A fuel management design method based on balanced cyclic perturbation

Abstract

The present invention discloses a fuel management design method based on balancing cycle perturbations, comprising: setting multiple balancing cycles according to the cycle length requirements of a nuclear power plant; determining the operational flexibility requirements of the nuclear power plant; determining a final core solution for each balancing cycle; branching a burnup model for each balancing cycle based on the final core solution according to the operational flexibility requirements of the nuclear power plant; selecting the burnup model of one balancing cycle and adopting the type and number of new components of another balancing cycle to form a perturbation transition from the burnup model of the former to the burnup model of the latter; completing the perturbation transition between all balancing cycles; and decoupling the cycle coupling between the primary cycle, transition cycle, and balancing cycle, significantly reducing the difficulty and workload of fuel management design. While ensuring the operational flexibility of the power plant, the method also effectively improves the efficiency of fuel management design, making it worthy of widespread use.

Description

Technical Field

[0001] The present invention relates to the field of nuclear power technology, and in particular to a fuel management design method based on balanced cycle disturbance. Background Art

[0002] The core of nuclear power plant core fuel management is to develop the optimal fuel usage plan while ensuring the safety of the power plant, meet the power plant's cycle length requirements, meet the changing needs of power load, improve component utilization, reduce neutron leakage, and reasonably arrange overhaul time to avoid peak power consumption periods, thereby effectively reducing the power plant's operating costs.

[0003] Currently, mainstream nuclear power plant fuel management in China utilizes a single 18-month refueling cycle or alternating long and short fuel cycles. With the increasing demand for highly flexible nuclear power plant operations, a more flexible cycle length is required. This is primarily due to the following factors: 1) Declining electricity demand has led to a corresponding decrease in nuclear power plant power generation capacity, significantly increasing the need for peak load regulation; 2) Fluctuating outage times have led to an increase in delayed and extended outages at power plants, necessitating a more flexible outage window; and 3) a balanced cycle refueling method of ±4 new components cannot meet power plant needs.

[0004] The traditional core fuel management strategy demonstration method requires the establishment of a series of fuel management models to obtain a power distribution with typical characteristics. Since the traditional fuel management design includes the first cycle, transition cycle and balance cycle, there is a strong coupling relationship between the cycles. Considering the requirements of the above-mentioned high-flexibility fuel management strategy, various operating requirements need to be coupled with the cycles at the same time. The design of the core fuel management model is massive, which not only greatly increases the difficulty and workload of fuel management design, but also the envelope neutronics parameters obtained based on massive fuel management must be quite bad, and subsequent accident analysis may not be able to be completed. Even if the accident analysis is passed by restricting the operating conditions, it will inevitably reduce the operating flexibility of the power plant and cannot meet the future requirements for operational flexibility. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that the traditional core fuel management strategy demonstration method greatly increases the difficulty and workload of fuel management design. At the same time, the envelope neutronics parameters obtained based on massive fuel management must be quite poor, and subsequent accident analysis may not be completed. Even if the accident analysis is passed by restricting the operating conditions, it will inevitably reduce the operating flexibility of the power plant.

[0006] The present invention aims to provide a fuel management design method based on balanced cycle disturbance, comprising:

[0007] Set up multiple balancing cycles according to the cycle length requirements of the nuclear power plant;

[0008] Determine operational flexibility requirements for nuclear power plants;

[0009] Designing a core plan for each balancing cycle and determining a final core plan for each balancing cycle, wherein the final core plan is formed by the number of refueling assemblies, the positions of the refueling assemblies, the enrichment of the refueling assemblies, and the positions of the old assemblies;

[0010] According to the operational flexibility requirements of the nuclear power plant, the burnup model for each equilibrium cycle is branched based on the final core scheme;

[0011] The fuel consumption model of one balancing cycle is selected, and the type and number of new components of the other balancing cycle are adopted to form a perturbation transition from the fuel consumption model of the former to the fuel consumption model of the latter;

[0012] Complete perturbation transitions between all equilibration cycles.

[0013] When the above technical solution is adopted,

[0014] 1. The cycle coupling between the first cycle, transition cycle and balance cycle is decoupled, greatly reducing the difficulty and workload of fuel management design.

[0015] 2. Decoupled the coupling relationship between the operating requirements and cycles of different nuclear power plants.

[0016] 3. It can effectively consider the high-flexibility operation needs of nuclear power plants, such as long-term low power, extended operation, and alternating long and short operation.

[0017] 4. While ensuring the flexibility of power plant operation, it also effectively improves the efficiency of fuel management design and is worthy of promotion and use.

[0018] As a possible design, when the cycle length is 14 to 22 months, the balancing cycle includes at least 14 months, 16 months, 18 months, 20 months and 22 months.

