U3Si2-UO2 dual-phase structure fuel rod

Abstract

The invention discloses a U3Si2-UO2 dual-phase structure fuel rod, which comprises an inner layer filled with U3Si2 small balls in a dispersion manner, and an outer layer filled with U3Si2 small balls in a dispersion manner, the outer layer is a UO2 fuel layer of an annular structure, and the outer layer wraps the inner layer; and the outer layer is wrapped with the wrapping shell, and an air cavity is formed between the outer layer and the wrapping shell. On the basis of ATF accident-resistant fuel, a fuel rod of a modular layered structure is provided, and U3Si2 small balls are embedded into a UO2 matrix to form a U3Si2-UO2 dual-phase structure fuel rod structure, so that the uranium density is improved, and the accident fault-tolerant capability is enhanced. When the volume ratio of the uranium silicide pellets in the inner layer area is 35%, the result is optimal, high initial keff, long service life and deep burnup are achieved, the possibility of reactor core operation accidents can be effectively reduced through the temperature reactivity coefficient with the minimum fluctuation, the design conforms to the design criterion of the pressurized water reactor, and the method is suitable for popularization and application. And the method has reference significance on related research of ATF accident fault-tolerant materials.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of nuclear reactor fuel, more particularly, the present application relates to a U3Si2-UO2 dual-phase structure fuel rod. BACKGROUND

[0002] Hualong No.1 (HPR1000) is the third generation nuclear power water reactor core in China, which is also a core with independent intellectual property rights. The core is composed of 177 fuel assemblies, and the operation mode is Mode-G; the reactor output thermal power is 3050MW, and the corresponding linear power density is 173.8W / cm. Compared with the traditional second-generation million-kilowatt core, Hualong No.1 reactor reduces the linear power density while increasing the total power output, thereby increasing the core safety margin. HPR1000 absorbs the reactor design experience at home and abroad, and has the advantages of advanced nature, economy and safety. The results obtained by using 177 cores for Monte Carlo program simulation are more realistic and more convenient for studying the neutron physics performance of different materials.

[0003] The Fukushima nuclear reactor material leakage accident in Japan in 2011 caused a major disaster, and also led people to question the UO2-Zr fuel alloy system used in the Fukushima boiling water reactor, so the design and development of accident tolerant fuel (ATF) emerged as the times require, which has the characteristics of better high-temperature mechanical properties, chemical stability and fission product containment capability. The improvement of the accident tolerance capability of nuclear fuel can be achieved by many methods, and the use of high uranium density fuel to improve the thermal conductivity and uranium density is one of the very excellent methods.

[0004] The ATF candidate materials are UN, U3Si2 and U3Si5, which all show great thermal conductivity compared with UO2. More importantly, considering the accident tolerance, the electrical conductivity of these candidate materials is proportional to the temperature, and increases with the increase of temperature - which is in sharp contrast to UO2. Under normal operation and accident conditions, the improvement of these thermal conductivities greatly reduces the cladding and fuel peak temperature, and also enhances the overall bearing capacity of the system under severe accident conditions. At the same time, compared with oxides, silicides such as U3Si2 provide higher metal density and better resistance to steam oxidation than UN. Therefore, U3Si2 is one of the good ATF candidate materials.

[0005] Despite its many superior properties, U3Si2's oxidation resistance under accident conditions has been questioned. Migdisov et al. investigated the mechanism of U3Si2's instability in light water reactor environments at temperatures above 300°C, finding that the oxidation stability of pure uranium silicide is determined by the USiO4 protective layer formed on its surface. This protective layer destabilizes at temperatures above 300°C, leading to the complete oxidation of uranium silicide to silicon dioxide and ultimately core fragmentation. Furthermore, the study found that pure U3Si2 has poorer oxidation resistance than UO2, exhibiting lower oxidation stability in light water reactor environments. Therefore, U3Si2 has an adverse effect in light water reactor environments under cladding failure conditions. Given that the operating temperature of the 177 core light water reactor is above 300 degrees Celsius, the reactivity of pure silicided U3Si2 would be problematic for the operation of U3Si2 pellets in the reactor and for the stability of uranium as a light water reactor fuel in severe accidents. If it is to be used in light water reactors to replace UO2, it must be improved. U3Si2-UO2 dual-phase fuel pellets are considered one of the feasible improvement options.

