A method for studying the irradiation damage behavior of magnesium-based fuel matrix under simulated service conditions

Abstract

The present invention discloses a method for studying the irradiation damage behavior of a magnesium-based fuel matrix under simulated service conditions. The method comprises the following steps: using SRIM software to respectively calculate the penetration depths of Mg+ and He+ of different energies in a magnesium alloy; preparing a target material capable of adjusting a certain beam density of Mg+; extracting the vacuum of an irradiation target chamber, setting the neutron injection rate required for the irradiation experiment according to the SRIM calculation results, and simultaneously injecting Mg+ and He+ ion beams into the sample; using FIB to prepare transmission electron microscope samples along the irradiation depth of the irradiated sample for characterizing the irradiation damage behavior of the magnesium-based fuel matrix caused by neutron irradiation and fission gas; and by using He+ and Mg+ dual-beam ion coordinated irradiation of magnesium alloy samples, the method can effectively and conveniently realize the study of the irradiation damage behavior of the Mg alloy fuel matrix material under service conditions, and simultaneously realize the rapid screening of heat-resistant Mg alloy systems for fuel matrices.

Description

Technical Field

[0001] The present invention relates to research on nuclear fuel cycle and radiation effects, and in particular to a method for studying the radiation damage behavior of a magnesium-based fuel matrix under simulated service conditions. Background Art

[0002] Following the U.S. Department of Energy's "De-enrichment Program," UMo / Al fuel, due to its high uranium loading and excellent service performance, has become the mainstream development direction for research reactor fuel elements worldwide. However, as service temperatures rise and burnup increases, UMo / Al fuel still faces failure risks such as pillow deformation and blistering due to radiation swelling and reduced thermal conductivity, seriously affecting reactor operational safety.

[0003] To address this issue, researchers have attempted to replace Al with a magnesium (Mg) matrix that does not react with U or Mo, resulting in the formation of UMo / Mg / Al fuel, which is widely considered the most promising solution. Although multiple off-core research results have shown that UMo / Mg / Al fuel exhibits good mechanical and thermal properties, it is not yet known whether UMo / Mg / Al fuel, especially the Mg alloy as the fuel matrix, can still maintain good high-temperature strength and ductility after being damaged by high-dose fast neutron irradiation, without significantly affecting its neutron economy and thermal conductivity. Therefore, screening a heat-resistant Mg alloy system for nuclear use and understanding its service performance are the primary issues that need to be urgently addressed in this field.

[0004] Under service conditions, Mg alloy fuel matrices are primarily damaged by the combined effects of neutron irradiation and the recoil of fuel fission fragments (fission gases), which in turn affects their thermal and mechanical properties. The high cost, long cycle times, and numerous interfering factors (such as a broad neutron energy spectrum and uneven temperature distribution) of reactor neutron irradiation hinder the selection of Mg alloy matrix materials and the study of their irradiation damage behavior.

[0005] Ion irradiation, because its initial processes, such as atomic displacement, closely resemble those of neutron irradiation, offers numerous advantages, including single, stable energy, controllable temperature, low experimental cost, short cycle times, and virtually no radioactivity. Therefore, ion irradiation is widely used internationally to simulate the neutron damage behavior of materials. However, while conventional nuclear structural materials only need to consider damage caused by neutron irradiation, magnesium alloys, as fuel matrix materials, must consider the combined effects of neutron irradiation and fission gas. However, no methods have been reported to study the irradiation damage behavior of magnesium-based fuel matrices under service conditions. Therefore, an effective and convenient research method is necessary. Summary of the Invention

[0006] In response to the problems existing in the prior art, the purpose of the present invention is to provide a research method for the radiation damage behavior of magnesium-based fuel matrices under simulated service conditions, which is mainly used to effectively and conveniently realize the research on the radiation damage behavior of Mg alloy fuel matrix materials under service conditions, and at the same time realize the rapid screening of heat-resistant Mg alloy systems for fuel matrices.

[0007] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows.

[0008] A method for studying the irradiation damage behavior of magnesium-based fuel matrix under simulated service conditions is proposed. + and Mg + Dual-beam ion coordinated irradiation simulates the radiation damage in magnesium-based fuel matrix under service conditions, in which He gas is used to generate He + Ion irradiation simulates the radiation damage caused by the recoil of fuel fission gas; MgO is used as a target to generate ions (Mg + ) Irradiation simulation of radiation damage caused by neutron irradiation, comprising the following steps:

[0009] Step 1: SRIM simulation: SRIM software is used to calculate different energy Mg + and He + The depth of incidence in magnesium alloys is determined by the energy range of the ion accelerator and the depth of focused ion beam micro-nano processing. + and He + The coordinated irradiation of Mg + and He + There are common observable damage areas in irradiation;

[0010] Step 2: Beam current adjustment: Prepare a beam current density Mg + The target material is selected and the beam centering and irradiation area are debugged;

[0011] Step 3: Sample pretreatment before irradiation: mainly includes sample cutting, mechanical grinding and polishing, electrolytic polishing, ultrasonic cleaning and metallographic inspection;

[0012] Step 4: Dual-beam ion coordinated irradiation experiment: Draw the vacuum of the irradiation target chamber, set the neutron injection required for the irradiation experiment according to the SRIM calculation results, and set the required irradiation temperature. + and He + The ion beam is simultaneously injected into the sample;

[0013] Step 5. Preparation and characterization of irradiation damaged samples: Referring to the results of the irradiation damage layer depth calculated by SRIM, the irradiated samples were micro-nano processed along the irradiation depth direction using a focused ion beam scanning electron microscope (FIB) to prepare transmission electron microscope samples for characterizing the irradiation damage behavior of the magnesium-based fuel matrix caused by neutron irradiation and fission gas.

