CN115773901A - Steam generator corrosion product online sampling device and steam generator operation state evaluation method - Google Patents

Abstract

The invention discloses an online sampling device for corrosion products of a steam generator, which comprises a sampling inlet pipeline, a sampling loop, a bypass and a sampling trench, wherein two ends of the sampling loop and the bypass are respectively communicated with the sampling inlet pipeline and the sampling trench, a plurality of filters are sequentially arranged on the sampling loop, a sampling bypass is arranged between every two adjacent filters, and the other end of the sampling bypass is communicated to the sampling trench. The online sampling device for the corrosion products of the steam generator can sample the corrosion products of the steam generator online, and realizes accurate calculation of the accumulated dirt input of the steam generator of the CRP1000 unit; according to the sediment enrichment and the unit operation condition, a sediment thickness, thermal resistance and secondary side steam pressure prediction model in the service life of the CRP1000 unit steam generator is provided, the application effect of treatment measures is predicted and evaluated, and guidance can be provided for the safe and economic operation of the CRP1000 unit steam generator in China.

Description

On-line sampling device for steam generator corrosion products and operating status of steam generator assessment method

technical field

The invention relates to nuclear power, in particular to an online sampling device for corrosion products of a steam generator in a nuclear power plant and an evaluation method for the operating state of the steam generator.

Background technique

The steam generator is a very important heat exchanger in the secondary circuit. The poor water quality of the secondary circuit will have a great impact on the steam generator. The deposits on the heat transfer pipes will affect the heat transfer characteristics of the steam generator, and the deposits on the tube support plates will increase the flow resistance and affect the hydraulic characteristics. At the same time, the impurities in the water will concentrate and deposit in the position where the water flow is not smooth, such as the gap between the tube plate and the tube support plate, forming a corrosive environment and affecting the integrity of the SG (steam generator) heat transfer tube. Therefore, it is necessary for the power station to monitor the content of corrosion products in the water supply and SG sewage to judge the migration of corrosion products in the water supply to the SG and the chemical environment of the water in the SG. It is also one of the necessary basis for evaluating the mechanical or chemical cleaning of the SG.

At present, the CPR1000 unit monitors the total iron content of the main feed water of the secondary circuit during the daily period. Sampling in the way of online filtration cumulative flow 7d. This method temporarily establishes the sampling flow rate, and the inner surface of the sampling line needs to re-establish the rebalance of deposition or re-release, resulting in insufficient sampling representativeness. In addition, the sample sensitivity is insufficient. When grabbing a sample, it can only represent the state of the unit at a certain moment. The time state establishes the connection, and the iron transmission calculation cannot be performed accurately.

For AP1000 third-generation nuclear power units, it is clearly required in the system design stage to continuously monitor the amount and change trend of corrosion products in the secondary circuit feed water and steam generator sewage, so as to judge the deposition of suspended solids in the steam generator. At present, the steam generators of the second-generation adding units that account for the majority in my country lack online sampling devices and evaluation methods.

Contents of the invention

In view of this, in order to overcome the defects of the prior art, the object of the present invention is to provide an on-line sampling device for corrosion products of steam generators.

In order to achieve the above object, the present invention adopts the following technical solutions:

An on-line sampling device for corrosion products of a steam generator, comprising a sampling inlet pipeline, a sampling loop and a bypass, and a sampling ditch, the two ends of the sampling loop and the bypass are respectively connected with the sampling inlet pipeline and the sampling trench, the A plurality of filters are sequentially arranged on the sampling circuit, a sampling bypass is arranged between adjacent filters, and the other end of the sampling bypass is connected to the sampling ditch.

According to some preferred implementation aspects of the present invention, the pore sizes of the filter membranes in each of the filters are the same or different.

According to some preferred implementation aspects of the present invention, the pore diameters of the filter membranes in each of the filters are different, and the pore diameters of the filter membranes are from the filter near one end of the sampling inlet pipeline to the filter near the sampling ditch end. slowing shrieking.

According to some preferred implementation aspects of the present invention, three filters are sequentially arranged on the sampling circuit, and the pore diameters of the filter membranes in each filter are different.