[0006] Theoretically, fabricating a composite core using U3Si2 and UO2 can leverage the advantages of both materials simultaneously. U3Si2 can increase the uranium density and thermal conductivity of the core, while UO2 possesses stronger corrosion resistance and acts as a barrier to prevent direct water contact with U3Si2, thus reducing risks. Summary of the Invention

[0007] One object of the present invention is to solve at least the above-mentioned problems and / or defects, and to provide at least the advantages described below.

[0008] To achieve these and other advantages according to the present invention, the present invention provides a U3Si2-UO2 dual-phase fuel rod, comprising:

[0009] The inner layer is filled with U3Si2 microspheres.

[0010] The outer layer is a ring-shaped UO2 fuel layer that wraps around the outside of the inner layer.

[0011] A shell is provided to cover the outside of the outer layer, and an air cavity is provided between the outer layer and the shell.

[0012] Preferably, the U3Si2 microspheres in the inner layer are separated by UO2 fuel.

[0013] Preferably, the U3Si2 microspheres have different or the same diameter.

[0014] Preferably, the diameter of the U3Si2 microspheres is 580–787 μm.

[0015] Preferably, the U3Si2 microspheres have a filling rate of 20% to 52% in the inner layer, and a total volume of 1.19 million to 2.97 million cm³. 3 .

[0016] Preferably, the UO2 fuel layer 235 The U enrichment level was 4.4%.

[0017] Preferably, the U3Si2 microspheres are... 235 The U enrichment level was 4.4%.

[0018] Preferably, the material of the cladding is Zr-4 alloy.

[0019] An application of a U3Si2-UO2 dual-phase fuel rod is disclosed, wherein the U3Si2-UO2 dual-phase fuel rod is used for loading fuel assemblies in a nuclear reactor; wherein the fuel assembly is arranged in a 17×17 configuration, comprising 264 U3Si2-UO2 dual-phase fuel rods and 25 control rods; the reactor core comprises 289 fuel assemblies arranged in a 17×17 configuration.

[0020] This invention offers at least the following advantages: Based on ATF-resistant fuel, this invention proposes a modular, layered fuel rod structure. U3Si2 microspheres are embedded within a UO2 matrix to form a U3Si2-UO2 dual-phase fuel rod structure, thereby increasing uranium density and enhancing accident tolerance. This invention employs a silicide microsphere dispersion scheme derived from TRISO particle technology, designing three different U3Si2 microsphere loading schemes with varying diameters. Monte Carlo simulations are used to conduct in-depth studies on the neutronics performance, physical parameters, and safety parameters of each scheme. Results show that the U3Si2-UO2 dual-phase fuel rod structure exhibits high uranium density and good neutron economy. Simultaneously, the core neutron spectrum exhibits hardening in the low-energy region, and the degree of hardening varies with burnup and neutron poison content. When comparing different fuel volume loading schemes, it was found that when the silicide microspheres in the inner layer of the fuel rod account for 35% of the fuel volume, it has a higher initial k-value. eff The longer lifespan, deeper burnup, and minimal temperature reactivity coefficient can effectively reduce the possibility of core operation accidents. The stable effective fraction of delayed neutrons and the relatively stable lifetime of transient neutrons are most conducive to the safe operation of the reactor. Therefore, U3Si2-UO2 two-phase fuel rods with a uranium silicide sphere content of 35% in the inner layer of the fuel rod are potentially feasible candidates for accident-tolerant fuel (ATF).