[0014] Based on the technical solution provided by the present invention, further improvements are made.

[0015] Different energies of Mg calculated according to SRIM + ions and He + The depth of the damaged layer of ions in Mg alloy and the maximum beam density that can be obtained under different irradiation energies are used to determine the Mg + The ion irradiation energy is 1.5MeV, He + The ion irradiation energy was 100 keV.

[0016] Further optimization of the above technical solution: the higher the electronegativity of the element, the easier it is to combine electrons to form negative ions. Since Mg has negative electron affinity, it is not easy to form metastable negative ions, so it is difficult to obtain strong Mg + As for the ion beam current, only the beam current drawn out by MgO can reach above 10nA after reaching the target chamber, which meets the experimental requirements. Therefore, the target material is MgO.

[0017] After further optimization and improvement, the irradiated sample size is 1 mm×3 mm×5 mm.

[0018] Preferably, considering Mg + and He + Comparative analysis of radiation damage between single / co-irradiated samples, the He + The ion irradiation area is 10mm×10mm, Mg + The ion irradiation area is 10mm×6mm, He + ions and Mg + The ion cooperative irradiation area is 10 mm × 3 mm.

[0019] Further optimization and improvement to ensure Mg + and He + The ion beam has a sufficiently large cooperative irradiation area and independent irradiation area, and the Mg + and He + The incident angle of the ion beam and the sample normal are both 22.5°, Mg + and He + The angle between the ion beams is 45°.

[0020] Preferably, the irradiation temperature is 200°C;

[0021] With further optimization and improvement, the effective depth range of the FIB micro-nano processed sample is 500nm-1000nm.

[0022] Compared with the prior art, the technical effect achieved by the present invention is: providing a research method for the irradiation damage behavior of magnesium-based fuel matrix under simulated service conditions, by using He + and Mg + Dual-beam ion collaborative irradiation of magnesium alloy specimens can effectively and conveniently study the radiation damage behavior of Mg alloy fuel matrix materials under service conditions, while also enabling rapid screening of heat-resistant Mg alloy systems for fuel matrices. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 1.5MeV Mg + SRIM simulation results of ion-irradiated Mg alloy.

[0024] Figure 2 100keV He + SRIM simulation results of ion-irradiated Mg alloy.

[0025] Figure 3 For He + and Mg + Dual-beam ion single / cooperative irradiation area and size.

[0026] Figure 4 For He + and Mg + Incident beam angle distribution of dual-beam ion cooperative irradiation. DETAILED DESCRIPTION

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] like Figure 1-Figure 4 As shown, a research method for simulating the irradiation damage behavior of a magnesium-based fuel matrix under service conditions includes the following steps:

[0029] Step 1: Use the “Ion Distributive and Quick Calculation of Damage” function of the Stopping and Range of Ions to Matter (SRIM) software to calculate the Mg distribution at different energies (10 keV-10 MeV). + and He + The incident depth in magnesium alloy, combined with the acceleration energy of the ion accelerator itself and the micro-nano processing depth of FIB in magnesium alloy, are Mg+ and He + The ion beam selects the appropriate injection energy to obtain the data of the irradiation defect (vacancy) concentration distribution with depth, and then uses the calculation formula between the off-site damage rate (D isl ocation PerAtom, dpa) and the irradiation defect concentration to obtain the Mg at a specific energy. + / He + The relationship curve between ion beam irradiation damage (dpa)-irradiation depth-ion concentration is used for Mg + and He + The coordinated irradiation of Mg + and He + There is a common irradiation damage area within a certain depth of the magnesium alloy caused by ion beam;

[0030] Step 2: The ion irradiation experiment requires that the sample surface is flat and free of stress damage layer. Therefore, before the ion irradiation experiment, the sample needs to be pretreated, mainly including sample cutting, mechanical grinding and polishing, electrolytic polishing, ultrasonic cleaning and metallographic inspection. The sample is preliminarily processed using equipment such as a wire cutting machine to ensure that the sample can be placed in the irradiation target chamber. Sandpaper of different particle sizes (400#, 600#, 800#, 1000#, 1500#, 2000#, 5000#) is used to grind and polish the cut sample surface in sequence until the sample surface reaches a mirror effect. Electrolytic polishing is used to remove fine scratches and stress layers after mechanical grinding and polishing. The electrolyte is 10% perchloric acid + 90% alcohol solution, and the temperature is between -30℃ and -25℃. After polishing, it is immediately rinsed with alcohol, and the sample surface is observed with a metallographic microscope to confirm that there are no scratches or distortion on the surface.