According to some preferred implementation aspects of the present invention, the pore sizes of the filter membranes in the filter are 0.4-3um, 0.1-0.4um and 0.05-0.1um in sequence. In some embodiments, the online sampling device adopts a three-stage filtration method, the filter membrane pore size is 3um, 0.4um and 0.1um, and the filtered sampling liquid is analyzed, and the bypass device is used to analyze the total iron. The results of the two sampling methods Perform mutual verification to ensure the accuracy of sampling results. And the three different filter membrane apertures of the device can switch the corresponding sampling membrane apertures according to the condition of the unit and the pH value control agent. For example, two-stage filtration is used in the startup phase of the unit; Three-stage filtration is used for NH ₃ and ETA mixing control.

According to some preferred implementation aspects of the present invention, the sampling inlet pipeline is provided with a main valve; the sampling circuit is provided with a sampling valve; and the bypass valve is provided with a bypass valve.

According to some preferred implementation aspects of the present invention, a sampling bypass valve and/or a sampling flow meter are arranged on the sampling bypass.

According to some preferred implementation aspects of the present invention, a sampling flowmeter is arranged on the sampling circuit; a bypass rotameter is arranged on the bypass.

According to some preferred implementation aspects of the present invention, the sampling circuit is provided with a sampling pump and a pressure indicating gauge.

According to some preferred implementation aspects of the present invention, the Reynolds number of the fluid in the sampling tube is greater than or equal to 8000. In some embodiments, the sampling device adopts a small diameter of 1/4 inch; the flow velocity in the sampling tube is 1.8m/s, the wall thickness is 0.89mm; the sampling flow rate is 1772mL/min, and the Reynolds number in the sampling tube is 9220.

The present invention also provides a method for evaluating the operating state of a steam generator, comprising the following steps:

Simultaneous online sampling of steam generator feed water and drainage through the above-mentioned online sampling device to obtain the quality of corrosion products of feed water and drainage within the sampling time;

Combining the quality of the obtained corrosion products with the operating state of the unit, calculate the amount of corrosion products accumulated in the steam generator under the current state, and perform cumulative calculations;

According to the accumulation of corrosion products in the current steam generator and the operation status of the unit, the amount of corrosion products in the life cycle of the unit is evaluated.

The quality and concentration of corrosion products combined with the current unit status is: if the sampling concentration is 6ppb at 50% load, then the actual concentration is 3ppb when converted to 100% load.

In some embodiments, the prediction and evaluation of corrosion products is: according to the current concentration level of corrosion products, combined with the historical experience of the CPR1000 unit under the current pH value control agent, predict the cumulative amount of corrosion products within the life cycle, including worst, appropriate and The best of the three situations.

In some embodiments, corresponding soft chemical cleaning and hardening cleaning methods are proposed according to the calculation results of corrosion products combined with the operation status of unit equipment, and the application effect after chemical cleaning is predicted.

According to some preferred implementation aspects of the present invention, the sampling time is 7d in the stable operation stage of the unit; the cumulative sampling time of corrosion products in the start-up stage of the unit is 1d, increasing the sampling frequency and reducing the uncertainty of the concentration data.

According to some preferred implementation aspects of the present invention, the cumulative calculation is performed according to the following formula:

In the formula, m is the amount of corrosion products accumulated in a single steam generator in a certain fuel cycle; m _{feed water} is the cumulative amount of corrosion products in a week that migrates from the feed water in a certain fuel cycle to the secondary side of a single steam generator; m _blowdown is A week's accumulation of blowdown corrosion products of a single steam generator in a certain fuel cycle;

m _{feed water} = F _{feed water} × C _{Fe feed water}

m _blowdown = F _blowdown × C _{Fe blowdown}

In the formula, F _{feed water} is the cumulative feed water flow of a single steam generator in a week; C _{Fe feed water} is the iron content of the feed water for the week; C _{Fe blowdown} is the iron content of the blowdown for the week; F _blowdown is the cumulative drainage flow of a single steam generator for a week.

