Metallographic etching agent and metallographic etching method for U3Si2 pellet fuel

Abstract

The invention discloses a U3Si2 pellet fuel metallographic etchant and a metallographic etching method, and relates to the technical field of reactor fuel etchants, the metallographic etchant comprises glacial acetic acid, concentrated nitric acid and deionized water, and the volume ratio of glacial acetic acid to concentrated nitric acid to deionized water is (52-60): (26-34): (10-18). The specific method for etching the U3Si2 pellet fuel comprises the steps that the polished U3Si2 pellet fuel is placed in an etching agent to be soaked and etched, and the etched U3Si2 pellet fuel is washed with clear water and then dried. By adopting the etching agent and the etching method, the morphology and size distribution of crystal grains can be clearly observed under a metallographic microscope, a metallographic analysis technical support is provided for grading the grain size of U3Si2 fuel and optimizing a preparation process of the U3Si2 fuel, and the etching agent and the etching method are simple to operate, good in using effect and suitable for fuel laboratory development and fuel engineering application production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of reactor fuel etchant, in particular to a U3Si2 pellet fuel metallographic etchant and a metallographic etching method. BACKGROUND

[0002] U3Si2 pellet fuel is an advanced nuclear fuel with high uranium density and high thermal conductivity. Its preparation process and comprehensive performance have become a research hotspot in the field of accident tolerant fuel (ATF) in recent years. Currently, high-density, high-purity pellet is mainly prepared through powder metallurgy and multi-element pressurized reaction sintering technology. Related research has verified its potential in reactor safety and economy. Compared with traditional UO2 fuel, U3Si2 has high thermal conductivity. The thermal conductivity of U3Si2 pellet is significantly better than that of UO2, and increases linearly with temperature, which helps to reduce the fuel center temperature during reactor operation and reduce the risk of pellet cracking caused by thermal stress. At the same time, U3Si2 pellet also has high uranium density and accident tolerance. Its uranium density is significantly higher than that of UO2, which can increase the power density of the core. As a candidate material for accident tolerant fuel, it can delay the overheating of the cladding and the release of radioactive substances under extreme conditions such as loss of coolant accident. Together with BeO, SiC and modified UO2 technology, it constitutes an important direction of ATF research and development.

[0003] The metallographic microstructure of the fuel pellet directly affects the thermal conductivity and irradiation swelling performance of the fuel pellet. In the development and production process of the fuel pellet, the metallographic structure is an important technical index for characterizing the performance of the fuel pellet. In order to master the metallographic structure of the fuel pellet, an efficient and convenient metallographic etching method is crucial to obtain clear grain morphology and size distribution parameters.

[0004] However, there is no relevant literature on the metallographic etching method of U3Si2 pellet fuel, and the metallographic etching method of UO2 pellet fuel is not suitable for U3Si2 pellet fuel. Therefore, there are still some technical defects in the metallographic etching of U3Si2 pellet fuel, which is not conducive to the grain size rating of U3Si2 pellet fuel in the development process. SUMMARY

[0005] In view of the problem that there is no etchant and etching method suitable for U3Si2 pellet fuel at present, the purpose of the present application is to provide a U3Si2 pellet fuel metallographic etchant and a metallographic etching method. The etchant and etching method can clearly observe the morphology and size distribution of the grains under the metallographic microscope, and the operation is simple, the use effect is good, and it is suitable for fuel laboratory development and fuel engineering application production.

[0006] The present application is realized by the following technical solutions:

[0007] In a first aspect, the present application provides a U3Si2 pellet fuel metallographic etchant, the metallographic etchant comprising glacial acetic acid, concentrated nitric acid and deionized water, the volume ratio of the glacial acetic acid, the concentrated nitric acid and the deionized water being (52-60):(26-34):(10-18).

[0008] In a specific embodiment, the volume ratio of the glacial acetic acid, the concentrated nitric acid and the deionized water is 56:30:14.

[0009] In a second aspect, the present application provides a U3Si2 pellet fuel metallographic etching method, which uses the above-mentioned U3Si2 pellet fuel metallographic etchant for etching.

[0010] In a specific embodiment, the specific method for etching the U3Si2 pellet fuel is to immerse the polished U3Si2 pellet fuel in the etchant for etching, and then rinse and dry the etched U3Si2 pellet fuel with clean water.

[0011] In a specific embodiment, the U3Si2 pellet fuel is immersed in the etchant for 30-50 seconds.

[0012] In a specific embodiment, the polishing method of the U3Si2 pellet fuel is to grind the U3Si2 pellet fuel on a polishing machine using metallographic water film sandpaper, and then polish the ground U3Si2 pellet fuel to a mirror surface on the polishing machine.

[0013] In a specific embodiment, the metallographic water film sandpaper is metallographic water film sandpaper with a grit of 800-1200#, and the grinding time of each metallographic water film sandpaper is 3-5 minutes.

[0014] In a specific embodiment, the rotation speed of the polishing machine is set to 300-500 r / min.

[0015] In a specific embodiment, the rotation speed of the polishing machine is set to 400 r / min.

[0016] In a specific embodiment, the U3Si2 pellet fuel needs to be inlaid before polishing.

[0017] In a specific embodiment, the specific method of inlaying is to place the U3Si2 pellet fuel on the sample table of a hot inlaying machine, and then fill the inlaying resin material for hot pressing inlaying.

[0018] In a specific embodiment, the hot-pressing parameters are set as follows: pressure: 100 bar~105 bar; temperature: 175℃~180℃; heating time: 4min~5min; cooling time: 3min~4min.

[0019] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0020] (1) The etching method in the present application can clearly observe the metallographic structure of U3Si2 fuel under a metallographic microscope, and provides metallographic analysis technical support for the grain size rating of U3Si2 fuel and the optimization of the preparation process of U3Si2 fuel.

