Method for Replicating Oxidation Corrosion Product Deposition Layer in Pressurized Water Reactor Core

Abstract

The present invention provides a method for reproducing the oxidation corrosion product deposition layer of a pressurized water reactor core, which relates to the simulation technology field of pressurized water reactors and is designed to solve the problem that the deposition of core oxidation corrosion products cannot be conveniently and quickly reproduced. The method for reproducing the oxidation corrosion product deposition layer of a pressurized water reactor core includes: preparing an intermediate layer: forming a wet gel from nickel salt and iron salt, coating it on the surface of the alloy, and heating to obtain the intermediate layer; preparing the oxidation corrosion product deposition layer: mixing nano-nickel ferrite powder, binder, and pore-forming agent and grinding them into a paste; coating the paste on the intermediate layer and heating to obtain the oxidation corrosion product deposition layer. The method for reproducing the oxidation corrosion product deposition layer of a pressurized water reactor core provided by the present invention has simple process, is convenient and fast, has low requirements for equipment, causes little harm to the environment, has low energy consumption, and the morphological parameters of the generated oxidation corrosion product deposition layer conform to the parameter range of the core deposition layer.

Description

Technical Field

[0001] The present invention relates to the technical field of pressurized water reactor simulation, and in particular, to a method for reproducing an oxidation corrosion product deposition layer on a pressurized water reactor core. Background Art

[0002] The pressurized water reactor core is in a harsh environment of high temperature, high pressure and high radioactivity for a long time, and the fuel performance of the core is a key factor affecting the safety and economy of the reactor. During the operation of the nuclear reactor, the steam generator heat transfer tubes with the largest heat transfer area in the primary loop are continuously scoured, abraded and corroded by the high-pressure subcooled coolant, forming a large amount of oxidation corrosion products. Driven by subcooled boiling, metal ions and corrosion products in the primary loop will deposit on the surface of the fuel cladding at the upper part of the core, forming a thin, loose and porous scaling layer. This oxidation corrosion deposit appearing on the surface of the fuel cladding is called CRUD (Chalk River Unidentified Deposit).

[0003] The main component of the oxidation corrosion product deposition layer is nickel ferrite (NiFe2O4), and its porous morphology is composed of micron-scale "chimneys" and nanoscale "capillaries". The deposition of oxidation corrosion products will cause a series of safety problems. Generally speaking, there are mainly two aspects of hazards: on the one hand, when the oxidation corrosion product deposition layer reaches a certain thickness, the heat transfer efficiency will be reduced; on the other hand, the oxidation corrosion product deposition layer has a loose porous structure inside, which has the effect of intensifying boiling. The reduction of the heat transfer efficiency on the surface of the fuel rod will cause the temperature of the fuel rod to rise. In severe cases, it may lead to local corrosion of the fuel rod or even local melting of the reactor core; the intensification of boiling in the deposition layer with a loose structure will cause boron to precipitate from the coolant and be adsorbed by the porous morphology of the deposition layer, resulting in an uneven distribution state of boron on the axial surface of the fuel rod. Since 10 B has a significant neutron absorption capacity, the boron adsorption phenomenon in the oxidation corrosion product deposition layer will cause the power distribution to distort towards the bottom of the reactor, triggering a core power drift phenomenon, namely fouling-induced power drift. Research shows that the local power change caused by fouling-induced power drift can be as high as more than 15%. Fouling-induced power drift will not only cause the nuclear reactor to reduce power or even trip emergently, reducing the neutron economy of the nuclear reactor; but also affect the residual reactivity and shutdown margin of the core, and even cause the cladding to fail, threatening the integrity of the nuclear reactor safety barrier.

[0004] Since the deposition of oxidation corrosion products on the surface of the fuel cladding is a long solute migration process that requires precise control of water chemistry conditions, including the concentrations of Fe, Ni, O, H and other ions, as well as long-term heat transfer, mass transfer and deposition, it takes a large amount of time cost to evaluate the impact of the core oxidation corrosion product deposition layer on core safety. For example, Westinghouse in the United States specifically constructed the WALT experimental system, and obtained the deposition of oxidation corrosion products on the fuel rod cladding only after controlling the water chemistry conditions of the WALT experimental system and running continuously for thousands of hours. Therefore, developing a convenient and fast reproduction technology for core oxidation corrosion product deposition is of great significance for analyzing its impact on flow heat transfer, core neutron physics and reactor safety.

