053] In the formula:

[0054] A represents the total activity of the activated corrosion products of the sediment source term;

[0055] A i The activity of nuclide i, an activated corrosion product in the sediment source term;

[0056] The third modeling and computing device is used to establish a third model and calculate the total internal surface area S of the pipe based on the third model. pipe and the count rate (cps) of nuclide i with unit activity in the sediment source term in the detector. Bq,i ;

[0057] The total count rate (CPS) of the pipe deposition source term to the detector was calculated according to formula (6):

[0058]

[0059] Preferably, the first modeling computing device further includes:

[0060] The first modeling module is used to establish the first model and calculate the contribution D of nuclide i per unit activity in the primary coolant based on the first model. c,i and the total volume of fluid in the pipe V pipe ;

[0061] The dose rate contribution calculation module is used to calculate the effective dose rate D of the pipe surface contributed by the activated corrosion products in the deposition, according to the formulas (1) and (2). d The effective dose rate D on the pipe surface contributed by the activated corrosion products in the deposition d The unit is mSv / h.

[0062] Preferably, the first model is a Monte Carlo model, and the calculation method of the first modeling module is the Monte Carlo method; or, the first model is a point kernel integral model.

[0063] Preferably, the second modeling computing device further includes:

[0064] The second modeling module is used to establish the second model and calculate the contribution D of the activated corrosion product per unit activity nuclide i based on the second model. d,i and the total internal surface area S of the pipeline pipe ;;

[0065] The sedimentation source term surface activity calculation module is used to calculate the surface activity A of the activated corrosion product nuclide i in the sedimentation source term according to formulas (3), (4) and (5). s,i The surface activity A of the activated corrosion product nuclide i in the deposition source term s,i The unit is Bq / cm 2 .

[0066] Preferably, the second model is a Monte Carlo model, and the calculation method of the second modeling module is the Monte Carlo method; or, the second model is a point kernel integral model.

[0067] Preferably, the third modeling computing device further includes:

[0068] The third modeling module is used to establish the third model and calculate the total internal surface area S of the pipe based on the third model. pipe and the count rate (cps) of nuclide i with unit activity in the sediment source term in the detector. Bq,i ;

[0069] The deposition source term contribution calculation module is used to calculate the total count rate (CPS) of the pipeline deposition source term to the detector according to formula (6), wherein the unit of the total count rate (CPS) of the pipeline deposition source term to the detector is c / s.

[0070] Preferably, the third model is a Monte Carlo model, and the calculation method of the third modeling module is the Monte Carlo method.

[0071] Preferably, the measuring device includes

[0072] The deposition energy dispersive spectroscopy (EDS) module is used to measure the activity ratio ε of the activated corrosion product nuclide i. i ;

[0073] A pipeline surface dose rate measurement module is used to measure the pipeline surface dose rate D;

[0074] The activity concentration measurement module is used to measure the activity concentration C of nuclide i in the primary coolant. i .

[0075] A method for assessing the background of pipeline deposition source terms under nuclear power plant power operation conditions is also provided, including...

[0076] S1. Measure the activity ratio ε of the activated corrosion product nuclide i. i The surface dose rate D of the pipeline and the activity concentration C of nuclide i in the primary coolant. i ;

[0077] S2. Establish a first model, and calculate the contribution D of nuclide i per unit activity in the primary coolant based on the first model. c,i and the total volume of fluid in the pipe V pipe ;

[0078] The effective dose rate D on the pipe surface contributed by the activated corrosion products in the deposition was calculated according to formulas (1) and (2). d ;

[0079] D d =DD coolant (1)

[0080]

[0081] in:

[0082] D coolant The effective dose rate at the pipe surface contributed by the radionuclides in the primary coolant;

[0083] S3. Establish a second model, and calculate the contribution D of the activated corrosion product per unit activity nuclide i based on the second model. d,i and the total internal surface area S of the pipeline pipe ;

[0084] The surface activity A of the activated corrosion product nuclide i in the sediment source term is calculated according to formulas (3), (4) and (5). s,i :

[0085]

[0086]

[0087]

[0088] In the formula:

[0089] A represents the total activity of the activated corrosion products of the sediment source term;

[0090] A i The activity of nuclide i, an activated corrosion product in the sediment source term;

[0091] S4'. Establish a third model, and calculate the dose rate contribution D of nuclide i with unit activity in the deposited source term in the detector based on the third model. de,i ;

[0092] The contribution D of the pipeline deposition source term to the detector dose rate was calculated according to formula (7). de :

[0093]

[0094] The beneficial effects of implementing the present invention are as follows: In the pipeline deposition source term background assessment system and method under nuclear power plant power operation conditions of the present invention, by measuring the activity ratio of activated corrosion product nuclide i, pipeline surface dose rate, and activity concentration of nuclide i in the primary coolant, a first model, a second model, and a third model are established, and the pipeline deposition source term to detector total count rate CPS is calculated, thereby realizing the assessment of the deposition source term background.