According to some preferred implementation aspects of the present invention, the total iron content of the feed water and the total iron content of the drainage are both calculated by the following formula:

The total iron content is:

C _{total iron} (ppb) = suspended iron content C _Fe (ppb) + filtrate iron content C ₂ (ppb)

Suspended iron content C _Fe (ppb) is calculated by the following formula:

In the formula, the cellulose acetate filter membrane used for sampling was taken out and dissolved in concentrated acid to obtain the iron concentration C ₁ (ppb) of the filter membrane, and another blank filter membrane was dissolved and analyzed at constant volume to obtain the iron concentration C ₀ of the blank filter membrane (ppb).

Due to the adoption of the above technical solution, compared with the prior art, the present invention is beneficial in that: the steam generator corrosion product online sampling device of the present invention can conduct online sampling of the steam generator corrosion product, and realizes Accurate calculation of fouling input of steam generator of CRP1000 unit; according to sediment enrichment and unit operation status, a prediction model of sediment thickness, thermal resistance and secondary side steam pressure during the lifetime of steam generator of CRP1000 unit is proposed, and the Prediction and evaluation of the application effect of treatment measures can provide guidance for the safe and economical operation of steam generators of CRP1000 units in my country.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings that need to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those skilled in the art, other drawings can also be obtained based on these drawings without creative effort.

Fig. 1 is a schematic structural view of a steam generator corrosion product on-line sampling device in a preferred embodiment of the present invention;

Fig. 2 is the sediment thickness prediction figure that the preferred embodiment of the present invention provides;

Fig. 3 is the deposit heat transfer thermal resistance prediction figure provided by the preferred embodiment of the present invention;

Fig. 4 is a prediction diagram of the influence of deposits on the secondary side steam pressure provided by the preferred embodiment of the present invention.

Detailed ways

In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described implementation Examples are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

Example 1 On-line Sampling Device for Steam Generator Corrosion Products

Referring to Figure 1, the steam generator corrosion product online sampling device in this embodiment is a multi-stage filter membrane online sampling device suitable for the steam generator of a CRP1000 nuclear power unit, specifically including a sampling inlet pipeline, a sampling circuit, a bypass, and a sampling trench 1. Three filters and sampling bypasses arranged in sequence on the sampling circuit. The two ends of the sampling circuit and the bypass are respectively connected with the sampling inlet pipeline and the sampling ditch. A sampling bypass is arranged between adjacent filters. The sampling bypass The other end of the road is connected to the sampling ditch.

A main valve is arranged on the sampling inlet pipeline. A sampling valve, a pressure indicating gauge and a sampling flowmeter are arranged on the sampling circuit. A bypass valve and a bypass rotameter are arranged on the bypass. A sampling bypass valve and a sampling flowmeter are arranged on the sampling bypass.

The pore size of the filter membrane in each filter is different, and the pore size of the filter membrane gradually decreases from the filter near the end of the sampling inlet pipeline to the filter near the end of the sampling ditch. In this embodiment, the pore diameters of the filter membranes in the filter are 0.4-3um, 0.1-0.4um, and 0.05-0.1um. Preferably, the online sampling device adopts a three-stage filtration method, and the filter membrane pore diameters are 3um, 0.4um, and 0.1um. And the filtered sampling liquid is analyzed, the bypass device is used to analyze the total iron, and the results of the two sampling methods are mutually verified to ensure the accuracy of the sampling results. And the three different filter membrane apertures of the device can switch the corresponding sampling membrane apertures according to the condition of the unit and the pH value control agent. For example, two-stage filtration is used in the startup phase of the unit; Three-stage filtration is used for NH ₃ and ETA mixing control.