[0021] (2) The etching method in the present application is helpful for the grain size rating in the development process of U3Si2 pellet fuel, and has the characteristics of simple operation, good use effect, etc., and is suitable for fuel laboratory development and fuel engineering application production. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope, and for those skilled in the art, other related drawings can also be obtained without creative labor. In the drawings:

[0023] Figure 1 The U3Si2 pellet metallographic structure obtained by using the etchant and metallographic detection method of embodiment 1 of the present application is magnified by 200 times;

[0024] Figure 2 The U3Si2 pellet metallographic structure obtained by using the etchant and metallographic detection method of embodiment 1 of the present application is magnified by 500 times;

[0025] Figure 3 The U3Si2 pellet metallographic structure obtained by using the etchant and metallographic detection method of embodiment 2 of the present application is magnified by 200 times;

[0026] Figure 4 The U3Si2 pellet metallographic structure obtained by using the etchant and metallographic detection method of embodiment 2 of the present application is magnified by 500 times;

[0027] Figure 5 The U3Si2 pellet metallographic structure obtained by using the etchant and metallographic detection method of embodiment 3 of the present application is magnified by 200 times;

[0028] Figure 6U3Si2 pellet metallographic structure obtained by using the etchant and metallographic detection method of embodiment 3 of the present application, magnified 500 times;

[0029] Figure 7 U3Si2 pellet metallographic structure obtained by using the etchant and metallographic detection method of embodiment 4 of the present application, magnified 200 times;

[0030] Figure 8 U3Si2 pellet metallographic structure obtained by using the etchant and metallographic detection method of embodiment 4 of the present application, magnified 500 times;

[0031] Figure 9 U3Si2 pellet metallographic structure obtained by using the etchant and metallographic detection method of embodiment 5 of the present application, magnified 200 times;

[0032] Figure 10 U3Si2 pellet metallographic structure obtained by using the etchant and metallographic detection method of embodiment 5 of the present application, magnified 500 times;

[0033] Figure 11 U3Si2 pellet metallographic structure obtained by using the etchant and metallographic detection method of embodiment 6 of the present application, magnified 200 times;

[0034] Figure 12 U3Si2 pellet metallographic structure obtained by using the etchant and metallographic detection method of embodiment 6 of the present application, magnified 500 times;

[0035] Figure 13 U3Si2 pellet metallographic structure obtained by using the etchant and metallographic detection method of embodiment 7 of the present application, magnified 200 times;

[0036] Figure 14 U3Si2 pellet metallographic structure obtained by using the etchant and metallographic detection method of embodiment 7 of the present application, magnified 500 times;

[0037] Figure 15 U3Si2 pellet metallographic structure obtained by using the etchant and metallographic detection method of embodiment 8 of the present application, magnified 200 times;

[0038] Figure 16 U3Si2 pellet metallographic structure obtained by using the etchant and metallographic detection method of embodiment 8 of the present application, magnified 500 times;

[0039] Figure 17 U3Si2 pellet metallographic structure obtained by using the etchant and metallographic detection method of embodiment 9 of the present application, magnified 200 times;

[0040] Figure 18U3Si2 ingot metallographic structure obtained by using the etchant and metallographic test method of Example 9 of the present application, magnified 500 times;

[0041] Figure 19 U3Si2 ingot metallographic structure obtained by using the etchant and metallographic test method of Comparative Example 1 of the present application, magnified 200 times;

[0042] Figure 20 U3Si2 ingot metallographic structure obtained by using the etchant and metallographic test method of Comparative Example 1 of the present application, magnified 500 times;

[0043] Figure 21 U3Si2 ingot metallographic structure obtained by using the etchant and metallographic test method of Comparative Example 2 of the present application, magnified 200 times;

[0044] Figure 22 U3Si2 ingot metallographic structure obtained by using the etchant and metallographic test method of Comparative Example 2 of the present application, magnified 500 times;

[0045] Figure 23 U3Si2 ingot metallographic structure obtained by using the etchant and metallographic test method of Comparative Example 3 of the present application, magnified 200 times;

[0046] Figure 24 U3Si2 ingot metallographic structure obtained by using the etchant and metallographic test method of Comparative Example 3 of the present application, magnified 500 times;

[0047] Figure 25 U3Si2 ingot metallographic structure obtained by using the etchant and metallographic test method of Comparative Example 4 of the present application, magnified 200 times;

[0048] Figure 26 U3Si2 ingot metallographic structure obtained by using the etchant and metallographic test method of Comparative Example 4 of the present application, magnified 500 times;

[0049] Figure 27 U3Si2 ingot metallographic structure obtained by using the etchant and metallographic test method of Comparative Example 5 of the present application, magnified 200 times;

[0050] Figure 28 U3Si2 ingot metallographic structure obtained by using the etchant and metallographic test method of Comparative Example 5 of the present application, magnified 500 times;

[0051] Figure 29 U3Si2 ingot metallographic structure obtained by using the etchant and metallographic test method of Comparative Example 6 of the present application, magnified 200 times;

[0052] Figure 30U3Si2 ingot metallographic structure obtained by using the etchant and metallographic detection method of the present application comparative example 6, magnified 500 times;

[0053] Figure 31 U3Si2 ingot metallographic structure obtained by using the etchant and metallographic detection method of the present application comparative example 7, magnified 500 times;

[0054] Figure 32 U3Si2 ingot metallographic structure obtained by using the etchant and metallographic detection method of the present application comparative example 8, magnified 500 times;

[0055] Figure 33 U3Si2 ingot metallographic structure obtained by using the etchant and metallographic detection method of the present application comparative example 9, magnified 500 times. DETAILED DESCRIPTION

[0056] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with embodiments. The illustrative embodiments of the present application and their descriptions are only used to explain the present application and not as a limitation of the present application.

[0057] In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present application. However, it will be apparent to one ordinarily skilled in the art that the present application can be practiced without these specific details. In other instances, well-known materials or methods have not been described in detail in order to avoid obscuring the present application.