[0095] This invention proposes a set of assessment methods specifically for the background deposition of process piping during the power operation of nuclear power plants, which makes up for the current deficiency that the background deposition of nuclear power plants is only measured during shutdown.

[0096] Compared with traditional methods for measuring sediment source term background during reactor shutdown, the present invention has the following advantages:

[0097] 1. This invention makes the assessment of sediment source term background more timely and can more accurately reflect the contribution of current pipeline sediment source term background to detector measurement results compared to methods that only measure sediment source term background during reactor shutdown.

[0098] 2. This invention has the advantage of simple operation. It only requires additional measurement of the deposition source spectrum and the dose rate on the pipeline surface, and can be analyzed in conjunction with the results of the primary loop radiochemical sampling performed regularly by the power plant.

[0099] 3. This invention offers the advantage of rapid assessment. Even when there are significant differences between nuclear power plant detector measurement data and radiochemical sampling data, it can quickly assess the contribution of deposition source terms to the detector measurement results. Based on the assessment results, solutions can be adopted to update the background subtraction values ​​or eliminate the influence of deposition source terms. Attached Figure Description

[0100] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0101] Figure 1 This is a schematic diagram of the structure of the pipeline deposition source term background assessment system under nuclear power plant power operation conditions in some embodiments of the present invention;

[0102] Figure 2 This is a schematic flowchart of a pipeline deposition source term background assessment method under nuclear power plant power operation conditions in some embodiments of the present invention;

[0103] Figure 3This is a flowchart illustrating the background assessment method for pipeline deposition source terms under nuclear power plant power operation conditions in some other embodiments of the present invention. Detailed Implementation

[0104] 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.

[0105] The background assessment system and method for pipeline deposition source terms under nuclear power plant power operation conditions of this invention contains many abbreviations and key terms, some of which are defined as follows.

[0106] Deposition source: A general term for radiation sources consisting of radioactive nuclides deposited on the inner surface of pipelines or equipment in nuclear power plants.

[0107] Activated corrosion products: Non-radioactive metal corrosion or abrasion products in pipelines or equipment of nuclear power plant systems, which are then activated by neutrons in the reactor core to generate radionuclides.

[0108] Surface activity: The area activity of a radiation source deposited on the inner surface of a pipe or equipment, expressed in becquerels per square centimeter (Bq / cm²). 2 ).

[0109] Background radiation: The response of a detector to a radiation source other than the object being monitored, such as the surrounding radiation field and natural background radiation.

[0110] Figure 1 This invention illustrates a pipeline deposition source term background assessment system under nuclear power plant power operation conditions in some embodiments, used to assess the deposition source term background of process pipelines containing radioactive primary coolant during nuclear power plant power operation. The pipeline deposition source term background assessment system under nuclear power plant power operation conditions in this embodiment includes a measuring device 10, a first modeling calculation device 20, a second modeling calculation device 30, and a third modeling calculation device 40. The measuring device 10 is used to measure the activity ratio ε of the activated corrosion product nuclide i. i The surface dose rate D of the pipeline and the activity concentration C of nuclide i in the primary coolant. i The first modeling and computing device 20 is used to establish the first model and calculate the effective dose rate D on the pipe surface contributed by the activated corrosion products in the deposition. d The second modeling and computing device 30 is used to establish the second model and calculate the surface activity A of the activated corrosion product nuclide i in the deposition source term. s,i The third modeling and computing device 40 is used to establish the third model and calculate the total count rate (CPS) of the pipeline deposition source term to the detector.

[0111] like Figure 1 As shown, the measuring device 10 is used to measure the activity ratio ε of the activated corrosion product nuclide i.i The surface dose rate D of the pipeline and the activity concentration C of nuclide i in the primary coolant. i In some embodiments, the measuring device 10 includes a deposition energy spectrum measurement module 11, a pipe surface dose rate measurement module 12, and an activity concentration measurement module 13.

[0112] The deposition energy dispersive spectroscopy (EDS) module 11 is used to measure the activity ratio ε of nuclide i, which is an active corrosion product. i Preferably, the deposition energy spectrum measurement module 11 is used to measure the deposition source term spectrum in the room where the detector is located. For example, a portable gamma meter can be used to perform measurement and analysis near the pipe to obtain the gamma spectrum of the deposition source term.