Fe on the carbon steel surface is corroded to form Fe ²⁺ , which will combine with SO ₄ ^2- /Cl ^- /PO ₄ ^3- in water to form FeSO ₄ /FeCl ₂ /Fe ₃ (PO ₄ ) ₂ , with a particle size of 0.1-0.5μm, while the particle size of Fe ₂ O ₃ and Fe ₃ O ₄ is generally 0.5-5μm. Colloidal sampling analysis only analyzes the colloidal particles in the sample, so the sampling device uses a three-stage filter unit and different pore size filter elements (0.1μm, 0.4μm and 3μm) to obtain the colloidal particles in the sample, so as to analyze the particle size, size distribution, chemical elements Analysis of different projects. In this way, the morphology and characteristics of fouling can be analyzed, and hard fouling can be predicted.

The multi-stage filter membrane continuous sampling device with simultaneous on-line feed water and sewage of the steam generator adopts a three-stage filter method, and the filter membrane pore sizes are 3um, 0.4um and 0.1um, mainly collecting colloids and suspended solids in the corrosion products of the secondary circuit; After filtering, the sampled liquid was analyzed to obtain the content of dissolved iron. After the full power at the beginning of each cycle, the bypass device is used to analyze the total iron, and the results of the membrane sampling method are mutually checked once to ensure the accuracy of the sampling results.

The sampling device adopts a small diameter of 1/4 inch. When the flow velocity in the sampling tube is designed to be 1.8m/s and the wall thickness is 0.89mm, the sampling flow rate is shown in Table 1. It can be seen from the table that it is 1772mL/min. At this time, the Reynolds in the sampling tube is The number is shown in Table 2. It can be seen from the table that it is 9220, which is far more than 2000-3000. It ensures that the fluid in the sampling pipe is in turbulent flow. The flow rate can reduce the accumulation of iron products, improve the representativeness of samples, and sample analysis can more objectively characterize the state of the system.

Table 1 Sampling tube flow rate (mL/min) required for sample flow rate when reaching 1.8m/s

Reynolds number (dimensionless) of sample flow rate when table 2 reaches 1.8m/s

Example 2 Evaluation Method of Steam Generator Based on Corrosion Products

The invention provides an on-line sampling and an on-line sampling device for corrosion products of steam generators in nuclear power plants. Through simultaneous online sampling of multi-stage filter membranes for main feed water and sewage, combined with the operating status of the unit, the migration to the steam generator can be accurately calculated. The amount of internal corrosion products, and the amount of deposition on the steam generator tube bundle during the service life is predicted, the corresponding treatment method is recommended, and the effect of the treatment measures is evaluated. The method includes the following steps:

S1. Sampling and testing are carried out by adopting the multi-stage filter membrane continuous sampling device in which the steam generator feed water and sewage water are simultaneously online as shown in Example 1, so as to ensure the authenticity of the sampling.

S2. The quality of corrosion products obtained in S1 (C _{Fe water} for feed water, C _{Fe blowdown for} drainage), the cumulative amount of corrosion products (m _{feed water} and m _blowdown ) in the steam generator under the current state of the computer unit, and perform cumulative calculation ( m = Σm _{water supply} - Σm _sewage ).

S3. Combined with the current accumulation of corrosion products in the steam generator in S2, predict and evaluate the amount of corrosion products on the steam generator tube bundle within the life cycle of the unit.

S4. According to the prediction results of the amount of corrosion products in S3, put forward corresponding suggestions for treatment measures, and predict the effect after the measures are applied.

The evaluation method for the operating state of the CPR1000 unit in this embodiment uses a continuous on-line sampling device for multi-stage filter membranes for feed water and sewage to cumulatively calculate the amount of corrosion products of the steam generator under multi-power operating states, and to calculate the amount of corrosion products within the life cycle Predict and evaluate the amount of corrosion products and their impact, and finally put forward corresponding control measures to predict and evaluate the effect of the measures after application. Specifically include the following steps:

Step 1. Simultaneously online sampling of the steam generator feed water and drain water by the online sampling device in the above-mentioned embodiment 1 to obtain the quality of the corrosion products of the feed water and drain water within the sampling time. The sampling time in this embodiment is 7d.

