CN115773901A - Steam generator corrosion product online sampling device and steam generator operation state evaluation method - Google Patents
Steam generator corrosion product online sampling device and steam generator operation state evaluation method Download PDFInfo
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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
Technical Field
The invention relates to nuclear power, in particular to an online sampling device for corrosion products of a steam generator of a nuclear power station and an evaluation method for the operation state of the steam generator.
Background
The steam generator is a very important heat exchanger in the secondary circuit. The water quality of the two loops is poor, and the steam generator is greatly influenced. Deposits on the heat transfer tubes can affect the heat transfer characteristics of the steam generator, and deposits on the tube support plates can increase flow resistance, affecting hydraulic performance. Meanwhile, impurities in water can be concentrated and deposited at positions where water flow is not smooth, such as gaps of tube plates and tube supporting plates, so that a corrosive environment is formed, and the integrity of a Steam Generator (SG) heat transfer tube is influenced. Therefore, the power station needs to monitor the content of corrosion products in the feedwater and SG blowdown water to determine the migration amount of the feedwater corrosion products to the SG and the water chemical environment in the SG, and is one of the necessary bases for evaluating the SG for mechanical or chemical cleaning.
At present, a CPR1000 unit monitors the total iron content of main water supply of a two-loop in a daily period, wherein the period is once per week; and simultaneously sampling iron corrosion products in a steam generator sewage system and a main water supply system, temporarily establishing sampling flow during sampling, and sampling once every half year by adopting a mode of filtering accumulated flow 7d on line. According to the method, the sampling flow is temporarily established, the rebalancing that the inner surface of a sampling pipeline needs to be re-established for deposition or re-release leads to insufficient sampling representativeness, in addition, the sensitivity of the sample is insufficient, the state of the unit at a certain moment can only be represented when the sample is grabbed, the connection is not established for the long-time state of the unit, and the iron transmission calculation cannot be accurately carried out.
For an AP1000 third-generation nuclear power unit, the amount and the variation trend of corrosion products in secondary-loop feed water and steam generator sewage are required to be continuously supervised in the system design stage, so that the deposition condition of suspended matters in a steam generator is judged. At present, the steam generators of the second generation of the machine set occupying the main quantity in China lack an online sampling device and an evaluation method.
Disclosure of Invention
In view of the above, in order to overcome the defects of the prior art, the present invention aims to provide an online sampling device for corrosion products of a steam generator.
In order to achieve the purpose, the invention adopts the following technical scheme:
the utility model provides an online sampling device of steam generator corrosion product, includes sample inlet pipeline, sample return circuit and bypass, sample trench, the both ends of sample return circuit and bypass respectively with sample inlet pipeline and sample trench intercommunication, the last a plurality of filters that have set gradually of sample return circuit are adjacent be provided with the sample bypass between the filter, the other end intercommunication to of sample bypass to the sample trench.
According to some preferred aspects of the invention, the pore size of the filter membrane in each of said filters is the same or different.
According to some preferred embodiments of the present invention, the filter membrane of each of the filters has different pore sizes, and the pore size of the filter membrane gradually decreases from the filter near the sampling inlet pipeline end to the filter near the sampling trench end.
According to some preferred embodiments of the invention, the sampling loop is provided with three filters in sequence, and the pore size of the filter membrane in each filter is different.
According to some preferred embodiments of the invention, the filter membrane pore size in the filter is 0.4-3 um, 0.1-0.4 um and 0.05-0.1 um in this order. In some embodiments, the online sampling device adopts a three-stage filtration method, the aperture of the filter membrane is 3um, 0.4um and 0.1um, the filtered sampling liquid is analyzed, the bypass device analyzes total iron, and the results of the two sampling methods are mutually verified to ensure the accuracy of the sampling result. The aperture of three different filter membranes of the device can be switched to the corresponding aperture of the sampling filter membrane according to the condition of the unit and the difference of the pH value control agent, and if the unit is started, two-stage filtration is adopted; the full-power operation stage of the unit adopts three-stage filtration; the unit adopts NH 3 And when ETA is mixed and controlled, three-stage filtration is adopted.