[0113] Understandably, in other embodiments, the deposition energy spectrum measurement module 11 is used to measure the spectral patterns of deposition source terms in the field. The equipment that can be used is not limited to a portable gamma spectrometer, but can also be a gamma camera or other equipment capable of obtaining in-situ gamma energy spectra. If there are purification devices such as filters downstream of the pipeline, the spectral patterns of activated corrosion products can also be obtained by analyzing the objects they capture in the laboratory. Alternatively, some nuclear power plants have accumulated spectral patterns of deposition source terms in different systems and areas over many years of operation, and these spectral patterns can be used directly during evaluation.

[0114] The pipe surface dose rate measurement module 12 is used to measure the pipe surface dose rate D. Preferably, the pipe surface dose rate measurement module 12 is used to measure the dose rate at a fixed position on the pipe surface, and a portable dose rate monitoring device is generally used for measurement.

[0115] Activity concentration measurement module 13 is used to measure the activity concentration C of nuclide i in the primary coolant. i .

[0116] The first modeling computing device 20 is used to establish a first model and calculate the contribution D of nuclide i per unit activity in the primary coolant based on the first model. c,i and the total volume of fluid in the pipe V pipe The effective dose rate D on the pipe surface contributed by the activated corrosion products in the deposition was calculated according to formulas (1) and (2). d ;

[0117] D d =DD coolant (1)

[0118]

[0119] in:

[0120] D coolant The effective dose rate of the pipe surface contributed by the radionuclides in the primary coolant.

[0121] In some preferred embodiments, the first modeling calculation device 20 further includes a first modeling module 21 and a dose rate contribution calculation module 22.

[0122] The first modeling module 21 is used to establish the first model and calculate the contribution D of nuclide i per unit activity in the primary coolant based on the first model. c,i and the total volume of fluid in the pipe V pipe Preferably, the first model is a Monte Carlo model, and the calculation method of the first modeling module 21 is the Monte Carlo method; or, the first model is a point kernel integral model.

[0123] The dose rate contribution calculation module 22 is used to calculate the effective dose rate D of the pipe surface contributed by the activated corrosion products in the deposition according to formulas (1) and (2). d The effective dose rate D on the pipe surface contributed by activated corrosion products in the deposits d The unit is mSv / h.

[0124] The second modeling and computing device 30 is used to establish a second model, and to calculate the contribution D of the activated corrosion product per unit activity nuclide i based on the second model. d,i and the total internal surface area S of the pipeline pipe The surface activity A of the activated corrosion product nuclide i in the sediment source term is calculated according to formulas (3), (4) and (5). s,i :

[0125]

[0126]

[0127]

[0128] In the formula:

[0129] A represents the total activity of the activated corrosion products of the sediment source term;

[0130] A i The activity of nuclide i, an activated corrosion product in the sediment source term;

[0131] In some preferred embodiments, the second modeling calculation device 30 further includes a second modeling module 31 and a deposition source term surface activity calculation module 32.

[0132] The second modeling module 31 is used to establish a second model and calculate the contribution D of the activated corrosion product per unit activity nuclide i based on the second model. d,i and the total internal surface area S of the pipeline pipe Preferably, the second model is a Monte Carlo model, and the calculation method of the second modeling module 31 is the Monte Carlo method; or, the second model is a point kernel integral model.

[0133] The sedimentation source term surface activity calculation module 32 is used to calculate the surface activity A of the activated corrosion product nuclide i in the sedimentation source term according to formulas (3), (4) and (5). s,i The surface activity A of nuclide i, an activated corrosion product in the sediment source term. s,i The unit is Bq / cm 2 Understandably, the sediment source term surface activity calculation module 32 calculates the sediment source term surface activity according to formulas (3), (4) and (5).

[0134] The third modeling and calculation device 40 is used to establish the third model and calculate the total internal surface area S of the pipe based on the third model. pipe and the count rate (cps) of nuclide i with unit activity in the sediment source term in the detector. Bq,i And the total count rate (CPS) of the pipe deposition source term to the detector is calculated according to formula (6):

[0135]

[0136] In some preferred embodiments, the third modeling computing device 40 further includes a third modeling module 41 and a sedimentation source term contribution computing module 42.

[0137] The third modeling module 41 is used to build the third model and calculate the total internal surface area S of the pipe based on the third model. pipe and the count rate (cps) of nuclide i with unit activity in the sediment source term in the detector. Bq,i Preferably, the third model is a Monte Carlo model, and the calculation method of the third modeling module 41 is the Monte Carlo method.

[0138] The sedimentation source term contribution calculation module 42 is used to calculate the total count rate (CPS) of the pipe sedimentation source term to the detector according to formula (6). The unit of the total count rate (CPS) of the pipe sedimentation source term to the detector is c / s. Understandably, the sedimentation source term contribution calculation module 42 calculates the contribution of the sedimentation source term to the detector measurement results according to formula (6).