As mentioned above, the online sampling device is designed with three different filter membrane apertures, and the corresponding sampling filter aperture can be switched according to the condition of the unit and the pH control agent. For example, two stages are used in the startup stage of the unit, and three stages are used in the full power operation stage Filtration; when the unit adopts NH ₃ and ETA mixed control, it adopts three-stage filtration. . Multi-stage filtration is used to not only analyze the quality of corrosion products, but also collect and analyze their particle size characteristics. Analysis of filter samples by X-ray fluorescence spectroscopy (XRF) is recommended to determine the oxidation state of iron without dissolving the filter. Or completely dissolve the membrane in the filter area, and analyze the solution by atomic absorption spectrometry, and the obtained result can calculate the average equivalent concentration during the sampling period.

Take out the cellulose acetate filter membrane used for sampling and dissolve it with concentrated acid to obtain the iron concentration C ₁ (ppb) of the filter membrane, and then take a blank filter membrane and dissolve it to constant volume for analysis to obtain the iron concentration C ₀ (ppb) of the blank filter membrane , so the suspended iron concentration is calculated by the following formula:

The total iron concentration of the sample is:

C _{total iron} (ppb) = suspended iron content C _Fe (ppb) + filtrate iron content C ₂ (ppb)

The iron in the filtrate is collected and filtered, and the atomic absorption spectrometry is carried out to obtain the iron content C ₂ (ppb) in the filtrate.

The weekly iron content in water supply C _{Fe water supply} and the weekly sewage discharge iron content C _{Fe sewage discharge} are calculated according to the above formula.

Step 2. According to the obtained corrosion product quality, calculate the accumulated corrosion product amount in the steam generator under the current feedwater flow state, and perform cumulative calculation.

The feedwater in a certain fuel cycle migrates to the secondary side of a single steam generator, and the cumulative amount m _feedwater for a week is calculated by the following formula:

m _{feed water} = F _{feed water} × C _{Fe feed water}

F _{feed water} is the cumulative feed water flow of a single steam generator in one week.

In a certain fuel cycle, the cumulative volume m _of blowdown corrosion products of a single steam generator in a fuel cycle is calculated by the following formula:

m _blowdown = F _blowdown × C _{Fe blowdown}

F _blowdown is the accumulated blowdown flow of a single steam generator in one week.

The amount m of corrosion products entering the steam generator within a cycle period (such as 18 months) is calculated by the following formula:

m = ∑m _{water supply} - ∑m _sewage

m is the amount of corrosion products accumulated in a single steam generator within a certain fuel cycle (such as 18 months).

Step 3. According to the accumulation of corrosion products in the current steam generator, calculate the future heat transfer resistance and actual steam pressure of the deposit of the steam generator.

The thickness of the sediment depends in turn on the expected ingress rate of feed iron, sediment composition and porosity. The function of sediment thickness and service time can predict the future heat transfer resistance of the sediment and the vapor pressure of the secondary side. The model formula is shown below. Then judge the running state of the steam generator.

In the formula: k _f is the thermal conductivity of sediment, W/(m K); k _mg is the thermal conductivity of Fe ₃ O ₄ , W/(m K); k _v is the thermal conductivity of saturated steam, W /(m·K); _εf is the porosity of the sediment, obtained by measurement.

In the formula: R _f represents the future heat transfer resistance of the deposit; e _f is the thickness of the deposit, m, calculated according to the amount of corrosion products accumulated in a single steam generator in a certain fuel cycle, the density of corrosion products and the deposition area .

P=f·R _f

Where: P is the steam pressure, bar; f is the correction coefficient of thermal resistance and steam pressure.

The inputs commonly used to calculate the average deposit thickness for natural circulation steam generators in nuclear power plants are as follows:

In the 1970s and 1980s, the iron concentration in the feed water of PWR nuclear power units in steady state operation was usually 10ug·kg ^-1 or even higher. In the 1990s and early 2000s, there was a concerted effort within the industry to reduce the accumulation of SG internal corrosion products, with feedwater concentrations below 3 ug kg ^-1 being more typical, and in many cases below 1 ug kg- ¹ has been achieved ¹ level. In view of the steady-state iron concentration range shown by my country's PWR units, combined with domestic and foreign experience, the feedwater iron concentration under full power conditions in the future fuel cycle is estimated at 2ppb. In all cases, the average feed iron concentration during steady-state operation is assumed to be based on actual measurements over past cycles, or estimated at 3 ppb if no actual measurements have been made.