[0058] Throughout this specification, the term "one embodiment," "an embodiment," "one example," or "an example" means that a particular feature, structure, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. Therefore, the appearance of the phrases "in one embodiment," "in an embodiment," "in one example," or "in an example" in various places in the specification are not necessarily all referring to the same embodiment or example. Furthermore, the particular features, structures, or characteristics can be combined in any suitable manner in one or more embodiments or examples. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. In addition, those skilled in the art will be able to make and use the present application with the different embodiments or examples described in this specification and the features of the different embodiments or examples can be combined and combined without mutual contradiction.

[0059] The ranges disclosed herein are defined by their lower and upper limits. Ranges that include both endpoints are inclusive of the endpoints, and ranges that exclude both endpoints are not inclusive of the endpoints. Ranges are combinable and include any and all combinations of the stated ranges. For example, if a range of "60-120" and a range of "80-110" are listed, the ranges of "60-110," "60- 120," "80-120," and "80- 1 10" are also expressly stated in this application. In addition, where a minimum value of 1 and a maximum value of 3 are listed, the following ranges are also expressly stated: 1-3, 1-2, 2-3, and 1-2. In this application, the use of "or" means "and / or" unless stated otherwise. Furthermore, to the extent that any reference is made herein to a method, it is understood that such reference includes the process disclosed in the description, as well as the process disclosed in the claims. It is also understood that, unless otherwise specified, the use of any singular form of a noun in this application includes the plural form. For example, the use of the word "a" includes the use of "at least one" and the use of the word "the" includes the use of "at least one." It is also understood that, unless otherwise specified, the use of any plural form of a noun in this application includes the singular form. For example, the use of the word "two" includes the use of "one" and the use of the word "two" includes the use of "at least one." It is further understood that, unless otherwise specified, the use of any negative form of a noun in this application includes the positive form. For example, the use of the word "no" includes the use of "one" and the use of the word "none" includes the use of "at least one."

[0060] Unless otherwise indicated, all steps of the application can be performed in any order, preferably in the order presented. For example, the method comprising steps (a) and (b) means that the method can comprise steps (a) and (b) in the order presented, or the method can comprise steps (b) and (a) in the order presented. For example, the method comprising steps (a), (b), and (c) means that the method can comprise steps (a), (b), and (c) in the order presented, or the method can comprise steps (a), (c), and (b) in the order presented, or the method can comprise steps (c), (a), and (b) in the order presented, etc.

[0061] To solve the problem of the lack of etching agents and etching methods suitable for U3Si2 pellet fuel, an U3Si2 pellet fuel metallographic etching agent and a metallographic etching method are provided in an embodiment of the application. The etching agent and the etching method can clearly observe the morphology and size distribution of the crystal grains under a metallographic microscope, are simple to operate, have good use effect, and are suitable for fuel laboratory development and fuel engineering application production.

[0062] In a first aspect, the application provides an U3Si2 pellet fuel metallographic etching agent, the metallographic etching agent comprising glacial acetic acid, concentrated nitric acid, and deionized water, and the volume ratio of the glacial acetic acid, the concentrated nitric acid, and the deionized water being (52-60):(26-34):(10-18).

[0063] Preferably, the volume ratio of the glacial acetic acid, the concentrated nitric acid, and the deionized water is 56:30:14.

[0064] In a second aspect, the application provides a U3Si2 pellet fuel metallographic etching method, and the specific steps are as follows:

[0065] S1, place the U3Si2 pellet on the sample table of a hot mounting machine, fill the mounting resin material, and perform hot-pressing mounting; the hot-pressing mounting parameters are set as follows: pressure: 100-105 bar; temperature: 175-180℃; heating time: 4-5 min; cooling time: 3-4 min;

[0066] S2, take out the hot-mounted sample of the U3Si2 pellet, and grind it with 800#-1200# metallographic water sandpaper in sequence; place the ground surface of the sample on a polishing machine, and polish the sample to a mirror surface using a diamond suspension;

[0067] S3, measure 52-60 ml of glacial acetic acid, 10-18 ml of deionized water, and 26-34 ml of concentrated nitric acid to prepare a U3Si2 pellet special metallographic etchant; measure 20 ml of the etchant and place it in a plastic container, immerse the polished sample in the etchant for 30-50 s for etching treatment; and rinse the sample with clean water after etching and blow dry.

[0068] Place the U3Si2 pellet sample after etching treatment under a metallographic microscope, reasonably select the magnification according to the grain size, and collect the grain morphology image.

[0069] Example 1

[0070] The example provides a U3Si2 pellet fuel metallographic etching method, wherein the formula of the etchant used is: glacial acetic acid: 56 ml, deionized water: 14 ml, and concentrated nitric acid: 30 ml.

[0071] The specific etching method is as follows:

[0072] S1, place the U3Si2 pellet on the sample table of a hot mounting machine, fill the mounting resin material, and perform hot-pressing mounting; the hot-pressing mounting parameters are set as follows: pressure: 100 bar; temperature: 180℃; heating time: 4 min; cooling time: 3 min;

[0073] S2, take out the hot-mounted sample of the U3Si2 pellet, and grind it with 800#-1200# metallographic water sandpaper in sequence; place the ground surface of the sample on a polishing machine, and polish the sample to a mirror surface using a diamond suspension;

[0074] S3, measure glacial acetic acid: 56 ml, deionized water: 14 ml, concentrated nitric acid: 30 ml, configure into U3Si2 chip special metallographic etchant; measure 20 ml etchant into plastic vessel, put polished sample into etchant, immerse for 40 s for etching treatment; after etching, rinse with clean water and dry, get etched U3Si2 chip fuel sample.

[0075] Under metallographic microscope, collect grain morphology image of etched U3Si2 chip fuel sample, as shown in Figure 1 It is U3Si2 chip metallographic structure graph after magnification 200 times, as shown in Figure 2 It is U3Si2 chip metallographic structure graph after magnification 500 times. From Figure 1 and Figure 2 Grain boundary morphology in U3Si2 chip can be clearly seen.

[0076] Example 2

[0077] This example provides a U3Si2 chip fuel metallographic etching method, which is different from example 1 in that the etchant used in this example is different from example 1, and other processes are the same as example 1, specifically: glacial acetic acid: 52 ml, deionized water: 10 ml, concentrated nitric acid: 26 ml.