[0021] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the transverse cross-sectional structure of the U3Si2-UO2 dual-phase fuel rod of the present invention;

[0023] Figure 2 A schematic diagram of the arrangement of U3Si2-UO2 dual-phase fuel rods in a fuel assembly;

[0024] Figure 3 The effective multiplication factor (k) of the reactor core loaded with U3Si2-UO2 dual-phase fuel rods of Examples 1-3 and UO2 fuel rods of Comparative Example 1 is given. eff ) Change over time;

[0025] Figure 4 The effective multiplication factor (k) before core operation for reactors loaded with U3Si2-UO2 dual-phase fuel rods of Examples 1-3 and UO2 fuel rods of Comparative Example 1 is... eff ) Change over time;

[0026] Figure 5 The graph shows the core burnup over time for reactors loaded with U3Si2-UO2 dual-phase fuel rods from Examples 1-3 and UO2 fuel rods from Comparative Example 1.

[0027] Figure 6 The neutron energy spectrum of the reactor core loaded with UO2 fuel rods of Comparative Example 1 is shown in the low-energy region.

[0028] Figure 7 Neutron energy spectrum in the low-energy region of the reactor core loaded with U3Si2-UO2 dual-phase fuel rods of Example 1;

[0029] Figure 8 Neutron energy spectrum in the low-energy region of the reactor core loaded with U3Si2-UO2 dual-phase fuel rods of Example 2;

[0030] Figure 9 The neutron energy spectrum in the low-energy region of the reactor core loaded with the U3Si2-UO2 dual-phase fuel rods of Example 3;

[0031] Figure 10 A diagram showing the fissile nuclides of a reactor core loaded with UO2 fuel rods (Comparative Example 1) over its lifetime.

[0032] Figure 11 A diagram showing the fissile nuclides of a reactor core loaded with U3Si2-UO2 dual-phase fuel rods from Example 1 as it changes over its lifetime.

[0033] Figure 12 A diagram showing the fissile nuclides of a reactor core loaded with U3Si2-UO2 dual-phase fuel rods from Example 2 as it changes over its lifetime.

[0034] Figure 13 A diagram showing the fissile nuclides of a reactor core loaded with U3Si2-UO2 dual-phase fuel rods from Example 3 as it changes over its lifetime.

[0035] Figure 14 The graph shows the change of fissile nuclides in a reactor core loaded with UO2 fuel rods of Comparative Example 1 over time.

[0036] Figure 15 The graph shows the change of fissile nuclides in the reactor core loaded with the U3Si2-UO2 dual-phase fuel rods of Example 1 over time.

[0037] Figure 16 The graph shows the change of fissile nuclides in the reactor core loaded with the U3Si2-UO2 dual-phase fuel rods of Example 2 over time.

[0038] Figure 17 The graph shows the change of fissile nuclides in the reactor core loaded with the U3Si2-UO2 dual-phase fuel rods of Example 3 over time.

[0039] Figure 18 The graph shows the slow-emission neutron fraction over time for reactor cores loaded with U3Si2-UO2 dual-phase fuel rods of Examples 1-3 and UO2 fuel rods of Comparative Example 1, respectively.

[0040] Figure 19 The graph shows the transient neutron fraction over time for reactor cores loaded with U3Si2-UO2 dual-phase fuel rods of Examples 1-3 and UO2 fuel rods of Comparative Example 1, respectively.

[0041] Figure 20 The graph shows the change of fuel temperature coefficient over time in the reactor cores loaded with U3Si2-UO2 dual-phase fuel rods of Examples 1-3 and UO2 fuel rods of Comparative Example 1, respectively.

[0042] Figure 21 The graph shows the temperature coefficient of the moderator in the reactor core loaded with U3Si2-UO2 dual-phase fuel rods of Examples 1-3 and UO2 fuel rods of Comparative Example 1, respectively, as a function of time.

[0043] Figure 22 The graph shows the change of the total reactivity temperature coefficient over time for the reactor cores loaded with U3Si2-UO2 two-phase structure fuel rods of Examples 1-3 and UO2 fuel rods of Comparative Example 1, respectively. Detailed Implementation

[0044] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0045] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0046] Example 1

[0047] like Figure 1 As shown, a U3Si2-UO2 dual-phase fuel rod includes:

[0048] The inner layer, which is diffusely filled with 235 U3Si2 microsphere 1 with a U enrichment of 4.4%, and the distance between U3Si2 microsphere 1 and U3Si2 microsphere 1 is... 235 The UO2 fuel has a U enrichment of 4.4%, and the U3Si2 microspheres 1 have a diameter of 580 μm and a filling rate of 20% in the inner layer. Figure 1 The grid shown is for modeling purposes. In actual filling, the grid does not exist. The distribution of U3Si2 spheres 1 in the inner layer is random and irregular.