Corrosion products from the secondary circuit of the nuclear power plant are transported to the secondary side of the steam generator along with the feed water. It will remain in suspension or gradually deposit in the SG, and it can also be removed by the sewage system. The blowdown efficiency of the blowdown system is usually low, and most of the corrosion products will continue to accumulate on the heat transfer tubes, support plates and tube sheets. Although there can be considerable variation between NPPs, the distribution of deposits within the SG is roughly as follows: tube bundles, containing 75% of the support plate, 10% of the tube sheet, and 15% of the blowdown. A significant portion of the corrosion products transported into the SG comes from the process of restarting the unit after a major overhaul. Taking this experience into account, the increased mass of this deposit needs to be assumed when predicting future deposit thicknesses and corresponding trends in heat transfer resistance. Based on industry experience, it is assumed that the unit transports an additional 12% of corrosion products to the SG during a start-up. Generally, the scale composition of SG heat transfer tubes in nuclear power plants is assumed to be 95% Fe ₃ O ₄ , 1% metallic copper, 1% nickel ferrite and 3% other components. This composition is considered typical for copper-free PWR nuclear power plants. The porosity of sediments follows a typical evolution process, which is about 30% at the beginning of commercial operation, and decreases to about 20% after 10 years of operation. Due to continuous maturation/densification, the porosity will drop to about 4% after many years.

According to the above input, the sediment thickness on the SG tube bundle of a CRP1000 nuclear power unit during its 60-year service period was calculated, and the predicted results are shown in Figure 2. The blue line is a typical trend without measures, and it can be seen that the sediment thickness increases linearly with the increase of operating time. After 60 years of operation, the mass of sediment on the secondary side of the SG tube bundle reached 2466kg, with an average thickness of about 95um.

According to the current concentration level of corrosion products, combined with the use of pH value control agent, the cumulative amount of corrosion products on the steam generator tube bundle during the life cycle is predicted, including the worst, appropriate and best three situations. The thickness of the sediment on the tube bundle depends in turn on the expected ingress rate of the feed iron, sediment composition and porosity. According to the operation experience of the CRP1000 unit, the concentration of iron in the feed water is selected as three levels of 5ppb, 2ppb and 0.7ppb respectively, and the calculation is carried out according to the formulas in steps 1 and 2. Figure 2 shows the sediment quality at the concentration of 2ppb. As shown in the figure, the deposit thickness increases linearly with the increase of run time. After 60 years of operation, the mass of sediment on the secondary side of the SG tube bundle reached 2466kg, with an average thickness of about 95um. The function of sediment thickness and service time determines the future heat transfer resistance and steam side pressure reduction of the sediment, as shown in Figure 3 and Figure 4, and then judges the operating status of the steam generator.

Step 4. Evaluation and prediction of the application effect of governance measures

After the deposits in the steam generator are enriched to a certain extent, chemical cleaning is required. In general, a chemical cleaning process designed to remove all magnet-based deposits from the steam generator (SG) is called hard chemical cleaning. Processes designed to remove only a portion of magnet-based deposits, or only the non-magnet-based portion of the deposit, are known as soft chemical cleaning. Soft chemical cleaning ASCA technology is also called diluted chemical cleaning. The corrosion amount of carbon steel is 20-100um, which is far less than the 200um of hardening cleaning. So it can be applied multiple times. The hardness chemical cleaning is only applied once in the service life, and B&W recommends that the sediment weight on the SG tube bundle reach 108-150g/m ² during SG chemical cleaning.

The red trend line is the application effect of the soft chemical cleaning ASCA (Advanced scale conditioning agent). After each application, a part of the accumulated deposits in the SG can be cleaned out. After multiple applications, the surface of the heat transfer tube of the steam generator can be deposited gradually cleared away. Hard chemical cleaning SGCC (Steam generator chemical clean) can remove all the deposits in the steam generator at one time, and the deposits in the SG are restored to the initial state of commercial operation. The state of the deposits after application is shown in the green trend line in the figure.