[0078] The specific etching method is:

[0079] S1, put U3Si2 chip on sample table of hot mounting machine, fill mounting resin material, and perform hot press mounting; the hot press mounting parameters are set as follows: pressure: 100 bar; temperature: 180℃; heating time: 4 min; cooling time: 3 min;

[0080] S2, take out hot mounting sample of U3Si2 chip, and grind U3Si2 chip metallographic sample on polishing and grinding machine using 800#-1200# metallographic water abrasive paper in sequence; the polishing and grinding machine rotation speed is set to 400 r / min, and the grinding time of each abrasive paper is 4 min; place the ground sample on polishing machine, and polish the sample to mirror surface using diamond suspension.

[0081] S3, measure glacial acetic acid: 52 ml, deionized water: 10 ml, concentrated nitric acid: 26 ml, configure into U3Si2 chip special metallographic etchant; measure 20 ml etchant into plastic vessel, put polished sample into etchant, immerse for 40 s for etching treatment; after etching, rinse with clean water and dry, get etched U3Si2 chip fuel sample. From Figure 3 and Figure 4 Grain boundary morphology in U3Si2 chip can also be clearly seen.

[0082] Example 3

[0083] The embodiment provides a U3Si2 pellet fuel metallographic etching method, and different from the embodiment 1, the etchant used in the embodiment is different from the embodiment 1, and other processes are the same as the embodiment 1, and specifically, the ice acetic acid is 60 ml, the deionized water is 18 ml, and the concentrated nitric acid is 34 ml.

[0084] The specific etching method is as follows:

[0085] S1, the U3Si2 pellet is placed on the sample table of the hot mounting machine, the mounting resin material is filled, and the hot pressing mounting is carried out; the hot pressing mounting parameters are set as follows: the pressure is 100 bar; the temperature is 180 DEG C; the heating time is 4 min; and the cooling time is 3 min;

[0086] S2, the hot mounting sample of the U3Si2 pellet is taken out, and the U3Si2 pellet metallographic sample is ground on the polishing and grinding machine in sequence by using 800#-1200# metallographic water abrasive paper; the rotating speed of the polishing and grinding machine is set to 400 r / min, and the grinding time of each abrasive paper is 4 min; the sample surface is placed on the polishing machine, and the sample is polished to a mirror surface by using diamond suspension;

[0087] S3, the ice acetic acid is 60 ml, the deionized water is 18 ml, and the concentrated nitric acid is 34 ml, and the U3Si2 pellet special metallographic etchant is configured; 20 ml of the etchant is taken and placed in a plastic container, the polished sample is soaked in the etchant for 40 s for etching treatment; after the sample is etched, it is washed with clean water and dried, and the etched U3Si2 pellet fuel sample is obtained. Figure 5 and Figure 6 It can also be clearly seen that the grain boundary morphology in the U3Si2 pellet.

[0088] Example 4

[0089] The embodiment provides a U3Si2 pellet fuel metallographic etching method, and different from the embodiment 1, the etchant used in the embodiment is different from the embodiment 1, and other processes are the same as the embodiment 1, and specifically, the ice acetic acid is 60 ml, the deionized water is 18 ml, and the concentrated nitric acid is 34 ml.

[0090] The specific etching method is as follows:

[0091] S1, the U3Si2 pellet is placed on the sample table of the hot mounting machine, the mounting resin material is filled, and the hot pressing mounting is carried out; the hot pressing mounting parameters are set as follows: the pressure is 100 bar; the temperature is 180 DEG C; the heating time is 4 min; and the cooling time is 3 min;

[0092] S2, take out the hot-embedded sample of U3Si2 pellet, and grind the U3Si2 pellet metallographic sample on a polishing and grinding machine using 800#-1200# metallographic water abrasive paper in sequence; the rotating speed of the polishing and grinding machine is set to 400 r / min, and the grinding time of each abrasive paper is 4 min; the sample surface is placed on a polishing machine, and the sample is polished to a mirror surface using a diamond suspension;

[0093] S3, measure ice acetic acid: 56 ml, deionized water: 14 ml, and concentrated nitric acid: 30 ml to configure a U3Si2 pellet special metallographic etchant; measure 20 ml of the etchant and put it into a plastic container, and then immerse the polished sample in the etchant for 50 s for etching treatment; after etching, the sample is washed with clean water and dried to obtain an etched U3Si2 pellet fuel sample. Figure 7 and Figure 8 The grain boundary morphology in the U3Si2 pellet can also be clearly seen.

[0094] Example 5

[0095] The embodiment provides a U3Si2 pellet fuel metallographic etching method, wherein the formula of the etchant used is: ice acetic acid: 56 ml, deionized water: 14 ml, and concentrated nitric acid: 30 ml. Different from example 1, the immersion time of the etchant in step S3 of the embodiment is 50 s, and other processes are the same as those of example 1.

[0096] The specific etching method is as follows:

[0097] S1, place the U3Si2 pellet on the sample table of the hot-embedding machine, fill the embedding resin material, and perform hot-pressing embedding; the hot-pressing embedding parameters are set as follows: pressure: 100 bar; temperature: 180℃; heating time: 4 min; and cooling time: 3 min;

[0098] S2, take out the hot-embedded sample of U3Si2 pellet, and grind the U3Si2 pellet metallographic sample on a polishing and grinding machine using 800#-1200# metallographic water abrasive paper in sequence; the rotating speed of the polishing and grinding machine is set to 400 r / min, and the grinding time of each abrasive paper is 4 min; the sample surface is placed on a polishing machine, and the sample is polished to a mirror surface using a diamond suspension;

[0099] S3, measure ice acetic acid: 56 ml, deionized water: 14 ml, and concentrated nitric acid: 30 ml to configure a U3Si2 pellet special metallographic etchant; measure 20 ml of the etchant and put it into a plastic container, and then immerse the polished sample in the etchant for 50 s for etching treatment; after etching, the sample is washed with clean water and dried to obtain an etched U3Si2 pellet fuel sample. Figure 9 and Figure 10The grain boundary morphology in the U3Si2 pellet can also be clearly seen.