[0005] At present, there are various coating preparation technologies, including commonly used chemical vapor deposition, physical vapor deposition, anodic oxidation, etching and spraying, etc. Since the core oxidation corrosion product deposition layer is a nickel ferrite (NiFe2O4) layer with nano-scale "capillaries" and micro-scale "chimneys", spraying, chemical vapor deposition and physical vapor deposition usually can only obtain dense coatings; anodic oxidation of stainless steel can obtain nano-scale "capillaries", but cannot obtain micro-scale "chimneys", and the main component is iron oxide (Fe2O3); various etching technologies are difficult to obtain nano-scale "capillaries" on the surface of the zirconium alloy of the fuel rod cladding. Summary of the Invention

[0006] The first object of the present invention is to provide a method for reproducing the core oxidation corrosion product deposition layer of a pressurized water reactor to solve the technical problem that the existing technology cannot reproduce the core oxidation corrosion product deposition conveniently and quickly.

[0007] The method for reproducing the core oxidation corrosion product deposition layer of a pressurized water reactor provided by the present invention includes:

[0008] Preparing an intermediate layer: forming a wet gel from nickel salt and iron salt, coating it on the surface of the alloy, and heating to obtain the intermediate layer;

[0009] Preparing the oxidation corrosion product deposition layer: mixing nano nickel ferrite powder, binder and pore-forming agent and grinding them into a paste; coating the paste on the intermediate layer and heating to obtain the oxidation corrosion product deposition layer.

[0010] The beneficial effects brought by the method for reproducing the core oxidation corrosion product deposition layer of the present invention are:

[0011] First, a dense nickel ferrite (NiFe₂O₄) intermediate layer is formed on the fuel rod cladding using the sol-gel method. Then, based on the intermediate layer, a porous nickel ferrite (NiFe₂O₄) corrosion product layer is sintered from nickel ferrite (NiFe₂O₄) powder. The sintering bond between the nickel ferrite (NiFe₂O₄) nanoparticles in the intermediate layer and the nickel ferrite (NiFe₂O₄) powder in the porous layer enables the formation of a firm porous nickel ferrite (NiFe₂O₄) layer on the fuel rod cladding. During the sintering of nickel ferrite (NiFe₂O₄) powder, a binder, a pore former, and nickel ferrite (NiFe₂O₄) powder form a paste layer. The pore former and binder in the paste layer decompose to form gases at a certain temperature (200 and 400 degrees Celsius), and the escaping gases form micron-scale voids in the sintered layer. During the low-temperature (less than 1000 degrees Celsius) sintering of ceramic powder, particle bonding occurs and the grains have not grown yet, and the sintered layer has nano-scale voids. Through the above two steps, a firm nickel ferrite (NiFe₂O₄) layer with nano-scale "capillaries" and micron-scale "chimneys" can be formed on the fuel rod cladding.

[0012] This preparation method has a simple process, is convenient and fast, has low requirements for equipment, causes little harm to the environment, has low energy consumption, and the morphological parameters of the generated oxidation corrosion product deposition layer conform to the parameter range of the core deposition layer.

[0013] In the preferred technical solution, in the step of preparing the intermediate layer, nickel salt and iron salt are added to deionized water, stirred to form an iron-nickel solution, polyethylene glycol is continuously added and stirred until the solution is saturated to form crystals, and then sodium hydroxide solution is added until it turns reddish-brown, and heated to form a wet gel.

[0014] In the preferred technical solution, the nickel salt includes one or more of nickel acetate, nickel chloride, nickel sulfate, and nickel nitrate;

[0015] In the preferred technical solution, the iron salt includes one or more of ferric chloride, ferric sulfate, and ferric nitrate;

[0016] In the preferred technical solution, the polyethylene glycol includes one or more of PEG-2000, PEG-3000, and PEG-5000.

[0017] In the preferred technical solution, the molar concentration of the iron-nickel solution is 1.5 mol / L to 3.0 mol / L, and / or the molar concentration of the sodium hydroxide is 1.2 mol / L to 2.0 mol / L.

[0018] In the preferred technical solution, the preparation of the intermediate layer includes: first heating to 55 °C to 60 °C to form a wet gel, spin-coating the wet gel on the zirconium alloy surface, and keeping it warm in a muffle furnace at 100 °C for 55 min to 65 min.

[0019] In a preferred technical solution, obtaining the oxidation corrosion product deposition layer after heating includes first heating to 200°C at a rate of 5°C / min, holding at 200°C for 2 hours, then heating to 400°C at a rate of 5°C / min, holding at 400°C for 2 hours, and heating to 750°C - 900°C within 4 hours, calcining at 750°C - 900°C for 4 hours, and cooling to room temperature in the furnace to obtain the oxidation corrosion product deposition layer.