If the application strategy of ASCA is adopted, about 317.5 kg of sediment will be washed out from the SG each time. Based on industry experience, including the application of units in Japan, Korea and the United States. After the application of soft chemical cleaning, the heat transfer will be significantly enhanced in the short term. In the case of multiple applications, the thermal resistance can still be further reduced. If it has been used for many times, the thermal resistance will eventually return to the clean state at the beginning of commercial operation. (Thermal resistance change is 0).

The thermal resistance and steam pressure of the accumulated deposits in the steam generator of a CRP1000 unit are predicted and calculated. As the operation time increases, if there is no intervention and treatment, after 60 years of service, the deposits on the tube bundle will be enriched on average When the thickness is about 95um, the thermal resistance of the corresponding deposit increases by 3.08×10 ^-5 m ² ·°C·W ^-1 (corresponding to a decrease in vapor pressure of 460kPa). After the initial application of ASCA, the fouling thermal resistance decreased by about 4.54×10 ^-6 m ² ·℃·W ^-1 (corresponding to a 60kPa increase in steam pressure). As shown in Figures 3 and 4, this effect may result from the outer scale layer promoting boiling more effectively, or from a thinning of the solidified mature inner layer, or both. The application of ASCA can produce such results, which has been confirmed by laboratory tests and experience in many nuclear power plants in the past few years.

After a typical full-bundle hard chemical cleaning SGCC (steam generator chemical clean) application, the initial best estimate of the deposition thermal resistance returns to the clean state value at the beginning of commercial operation (the thermal resistance change is 0); the thermal resistance is significant in the next cycle increase; during subsequent years of operation, the thermal resistance to heat transfer drops rapidly due to the formation of a thin, heat-transfer-enhancing deposit, and then increases again at a similar rate as when the deposit was not removed. The magnitude of the initial increase and subsequent decrease is largely based on the operating conditions of actual nuclear power plants. The surge in short-term thermal resistance after hard chemical cleaning comes from industry experience in many nuclear power plants. Nuclear power plants should carefully implement SGCC hard chemical cleaning. Although the effect of hard chemical cleaning is better (it can restore the steam pressure to the initial state of commercial operation), the corrosion of the internal components of the steam generator is relatively serious, and the overhaul period of the unit is seriously delayed, and the cost of hard chemical cleaning itself is relatively high. The economic impact of nuclear power plants is relatively large.

The present invention has the advantages of designing a set of on-line graded sampling device for steam generator main feed water and sewage, which can accurately accumulate the quality of steam generator corrosion products in real time, and realize accurate calculation of input of fouling of steam generator of CRP1000 unit; according to Sediment enrichment and unit operation status, put forward the prediction model formula of sediment thickness, thermal resistance and secondary side steam pressure during the steam generator life of CRP1000 unit, and predict and evaluate the application effect of control measures, which can be used for my country CRP1000 unit steam generators provide guidance for safe and economical operation, filling the gaps in the supervision and management of CRP1000 and other similar types of steam generators.

The above-mentioned embodiments are only to illustrate the technical concept and characteristics of the present invention, and the purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and not to limit the protection scope of the present invention. All equivalent changes or modifications made according to the spirit of the present invention shall fall within the protection scope of the present invention.

Claims (14)

