Efficient decontamination method for charging pump of pressurized water reactor nuclear power unit

Abstract

The invention discloses an efficient decontamination method for a charging pump of a pressurized water reactor nuclear power unit, and belongs to the technical field of chemical decontamination of nuclear power stations. The method comprises the following process steps: (1) soaking the hydraulic circulation component of the charging pump to be decontaminated in a low-concentration citric acid system cleaning solution for 30-50 minutes, and (2) washing the component of the charging pump with water, and spraying a foam decontaminant to completely cover the surface of the component, and (3) washing components of the charging pump with high-pressure water, and thoroughly removing sediments on the surface of the charging pump under the assistance of the foam detergent. According to the method, the loose sediments on the surface of the hydraulic circulation component of the charging pump of the pressurized water reactor nuclear power unit can be quickly and efficiently removed, and chemical decontamination factors are increased.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical decontamination of nuclear power plants, and in particular relates to a high-efficiency decontamination method for a charging pump of a pressurized water reactor nuclear power unit. Background Art

[0002] Nuclear power is a clean energy source with the characteristics of stability, high efficiency and scalability. Pressurized water reactors have become the main type of new nuclear power reactors in my country due to their compact structure, small size, high power density, high average burnup, low escape of radioactive fission products, good power self-stabilization and self-adjustment characteristics, high safety and reliability. As an important primary circuit equipment, the charging pump is used to provide charging water containing boric acid solution to the reactor coolant system and injection water for the mechanical seal of the reactor main pump under normal, startup and shutdown conditions of the power station; maintain a certain water volume in the reactor coolant system (primary circuit) and suppress the concentration of chemical corrosion; provide boron-containing water to the reactor cooling system under accident conditions. It is an important equipment used for primary circuit chemical and volume control systems and water supply to the mechanical seal of the reactor coolant circulation pump. It has the characteristics of high head and high speed and is a nuclear safety level II equipment.

[0003] Due to the working characteristics of the charging pump: its working medium is a fluid with a certain level of radioactivity, and the working temperature is relatively low (<60°C), which inevitably causes loose sediments to be deposited on the surface of the hydraulic fluid components of the charging pump. The loose sediments have a certain level of radioactivity. In order to ensure the work safety of maintenance personnel, reducing the radioactivity level of the charging pump is a prerequisite for maintenance work. Therefore, effectively removing sediments from the charging pump is the key to reducing the radioactivity level. Summary of the invention

[0004] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0005] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0006] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a method for efficiently decontaminating a charging pump of a pressurized water reactor nuclear power unit.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions, including:

[0008] Soak the hydraulic flow parts of the charging pump to be decontaminated in the cleaning solution and then rinse with water. Spray foam detergent to completely cover the surface of the parts. Keep it for 5 to 10 minutes and then rinse with high-pressure water to remove the sediment on the surface of the charging pump.

[0009] As a preferred embodiment of the method for efficiently decontaminating the charging pump of a pressurized water reactor nuclear power unit of the present invention, the cleaning liquid includes, by mass fraction, 0.3% to 0.4% citric acid, 0.1% to 0.2% auxiliary agent, and the rest is water. The medium concentration and the use temperature conditions can effectively reduce the bonding strength between the sediment and the surface of the charging pump material.

[0010] As a preferred solution of the method for efficiently decontaminating the charging pump of a pressurized water reactor nuclear power unit described in the present invention, the auxiliary agent includes one or more of EDTA and DTPA.

[0011] As a preferred scheme of the high-efficiency decontamination method for the charging pump of a pressurized water reactor nuclear power unit described in the present invention, the soaking temperature is 80-95° C. and the soaking time is 30-50 minutes.

[0012] As a preferred solution of the method for efficiently decontaminating the charging pump of a pressurized water reactor nuclear power unit of the present invention, the temperature of the water flushing is 75-80° C. to clean and remove the residual acid on the surface of the component.