[0139] Understandably, in some embodiments, the first modeling module 21, the second modeling module 31, and the third modeling module 41 are integrated into a single functional module. For example, the first modeling module 21, the second modeling module 31, and the third modeling module 41 are integrated into a three-dimensional model transcription module. This three-dimensional model transcription module can generate the corresponding input card for Monte Carlo calculation software based on the three-dimensional model of the on-site pipeline and detector (including different pipe wall thicknesses, fine structure of the detector, etc.). Understandably, the three-dimensional model transcription module can be a common model transcription device, such as a Monte Carlo model transcription device, or a point kernel integral model transcription device, or other common hardware, software, or hardware-software hybrid model transcription devices. There are no restrictions here, as long as the three-dimensional model transcription function can be realized.

[0140] The following combination Figure 1-2 The specific steps of the pipeline deposition source term background assessment method under nuclear power plant power operation conditions in some embodiments of the present invention are described. The pipeline deposition source term background assessment method under nuclear power plant power operation conditions in the embodiments of the present invention is used to assess the deposition source term background of process pipelines containing radioactive primary coolant during nuclear power plant power operation. The pipeline deposition source term background assessment method under nuclear power plant power operation conditions in the embodiments of the present invention includes steps S1-S4, where step S1 is used to measure the activity ratio ε of activated corrosion product nuclide i. i The surface dose rate D of the pipeline and the activity concentration C of nuclide i in the primary coolant. i Step S2 is used to establish the first model and calculate the effective dose rate D on the pipe surface contributed by the activated corrosion products in the deposition. d Step S3 is used to establish the second model and calculate the surface activity A of the activated corrosion product nuclide i in the deposition source term. s,i Step S4 is used to establish the third model and calculate the total count rate (CPS) of the pipeline deposition source term to the detector.

[0141] like Figure 2 As shown, steps S1-S4 in the pipeline deposition source term background assessment method under nuclear power plant power operation conditions in this embodiment of the invention are as follows:

[0142] S1. Measure the activity ratio ε of the activated corrosion product nuclide i. i The surface dose rate D of the pipeline and the activity concentration C of nuclide i in the primary coolant. i In some embodiments, step S1 includes steps S11, S12, and S13.

[0143] Step S11 is used to measure the activity ratio ε of the activated corrosion product nuclide i. iPreferably, step S11 is used to measure the spectral pattern of the sediment source terms in the room where the detector is located. For example, a portable gamma meter can be used to perform the measurement and analysis near the pipe to obtain the gamma energy spectrum of the sediment source terms.

[0144] In some embodiments, step S11 involves measuring the total γ activity concentration using a portable γ spectrometer, and then measuring the γ energy spectrum (radioactive nuclide composition and activity percentage, as shown in Table 1) of the activated corrosion products in the pipeline using a detector of an online γ activity concentration monitoring device. Since activated corrosion product nuclides are present in both the primary coolant and the deposition source term in the pipeline, it is assumed here that the composition and activity percentage of activated corrosion product nuclides in the primary coolant are consistent with those in the pipeline deposition.

[0145] Nuclide Activity percentage Cr-51 5％ Mn-54 1％ Co-58 90％ Fe-59 1％ Co-60 1％ Ag-110m 1％ Sb-124 1％

[0146] Table 1 Examples of γ-ray spectra of sedimentary source terms

[0147] Understandably, in some other embodiments, step S11 is used to measure the spectral pattern of deposited source terms in the field. The equipment that can be used is not limited to a portable gamma spectrometer, but can also be a gamma camera or other equipment that can obtain the in-situ gamma energy spectrum. If there are purification devices such as filters downstream of the pipeline, the spectral pattern of activated corrosion products can also be obtained by analyzing the objects they capture in the laboratory. Alternatively, some nuclear power plants have accumulated the spectral patterns of deposited source terms in different systems and areas over many years of operation, and these spectral patterns can be used directly in the evaluation.

[0148] Step S12 is used to measure the dose rate D on the pipe surface. Preferably, step S12 is used to measure the dose rate at a fixed position on the pipe surface, and a portable dose rate detection device is generally used for measurement.

[0149] Specifically, in step S12, on the same date as step S11, the effective dose rate of the surface of the pipeline measured by the detector of the total γ online activity concentration monitoring device is measured and denoted as D, with the unit being mSv / h.

[0150] Step S13 is used to measure the activity concentration C of nuclide i in the primary coolant. i In some embodiments, step S13 acquires primary coolant radiochemical sampling data on the same date as the measurement in step S11, as shown in Table 2.

[0151]

[0152] Table 2. Examples of radiochemical sampling data for primary coolant.