[0049] The outer layer is a ring-shaped UO2 fuel layer 3. 235 The U enrichment is 4.4%, and the radius is 0.819 mm. The outer layer wraps around the outside of the inner layer.

[0050] The outer shell 5 is wrapped around the outer layer. The outer shell 5 is made of 0.57mm thick Zr-4 alloy. An air cavity 4 is provided between the outer layer and the outer shell.

[0051] Example 2

[0052] A U3Si2-UO2 dual-phase fuel rod, comprising:

[0053] The inner layer, which is diffusely filled with 235 U3Si2 microspheres with a U enrichment of 4.4% are arranged in a manner that is consistent with the U3Si2 microspheres. 235 The UO2 fuel has a U enrichment of 4.4%, and the U3Si2 microspheres have a diameter of 699 μm and a filling rate of 35% in the inner layer.

[0054] The outer layer is a ring-shaped UO2 fuel layer. 235 The U enrichment is 4.4%, and the radius is 0.819 mm. The outer layer wraps around the outside of the inner layer.

[0055] The outer shell is wrapped around the outer layer and is made of 0.57mm thick Zr-4 alloy. An air cavity is provided between the outer layer and the outer shell.

[0056] Example 3

[0057] A U3Si2-UO2 dual-phase fuel rod, comprising:

[0058] The inner layer, which is diffusely filled with 235 U3Si2 microspheres with a U enrichment of 4.4% are arranged in a manner that is consistent with the U3Si2 microspheres. 235 The UO2 fuel has a U enrichment of 4.4%, and the U3Si2 microspheres have a diameter of 787 μm, with a filling rate of 50% in the inner layer.

[0059] The outer layer is a ring-shaped UO2 fuel layer. 235 The U enrichment is 4.4%, and the radius is 0.819 mm. The outer layer wraps around the outside of the inner layer.

[0060] The outer shell is wrapped around the outer layer and is made of 0.57mm thick Zr-4 alloy. An air cavity is provided between the outer layer and the outer shell.

[0061] Comparative Example 1

[0062] Compared with the U3Si2-UO2 dual-phase fuel rod of Example 2, the fuel rod of this comparative example did not undergo dispersion filling of U3Si2 microspheres. That is, both the inner and outer layers of this comparative example are UO2 fuel with a 235U enrichment of 4.4%. The size of the fuel rod of this comparative example is the same as that of the U3Si2-UO2 dual-phase fuel rod of Examples 1-3.

[0063] The U3Si2-UO2 two-phase structure fuel rods of Examples 1-3 and the fuel rods of Comparative Example 1 were loaded into the reactor core. According to the Hualong One 177 reactor core configuration, the fuel assemblies in the core pressure vessel were arranged in a 17×17 pattern, totaling 177 groups. The fuel rods within each fuel assembly were also arranged in a 17×17 pattern, totaling 264 fuel rods and 25 control rods. The center-to-center spacing of the fuel rods was 12.6 mm. The arrangement of the fuel rods within the fuel assemblies is as follows: Figure 2 As shown.

[0064] A burnup calculation study was conducted on the reactor core under various loading schemes for a total of 1500 days, and the results are as follows: Figure 3 , Figure 4 and Figure 5 As shown, Scheme 1 is Comparative Example 1, and Schemes 2, 3, and 4 correspond to Examples 1, 2, and 3, respectively. The reactor core is expected to operate for a total of 1500 days. It can be seen that in the initial operational phase before day 80, the core's k... eff The changes are quite complex, especially in the 20% and 35% groups. While the fuel density increases, the water-to-uranium ratio decreases, and the spatial self-protection effect of the fuel within the core increases. This is significantly more pronounced than with pure UO2 at 80 days. effLow. However, as the operating depth increases, the k of the U3Si2-UO2 two-phase structure fuel increases. eff Re-increase, k eff The level is again related to fuel density.