[0100] Example 6

[0101] This example provides a U3Si2 pellet fuel metallographic etching method, wherein the formula of the etchant used is: glacial acetic acid: 56 ml, deionized water: 14 ml, concentrated nitric acid: 30 ml. Different from example 1, the speed of the polishing machine in step S2 of this example is set to 300 r / min, and other processes are the same as example 1.

[0102] The specific etching method is:

[0103] S1, place the U3Si2 pellet on the sample table of the hot mounting machine, fill the mounting resin material, and perform hot pressing mounting; the hot pressing mounting parameters are set as follows: pressure: 100 bar; temperature: 180℃; heating time: 4 min; cooling time: 3 min;

[0104] S2, take out the hot mounting sample of the U3Si2 pellet, and grind the U3Si2 pellet metallographic sample on the polishing machine using 800#-1200# metallographic water abrasive paper in turn; the speed of the polishing machine is set to 300 r / min, and each abrasive paper grinding time is 4 min; place the sample surface on the polishing machine, and polish the sample to a mirror surface using diamond suspension;

[0105] S3, measure glacial acetic acid: 56 ml, deionized water: 14 ml, concentrated nitric acid: 30 ml, and configure into a U3Si2 pellet special metallographic etchant; measure 20 ml of the etchant and place it in a plastic container, then place the polished sample in the etchant and soak for 40 s for etching treatment; after etching, rinse the sample with water and blow dry to obtain the etched U3Si2 pellet fuel sample. Figure 11 and Figure 12 The grain boundary morphology in the U3Si2 pellet can also be clearly seen.

[0106] Example 7

[0107] This example provides a U3Si2 pellet fuel metallographic etching method, wherein the formula of the etchant used is: glacial acetic acid: 56 ml, deionized water: 14 ml, concentrated nitric acid: 30 ml. Different from example 1, the speed of the polishing machine in step S2 of this example is set to 500 r / min, and other processes are the same as example 1.

[0108] The specific etching method is:

[0109] S1, place the U3Si2 pellet on the sample table of the hot-pressing machine, fill the embedding resin material, and perform hot-pressing embedding; the hot-pressing embedding parameters are set as follows: pressure: 100 bar; temperature: 180℃; heating time: 4 min; cooling time: 3 min;

[0110] S2, take out the hot-pressing sample of the U3Si2 pellet, and grind the U3Si2 pellet metallographic sample on a polishing and grinding machine using 800#-1200# metallographic water abrasive paper in sequence; the polishing and grinding machine is set to rotate at 500 r / min, and each abrasive paper is ground for 4 min; place the sample surface on a polishing machine, and polish the sample to a mirror surface using a diamond suspension;

[0111] S3, measure 56 ml of glacial acetic acid, 14 ml of deionized water, and 30 ml of concentrated nitric acid to prepare a U3Si2 pellet special metallographic etchant; measure 20 ml of the etchant and place it in a plastic container, and immerse the polished sample in the etchant for 40 s for etching treatment; after etching, rinse the sample with clean water and dry it to obtain an etched U3Si2 pellet fuel sample. Figure 13 and Figure 14 The grain boundary morphology in the U3Si2 pellet can also be clearly seen.

[0112] Example 8

[0113] The embodiment provides a U3Si2 pellet fuel metallographic etching method, wherein the formula of the etchant used is: glacial acetic acid: 56 ml, deionized water: 14 ml, and concentrated nitric acid: 30 ml. Different from example 1, the hot-pressing embedding parameters in step S1 of this embodiment are set as follows: pressure: 103 bar; temperature: 178℃; heating time: 4 min; and cooling time: 3 min. The other processes are the same as those in example 1.

[0114] The specific etching method is as follows:

[0115] S1, place the U3Si2 pellet on the sample table of the hot-pressing machine, fill the embedding resin material, and perform hot-pressing embedding; the hot-pressing embedding parameters are set as follows: pressure: 100 bar; temperature: 180℃; heating time: 4 min; cooling time: 3 min;

[0116] S2, take out the hot-pressing sample of the U3Si2 pellet, and grind the U3Si2 pellet metallographic sample on a polishing and grinding machine using 800#-1200# metallographic water abrasive paper in sequence; the polishing and grinding machine is set to rotate at 500 r / min, and each abrasive paper is ground for 4 min; place the sample surface on a polishing machine, and polish the sample to a mirror surface using a diamond suspension;

[0117] S3, measure glacial acetic acid: 56 ml, deionized water: 14 ml, concentrated nitric acid: 30 ml, configure into U3Si2 special metallographic etchant; measure 20 ml etchant into plastic vessels, put the polished sample in the etchant and immerse for 40 s for etching treatment; after etching, rinse the sample with clean water and dry to obtain the etched U3Si2 pellet fuel sample. Figure 15 and Figure 16 The grain boundary morphology in the U3Si2 pellet can also be clearly seen.

[0118] Example 9

[0119] This example provides a U3Si2 pellet fuel metallographic etching method, wherein the formula of the etchant used is: glacial acetic acid: 56 ml, deionized water: 14 ml, concentrated nitric acid: 30 ml. Different from example 1, the hot-pressing parameters in step S1 of this example are set as: pressure: 105 bar; temperature: 175℃; heating time: 5 min; cooling time: 4 min. Other processes are the same as example 1.

[0120] The specific etching method is:

[0121] S1, place the U3Si2 pellet on the sample table of the hot-pressing machine, fill the embedding resin material, and perform hot-pressing embedding; the hot-pressing embedding parameters are set as follows: pressure: 105 bar; temperature: 175℃; heating time: 5 min; cooling time: 4 min;

[0122] S2, take out the hot-pressing sample of the U3Si2 pellet, and grind the U3Si2 pellet metallographic sample on a polishing and grinding machine using 800#-1200# metallographic water abrasive paper in sequence; the polishing and grinding machine is set to rotate at 400 r / min, and each abrasive paper grinding time is 4 min; place the sample surface on a polishing machine, and polish the sample to a mirror surface using diamond suspension;

[0123] S3, measure glacial acetic acid: 56 ml, deionized water: 14 ml, concentrated nitric acid: 30 ml, configure into U3Si2 special metallographic etchant; measure 20 ml etchant into plastic vessels, put the polished sample in the etchant and immerse for 40 s for etching treatment; after etching, rinse the sample with clean water and dry to obtain the etched U3Si2 pellet fuel sample. Figure 17 and Figure 18 The grain boundary morphology in the U3Si2 pellet can also be clearly seen.