1. a steam generator corrosion product on-line sampling device, is characterized in that, comprises sampling inlet pipeline, sampling loop and bypass, sampling trench, and the two ends of described sampling loop and bypass are connected with described sampling inlet pipeline respectively It communicates with the sampling ditch, and the sampling circuit is provided with a plurality of filters in sequence, and a sampling bypass is arranged between adjacent filters, and the other end of the sampling bypass is connected to the sampling ditch. 2. The online sampling device according to claim 1, characterized in that the pore diameters of the filter membranes in each of the filters are the same or different. 3. The on-line sampling device according to claim 2, wherein the apertures of the filter membranes in each of the filters are different, and the apertures of the filter membranes are determined by the filter near one end of the sampling inlet pipeline. It gradually decreases toward the filter near the end of the sampling ditch. 4. The online sampling device according to claim 2, characterized in that three filters are sequentially arranged on the sampling circuit, and the pore diameters of the filter membranes in each filter are different. 5 . The online sampling device according to claim 4 , wherein the pore diameters of the filter membranes in the filter are 0.4-3 um, 0.1-0.4 um and 0.05-0.1 um in sequence. 6. The online sampling device according to any one of claims 1-5, wherein a main valve is arranged on the sampling inlet pipeline; a sampling valve is arranged on the sampling circuit; a bypass valve is arranged on the bypass way valve. 7. The online sampling device according to claim 1, characterized in that a sampling bypass valve and/or a sampling flowmeter are arranged on the sampling bypass. 8. The online sampling device according to claim 1, characterized in that, a sampling flowmeter is arranged on the sampling circuit; a bypass flowmeter is arranged on the bypass. 9. The online sampling device according to claim 1 or 8, characterized in that the Reynolds number of the fluid in the pipelines of the sampling circuit and the sampling bypass is greater than or equal to 8000. 10. A method for evaluating the operating state of a steam generator, comprising the steps of: By the on-line sampling device as described in any one of claims 1-9, the steam generator feed water and the drainage are sampled online simultaneously to obtain the quality of the corrosion products of the feed water and drainage within the sampling time; According to the quality of the obtained corrosion products, calculate the amount of corrosion products accumulated in the steam generator under the current state; According to the accumulation of corrosion products in the current steam generator, the future heat transfer resistance and actual steam pressure of the deposit in the steam generator are calculated. 11. The evaluation method according to claim 10, characterized in that, the sampling time is 7d in the stable operation stage of the unit; the cumulative sampling time of corrosion products in the start-up stage of the unit is 1d. 12. The evaluation method according to claim 10, wherein the cumulative calculation is carried out according to the following formula: m = ∑m _{water supply} - ∑m _sewage In the formula, m is the amount of corrosion products accumulated in a single steam generator in a certain fuel cycle; m _{feed water} is the cumulative amount of corrosion products in a week that migrates from the feed water in a certain fuel cycle to the secondary side of a single steam generator; m _blowdown is A week's accumulation of blowdown corrosion products of a single steam generator in a certain fuel cycle; m _{feed water} = F _{feed water} × C _{Fe feed water} m _blowdown = F _blowdown × C _{Fe blowdown} In the formula, F _{feed water} is the cumulative feed water flow of a single steam generator in a week; C _{Fe feed water} is the iron content in the feed water of the current week; C _{Fe blowdown} is the iron content of the sewage sewage in the current week; F _blowdown is the cumulative drainage flow of a single steam generator in a week. 13. The evaluation method according to claim 12, characterized in that, the total iron content of the feed water and the total iron content of the drainage are calculated by the following formula: The total iron content is: C _{total iron} (ppb) = suspended iron content C _Fe (ppb) + filtrate iron content C ₂ (ppb) Suspended iron content C _Fe (ppb) is calculated by the following formula:

In the formula, the cellulose acetate filter membrane used for sampling was taken out and dissolved in concentrated acid to obtain the iron concentration C ₁ (ppb) of the filter membrane, and another blank filter membrane was dissolved and analyzed at constant volume to obtain the iron concentration C ₀ of the blank filter membrane (ppb). 14. The evaluation method according to claim 10, characterized in that, the deposit future heat transfer resistance and actual steam pressure of the steam generator are calculated by the following formula:

In the formula: k _f is the thermal conductivity of sediment, W/(m K); k _mg is the thermal conductivity of Fe ₃ O ₄ , W/(m K); k _v is the thermal conductivity of saturated steam, W /(m K); ε _f is the porosity of the sediment;

In the formula: R _f represents the future heat transfer resistance of the sediment; e _f is the thickness of the sediment, m; P=f·R _f Where: P is the actual steam pressure, bar; f is the correction coefficient of thermal resistance and steam pressure.

Images