[0020] In a preferred technical solution, the binder includes one or more of diethylene glycol, triethanolamine, and diethanolamine.

[0021] In a preferred technical solution, the pore former includes one or more of polyethylene glycol and polyethylene glycol diglycidyl ether. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or in the background art, the following will briefly introduce the drawings required for use in the description of the embodiments or the background art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on the provided drawings without creative efforts.

[0023] Figure 1 It is a flowchart of the method for reproducing the oxidation corrosion product deposition layer of the pressurized water reactor core provided in Embodiment 1 of the present invention;

[0024] Figure 2 It is an electron microscope photograph of the intermediate layer prepared by the reproduction method provided in Embodiment 1 of the present invention;

[0025] Figure 3 It is an electron microscope photograph of the deposition layer prepared by the reproduction method provided in Embodiment 1 of the present invention;

[0026] Figure 4 It is an X-ray diffraction pattern of the deposition layer prepared by the reproduction method provided in Embodiment 1 of the present invention;

[0027] Figure 5 It is an electron microscope photograph of the deposition layer prepared by the reproduction method provided in Embodiment 2 of the present invention;

[0028] Figure 6 It is an electron microscope photograph of the deposition layer prepared by the reproduction method provided in Embodiment 3 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following provides a detailed description of specific embodiments of the present invention with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0030] The method for reproducing the oxidation corrosion product deposition layer of a pressurized water reactor core provided by the present invention includes:

[0031] Preparing an intermediate layer: forming a wet gel using nickel salts and iron salts, coating it on the alloy surface, and heating to obtain the intermediate layer;

[0032] Preparing the oxidation corrosion product deposition layer: mixing nano nickel ferrite powder, binder, and pore former and grinding them into a paste; coating the paste on the intermediate layer and heating to obtain the oxidation corrosion product deposition layer.

[0033] First, a dense nickel ferrite (NiFe2O4) intermediate layer is formed on the fuel rod cladding by the sol-gel method. Then, on the basis of the intermediate layer, a porous nickel ferrite (NiFe2O4) corrosion product layer is sintered using nickel ferrite (NiFe2O4) powder. The sintering bond between the nano nickel ferrite (NiFe2O4) particles of the intermediate layer and the nano nickel ferrite (NiFe2O4) powder of the porous layer enables the porous nickel ferrite (NiFe2O4) layer to be firmly formed on the fuel rod cladding. During the sintering of nickel ferrite (NiFe2O4) powder, the binder, pore former, and nano nickel ferrite (NiFe2O4) powder form a paste layer. The pore former and binder in the paste layer decompose to form gases at a certain temperature (200 and 400 degrees Celsius), and the escaping gases form micron-sized voids in the sintered layer; during the low-temperature (less than 1000 degrees Celsius) sintering process of the ceramic powder, the particles are bonded and the grains have not grown yet, and the sintered layer has nano-scale voids. Through the above two steps, a firm nickel ferrite (NiFe2O4) layer with nano-scale "capillaries" and micron-scale "chimneys" can be formed on the fuel rod cladding.

[0034] This preparation method has a simple process, is convenient and fast, has low requirements for equipment, causes little harm to the environment, has low energy consumption, and the morphology parameters of the generated oxidation corrosion product deposition layer conform to the parameter range of the core deposition layer.

[0035] Preferably, in the step of preparing the intermediate layer, nickel salts and iron salts are added to deionized water, stirred to form an iron-nickel solution, polyethylene glycol is continuously added and stirred until the solution is saturated to form crystals, and then sodium hydroxide solution is continuously added to turn it into a reddish-brown color, and heated to form a wet gel.

[0036] Preferably, the nickel salts include one or more of nickel acetate, nickel chloride, nickel sulfate, and nickel nitrate;

[0037] Preferably, the iron salts include one or more of ferric chloride, ferric sulfate, and ferric nitrate;

[0038] Preferably, the polyethylene glycol includes one or more of PEG-2000, PEG-3000, and PEG-5000.

[0039] Preferably, the molar concentration of the iron-nickel solution is 1.5 mol / L to 3.0 mol / L, and / or the molar concentration of sodium hydroxide is 1.2 mol / L to 2.0 mol / L. Herein, the molar concentration of the iron-nickel solution refers to the ratio of the sum of the amounts of substance of iron ions and nickel ions in the solution to the volume of the solution.

[0040] Preferably, preparing the intermediate layer includes: first heating to 55°C to 60°C to form a wet gel, spin-coating the wet gel on the surface of the zirconium alloy, and keeping it in a muffle furnace at 100°C for 1 hour.