[0153] S2. Establish the first model and calculate the contribution D of nuclide i per unit activity in the primary coolant based on the first model. c,i and the total volume of fluid in the pipe V pipeThe effective dose rate D on the pipe surface contributed by the activated corrosion products in the deposition was calculated according to formulas (1) and (2). d ;

[0154] D d =DD coolant (1)

[0155]

[0156] in:

[0157] D—Dose rate on the pipe surface, in mSv / h;

[0158] D d —Effective dose rate of the pipe surface contributed by activated corrosion products in the deposit, in mSv / h;

[0159] D coolant —Effective dose rate on the pipe surface contributed by radionuclides in the primary coolant, in mSv / h;

[0160] C i —The activity concentration of radionuclide i in the primary coolant, in Bq / cm³ 3 ;

[0161] D c,i —The contribution of a unit activity nuclide i in the primary coolant, expressed in mSv / h / Bq;

[0162] V pipe —Total volume of fluid inside the pipe, in cm³ 3 .

[0163] In some preferred embodiments, step S2 further includes steps S21 and S22:

[0164] S21. Establish the first model and calculate the contribution D of nuclide i per unit activity in the primary coolant based on the first model. c,i and the total volume of fluid in the pipe V pipe Preferably, the first model is a Monte Carlo model, and the calculation method in step S21 is the Monte Carlo method; or, the first model is a point kernel integral model. Understandably, the contributions of the primary coolant and different nuclides in the deposition layer to the dose rate on the pipe surface can be simulated not only using the Monte Carlo method, but also using deterministic methods such as point kernel integrals.

[0165] Specifically, in step S21, based on the total γ online activity concentration monitoring equipment and the layout of the measured pipelines, a first model is established, and the Monte Carlo method is used to calculate the dose contribution D of the unit activity nuclide i in the primary loop coolant. c,iThe location of the dose point in the model should be consistent with the measurement site in step S12, and the unit is mSv / h / Bq. Preferably, in step S21, based on the first model, the primary coolant and the deposited layer are respectively set as sources, and the contribution of the nuclides in the primary coolant and the deposited source terms to the dose rate on the pipe surface is calculated. Understandably, step S21 also calculates the contribution of the nuclides in the deposited source terms to the detector count based on the first model.

[0166] S22. The effective dose rate D on the pipe surface contributed by the activated corrosion products in the deposit is calculated according to formulas (1) and (2). d The effective dose rate D on the pipe surface contributed by activated corrosion products in the deposits d The unit is mSv / h.

[0167] S3. Establish a second model and calculate the contribution D of the activated corrosion product per unit activity nuclide i based on the second model. d,i and the total internal surface area S of the pipeline pipe ;

[0168] The surface activity A of the activated corrosion product nuclide i in the sediment source term is calculated according to formulas (3), (4) and (5). s,i :

[0169]

[0170]

[0171]

[0172] In the formula:

[0173] A – Total activity of activated corrosion products from sediment source term, in Bq;

[0174] A i —Activity of nuclide i, an activated corrosion product in the sediment source term, in Bq;

[0175] A s,i — Calculate the activity of nuclide i, an active corrosion product on the surface, in Bq / cm³. 2 ;

[0176] D d —Effective dose rate of REN pipe surface contributed by activated corrosion products in the deposition, in mSv / h;

[0177] ε i —Activity ratio of radionuclide i in activated corrosion products, see Table 1, dimensionless;

[0178] D d,i—The contribution of the activated corrosion products to the unit activity nuclide i, in mSv / h / Bq;

[0179] S pipe —Total internal surface area of ​​the pipe, in cm² 2 .

[0180] In some preferred embodiments, step S3 further includes steps S31 and S32:

[0181] S31. Establish a second model and calculate the contribution D of the activated corrosion products per unit activity nuclide i based on the second model. d,i and the total internal surface area S of the pipeline pipe Preferably, the second model is a Monte Carlo model, and the calculation method in step S31 is the Monte Carlo method; or, the second model is a point kernel integral model.

[0182] Specifically, in step S31, based on the actual layout of the total γ online activity concentration monitoring equipment and the measured pipeline, a second model is established, and the Monte Carlo method is used to calculate the dose contribution D of the nuclide i per unit activity in the pipe wall deposition. d,i The location of the dose point in the model should be consistent with the measurement site in step S12, and the unit is mSv / h / Bq. The deposition layer is a surface source, and to simplify modeling and source term definition, it can be considered as an extremely thin volume source.

[0183] S32. The surface activity A of the activated corrosion product nuclide i in the sediment source term is calculated according to formulas (3), (4) and (5). s,i The surface activity A of nuclide i, an activated corrosion product in the sediment source term. s,i The unit is Bq / cm 2 Understandably, step S32 calculates the surface activity of the deposition source term according to formulas (3), (4) and (5).