According to some preferred aspects of the invention, a main valve is provided on the sampling inlet pipeline; a sampling valve is arranged on the sampling loop; the bypass is provided with a bypass valve.
According to some preferred aspects of the invention, a sample bypass valve and/or a sample flow meter is provided on the sample bypass.
According to some preferred aspects of the invention, a sampling flow meter is disposed on the sampling loop; and a bypass rotameter is arranged on the bypass.
According to some preferred aspects of the invention, a sampling pump and a pressure indicator are provided on the sampling circuit.
According to some preferred aspects of the invention, the reynolds number of the fluid in the sampling tube is 8000 or greater. In some embodiments, the sampling device employs a 1/4 inch small tube diameter; the flow velocity in the sampling tube is 1.8m/s, and the wall thickness is 0.89mm; the sampling flow rate was 1772mL/min and the Reynolds number in the sampling tube was 9220.
The invention also provides an evaluation method of the operation state of the steam generator, which comprises the following steps:
simultaneously sampling the feed water and the drain water of the steam generator online by the online sampling device to obtain the quality of corrosion products of the feed water and the drain water in a sampling time;
combining the obtained corrosion product quality with the unit running state, calculating the corrosion product amount accumulated in the steam generator in the current state, and performing accumulated calculation;
and evaluating the amount of the corrosion products in the life cycle of the unit according to the current accumulation condition of the corrosion products in the steam generator and the operation condition of the unit.
The quality and concentration of corrosion products and the current unit state are combined as follows: when the sampling concentration is 6ppb at 50% load, the actual concentration is 3ppb when converted to 100 load.
In some embodiments, the corrosion product prediction is evaluated as: and predicting the accumulated amount of the corrosion products in the life cycle according to the concentration level of the current corrosion products and the historical experience of a CPR1000 unit under the current pH value control agent, wherein the accumulated amount of the corrosion products in the life cycle comprises three conditions of worst, proper and top.
In some embodiments, according to the calculation result of the corrosion product, the corresponding soft chemical cleaning and hardening cleaning methods are proposed by combining the operation conditions of the unit equipment, and the application effect after the chemical cleaning is predicted.
According to some preferred implementation aspects of the invention, the sampling time of the unit stable operation stage is 7d; the cumulative time of corrosion product sampling in the starting stage of the unit is 1d, the sampling frequency is increased, and the uncertainty of concentration data is reduced.
According to some preferred aspects of the invention, the cumulative calculation is performed according to the following formula:
in the formula, mThe amount of corrosion products accumulated in a single steam generator in a certain fuel cycle; m is a unit of Feed water Transferring the feed water in a certain fuel cycle to a corrosion product on the secondary side of a single steam generator for a week; m is Pollution discharge A cycle accumulation of corrosion products of a single steam generator discharging pollution in a certain fuel cycle;
m water supply ＝F Feed water ×C Fe feed water
m Pollution discharge ＝F Pollution discharge ×C Fe pollution discharge
In the formula, F Feed water Accumulating the feed water flow for one week of a single steam generator; c Fe feed water When Zhou Geishui iron content; c Fe pollution discharge Is when Zhou Paiwu iron content; f Pollution discharge The drainage flow is accumulated for one week of a single steam generator.