[0065] Meanwhile, the core lifespan of all four schemes reached more than 1085 days, which meets the 540-day design standard for pressurized water reactors, and the burnup depth all reached more than 50 GWd / MTU. The specific results are shown in Table 1.

[0066] Table 1 Calculation parameters for each scheme

[0067] Scheme Comparative Example 1 - 1200k Example 1 - 1200k Example 2 - 1200k Example 3 - 1200k Days on stream / day 1085 1108 1124 1134 Fuel consumption / GWd / MTU 50.2 50.7 51.2 51.8 initial k eff ]]> 1.34466 1.34579 1.34602 1.34319

[0068] Depend on Figure 6 , Figure 7 , Figure 8 , Figure 9 It can be seen that in all four schemes, the neutron spectrum shows a trend of least significant hardening at the beginning of the lifespan in the low-energy region, moderate hardening at the end of the lifespan, and the most significant hardening during the middle of the lifespan. At the beginning of the lifespan (BOC), due to the absence of strong neutron absorbers in the core during the first critical operation with loaded fuel, and the lack of neutron poison fission, the reduction in low-energy neutron capture effect becomes the decisive factor, making the spectrum least hardened compared to the end and middle of the lifespan. However, as burnup progresses to the end of the lifespan (EOC), the reduced total fuel volume leads to an increased moderator-to-fuel volume ratio, increasing the frequency of neutron-moderate collisions. More high-energy neutrons are slowed to the hot zone, and the reduced neutron poison concentration weakens the low-energy neutron capture effect. These combined effects result in a less pronounced hardening of the overall spectrum compared to the middle of the lifespan. The evolution of the energy spectrum from hard to soft is a key parameter that requires dynamic equilibrium in core physics design, directly affecting the reactivity temperature coefficient and power distribution.

[0069] Fissile nuclides include 239 Pu、 233 U、 235 U, secondary fissile nuclides have 240 Pu、 241 The level of fissile nuclides (Pu) is closely related to the operation of a reactor and directly affects its performance and safety.

[0070] in 235 U is the main fuel in pressurized water reactors, with a large thermal neutron fission cross section, accounting for more than 90% of the initial reactivity. 235 U directly determines the initial fuel enrichment and critical state of the reactor core, and is gradually consumed during burnup, leading to a decrease in reactivity. 239 Pu is by 238 U is generated after capturing a neutron and undergoing two β decays. 239 Pu thermal neutron fission cross section is relatively large 235U is much lower, but the effective fission probability is affected by the energy spectrum, contributing a significant fission share in the middle and late stages of burnup. 239 Pu can delay reactivity decline and extend fuel life; its accumulation affects core burnup depth and reprocessing strategies. In pressurized water reactors, 235 U is the core of the fission reaction, while secondary fissile nuclides such as 239Pu maintain the stability of the reactor in the mid-to-late stages of operation through dynamic multiplication and fission. Together, they shape the core's burnup characteristics, power distribution, and safety parameters, and are key factors in fuel cycle design and physical simulation optimization. Meanwhile, the complexity of secondary nuclides necessitates strategies for core management and waste disposal.

[0071] During core operation, this design focuses on the operation of four types of fuel rods at 1200K fuel and 600K moderator in a 177 core for 1500 days. 239 Pu、 235 U、 240 Pu、 241 The changes in the four fissile nuclides and secondary fissile nuclides of type Pu are shown in the following figures. Figure 10 , Figure 11 , Figure 12 and Figure 13 As shown.

[0072] Changes in fissile nuclides reflect the stability of the reactor during operation. Figures 10-13 The data shows that the changes in fissile nuclides in the three schemes of loading U3Si2-UO2 dual-phase fuel rods are not significant compared with those of conventional fuel UO2, indicating that the U3Si2-UO2 dual-phase fuel designed in this study has good stability during operation.

[0073] The variations of xenon-135, iodine-135, and samarium-149 with operating time in each scheme were summarized, such as... Figure 14 Figure 15 , Figure 16 , Figure 17 As shown.