[0013] As a preferred solution of the method for efficiently decontaminating the charging pump of a pressurized water reactor nuclear power unit of the present invention, the foam decontaminant comprises a foaming agent, a foam stabilizer and a dispersant;

[0014] The concentration of the foaming agent is 2.0-3.0 g / L, the concentration of the foam stabilizer is 1.0-2.0 g / L, and the concentration of the dispersant is 1.0-2.0 g / L. The foam decontaminant has a good foaming ratio and liquid holding half-life, and has good sediment coating performance, which can improve the sediment decontamination effect of the hydraulic components of the charging pump.

[0015] As a preferred solution of the method for efficiently decontaminating the charging pump of a pressurized water reactor nuclear power unit of the present invention, the foaming agent includes alkyl glycoside.

[0016] As a preferred solution of the method for efficiently decontaminating the charging pump of a pressurized water reactor nuclear power unit described in the present invention, the foam stabilizer includes xanthan gum.

[0017] As a preferred solution of the method for efficiently decontaminating the charging pump of a pressurized water reactor nuclear power unit of the present invention, the dispersant includes PAA.

[0018] As a preferred solution of the method for efficiently decontaminating the charging pump of a pressurized water reactor nuclear power unit of the present invention, the pressure of the high-pressure water flushing is ≥5MPa to ensure the stripping ability of the high-pressure water.

[0019] Beneficial effects of the present invention:

[0020] The method of the invention realizes the rapid and efficient removal of loose sediments on the surface of the hydraulic circulation component of the charging pump of the pressurized water reactor nuclear power unit, and improves the chemical decontamination factor. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. Among them:

[0022] Figure 1 This is a flow chart of efficient decontamination of the charging pump of the present invention.

[0023] Figure 2 These are photos of the simulated sediment on the surface of the ZG04Cr13Ni4Mo sample of the impeller material of the charging pump in Example 1 of the present invention before and after cleaning; the left one is before cleaning, and the right one is after cleaning.

[0024] Figure 3 These are photos of the simulated sediment on the surface of the ZG04Cr13Ni4Mo sample of the upper charging pump impeller material in Comparative Example 1 of the present invention before and after cleaning; the left is before cleaning, and the right is after cleaning. DETAILED DESCRIPTION

[0025] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0026] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0027] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor is it a separate or selective embodiment that is mutually exclusive with other embodiments.

[0028] The raw materials used in the present invention are all commercially available unless otherwise specified.

[0029] Sample preparation: simulated sediments were prepared on the surface of the impeller material ZG04Cr13Ni4Mo of the upper charging pump. The preparation process was as follows: the sample was processed into a sample of 100mm×60mm×(5~10)mm, and polished to 1000# with water sandpaper step by step, rinsed with anhydrous ethanol, and weighed after drying for later use. A PVC board was placed on the stainless steel storage partition in the water bath to avoid contact between the sample and the partition. The test piece was placed flat on the PVC board, pure water was added until the sample was completely submerged, and then 0.15g of ferroferric oxide powder was evenly spread on each sample, and the constant temperature water bath was adjusted to 60℃ and left to stand for 60 days.

[0030] Example 1

[0031] The ZG04Cr13Ni4Mo sample with sediment was Figure 1 The cleaning process is as follows:

[0032] 1) The above material with sediment was completely immersed in a cleaning solution of 0.3% citric acid + 0.2% DTPA at a temperature of 85° C. for 50 minutes.

[0033] 2) Rinse the sample surface with water at a temperature of 80°C.

[0034] 3) Spray the foam detergent on the surface of the sample and let the sample stand in the detergent foam for 5 minutes. The main components of the foam detergent are: foaming agent (APG) 3g / L + foam stabilizer (xanthan gum) 2g / L + dispersant (PAA) 2g / L.

[0035] 4) Rinse the sample with 5MPa high-pressure water.

[0036] Macro photos before and after cleaning Figure 2 The calculation results of the removal rate of deposits on the sample surface are shown in Table 1, and the removal rate is 100%.