[0041] Preferably, depositing the oxidation corrosion product layer obtained after heating includes: first heating up to 200°C at a rate of 5°C / min, keeping it at 200°C for 2 hours, then heating up to 400°C at a rate of 5°C / min, keeping it at 400°C for 2 hours, and heating up to 750°C to 900°C within 4 hours, calcining at 750°C to 900°C for 4 hours, and cooling down to room temperature with the furnace to obtain the oxidation corrosion product layer.

[0042] Preferably, the binder includes one or more of diethylene glycol, triethanolamine, and diethanolamine.

[0043] Preferably, the pore former includes one or more of polyethylene glycol and polyethylene glycol diglycidyl ether.

[0044] Example 1:

[0045] A method for reproducing the oxidation corrosion product layer of a pressurized water reactor core includes the following steps:

[0046] Step 1: Prepare a dense intermediate layer:

[0047] Add nickel acetate and iron nitrate to deionized water according to a molar ratio of 1:2, stir to form a 2.0 mol / L iron-nickel solution, continue to add polyethylene glycol PEG-3000 and stir until the solution is saturated to form crystals; continue to add a 1.0 mol / L sodium hydroxide solution until the solution turns reddish-brown, heat to 60°C to form a wet gel; spin-coat the wet gel on the surface of the zirconium alloy at 3000 rpm, and place it in a muffle furnace, and keep it at a temperature of 100°C for 55 minutes to obtain the intermediate layer;

[0048] Step 2: Prepare the oxidation corrosion product layer:

[0049] Mix 9 g of nickel ferrite nanoparticles, 1.5 mL of diethylene glycol, and 1.0 mL of polyethylene glycol diglycidyl ether in proportion and grind them into a viscous paste; coat the paste on the intermediate layer prepared in Step 1, put it into a muffle furnace for calcination, heat it up to 200 °C and 400 °C at a rate of 5 °C / min and hold for 2 hours at 200 °C and 400 °C respectively; then heat it up to 800 °C, the time taken to heat from 400 °C to 800 °C is less than or equal to 4 hours, calcine at 800 °C for 4 hours, and cool down to room temperature with the furnace, then the oxidation corrosion product deposition layer is obtained.

[0050] Observe the prepared sample under an electron microscope as Figure 2 shown, which is a dense film; observe the prepared sample under an electron microscope as Figure 3 shown, and "capillaries" with an average pore diameter of 200 nm and "chimneys" with an average pore diameter of 1 μm are obtained; analyze and detect with an X-ray diffractometer, and the detection results are as Figure 4 shown.

[0051] Example 2

[0052] A method for reproducing the oxidation corrosion product deposition layer of a pressurized water reactor core, comprising the following steps:

[0053] Step 1: Prepare a dense intermediate layer:

[0054] Add nickel acetate and iron nitrate to deionized water according to a molar ratio of 1:2, stir to form a 2.0 mol / L iron-nickel solution, continue to add polyethylene glycol PEG-3000, and stir until the solution is saturated to form crystals; continue to add a 1.0 mol / L sodium hydroxide solution until the solution turns reddish-brown, heat to 55 °C to form a wet gel; spin-coat the wet gel on the zirconium alloy surface at 3000 rpm and place it in a muffle furnace, and keep it at a temperature of 100 °C for 65 minutes to obtain the intermediate layer;

[0055] Step 2: Prepare the oxidation corrosion product deposition layer

[0056] Mix 5 g of nickel ferrite nanoparticles, 1.5 mL of diethylene glycol, and 1.0 mL of polyethylene glycol diglycidyl ether in proportion and grind them into a viscous paste; coat the paste on the intermediate layer prepared in Step 1, put it into a muffle furnace for calcination, heat it up to 200 °C and 400 °C at a rate of 5 °C / min and hold for 2 hours at 200 °C and 400 °C respectively; then heat it up to 900 °C, the time taken to heat from 400 °C to 900 °C is less than or equal to 4 hours, calcine at 900 °C for 4 hours, and cool down to room temperature with the furnace, then the oxidation corrosion product deposition layer is obtained.

[0057] Observe the prepared sample under an electron microscope as Figure 5As shown, "capillaries" with an average pore diameter of 500 nm and "chimneys" with an average pore diameter of 3 μm are obtained.