[0124] Comparative Example 1

[0125] The comparative example provides a U3Si2 pellet fuel metallographic etching method, which is different from example 1 in that the amount of glacial acetic acid used in this example is 50 ml, which belongs to the case of small amount of glacial acetic acid. The specific formula of the etchant used is: glacial acetic acid: 50 ml, deionized water: 14 ml, concentrated nitric acid: 30 ml.

[0126] The specific etching method is:

[0127] S1, place the U3Si2 pellet on the sample table of the hot mounting machine, fill the mounting resin material, and perform hot-pressing mounting; the hot-pressing mounting parameters are set as follows: pressure: 100 bar; temperature: 180°C; heating time: 4 min; cooling time: 3 min;

[0128] S2, take out the hot-mounted sample of the U3Si2 pellet, and grind the U3Si2 pellet metallographic sample on the polishing and grinding machine using 800#-1200# metallographic water abrasive paper in sequence; the polishing and grinding machine is set to rotate at 400 r / min, and each abrasive paper grinding time is 4 min; place the sample surface on the polishing machine, and polish the sample to a mirror surface using diamond suspension;

[0129] S3, measure glacial acetic acid: 50 ml, deionized water: 14 ml, and concentrated nitric acid: 30 ml, and configure them into a U3Si2 pellet special metallographic etchant; measure 20 ml of the etchant and place it in a plastic container, then immerse the polished sample in the etchant for 40 s for etching treatment; after etching, rinse the sample with water and dry it to obtain an etched U3Si2 pellet fuel sample. Figure 19 and Figure 20 It can be seen that the grain boundary morphology in the U3Si2 pellet is relatively blurred, and the grain boundary has been over-etched.

[0130] Comparative example 2

[0131] The comparative example provides a U3Si2 pellet fuel metallographic etching method, which is different from example 1 in that the amount of glacial acetic acid used in this example is 62 ml, which belongs to the case of excess glacial acetic acid. The specific formula of the etchant used is: glacial acetic acid: 62 ml, deionized water: 14 ml, concentrated nitric acid: 30 ml.

[0132] The specific etching method is:

[0133] S1, place the U3Si2 pellet on the sample table of the hot mounting machine, fill the mounting resin material, and perform hot-pressing mounting; the hot-pressing mounting parameters are set as follows: pressure: 100 bar; temperature: 180°C; heating time: 4 min; cooling time: 3 min;

[0134] S2, take out the hot-embedded sample of U3Si2 pellet, and grind the U3Si2 pellet metallographic sample on a polishing machine using 800#-1200# metallographic water abrasive paper in sequence; the polishing machine rotation speed is set to 400 r / min, and the grinding time of each abrasive paper is 4 min; the sample surface is placed on a polishing machine, and the sample is polished to a mirror surface using a diamond suspension;

[0135] S3, measure glacial acetic acid: 62 ml, deionized water: 14 ml, and concentrated nitric acid: 30 ml to configure a U3Si2 pellet special metallographic etchant; measure 20 ml of the etchant and place it in a plastic container, and then immerse the polished sample in the etchant for 40 s for etching treatment; after the sample is etched, it is washed with clean water and dried to obtain an etched U3Si2 pellet fuel sample. Figure 21 and Figure 22 It can be seen that the grain boundary morphology in the U3Si2 pellet is relatively blurred, and the grain boundary is over-etched.

[0136] Comparative Example 3

[0137] This comparative example provides a U3Si2 pellet fuel metallographic etching method, which is different from Example 1 in that the amount of concentrated nitric acid used in this example is 25 ml, which belongs to the case of a small amount of concentrated nitric acid. The specific formula of the etchant used is: glacial acetic acid: 56 ml, deionized water: 14 ml, and concentrated nitric acid: 25 ml.

[0138] The specific etching method is as follows:

[0139] S1, place the U3Si2 pellet on the sample table of the hot-embedding machine, fill the embedding resin material, and perform hot-pressing embedding; the hot-pressing embedding parameters are set as follows: pressure: 100 bar; temperature: 180℃; heating time: 4 min; cooling time: 3 min;

[0140] S2, take out the hot-embedded sample of U3Si2 pellet, and grind the U3Si2 pellet metallographic sample on a polishing machine using 800#-1200# metallographic water abrasive paper in sequence; the polishing machine rotation speed is set to 400 r / min, and the grinding time of each abrasive paper is 4 min; the sample surface is placed on a polishing machine, and the sample is polished to a mirror surface using a diamond suspension;

[0141] S3, measure glacial acetic acid: 56 ml, deionized water: 14 ml, and concentrated nitric acid: 25 ml to configure a U3Si2 pellet special metallographic etchant; measure 20 ml of the etchant and place it in a plastic container, and then immerse the polished sample in the etchant for 40 s for etching treatment; after the sample is etched, it is washed with clean water and dried to obtain an etched U3Si2 pellet fuel sample. Figure 23 and Figure 24It can be seen that, compared with Comparative Example 2, the grain boundary morphology in the U3Si2 pellet is more blurred.

[0142] Comparative Example 4

[0143] This comparative example provides a U3Si2 pellet fuel metallographic etching method, which is different from Example 1 in that the amount of concentrated nitric acid used in this example is 35 ml, which belongs to the case of excessive concentrated nitric acid. The specific formula of the etchant used is: glacial acetic acid: 56 ml, deionized water: 14 ml, concentrated nitric acid: 35 ml.