[0184] S4. Establish a third model and calculate the total internal surface area S of the pipeline based on the third model. pipe and the count rate (cps) of nuclide i with unit activity in the sediment source term in the detector. Bq,i ;

[0185] The total count rate (CPS) of the pipe deposition source term to the detector was calculated according to formula (6):

[0186]

[0187] In the formula:

[0188] CPS—Total count rate of pipeline deposition source terms to the detector, expressed in c / s;

[0189] A s,i— Calculate the surface activity of nuclide i, an active corrosion product, on the surface, in Bq / cm². 2 ;

[0190] cps Bq,i — The count rate of nuclide i with unit activity in the sediment source term in the detector, in c / s / Bq;

[0191] S pipe —Total internal surface area of ​​the pipe, in cm² 2 .

[0192] In some preferred embodiments, step S4 further includes steps S41 and S42:

[0193] S41. Establish a third model and calculate the total internal surface area S of the pipeline based on the third model. pipe and the count rate (cps) of nuclide i with unit activity in the sediment source term in the detector. Bq,i Preferably, the third model is a Monte Carlo model, and the calculation method in step S41 is the Monte Carlo method.

[0194] Specifically, step S41 establishes a Monte Carlo model based on the actual detector's structure, including lead shielding, collimator, detector crystal, and detector housing, and calculates the count contribution (cps) of nuclide i per unit activity in the source term deposited on the pipe wall. Bq,i The unit is c / s / Bq.

[0195] S42. The total count rate (CPS) of the pipeline deposition source term to the detector is calculated according to formula (6). The unit of the total count rate (CPS) of the pipeline deposition source term to the detector is c / s.

[0196] In another embodiment of the present invention, if the total γ online monitoring device measures the absorbed dose rate (Gy / h) in step S1, step S4 can be modified to calculate the dose rate contribution D of the unit activity nuclide i in the detector in the tube wall deposition. de,i Formula (6) is modified to formula (7). For example... Figure 3 As shown, the pipeline deposition source term background assessment method under nuclear power plant power operation conditions in another embodiment of the present invention includes the following steps S1, S2, S3, and S4'.

[0197] S1. Measure the activity ratio ε of the activated corrosion product nuclide i. i The surface dose rate D of the pipeline and the activity concentration C of nuclide i in the primary coolant. i ;

[0198] S2. Establish the first model and calculate the contribution D of nuclide i per unit activity in the primary coolant based on the first model. c,i and the total volume of fluid in the pipe V pipe ;

[0199] The effective dose rate D on the pipe surface contributed by the activated corrosion products in the deposition was calculated according to formulas (1) and (2). d ;

[0200] D d =DD coolant (1)

[0201]

[0202] in:

[0203] D coolant The effective dose rate at the pipe surface contributed by the radionuclides in the primary coolant;

[0204] S3. Establish a second model and calculate the contribution D of the activated corrosion product per unit activity nuclide i based on the second model. d,i and the total internal surface area S of the pipeline pipe ;

[0205] The surface activity A of the activated corrosion product nuclide i in the sediment source term is calculated according to formulas (3), (4) and (5). s,i :

[0206]

[0207]

[0208]

[0209] In the formula:

[0210] A represents the total activity of the activated corrosion products of the sediment source term;

[0211] A i The activity of nuclide i, an activated corrosion product in the sediment source term;

[0212] S4'. Establish a third model, and calculate the dose rate contribution D of nuclide i with unit activity in the deposited source term in the detector based on the third model. de,i ;

[0213] The contribution D of the pipeline deposition source term to the detector dose rate was calculated according to formula (7). de :

[0214]

[0215] In the formula:

[0216] D de — Contribution of the pipeline deposition source term to the detector dose rate, in Gy / h;

[0217] D de,i — The contribution of 1Bq nuclide i in the sedimentation source term to the detector dose rate, in Gy / h / Bq;

[0218] A s,i — Calculate the surface activity of nuclide i, an active corrosion product, on the surface, in Bq / cm². 2 ;

[0219] S pipe —Total internal surface area of ​​the pipe, in cm² 2 .

[0220] In another embodiment of the present invention, the pipeline deposition source term background assessment method under nuclear power plant power operation conditions is consistent with the aforementioned embodiment in other parts, and will not be repeated here.

[0221] The present invention provides a design scheme for a pipeline deposition source term background assessment system and method under nuclear power plant power operation conditions. This system and method establishes a background assessment method framework for primary coolant pipeline deposition source terms during nuclear power plant power operation. Through deposition spectrum measurement, pipeline surface dose rate measurement, and primary coolant radiochemical sampling measurement, the Monte Carlo method is used to calculate the contributions of different nuclides in the primary coolant and deposition layer to the pipeline surface dose rate and the contributions of different nuclides in the deposition layer to the detector count rate. This yields the deposition source term surface activity calculation and finally, the impact of the deposition source term on the detector measurement results.