According to some preferred aspects of the invention, the total iron content of the feedwater and the total iron content of the drainage are calculated by the following formulas:
the total iron content is:
C total iron (ppb) = suspended iron content C Fe (ppb) + iron content of the filtrate C 2 (ppb)
Suspended iron content C Fe (ppb) is calculated from the formula:
in the formula, the acetate fiber filter membrane used for sampling is taken out, dissolved by concentrated acid to constant volume and then analyzed to obtain the iron concentration C of the filter membrane 1 (ppb), dissolving another blank filter membrane, and performing constant volume analysis to obtain blank filter membrane iron concentration C 0 (ppb)。
Due to the adoption of the technical scheme, compared with the prior art, the invention has the beneficial effects that: 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 safe and economic operation of the CRP1000 unit steam generator in China.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a schematic diagram of an online sampling device for corrosion products from a steam generator according to a preferred embodiment of the present invention;
FIG. 2 is a graph of a deposit thickness prediction provided by a preferred embodiment of the present invention;
FIG. 3 is a graph illustrating the prediction of thermal transfer resistance of deposits according to a preferred embodiment of the present invention;
fig. 4 is a diagram for predicting the influence of the deposits on the secondary side steam pressure according to the preferred embodiment of the present invention.
Detailed Description
In order to make those skilled in the art better understand the technical solution of the present invention, the technical solution in the embodiment of the present invention will be clearly and completely described below with reference to the drawings in the embodiment of the present invention, and it is obvious that the described embodiment is only a part of the embodiment of the present invention, and not a whole embodiment. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, shall fall within the protection scope of the present invention.
EXAMPLE 1 Online sampling device for Corrosion products of steam Generator
Referring to fig. 1, the online sampling device for corrosion products of a steam generator in the embodiment is a multistage filter membrane online sampling device suitable for a steam generator of a CRP1000 nuclear power unit, and specifically comprises a sampling inlet pipeline, a sampling loop, a bypass, a sampling trench, three filters and a sampling bypass, wherein the three filters and the sampling bypass are sequentially arranged on the sampling loop, two ends of the sampling loop and the two ends of the bypass are respectively communicated with the sampling inlet pipeline and the sampling trench, a sampling bypass is arranged between adjacent filters, and the other end of the sampling bypass is communicated to the sampling trench.
A main valve is arranged on the sampling inlet pipeline. The sampling loop is provided with a sampling valve, a pressure indicator and a sampling flowmeter. The bypass is provided with a bypass valve and a bypass rotameter. The sampling bypass is provided with a sampling bypass valve and a sampling flowmeter.
The aperture of the filter membrane in each filter is different, and the aperture of the filter membrane is gradually reduced from the filter close to one end of the sampling inlet pipeline to the filter close to one end of the sampling trench. In this embodiment, the filter membrane aperture in the filter is 0.4-3 um, 0.1-0.4 um and 0.05-0.1 um in proper order, and preferred online sampling device adopts the tertiary filtration method, and the filter membrane aperture is 3um, 0.4um and 0.1um to sample liquid carries out the analysis after filtering, and the bypass device carries out the analysis to total iron, and two kinds of sampling method results carry out mutual verification, guarantee the accuracy of sample result. The aperture of three different filter membranes of the device can be switched to the corresponding aperture of the sampling filter membrane according to the condition of the unit and the difference of pH value control agents, and if the unit is started, two-stage filtration is adopted; the full-power operation stage of the unit adopts three-stage filtration; the unit adopts NH 3 And when ETA is mixed and controlled, three-stage filtration is adopted.
Fe on the surface of carbon steel is corroded to form Fe 2+ Will react with SO in water 4 2- /Cl - /PO 4 3- Combined into FeSO 4 /FeCl 2 /Fe 3 (PO 4 ) 2 Having a particle size of 0.1-0.5 μm and Fe 2 O 3 And Fe 3 O 4 The particle size of (B) is generally 0.5 to 5 μm. The colloid sampling analysis only analyzes colloid particles in a sample, so the sampling device adopts a three-stage filtering unit and filter elements with different pore diameters (0.1 μm, 0.4 μm and 3 μm) to obtain the colloid particles in the sample so as to analyze different items such as particle size, size distribution, chemical elements and the like. Thereby analyzing the scale morphology and characteristics and enabling prediction of hard scale.