[0058] Example 3

[0059] A method for reproducing the oxide corrosion product deposition layer in a pressurized water reactor core includes the following steps:

[0060] Step 1: Prepare a dense intermediate layer

[0061] Nickel acetate and iron nitrate are added to deionized water in a molar ratio of 1:2, stirred to form a 2.0 mol / L iron-nickel solution, and polyethylene glycol PEG-3000 is continuously added and stirred until the solution is saturated to form crystals. Then, a 1.0 mol / L sodium hydroxide solution is added until the solution turns reddish-brown, and it is heated to 60 °C to form a wet gel. The wet gel is spin-coated on the zirconium alloy surface at 3000 rpm and placed in a muffle furnace, and maintained at a temperature of 100 °C for one hour to obtain the intermediate layer;

[0062] Step 2: Prepare the oxide corrosion product deposition layer

[0063] 15 g of nano-nickel ferrite powder, 1.5 mL of diethylene glycol, and 1.0 mL of polyethylene glycol diglycidyl ether are mixed and ground into a viscous paste. The paste is coated on the intermediate layer prepared in Step 1 and placed in a muffle furnace for calcination. It is heated from room temperature to 200 °C and 400 °C at a rate of 5 °C / min and held at 200 °C and 400 °C for 2 hours each. Then, it is heated to 750 °C, and the time taken to heat from 400 °C to 750 °C is less than or equal to 4 hours. It is calcined at 750 °C for 4 hours and cooled to room temperature with the furnace, and thus the oxide corrosion product deposition layer is obtained.

[0064] The prepared sample is observed under an electron microscope as Figure 6 shown, and "capillaries" with an average pore diameter of 100 nm and "chimneys" with an average pore diameter of 1 μm are obtained.

[0065] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be determined by the scope defined by the claims.

[0066] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the term "comprises" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprises a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0067] In the above embodiments, the descriptions of directions such as “upper” and “lower” are all based on the drawings.

[0068] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0069] Thus, the present invention will not be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for reproducing an oxide corrosion product deposition layer in a pressurized water reactor core, characterized in that Comprising: Preparing an intermediate layer: forming a wet gel from a nickel salt and an iron salt, coating the wet gel on the surface of an alloy, and heating to obtain the intermediate layer; Preparing an oxidation corrosion product deposition layer: mixing nano nickel ferrite powder, a binder, and a pore former and grinding them into a paste; coating the paste on the intermediate layer and heating to obtain the oxidation corrosion product deposition layer; first heating at a rate of 5 °C / min to 200 °C, holding at 200 °C for 2 hours, then heating at a rate of 5 °C / min to 400 °C, holding at 400 °C for 2 hours, and heating to 750 °C - 900 °C within 4 hours, calcining at 750 °C - 900 °C for 4 hours, and cooling in the furnace to room temperature to obtain the oxidation corrosion product deposition layer.

2. The method for reproducing the oxide corrosion product deposition layer in the pressurized water reactor core according to claim 1, characterized in that, In the step of preparing the intermediate layer, adding the nickel salt and the iron salt into deionized water, stirring to form an iron-nickel solution, continuously adding polyethylene glycol and stirring until the solution is saturated to form crystals, and continuously adding sodium hydroxide solution until it turns reddish-brown, and heating to form a wet gel.

3. The method for reproducing the oxide corrosion product deposition layer in the pressurized water reactor core according to claim 2, wherein The nickel salt includes one or more of nickel acetate, nickel chloride, nickel sulfate, and nickel nitrate.

4. The method for reproducing the oxide corrosion product deposition layer of the pressurized water reactor core according to claim 2, wherein The iron salt includes one or more of ferric chloride, ferric sulfate, and ferric nitrate.

5. The method for reproducing the oxide corrosion product deposition layer in the pressurized water reactor core according to claim 2, wherein The polyethylene glycol includes one or more of PEG-2000, PEG-3000, and PEG-5000.

6. The method for reproducing the oxide corrosion product deposition layer in the pressurized water reactor core according to claim 2, wherein The molar concentration of the iron-nickel solution is 1.5 mol / L - 3.0 mol / L, and / or the molar concentration of the sodium hydroxide is 1.2 mol / L - 2.0 mol / L.

7. The method for reproducing the oxidation corrosion product deposition layer of the pressurized water reactor core according to claim 2, characterized in that, The preparation of the intermediate layer includes: first heating to 55 °C - 60 °C to form a wet gel, spin-coating the wet gel on the surface of a zirconium alloy, and holding in a muffle furnace at 100 °C for 55 min - 65 min.

8. The method for reproducing the oxide corrosion product deposition layer in a pressurized water reactor core according to any one of claims 1-7, characterized in that, The binder includes one or more of diethylene glycol, triethanolamine, and diethanolamine.

9. The method for reproducing the oxide corrosion product deposition layer of a pressurized water reactor core according to any one of claims 1-7, characterized in that, The pore former includes one or more of polyethylene glycol and polyethylene glycol diglycidyl ether.

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