[0019] As a possible design, the operational flexibility requirements include normal core operation, long-term low power, extended operation, and end-of-life power reduction.

[0020] As a possible design, the long-term low power is embodied by a long-term low power operation model.

[0021] As a possible design, the extended operation is embodied by an extended operation model.

[0022] As a possible design, the end-of-life power reduction is reflected by an end-of-life power reduction model.

[0023] As a possible design, the normal core operation is reflected by a normal burnup model.

[0024] As a possible design, the fuel consumption model is an ARO fuel consumption model.

[0025] As a possible design, the fuel consumption model of one of the balancing cycles is selected, and the new component type and number of the other balancing cycle are adopted to form a perturbation transition from the former fuel consumption model to the latter fuel consumption model. Specifically, based on the core loading and fuel consumption information of one cycle, the core loading and fuel consumption design of the next cycle is carried out. The next cycle adopts the loading information of the other balancing cycle. The loading information includes the enrichment, number, and placement of the new components. The position of the old components is adjusted according to safety requirements.

[0026] As a possible design, the type and number of the new components are consistent with the core solution of the post-disturbance balance cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the examples. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be considered as limiting the scope. A person of ordinary skill in the art can also derive other relevant drawings based on these drawings without inventive effort. In the drawings:

[0028] Figure 1 This is a distribution diagram of the M index in the long cycle demonstration of a certain location in the embodiment;

[0029] Figure 2 This is a distribution diagram of the M index after the cyclic balance cyclic disturbance at a certain location in the embodiment. DETAILED DESCRIPTION

[0030] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with examples and drawings. The exemplary embodiments of the present invention and their descriptions are only used to explain the present invention and are not intended to limit the present invention.

[0031] It should be noted that when an element is referred to as being “fixed on” or “disposed on” another element, it may be directly on the other element or indirectly on the other element. When an element is referred to as being “connected to” another element, it may be directly connected to the other element or indirectly connected to the other element.

[0032] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined. "Several" means one or more, unless otherwise specifically defined.

[0033] In the description of the present invention, it should be understood that the terms "up", "down", "front", "back", "left", "right", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0034] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and may encompass internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0035] Since the traditional core fuel management design method can no longer meet the growing operation and design requirements, a more flexible core fuel management design method is needed to meet the growing and changing operation requirements.

[0036] The present invention provides a fuel management design method based on balanced cycle disturbance, the design method comprising the following steps:

[0037] S1. Set up multiple balancing cycles according to the cycle length requirements of the nuclear power plant;

[0038] For example: if the material is replaced every 14 to 22 months, in order to cover the design of the material replacement every 14 to 22 months, the number of balancing cycles can be 4, and the 4 balancing cycles can specifically be 14 months, 16 months, 18 months, 20 months and 22 months.

[0039] S2. Determine the operational flexibility requirements of nuclear power plants;

[0040] Operational flexibility requirements primarily include, but are not limited to, normal core operation, long-term low power, extended operation, and end-of-life power reduction. Normal core operation can be reflected by a normal burnup model. Long-term low power can be reflected by a long-term low power operation model. Extended operation can be reflected by an extended operation model. The end-of-life power reduction can be reflected by an end-of-life power reduction model.

[0041] The normal fuel consumption model, the long-term low-power operation model, the extended operation model, and the end-of-life power reduction model are all common models in this field, so their specific construction methods are not elaborated here.

[0042] S3. Design a core solution for each balancing cycle and determine the final core solution for each balancing cycle, wherein the final core solution is formed by the number of refueling components, the position of the refueling components, the enrichment of the refueling components, and the position of the old components;

[0043] In this step, there is no need to consider how to design the transition cycle, so the coupling between the balancing cycles is not involved, thereby reducing the number of schemes that need to be considered and also helping to improve the operational flexibility of the nuclear power plant.

[0044] S4. Based on the final core solution and the operational flexibility requirements of the nuclear power plant, generate a branched burnup model for each equilibrium cycle.

[0045] S5. Selecting a fuel consumption model for one balancing cycle and adopting the type and number of new components for another balancing cycle to form a perturbation transition from the fuel consumption model of the former to the fuel consumption model of the latter;

[0046] For example, if it is necessary to switch from a balancing cycle with a cycle length of 14 months to a balancing cycle with a cycle length of 20 months, then the balancing cycle with a cycle length of 14 months is used and the types and numbers of new components of the balancing cycle with a cycle length of 20 months are used to perturb the balancing cycle with a cycle length of 20 months. The final core plan formed after the perturbation of the balancing cycle with a cycle length of 14 months is consistent with the core plan of the balancing cycle with a cycle length of 0 months, that is, the types and numbers of new components of the former and the latter are the same.

[0047] S6. Complete the perturbation transition between all equilibrium cycles.