[0031] Step 3: First, according to Mg + The characteristics of the ion beam can produce high beam current density Mg from pure Mg and various Mg-containing compounds. + Ion beam target; secondly, combined with the energy range of the accelerator, adjust and test Mg at different energies + The beam current density of the ion beam is determined by screening the optimal injection energy based on the obtained beam current intensity; and the appropriate He is adjusted using the same method. + The injection energy of the ion beam is controlled by adjusting the shape of the magnetic confinement coil and the deflection electrode. + and He + Ion beam centering and irradiation area;

[0032] Step 4: Start the mechanical pump and molecular pump in sequence to reduce the vacuum degree of the irradiation target chamber to 1×10 -4Pa, the sample is heated by heating the accelerating resistance wire behind the irradiation sample stage, and the temperature of the sample is controlled by a temperature measuring thermocouple; then, according to the relationship between the ion beam irradiation damage (dpa) and the ion injection amount obtained by SRIM calculation, the Mg + and He + Ion beam fluence counter, and Mg + and He + The ion beam is injected into the sample at the same time, and the irradiation experiment is completed when the counter stops counting;

[0033] Step 5: Refer to the specific energy Mg obtained by SRIM calculation + and He + The depth of the irradiation damage layer of the ion beam is determined, and the irradiated sample is micro-nano processed along the irradiation depth direction using a focused ion beam scanning electron microscope (FIB). The area of ​​the processed sample is controlled by adjusting the beam size, micro-nano processing time, and processing area size. When a sample of sufficient area is obtained, the sample is welded to the nanomanipulator using an ion beam, and the ion beam current is adjusted again to thin the sample step by step until the electron beam can easily penetrate the sample, completing the preparation of the transmission electron microscope sample. The different imaging modes of the transmission electron microscope can be used to observe the number, size, type, density and distribution of irradiation defects in the sample, thereby realizing the characterization and analysis of the irradiation damage behavior of the magnesium-based fuel matrix.

[0034] The above is a preferred embodiment of the present invention. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the principles and core ideas of the present invention. These modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method for studying the irradiation damage behavior of a magnesium-based fuel matrix under simulated service conditions, comprising the following steps: Step 1: SRIM simulation: SRIM software is used to calculate different energy Mg + and He + The depth of incidence in magnesium alloys is determined by the energy range of the ion accelerator and the depth of focused ion beam micro-nano processing. + and He + The coordinated irradiation of Mg + and He + There are common observable damage areas in irradiation; Step 2: Beam current adjustment: Prepare a beam current density Mg + The target material is selected and the beam centering and irradiation area are debugged; Step 3: Pre-treat the sample before irradiation to ensure that the sample surface is flat and has no stress damage layer; Step 4: Dual-beam ion coordinated irradiation experiment: Draw the vacuum of the irradiation target chamber, set the neutron injection required for the irradiation experiment according to the SRIM calculation results, and set the required irradiation temperature. + and He + The ion beam is simultaneously injected into the sample; Step 5. Preparation and characterization of irradiation damaged samples: Referring to the results of the irradiation damage layer depth calculated by SRIM, the irradiated samples are micro-nano processed along the irradiation depth direction using a focused ion beam to prepare transmission electron microscopy samples for characterizing the irradiation damage behavior of the magnesium-based fuel matrix caused by neutron irradiation and fission gas.

2. The method according to claim 1, characterized in that Different energies of Mg calculated according to SRIM + ions and He + The depth of the damaged layer of ions in Mg alloy and the maximum beam density that can be obtained under different irradiation energies are used to determine the Mg + The ion irradiation energy is 1.5MeV, He + The ion irradiation energy was 100 keV.

3. The method according to claim 2, characterized in that The method according to claim 1, characterized in that the sample pretreatment before irradiation includes sample cutting, mechanical grinding and polishing, electrolytic polishing, ultrasonic cleaning and metallographic inspection.

4. The method according to claim 3, characterized in that The target material is MgO.

5. The method according to claim 4, characterized in that The irradiated sample has a size of 1 mm×3 mm×5 mm.

6. The method according to claim 1, characterized in that Consider Mg + and He + Comparative analysis of radiation damage between single / co-irradiated samples, the He + The ion irradiation area is 10mm×10mm, Mg + The ion irradiation area is 10mm×6mm, He + ions and Mg + The ion cooperative irradiation area is 10 mm × 3 mm.

7. The method according to claim 1, characterized in that The Mg + and He + The incident angle of the ion beam and the sample normal are both 22.5°, Mg + and He + The angle between the ion beams is 45°.

8. The method according to claim 1, characterized in that The irradiation temperature is 200°C.

9. The method according to claim 1, characterized in that The effective depth range of the focused ion beam micro-nano processing sample is 600 μm-1000 μm.

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