The multistage filter membrane continuous sampling device for simultaneously online water supply and sewage discharge of the steam generator adopts a three-stage filtration method, the aperture of the filter membrane is 3um, 0.4um and 0.1um, and colloid and suspended matters in corrosion products of the two loops are mainly collected; and analyzing the filtered sample liquid to obtain the content of dissolved iron. After the full power of each cycle initial stage, the total iron is analyzed by adopting a bypass device, and the results of the filter membrane sampling method are mutually verified once, so that the accuracy of the sampling result is ensured.
The sampling device adopts 1/4 inch small pipe diameter, the flow velocity in the sampling pipe is 1.8m/s, when the wall thickness is 0.89mm, the sampling flow is shown in table 1, the table lookup can be known as 1772mL/min, the Reynolds number in the sampling pipe is shown in table 2 at the moment, the table lookup can be known as 9220 and far exceeds 2000-3000, the fluid in the sampling pipe is ensured to be in turbulent flow, when the pipeline fluid is in a turbulent flow state, the disturbance in the vertical direction in the pipeline is increased, the flow velocity close to the wall surface is increased, the product accumulation of iron is reduced, the representativeness of the sample is improved, and the system state can be objectively characterized by sample analysis.
TABLE 1 sampling tube flow required to reach a sample flow of 1.8m/s (mL/min)
TABLE 2 Reynolds number of sample flow up to 1.8m/s (dimensionless)
Example 2 method of evaluating steam generator based on corrosion products
The invention provides an online sampling and online sampling device for corrosion products of a steam generator of a nuclear power station, which accurately calculates the amount of the corrosion products transferred to the inside of the steam generator by simultaneously sampling main feed water and sewage water through a multistage filter membrane in an online manner and combining the running state of a unit, predicts the deposition amount on a pipe bundle of the steam generator in the service life, recommends a corresponding treatment method and evaluates the effect after the application of the treatment measures, wherein the method comprises the following steps:
s1, sampling and testing are carried out by adopting the multistage filter membrane continuous sampling device which is used for simultaneously carrying out online sampling on the water supply and sewage of the steam generator and ensures the authenticity of sampling.
S2, the quality of the corrosion product obtained in the S1 (C of feed water) Fe feed water C of water discharge Fe pollution discharge ) Calculating the amount (m) of accumulated corrosion products in the steam generator in the current state of the unit Feed water And m Pollution discharge ) And performs cumulative calculation (m = ∑ m) Feed water -∑m Pollution discharge )。
And S3, predicting and evaluating the amount of corrosion products on the steam generator tube bundle in the service life of the unit by combining the current corrosion product accumulation condition in the steam generator in the S2.
And S4, according to the prediction result of the amount of the corrosion products in the S3, providing a corresponding treatment measure suggestion, and predicting the effect after the measure is applied.
According to the evaluation method of the CPR1000 unit running state, the corrosion product amount of the steam generator in the multi-power running state is accumulated and calculated through the continuous online sampling device of the multi-stage filter membranes of the feed water and the sewage, the corrosion product amount and the influence thereof in the life cycle are predicted and evaluated, finally, corresponding treatment measures are provided, and the effect after the measures are applied is predicted and evaluated. The method specifically comprises the following steps:
step 1, the water supply and the water discharge of the steam generator are simultaneously sampled online by the online sampling device in the embodiment 1, so that the quality of corrosion products of the water supply and the water discharge within the sampling time is obtained, and the sampling time in the embodiment is 7d.
As mentioned above, the on-line sampling device is designed with three different filter membrane apertures, and the corresponding sampling filter membrane apertures can be switched according to the unit conditions and different pH value control agents, if the unit is started by two stages, the unit can work fullyThree-stage filtration is adopted in the rate operation stage; the set adopts NH 3 When ETA is mixed and controlled, three-stage filtration is adopted. . And by adopting multi-stage filtration, the quality of the corrosion product is analyzed, and the particle size characteristics of the corrosion product are also collected and analyzed. It is recommended to analyze the filter membrane samples using X-ray fluorescence spectroscopy (XRF) to determine the oxidation state of the iron without dissolving the filter membrane. Or the membrane in the filtering area is completely dissolved, the solution is analyzed by an atomic absorption spectrometry, and the obtained result can be used for calculating the average equivalent concentration during sampling.