[0144] The specific etching method is as follows:

[0145] S1, place the U3Si2 pellet on the sample table of the hot mounting machine, fill the mounting resin material, and perform hot pressing mounting; the hot pressing mounting parameters are set as follows: pressure: 100 bar; temperature: 180℃; heating time: 4 min; cooling time: 3 min;

[0146] S2, take out the hot mounting sample of the U3Si2 pellet, and grind the U3Si2 pellet metallographic sample on the polishing and grinding machine using 800#-1200# metallographic water abrasive paper in sequence; the polishing and grinding machine speed is set to 400 r / min, and each abrasive paper grinding time is 4 min; place the sample surface on the polishing machine, and polish the sample to a mirror surface using diamond suspension;

[0147] S3, measure glacial acetic acid: 56 ml, deionized water: 14 ml, and concentrated nitric acid: 35 ml to prepare a U3Si2 pellet special metallographic etchant; measure 20 ml of the etchant and place it in a plastic container, then immerse the polished sample in the etchant for 40 s for etching treatment; after etching, rinse the sample with water and dry it to obtain an etched U3Si2 pellet fuel sample. Figure 25 and Figure 26 It can be seen that, compared with Comparative Example 2, the grain boundary morphology in the U3Si2 pellet is more blurred.

[0148] Comparative Example 5

[0149] This comparative example provides a U3Si2 pellet fuel metallographic etching method, which is different from Example 1 in that the amount of deionized water used in this example is 9 ml, which belongs to the case of a small amount of deionized water. The specific formula of the etchant used is: glacial acetic acid: 56 ml, deionized water: 9 ml, concentrated nitric acid: 30 ml.

[0150] The specific etching method is as follows:

[0151] S1, place the U3Si2 ingot on the sample table of the hot-embedding machine, fill the embedding resin material, and perform hot-press embedding; the hot-press embedding parameters are set as follows: pressure: 100 bar; temperature: 180°C; heating time: 4 min; cooling time: 3 min;

[0152] S2, take out the hot-embedded sample of the U3Si2 ingot, and grind the U3Si2 ingot metallographic sample on a polishing and grinding machine using 800#-1200# metallographic water abrasive paper in sequence; the polishing and grinding machine is set to rotate at 400 r / min, and each abrasive paper is ground for 4 min; place the sample surface on a polishing machine, and polish the sample to a mirror surface using a diamond suspension;

[0153] S3, measure 56 ml of glacial acetic acid, 9 ml of deionized water, and 30 ml of concentrated nitric acid to prepare a U3Si2 ingot special metallographic etchant; measure 20 ml of the etchant and place it in a plastic container, and then immerse the polished sample in the etchant for 40 s for etching treatment; after etching, rinse the sample with water and dry it to obtain an etched U3Si2 ingot fuel sample. Figure 27 and Figure 28 It can be seen that, compared with Comparative Example 2, the grain morphology in the U3Si2 ingot is clearer, but the grain boundary is still not visible.

[0154] Comparative Example 6

[0155] This comparative example provides a U3Si2 ingot fuel metallographic etching method, which is different from Example 1 in that the amount of deionized water used in this example is 20 ml, which belongs to the case of excessive deionized water. The specific formula of the etchant used is: glacial acetic acid: 56 ml, deionized water: 20 ml, and concentrated nitric acid: 30 ml.

[0156] The specific etching method is as follows:

[0157] S1, place the U3Si2 ingot on the sample table of the hot-embedding machine, fill the embedding resin material, and perform hot-press embedding; the hot-press embedding parameters are set as follows: pressure: 100 bar; temperature: 180°C; heating time: 4 min; cooling time: 3 min;

[0158] S2, take out the hot-embedded sample of the U3Si2 ingot, and grind the U3Si2 ingot metallographic sample on a polishing and grinding machine using 800#-1200# metallographic water abrasive paper in sequence; the polishing and grinding machine is set to rotate at 400 r / min, and each abrasive paper is ground for 4 min; place the sample surface on a polishing machine, and polish the sample to a mirror surface using a diamond suspension;

[0159] S3, measure glacial acetic acid: 56 ml, deionized water: 20 ml, concentrated nitric acid: 30 ml, configure into U3Si2 ingot special metallographic etchant; measure 20 ml etchant and put into plastic container, put polished sample into etchant and immerse for 40 s for etching treatment; after etching, rinse sample with clean water and dry, to obtain etched U3Si2 ingot fuel sample. From Figure 29 and Figure 30 It can be seen that compared with Comparative Example 2, the grain morphology in the U3Si2 ingot is clearer, but the grain boundary still cannot be observed.

[0160] Comparative Example 7

[0161] This example provides a U3Si2 ingot fuel metallographic etching method, which is different from Example 1 in that the formula of the etchant of this example does not contain glacial acetic acid, and the amount of glacial acetic acid is replaced by concentrated nitric acid. The specific formula of the etchant used is deionized water: 14 ml, concentrated nitric acid: 86 ml.

[0162] The specific etching method is as follows:

[0163] S1, place the U3Si2 ingot on the sample table of the hot mounting machine, fill the mounting resin material, and perform hot pressing mounting; the hot pressing mounting parameters are set as follows: pressure: 100 bar; temperature: 180℃; heating time: 4 min; cooling time: 3 min;

[0164] S2, take out the hot mounting sample of the U3Si2 ingot, and grind the U3Si2 ingot metallographic sample on the polishing and grinding machine using 800#-1200# metallographic water abrasive paper in sequence; the rotation speed of the polishing and grinding machine is set to 400 r / min, and the grinding time of each abrasive paper is 4 min; place the ground sample on the polishing machine, and polish the sample to a mirror surface using diamond suspension;

[0165] S3, measure deionized water: 14 ml, concentrated nitric acid: 86 ml, configure into U3Si2 ingot special metallographic etchant; measure 20 ml etchant and put into plastic container, put polished sample into etchant and immerse for 40 s for etching treatment; after etching, rinse sample with clean water and dry, to obtain etched U3Si2 ingot fuel sample. From Figure 31 It can be seen that the grains and grain boundaries in the U3Si2 ingot cannot be clearly observed.