[0222] In some embodiments of the present invention, the pipeline deposition source term background assessment system and method under nuclear power plant power operation conditions uses the Monte Carlo method to calculate the contribution of different nuclides in the primary coolant and deposition layer to the pipeline surface dose rate and the contribution of different nuclides in the deposition layer to the detector count rate, thereby obtaining the conversion coefficients between the activity of different nuclides and the pipeline surface dose rate and detector count rate.

[0223] In some embodiments of the present invention, the pipeline deposition source term background assessment system and method under nuclear power plant power operation conditions calculates the surface activity of deposition activation corrosion products by using deposition spectrum, pipeline surface dose rate, and conversion coefficients of the activity of different nuclides with pipeline surface dose rate and detector count rate.

[0224] Furthermore, the design schemes for background assessment of deposition source terms in pipelines containing radioactive liquids in nuclear power plants and other nuclear facilities are all within the protection scope of the pipeline deposition source term background assessment system and method under nuclear power plant power operation conditions in the embodiments of this invention. The technical solutions of the pipeline deposition source term background assessment system and method under nuclear power plant power operation conditions in the embodiments of this invention are closer to the actual situation on-site at nuclear power plants.

[0225] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for assessing the background of pipeline deposition source terms under nuclear power plant power operation conditions, characterized in that, include S1. Measure the activity ratio of nuclide i, a product of activated corrosion. Pipeline surface dose rate and the activity concentration of radionuclide i in the primary coolant ; S2. Establish a first model, and calculate the contribution of nuclide i per unit activity in the primary coolant based on the first model. and the total volume of fluid in the pipe Wherein, the first model is a Monte Carlo model, or the first model is a point kernel integral model; The effective dose rate of the pipe surface contributed by the activated corrosion products in the deposition was calculated according to formulas (1) and (2). ; （1） （2） in: The effective dose rate at the pipe surface contributed by the radionuclides in the primary coolant; S3. Establish a second model and calculate the contribution of the activated corrosion products per unit activity nuclide i based on the second model. and the total internal surface area of ​​the pipeline Wherein, the second model is a Monte Carlo model, or the second model is a point kernel integral model; The surface activity of the activated corrosion product nuclide i in the sediment source term was calculated according to formulas (3), (4) and (5). : （3） （4） （5） In the formula: The total activity of the activated corrosion products of the sediment source term; The activity of nuclide i, an activated corrosion product in the sediment source term; S4. Establish a third model and calculate the total internal surface area of ​​the pipeline based on the third model. and the count rate of nuclide i with unit activity in the sediment source term in the detector The third model is a Monte Carlo model. The total count rate of the pipeline deposition source term to the detector was calculated according to formula (6). : （6）。 2. The method for assessing the background of pipeline deposition source terms under nuclear power plant power operation conditions according to claim 1, characterized in that, In step S2 The effective dose rate on the pipe surface contributed by the activated corrosion products in the deposition. The unit is mSv / h.

3. The method for assessing the background of pipeline deposition source terms under nuclear power plant power operation conditions according to claim 2, characterized in that, When the first model is a Monte Carlo model, the calculation method for step S2 is the Monte Carlo method.

4. The method for assessing the background of pipeline deposition source terms under nuclear power plant power operation conditions according to claim 1, characterized in that, In step S3 The surface activity of the activated corrosion product nuclide i in the deposition source term The unit is Bq / cm 2 .

5. The method for assessing the background of pipeline deposition source terms under nuclear power plant power operation conditions according to claim 4, characterized in that, When the second model is a Monte Carlo model, the calculation method for step S3 is the Monte Carlo method.

6. The method for background assessment of pipeline deposition source terms under nuclear power plant power operation conditions according to claim 1, characterized in that, In step S4 The pipeline deposition source term affects the total count rate of the detector. The unit is c / s.

7. The method for assessing the background of pipeline deposition source terms under nuclear power plant power operation conditions according to claim 6, characterized in that, The calculation method for step S4 is the Monte Carlo method.