Taking out the acetate fiber filter membrane used for sampling, dissolving the acetate fiber filter membrane by concentrated acid to constant volume, and analyzing to obtain the iron concentration C of the filter membrane 1 (ppb), dissolving another blank filter membrane, and performing constant volume analysis to obtain blank filter membrane iron concentration C 0 (ppb) thus the suspended iron concentration is calculated from the following formula:
the total iron concentration of the sample is:
C total iron (ppb) = suspended iron content C Fe (ppb) + iron content of the filtrate C 2 (ppb)
Collecting the filtered liquid of iron in the filtrate, and performing atomic absorption spectrometry to obtain filtrate iron content C 2 (ppb)。
When Zhou Geishui iron content C Fe feed water When the iron content is Zhou Paiwu C Fe pollution discharge Is calculated according to the formula.
And 2, calculating the amount of corrosion products accumulated in the steam generator under the current water supply flow state according to the obtained quality of the corrosion products, and performing accumulated calculation.
The water supply in a certain fuel cycle migrates to the secondary side corrosion product of a single steam generator for a week cumulant m Feed water Calculated by the following formula:
m feed water ＝F Feed water ×C Fe feed water
F Water supply The feed water flow is accumulated for one week of the single steam generator.
One-week cumulative amount m of pollution and corrosion products of single steam generator in certain fuel cycle Pollution discharge Calculated by the following formula:
m pollution discharge ＝F Pollution discharge ×C Fe pollution discharge
F Pollution discharge Accumulating the flow of the discharged sewage for one week of a single steam generator.
The amount of corrosion products m entering the steam generator during a cycle (e.g., 18 months) is calculated by:
m＝∑m water supply -∑m Pollution discharge
m is the amount of corrosion products accumulated in a single steam generator during a fuel cycle (e.g., 18 months).
And 3, calculating future heat transfer resistance and actual steam pressure of the deposit of the steam generator according to the accumulated state of the corrosion products in the current steam generator.
The thickness of the deposit is in turn dependent on the expected rate of feed iron entry, the deposit composition and the porosity. The function of the deposit thickness and the service time can predict the future heat transfer resistance and the secondary side steam pressure of the deposit, and the model formula is shown as follows. And then the operation state of the steam generator is judged.
In the formula: k is a radical of formula f The thermal conductivity of the deposit, W/(m.K); k is a radical of mg Is Fe 3 O 4 W/(m.K); k is a radical of v Is the saturated steam thermal conductivity, W/(m.K); epsilon f The sediment porosity is measured.
In the formula: r f Representing the future heat transfer resistance of the deposit; e.g. of the type f M, the thickness of the deposit, depending on the amount of corrosion products accumulated in a single steam generator during a given fuel cycle, the amount of corrosion productsThe density and the deposition area are calculated.
P＝f·R f
In the formula: p is steam pressure, bar; f is the correction coefficient of thermal resistance and steam pressure.
Inputs typically used to calculate the average deposit thickness for natural circulation steam generators in nuclear power plants are as follows:
in the 70 s and 80 s of the 20 th century, the concentration of iron supplied to water during the steady-state operation of a pressurized water reactor nuclear power unit is usually 10 ug/kg -1 And even higher. In the 90 s of the 20 th century and the early 21 st century, the industry jointly strives to reduce the accumulation of corrosion products in SG, and the concentration of feed water is lower than 3 ug/kg -1 Is more typical and in many cases reaches less than 1ug kg -1 The level of (c). In view of the steady-state iron concentration range of PWR units in China, the iron concentration of the feed water under the condition of full power in future fuel cycle is estimated according to 2ppb by combining domestic and foreign experiences. In all cases, assuming that the average feedwater iron concentration during steady state operation over the past cycle was obtained from actual measurements, if not, it can be estimated at 3ppb.