[0074] In summary, it can be clearly seen that... 135 I, 135 Xe remains very stable from the beginning to the end of its lifetime, without significant changes. 149 Sm begins to accumulate from the beginning of the reactor's lifespan, and in all four schemes, it reaches its peak value around 600 days into the reactor's lifespan, after which it gradually decreases as the reactor continues to operate. 149 Sm, as a neutron poison, exhibits a trend of first increasing and then decreasing, which can significantly affect the thermal neutron flux distribution throughout the reactor's lifetime.

[0075] Although in the early stages of its service life, the k of the U3Si2-UO2 dual-phase fuel rod structure is... eff The value is low, but as fuel consumption increases, its k value increases.eff The value gradually increases, mainly due to the fuel density and the spatial self-shielding effect of the fuel within the core. Because the U3Si2-UO2 dual-phase fuel has a high uranium density, the water-uranium ratio within the core changes, leading to a change in k in the early stages of reactor operation. eff The core burnup showed significant fluctuations. Core burnup increased monotonically, and at the same time, higher uranium density resulted in relatively lower burnup. However, overall, the difference was not significant compared to pure UO2 fuel, indicating that U3Si2-UO2 fuel could operate stably for 1500 days. The core lifespan of all schemes far exceeded the 540-day design standard for pressurized water reactors, and the burnup depth also met expectations.

[0076] The above analysis shows that U3Si2-UO2 dual-phase fuel rods can effectively increase uranium density, thereby achieving high uranium density and improving reactor performance.

[0077] The delayed neutron effective fraction β of the reactor core loaded with U3Si2-UO2 dual-phase fuel rods of Examples 1-3 and fuel rods of Comparative Example 1 eff like Figure 18 As shown. Comparison Figure 18 The data shows that the effective neutron fraction variation range of the three schemes loading U3Si2-UO2 dual-phase fuel rods is not much different from that of traditional UO2 fuel. The effective neutron fraction has a great impact on the safety of the reactor core. The effective neutron fraction of the three schemes is within an appropriate range. At the same time, it can be seen that compared with the first scheme, the third scheme has the most stable variation, so its safety is superior.

[0078] The transient neutron lifetimes of reactor cores loaded with U3Si2-UO2 dual-phase fuel rods from Examples 1-3 and Comparative Example 1 are as follows: Figure 19 As shown, it can be seen that with the increase of the U3Si2-UO2 ratio in the U3Si2-UO2 dual-phase fuel rod, the uranium density is higher and the transient neutron lifetime is lower. A reduced transient neutron lifetime can suppress rapid power increases and enhance reactor safety.

[0079] The temperature changes in the nuclear reactor medium mainly include fuel temperature changes and moderator temperature changes. Therefore, the reactivity temperature coefficients studied in this design include the fuel temperature coefficient (FTC) and the moderator temperature coefficient (MTC).

[0080] The FTC parameters of the reactor core loaded with U3Si2-UO2 dual-phase fuel rods from Examples 1-3 and fuel rods from Comparative Example 1 are as follows: Figure 20 As shown. By Figure 20 Analysis shows that the fuel temperature reactivity coefficients of all schemes are negative during their service life, and the absolute value is less than 5. This means that negative reactivity can be introduced when the core temperature rises, thus increasing the safety of the core.

[0081] The MTC parameters of the reactor core loaded with U3Si2-UO2 dual-phase fuel rods from Examples 1-3 and Comparative Example 1 are as follows: Figure 21 As shown, according to Figure 21 The data shows that the MTC value remains negative with an absolute value less than 50, indicating that the design effectively enhances the system's negative feedback mechanism while ensuring reactivity control. Throughout the reactor's lifetime, all schemes exhibit good negative moderator temperature reactivity coefficients, meeting reactor design criteria. The results for the U3Si2-UO2 two-phase fuel rod with a fuel volume ratio of 35% in the inner region are more stable and have better MTC parameters compared to the other two schemes.