[0166] Comparative Example 8

[0167] This example provides a U3Si2 ingot fuel metallographic etching method, which is different from Example 1 in that the formula of the etchant of this example does not contain concentrated nitric acid, and the amount of concentrated nitric acid is replaced by glacial acetic acid. The specific formula of the etchant used is glacial acetic acid: 86 ml, deionized water: 14 ml.

[0168] The specific etching method is:

[0169] S1, place the U3Si2 core block on the sample table of the hot embedding machine, fill the embedding resin material, and perform hot-press embedding; the hot-press embedding parameters are set as follows: pressure: 100 bar; temperature: 180°C; heating time: 4 min; cooling time: 3 min;

[0170] S2, take out the hot-embedded sample of the U3Si2 core block, and grind the U3Si2 core block metallographic sample on a polishing and grinding machine using 800#-1200# metallographic water abrasive paper in sequence; the polishing and grinding machine is set to rotate at 400 r / min, and each abrasive paper is ground for 4 min; place the sample surface on a polishing machine, and polish the sample to a mirror surface using a diamond suspension;

[0171] S3, measure 86 ml of glacial acetic acid and 14 ml of deionized water to prepare a U3Si2 core block special metallographic etchant; measure 20 ml of the etchant and place it in a plastic container, and then immerse the polished sample in the etchant for 40 s for etching treatment; after etching, rinse the sample with clean water and dry it to obtain an etched U3Si2 core block fuel sample. Figure 22 It can be seen that the crystal grains and grain boundaries in the U3Si2 core block cannot be clearly observed.

[0172] Comparative Example 9

[0173] This example provides a U3Si2 core block fuel metallographic etching method, which is different from Example 1 in that the etchant of this comparative example does not contain deionized water, and the amount of deionized water is replaced by glacial acetic acid. The specific formula of the etchant used is: glacial acetic acid: 70 ml, concentrated nitric acid: 30 ml.

[0174] The specific etching method is:

[0175] S1, place the U3Si2 core block on the sample table of the hot embedding machine, fill the embedding resin material, and perform hot-press embedding; the hot-press embedding parameters are set as follows: pressure: 100 bar; temperature: 180°C; heating time: 4 min; cooling time: 3 min;

[0176] S2, take out the hot-embedded sample of the U3Si2 core block, and grind the U3Si2 core block metallographic sample on a polishing and grinding machine using 800#-1200# metallographic water abrasive paper in sequence; the polishing and grinding machine is set to rotate at 400 r / min, and each abrasive paper is ground for 4 min; place the sample surface on a polishing machine, and polish the sample to a mirror surface using a diamond suspension;

[0177] S3, measure glacial acetic acid: 70 ml, concentrated nitric acid: 30 ml, configured into U3Si2 ingot special metallographic etchant; measure 20 ml etchant into plastic vessel, put polished sample into etchant, soak 40 s for etching treatment; sample is washed by clean water and dried after etching, get etched U3Si2 ingot fuel sample. Figure 33 It can be seen that the crystal grain and the grain boundary in U3Si2 ingot cannot be clearly observed.

[0178] Finally, it should be noted that: the above examples are used to illustrate the technical solutions of the present application, rather than limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should be covered in the scope of the claims and the description of the present application.

Claims

1. A U3Si2 chip fuel metallographic etchant, characterized in that, The metallographic etchant comprises glacial acetic acid, concentrated nitric acid and deionized water, wherein the volume ratio of glacial acetic acid, concentrated nitric acid and deionized water is (52~60):(26~34):(10~18).

2. The U3Si2 chip fuel metallographic etchant according to claim 1, characterized in that, The volume ratio of glacial acetic acid, concentrated nitric acid, and deionized water is 56:30:

14.

3. A metallographic etching method for U3Si2 pellet fuel, characterized in that, Etching was performed using the U3Si2 chip fuel metallographic etchant as described in claim 1 or 2.

4. The metallographic etching method for U3Si2 pellet fuel according to claim 3, characterized in that, The specific method for etching U3Si2 fuel pellets is as follows: after polishing, the U3Si2 fuel pellets are immersed in an etchant for etching. After etching, the U3Si2 fuel pellets are rinsed with water and then dried.

5. The metallographic etching method for U3Si2 pellet fuel according to claim 4, characterized in that, The U3Si2 fuel pellets are immersed in the etchant for 30 to 50 seconds.

6. The metallographic etching method for U3Si2 pellet fuel according to claim 4, characterized in that, The polishing method for the U3Si2 pellet fuel is as follows: the U3Si2 pellet fuel is ground on a polishing machine using metallographic water film sandpaper, and then the ground U3Si2 pellet fuel surface is placed on a polishing machine to polish the U3Si2 pellet fuel to a mirror finish.

7. The metallographic etching method for U3Si2 pellet fuel according to claim 6, characterized in that, The metallographic water film sandpaper used is 800# to 1200# metallographic water abrasive sandpaper, and the grinding time for each pass of the metallographic water film sandpaper is 3 min to 5 min.

8. The metallographic etching method for U3Si2 pellet fuel according to claim 6, characterized in that, The rotational speed of the polishing mill is set to 300 r / min to 500 r / min.

9. The metallographic etching method for U3Si2 pellet fuel according to claim 8, characterized in that, The rotational speed of the polishing mill is set to 400 r / min.

10. The metallographic etching method for U3Si2 pellet fuel according to claim 4, characterized in that, Before polishing, the U3Si2 fuel pellets need to be embedded.

11. The metallographic etching method for U3Si2 pellet fuel according to claim 10, characterized in that, The specific method of the inlay process is as follows: the U3Si2 fuel pellet is placed on the sample stage of the hot inlay machine, and inlay resin material is filled and hot-pressed inlay is performed.

12. The metallographic etching method for U3Si2 pellet fuel according to claim 11, characterized in that, The parameters for the hot-pressing embedding are set as follows: pressure: 100 bar to 105 bar; Temperature: 175℃~180℃; Heating time: 4min~5min; Cooling time: 3min~4min.

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