Corrosion products from the secondary circuit of the nuclear power plant are transported with feedwater to the secondary side of the steam generator. Will remain suspended or gradually settle within the SG and can also be removed by the blowdown system. Blowdown is generally inefficient and the vast majority of corrosion products will accumulate on the heat transfer tubes, support plates and tube sheets. Although the variation between nuclear power plants may be large, the deposit distribution within the SG is roughly as follows: the tube bundle comprises 75% of support plates, 10% of tube plates and 15% of sewage discharge. A significant portion of the corrosion products transported to the SG come from the unit restart after overhaul. In view of this experience, it is desirable to assume the added mass of this portion of the deposit when predicting future deposit thicknesses and corresponding heat transfer resistance trends. Based on experience in the industry, it is assumed that a unit additionally delivers 12% of the corrosion products to the SG in one start-up. Typical nuclear power plant SG heat transfer tubes have a scale composition assumed to be 95% Fe 3 O 4 1% of metallic copper, 1% of nickel ferrite and3% of other components. This composition is considered to be typical of copper-free pressurized water reactor nuclear power plants. Deposit porosity follows a typical evolution, with about 30% at the beginning of commercial operation and a reduction of about 20% after 10 years of operation, and the porosity will drop to about 4% after many years due to continued maturation/densification.
According to the input, the thickness of the deposit on the SG tube bundle of a CRP1000 nuclear power unit in 60-year service period is calculated, and the predicted result is shown in figure 2. The blue line is the typical trend without measures, and it is seen that the deposit thickness increases linearly with increasing run time. After 60 years of operation, the mass of the secondary side deposit of the SG tube bundle reaches 2466kg, and the average thickness is about 95um.
And predicting the accumulated amount of the corrosion products on the steam generator tube bundle in the life cycle according to the current concentration level of the corrosion products and the use condition of the pH value control agent, wherein the accumulated amount of the corrosion products comprises three conditions of worst, proper and top. The thickness of the deposit on the tube bundle depends in turn on the expected rate of entry of feedwater iron, the deposit composition, and the porosity. According to the operation experience of the CRP1000 unit, the iron concentration of the feed water is respectively selected to be 5ppb, 2ppb and 0.7ppb as three levels and is subjected to prediction calculation according to the formulas in the steps 1 and 2, and the quality of a deposit at the concentration of 2ppb is shown in a graph 2. As shown in the figure, the deposit thickness increases linearly with increasing run time. After 60 years of operation, the mass of the secondary side deposit of the SG tube bundle reaches 2466kg, and the average thickness is about 95um. The function of the deposit thickness and the service time determines the future heat transfer resistance of the deposit and the reduction degree of the pressure at the steam side, as shown in fig. 3 and 4, and then the operation state of the steam generator is judged.
Step 4, evaluating and predicting treatment measure application effect
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 of the magnetite-based deposits from the Steam Generator (SG) is referred to as a hard chemical cleaning. A process designed to remove only a portion of the magnet-based deposit, or only the non-magnet-based portion of the deposit, is then referred to as a soft chemical clean. The soft chemical cleaning ASCA technologyThe corrosion amount of the diluted chemical cleaning to carbon steel is 20-100um respectively, and the corrosion amount is far less than 200um of the hardening cleaning. So it can be applied for many times. Whereas the hardness chemical cleaning is applied only once during the lifetime, B&The weight of the sediment on the SG tube bundle reaches 108-150g/m when the SG chemical cleaning is recommended by the company W 2 。
The red trend line is the application effect of the soft chemical cleaning ASCA (Advanced scale conditioning agent), a part of accumulated deposits in the SG can be cleaned out after each application, and the deposits on the surface of the heat transfer tube of the steam generator can be gradually and completely removed after multiple applications. The hard chemical cleaning SGCC (Stem generator chemical clean) can completely remove all the deposits in the Steam generator at one time, the deposits in the SG are recovered to the initial condition of commercial operation, and the condition of the deposits after application is shown as a green trend line in the figure.