[0082] The overall temperature reactivity coefficient is formed by the combined effect of the temperature reactivity coefficients of the fuel and the moderator. This integrated result can more accurately assess the safety characteristics of the reactor core temperature coefficient. The numerical distribution of the overall temperature reactivity coefficient for different design schemes over their operational lifespan is shown below. Figure 22 As shown, the overall reactivity temperature coefficient indicates the negative feedback of the reactor. The lower the value of the reactor's negative feedback, the safer the system. As can be seen from the figure, the negative feedback of the three U3Si2-UO2 two-phase structure fuel rod loading schemes is not much different from that of UO2, indicating that all three schemes have sufficient safety.

[0083] In summary, it can be seen that the numerical characteristics of the effective neutron fraction and transient neutron lifetime of each scheme exhibit a nonlinear variation, which is related to the fuel burnup rate and core structure changes. Furthermore, by comparing the effective neutron fraction and transient neutron lifetime diagrams for different fuel volume comparison schemes, it can be clearly found that when the proportion of uranium silicide microspheres in the inner layer of the U3Si2-UO2 dual-phase fuel rod is 35%, the effective neutron fraction and transient neutron lifetime are relatively stable. Therefore, loading the U3Si2-UO2 dual-phase fuel rod of Example 2 is most conducive to the safe operation of the reactor. The fuel temperature coefficient and moderator temperature coefficient both remain negative, which conforms to the safety criteria of reactor design.

[0084] The total reactivity temperature coefficient (TRC), as a comprehensive result of the temperature reactivity coefficients of fuel and moderator, can more accurately assess the safety characteristics of the reactor core temperature coefficient. The results show that the TRC of all scenarios remains negative, and its absolute value increases with burnup. These simulation values ​​indicate that the reactor has a good negative feedback mechanism during operation and can effectively cope with the adverse effects of temperature rise.

[0085] This invention, through safety parameter analysis of reactor cores loaded with U3Si2-UO2 two-phase fuel rods, yields many important conclusions regarding transient neutron lifetime, fuel temperature coefficient, moderator temperature coefficient, and overall reactivity temperature coefficient. These conclusions provide important reference for reactor design and operation, and also help ensure the safety and stability of reactor daily operation.

[0086] The number of devices and processing scale described herein are for the purpose of simplifying the description of the invention. Applications, modifications, and variations of the invention will be readily apparent to those skilled in the art.

[0087] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A U3Si2-UO2 dual-phase fuel rod, characterized in that, include: The inner layer is filled with U3Si2 microspheres. The outer layer is a ring-shaped UO2 fuel layer that wraps around the outside of the inner layer. A shell is provided to cover the outside of the outer layer, and an air cavity is provided between the outer layer and the shell.

2. The U3Si2-UO2 dual-phase fuel rod as described in claim 1, characterized in that, The U3Si2 microspheres in the inner layer are separated by UO2 fuel.

3. The U3Si2-UO2 dual-phase structure fuel rod as described in claim 1, characterized in that, The diameters of the U3Si2 microspheres may be different or the same.

4. The U3Si2-UO2 dual-phase fuel rod as described in claim 1, characterized in that, The diameter of the U3Si2 microspheres is 580–787 μm.

5. The U3Si2-UO2 dual-phase fuel rod as described in claim 1, characterized in that, The U3Si2 microspheres have a filling rate of 20%–52% in the inner layer, and a total volume of 1.19 million–2.97 million cm³. 3 .

6. The U3Si2-UO2 dual-phase fuel rod as described in claim 1, characterized in that, The UO2 fuel layer 235 The U enrichment level was 4.4%.

7. The U3Si2-UO2 dual-phase fuel rod as described in claim 1, characterized in that, The U3Si2 microspheres 235 The U enrichment level was 4.4%.

8. The U3Si2-UO2 dual-phase fuel rod as described in claim 1, characterized in that, The cladding material is Zr-4 alloy.

9. An application of a U3Si2-UO2 dual-phase structure fuel rod as described in any one of claims 1-8, characterized in that, The U3Si2-UO2 dual-phase fuel rods are used for loading fuel assemblies in a nuclear reactor; wherein, the fuel assemblies are arranged in a 17×17 configuration, including 264 U3Si2-UO2 dual-phase fuel rods and 25 control rods; the reactor core includes 289 fuel assemblies, which are arranged in a 17×17 configuration.

Images