[0037] Table 1 Quality change and sediment removal rate of ZG04Cr20Ni9 test piece before and after cleaning in Example 1

[0038]

[0039] Comparative Example 1

[0040] The ZG04Cr13Ni4Mo sample with sediment was cleaned and decontaminated according to the following steps:

[0041] 1) The above material with sediment was completely immersed in a cleaning solution of 0.3% citric acid + 0.2% DTPA at a temperature of 85° C. for 50 minutes.

[0042] 2) The sample is rinsed with high-pressure water at a pressure of 5 MPa.

[0043] Macroscopic photos of the samples before and after cleaning Figure 3 As shown, the removal rate calculation results of the deposits on the sample surface are shown in Table 2. The removal rate is 91%, and the deposit removal effect is not as good as that of Example 1.

[0044] Table 2 Quality change and sediment removal rate of ZG04Cr20Ni9 test piece before and after cleaning in comparative example 1

[0045]

[0046] In summary, the present invention can effectively remove sediments and pollutants on the surface of the hydraulic circulation components of the charging pump by using a combination of steps of soaking with a low-concentration citric acid cleaning solution, water washing, spraying with a foam detergent, and high-pressure water washing. Citric acid, as an organic acid, can dissolve metal oxide scales such as iron oxide, and EDTA or DTPA is used as an auxiliary agent to further improve the cleaning effect. The present invention uses citric acid as the main agent. Citric acid has the characteristics of low corrosiveness, non-toxicity, and high safety, and is not easy to form sediment or suspended matter, thereby avoiding the problem of pipeline blockage. In addition, the waste liquid generated by the citric acid cleaning solution during use is relatively simple to handle and will not cause serious pollution to the environment. The method of the present invention achieves an efficient, safe, and environmentally friendly decontamination effect of the charging pump through scientific steps and reasonable temperature control, combined with an environmentally friendly and safe cleaning agent.

[0047] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A highly efficient decontamination method for a charging pump of a pressurized water reactor nuclear power unit, characterized in that: include, Soak the hydraulic flow parts of the charging pump to be cleaned in the cleaning liquid and then rinse with water. Spray the foam detergent to completely cover the surface of the parts. Keep it for 5 to 10 minutes and then rinse with high-pressure water to remove the sediment on the surface of the charging pump. The cleaning solution comprises, by mass fraction, 0.3% to 0.4% citric acid, 0.1% to 0.2% auxiliary agent, and the rest is water.

2. The method for efficiently decontaminating a charging pump of a pressurized water reactor nuclear power unit according to claim 1, characterized in that: The auxiliary agent includes one or more of EDTA and DTPA.

3. The high-efficiency decontamination method for charging pump of a pressurized water reactor nuclear power unit according to claim 1, characterized in that: The soaking temperature is 80-95°C.

4. The method for efficiently decontaminating the charging pump of a pressurized water reactor nuclear power unit according to claim 1 or 3, characterized in that: The soaking time is 30 to 50 minutes.

5. The high-efficiency decontamination method for charging pump of a pressurized water reactor nuclear power unit according to claim 1, characterized in that: The temperature of the water washing is 75-80°C.

6. The high-efficiency decontamination method for charging pump of a pressurized water reactor nuclear power unit according to claim 1, characterized in that: The foam detergent comprises a foaming agent, a foam stabilizer and a dispersant; Among them, the concentration of the foaming agent is 2.0-3.0 g / L, the concentration of the foam stabilizer is 1.0-2.0 g / L, and the concentration of the dispersant is 1.0-2.0 g / L.

7. The method for efficiently decontaminating the charging pump of a pressurized water reactor nuclear power unit according to claim 6, characterized in that: The foaming agent includes an alkyl glycoside.

8. The method for efficiently decontaminating the charging pump of a pressurized water reactor nuclear power unit according to claim 6, characterized in that: The foam stabilizer includes xanthan gum.

9. The method for efficiently decontaminating a charging pump of a pressurized water reactor nuclear power unit according to claim 6, characterized in that: The dispersant includes PAA.

10. The method for efficiently decontaminating a charging pump of a pressurized water reactor nuclear power unit according to claim 1, characterized in that: The pressure of the high-pressure water flushing is ≥5MPa.

Images