If the strategy of application of ASCA is used, about 317.5kg of sediment will be washed out of the SG each time. Based on industry experience, including the use of units in japan, korea, and the united states. After the soft chemical cleaning is applied, the heat transfer is obviously enhanced in a short period, the thermal resistance can be further reduced under the condition of multiple applications, and if the soft chemical cleaning is applied for multiple times, the thermal resistance is finally recovered to a cleaning state (the thermal resistance is changed to 0) at the initial stage of commercial transportation.
The thermal resistance and the steam pressure of the deposits accumulated in the steam generator in the life cycle of a certain CRP1000 unit are predicted and calculated, and the thermal resistance of the corresponding deposits is increased by 3.08 multiplied by 10 when the average thickness of the enriched deposits on the tube bundle is about 95 microns after 60 years of service along with the increase of the operation time, if the intervention and the treatment are not carried out -5 m 2 ·℃·W -1 (corresponding to a steam pressure reduction of 460 kPa). Fouling resistance reduction of about 4.54 x 10 after initial application of ASCA -6 m 2 ·℃·W -1 (corresponding to a steam pressure rise of 60 kPa). This effect may result from factors such as the outer scale layer promoting boiling more effectively, or the solidified mature inner layer becoming thinner, or both, as shown in fig. 3 and 4. The use of ASCA may produce results that have been confirmed by laboratory tests and the experience of many nuclear power plant applications over the past few years.
After a typical full-tube bundle hard chemical cleaning (SGCC) is applied, the initial best estimated deposition thermal resistance returns to the clean state value at the beginning of the commercial shipment (the thermal resistance changes to 0); the thermal resistance increases significantly in the following cycles; during the course of the next few years of operation, the heat transfer resistance drops dramatically and rapidly due to the formation of thin, heat transfer enhancing deposits, which then increase at a similar rate as when the deposits were not removed. The magnitude of the initial increase and subsequent decrease is based primarily on the operating conditions of the actual nuclear power plant. The rapid increase in short-term thermal resistance after a hard chemical clean is from industry experience in many nuclear power plants. The nuclear power plant should be cautiously subjected to SGCC hard chemical cleaning. Although the effect of the sclero-chemical cleaning is good (the steam pressure can be restored to the initial state of the commercial transportation), the component in the steam generator is seriously corroded, the overhaul period of the unit is seriously delayed, the cost of the sclero-chemical cleaning is high, and the economic effect of the nuclear power station is large.
The invention has the advantages that: a set of online grading sampling device for main feed water and sewage of the steam generator is designed, so that the quality of corrosion products of the steam generator is accurately accumulated in real time, and the accurate calculation of the accumulated sewage input of the steam generator of the CRP1000 unit is realized; according to the accumulation of the sediments and the operation condition of the unit, a model formula for predicting the thickness and the thermal resistance of the sediments and the secondary side steam pressure in the service life of the CRP1000 unit steam generator is provided, the application effect of treatment measures is predicted and evaluated, guidance can be provided for the safe and economic operation of the CRP1000 unit steam generator in China, and the supervision, supervision and management blank of the CRP1000 equivalent type steam generator is filled.
The above embodiments are merely illustrative of the technical ideas and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.
Claims (14)
1. The utility model provides an online sampling device of steam generator corrosion product, its characterized in that, includes sample inlet pipeline, sample return circuit and bypass, sample trench, the both ends of sample return circuit and bypass respectively with sample inlet pipeline and sample trench intercommunication, the last a plurality of filters that have set gradually of sample return circuit, it is adjacent be provided with the sample bypass between the filter, the other end intercommunication of sample bypass to the sample trench.
2. The in-line sampling device of claim 1, wherein the pore size of the filter membrane in each of said filters is the same or different.
3. The in-line sampling device of claim 2, wherein the filter membrane of each of said filters has a different pore size, and the pore size of said filter membrane decreases from the filter near the end of said sampling inlet line to the filter near the end of the sampling trench.