8. A system for assessing the background of pipeline deposition source terms under nuclear power plant power operation conditions, characterized in that, It includes a measuring device (10), a first modeling calculation device (20), a second modeling calculation device (30), and a third modeling calculation device (40), wherein: The measuring device (10) is used to measure the activity ratio of the activated corrosion product nuclide i. Pipeline surface dose rate and the activity concentration of radionuclide i in the primary coolant ; The first modeling and computing device (20) is used to establish a first model and calculate the contribution of nuclide i per unit activity in the primary coolant based on the first model. and the total volume of fluid in the pipe The effective dose rate of the pipeline surface contributed by the activated corrosion products in the deposition was calculated according to formulas (1) and (2). ; （1） （2） in: The effective dose rate at the pipe surface contributed by the radionuclides in the primary coolant; The second modeling calculation device (30) is used to establish a second model and calculate the contribution of the activated corrosion product unit activity nuclide i based on the second model. and the total internal surface area of ​​the pipeline The surface activity of the activated corrosion product nuclide i in the sediment source term is calculated according to formulas (3), (4) and (5). : （3） （4） （5） In the formula: The total activity of the activated corrosion products of the sediment source term; The activity of nuclide i, an activated corrosion product in the sediment source term; The third modeling and computing device (40) is used to establish a third model and calculate the total inner surface area of ​​the pipe based on the third model. and the count rate of nuclide i with unit activity in the sediment source term in the detector ; The total count rate of the pipeline deposition source term to the detector was calculated according to formula (6). : （6）。 9. The pipeline deposition source term background assessment system under nuclear power plant power operation conditions according to claim 8, characterized in that, The first modeling computing device (20) further includes: The first modeling module (21) is used to establish the first model and calculate the contribution of the unit activity nuclide i in the primary coolant based on the first model. and the total volume of fluid in the pipe ; The dose rate contribution calculation module (22) is used to calculate the effective dose rate of the pipe surface contributed by the activated corrosion products in the deposition according to the formulas (1) and (2). The effective dose rate of the pipe surface contributed by the activated corrosion products in the deposition The unit is mSv / h.

10. The pipeline deposition source term background assessment system under nuclear power plant power operation conditions according to claim 9, characterized in that, The first model is a Monte Carlo model, and the calculation method of the first modeling module (21) is the Monte Carlo method; or, the first model is a point kernel integral model.

11. The pipeline deposition source term background assessment system under nuclear power plant power operation conditions according to claim 8, characterized in that, The second modeling computing device (30) further includes: The second modeling module (31) is used to establish the second model and calculate the contribution of the activated corrosion product unit activity nuclide i based on the second model. and the total internal surface area of ​​the pipeline ; The sedimentation source term surface activity calculation module (32) is used to calculate the surface activity of the activated corrosion product nuclide i in the sedimentation source term according to formulas (3), (4) and (5). The surface activity of the activated corrosion product nuclide i in the deposition source term The unit is Bq / cm 2 .

12. The pipeline deposition source term background assessment system under nuclear power plant power operation conditions according to claim 11, characterized in that, The second model is a Monte Carlo model, and the calculation method of the second modeling module (31) is the Monte Carlo method; or, the second model is a point kernel integral model.

13. The pipeline deposition source term background assessment system under nuclear power plant power operation conditions according to claim 8, characterized in that, The third modeling computing device (40) also includes: The third modeling module (41) is used to establish the third model and calculate the total inner surface area of ​​the pipe based on the third model. and the count rate of nuclide i with unit activity in the sediment source term in the detector ; The deposition source term contribution calculation module (42) is used to calculate the total count rate of the pipe deposition source term to the detector according to formula (6). The pipeline deposition source term affects the total count rate of the detector. The unit is c / s.

14. The pipeline deposition source term background assessment system under nuclear power plant power operation conditions according to claim 13, characterized in that, The third model is a Monte Carlo model, and the calculation method of the third modeling module (41) is the Monte Carlo method.

15. The pipeline deposition source term background assessment system under nuclear power plant power operation conditions according to any one of claims 8-14, characterized in that, The measuring device (10) includes The deposition energy dispersive spectroscopy (EDS) module (11) is used to measure the activity ratio of the nuclide i, which is a product of activated corrosion. ; Pipe surface dose rate measurement module (12) is used to measure the surface dose rate of the pipe. ; The activity concentration measurement module (13) is used to measure the activity concentration of nuclide i in the primary coolant. .

16. A method for assessing the background of pipeline deposition source terms under nuclear power plant power operation conditions, characterized in that, include S1. Measure the activity ratio of nuclide i, a product of activated corrosion. Pipeline surface dose rate and the activity concentration of radionuclide i in the primary coolant ; S2. Establish a first model, and calculate the contribution of nuclide i per unit activity in the primary coolant based on the first model. and the total volume of fluid in the pipe ; The effective dose rate of the pipe surface contributed by the activated corrosion products in the deposition was calculated according to formulas (1) and (2). ; （1） （2） in: The effective dose rate at the pipe surface contributed by the radionuclides in the primary coolant; S3. Establish a second model and calculate the contribution of the activated corrosion products per unit activity nuclide i based on the second model. and the total internal surface area of ​​the pipeline ; The surface activity of the activated corrosion product nuclide i in the sediment source term was calculated according to formulas (3), (4) and (5). : （3） （4） （5） In the formula: The total activity of the activated corrosion products of the sediment source term; The activity of nuclide i, an activated corrosion product in the sediment source term; S4'. Establish a third model, and calculate the dose rate contribution of nuclide i with unit activity in the deposited source term in the detector based on the third model. ; The contribution of the pipeline deposition source term to the detector dose rate was calculated according to formula (7). : （7）。

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