4. The on-line sampling device of claim 2, wherein three filters are sequentially arranged on the sampling loop, and the pore size of the filter membrane in each filter is different.
5. The on-line sampling device of claim 4, wherein the filter membrane pore size in the filter is 0.4-3 um, 0.1-0.4 um and 0.05-0.1 um in sequence.
6. The on-line sampling device according to any one of claims 1 to 5, wherein a main valve is provided on the sampling inlet pipeline; a sampling valve is arranged on the sampling loop; the bypass is provided with a bypass valve.
7. The on-line sampling device of claim 1, wherein a sampling bypass valve and/or a sampling flow meter is disposed on the sampling bypass.
8. The on-line sampling device of claim 1, wherein a sampling flow meter is disposed on the sampling loop; and a bypass flowmeter is arranged on the bypass.
9. The in-line sampling device of claim 1 or 8, wherein the reynolds number of the fluid in the conduits of the sampling loop and sampling bypass is 8000 or greater.
10. A method for evaluating an operating state of a steam generator, comprising the steps of:
simultaneously sampling the steam generator feed water and the drain water online by the online sampling device according to any one of claims 1 to 9 to obtain the quality of corrosion products of the feed water and the drain water during the sampling time;
calculating the amount of corrosion products accumulated in the steam generator in the current state according to the obtained quality of the corrosion products;
and calculating the future heat transfer resistance of the deposit and the actual steam pressure of the steam generator according to the current corrosion product accumulation condition in the steam generator.
11. The evaluation method according to claim 10, wherein the sampling time is 7d in the stable operation stage of the unit; the cumulative time of corrosion product sampling in the unit starting stage is 1d.
12. The evaluation method according to claim 10, wherein the cumulative calculation is performed according to the following formula:
m＝∑m feed water -∑m Pollution discharge
Wherein m is the amount of corrosion products accumulated in a single steam generator within a certain fuel cycle; m is Water supply Transferring the feed water in a certain fuel cycle to a corrosion product on the secondary side of a single steam generator for a week; m is Pollution discharge A cycle accumulation of corrosion products of a single steam generator discharging pollution in a certain fuel cycle;
m feed water ＝F Feed water ×C Fe feed water
m Pollution discharge ＝F Pollution discharge ×C Fe pollution discharge
In the formula, F Feed water Accumulating the feed water flow for one week of a single steam generator; c Fe feed water The iron content in the water in the week; c Fe pollution discharge The iron content of the sewage is discharged in the current week; f Pollution discharge The drainage flow is accumulated for one week of a single steam generator.
13. The evaluation method according to claim 12, wherein the total iron content of the feedwater and the total iron content of the drainage are each calculated by the following formula:
the total iron content is:
C total iron (ppb) = suspended iron content C Fe (ppb) + iron content of the filtrate C 2 (ppb)
Suspended iron content C Fe (ppb) is calculated from the formula:
in the formula, the acetate fiber filter membrane used for sampling is taken out, dissolved by concentrated acid to constant volume and then analyzed to obtain the iron concentration C of the filter membrane 1 (ppb), dissolving another blank filter membrane, and performing constant volume analysis to obtain blank filter membrane iron concentration C 0 (ppb)。
14. The evaluation method according to claim 10, wherein the deposit future heat transfer resistance and actual steam pressure of the steam generator are calculated by the following equations:
in the formula: k is a radical of f The thermal conductivity of the deposit, W/(m.K); k is a radical of mg Is Fe 3 O 4 W/(m.K); k is a radical of v Is the saturated steam thermal conductivity, W/(m.K); epsilon f Is the sediment porosity;
in the formula: r f Representing the future heat transfer resistance of the deposit; e.g. of the type f Is the deposit thickness, m;
P＝f·R f
in the formula: p is the actual steam pressure, bar; f is the correction coefficient of thermal resistance and steam pressure.
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