[0048] For example: complete the balance cycle disturbance between each two months of 14 months, 16 months, 18 months, 20 months and 22 months to achieve the switching of the balance cycle.

[0049] The above method can greatly reduce the number of schemes that need to be analyzed and the design difficulty by releasing the coupling relationship between any two balancing cycles, and is conducive to subsequent accident analysis, improving the operational flexibility of the power plant, and being promoted for use.

[0050] Comparative Example 1

[0051] Take the core of Unit 1-2 at a certain location (a reactor core of a million-kilowatt nuclear power plant, which consists of 157 fuel assemblies) as an example.

[0052] For example, a nuclear power plant has the following design requirements:

[0053] 1) The cycle length can meet the material replacement demand of 14 to 22 months;

[0054] 2) Ability to operate at low power for 3 months;

[0055] 3) Have the requirement of power reduction operation at the end of life;

[0056] 4) It has an extended operation requirement of 30 EFPD (equivalent full power days).

[0057] The general process for traditional core fuel management design is as follows: 1) Select a proven starting cycle; 2) Design a balancing cycle based on the fuel assembly enrichment and number of refueling assemblies provided by the power plant; 3) Design a transition cycle from the starting cycle to the balancing cycle; 4) Design a maneuvering cycle based on the balancing cycle. To cover refueling designs of 14-22 months, the core can be designed with refueling capabilities of 14, 16, 18, 20, and 22 months. At the same time, the burnup model must account for long-term low-power operation, end-of-life power reduction, and extended operation capabilities. Therefore, the number of scenarios that need to be considered for a single cycle is shown in Table 1.

[0058] Table 1 Number of solutions to be considered in one cycle

[0059]

[0060] Typically, a core fuel management strategy requires three transition cycles and one equilibrium cycle, so there are a total of 40 4 = 2,560,000 scenarios. While such a large number of scenarios is comprehensive, it also has obvious drawbacks. With too many scenarios, the number of neutrons in the envelope is bound to be extremely poor, making subsequent accident analysis impossible. Even if the accident analysis is successful by restricting operating conditions, it will inevitably reduce the plant's operational flexibility.

[0061] Example 1

[0062] Take the core of Unit 1-2 at a certain location (a reactor core of a million-kilowatt nuclear power plant, which consists of 157 fuel assemblies) as an example.

[0063] For example, a nuclear power plant has the following design requirements:

[0064] 5) The cycle length can meet the material replacement demand of 14 to 22 months;

[0065] 6) Ability to operate at low power for 3 months;

[0066] 7) Have the requirement of power reduction operation at the end of life;

[0067] 8) It has an extended operation requirement of 30 EFPD (equivalent full power days).

[0068] A fuel management design method based on balanced cycle disturbances comprises the following steps:

[0069] S1. Set up multiple balancing cycles according to the cycle length requirements of the nuclear power plant;

[0070] The first cycle is 18 months, followed by 14 months of refueling, 16 months of refueling, 20 months of refueling and 22 months, for a total of 5 balancing cycles.

[0071] S2. Determine the operational flexibility requirements of nuclear power plants;

[0072] The operational flexibility requirement is mainly for the fuel consumption model, which includes the normal fuel consumption model, the long-term low-power fuel consumption model, the end-of-life reduced-power model, and the extended operation model.

[0073] S3. Design a core solution for each balancing cycle and determine the final core solution for each balancing cycle, wherein the final core solution is formed by the number of refueling components, the position of the refueling components, the enrichment of the refueling components, and the position of the old components;

[0074] S4. Based on the final core solution and the operational flexibility requirements of the nuclear power plant, generate a branched burnup model for each equilibrium cycle.

[0075] S5. Selecting a fuel consumption model for one balancing cycle and adopting the type and number of new components for another balancing cycle to form a perturbation transition from the fuel consumption model of the former to the fuel consumption model of the latter;

[0076] S6. Complete the perturbation transition between all equilibrium cycles.

[0077] The details are as follows:

[0078] First, taking an 18-month cycle as an example, the optimal number of refueling components and enrichment combination are determined by optimizing the average batch unloading burnup, resulting in a balanced core design for the 18-month cycle. The burnup models include a normal burnup model, a long-term low-power burnup model, an end-of-life de-power model, and an extended operation model, for a total of four models. Next, the perturbation scenario of the 18-month refueling core is considered, with perturbations to 14-month, 16-month, 20-month, and 22-month refuelings. The perturbation method involves re-designing the core loading using the new component types and numbers for the remaining cycle lengths. This results in a total of 4 × 4 = 16 scenarios for the entire 18-month cycle.

[0079] Secondly, the above design is repeated with a cycle length of 14 months, a cycle length of 16 months, a cycle length of 20 months, and a cycle length of 22 months. Then, a total of 16×5=80 schemes need to be considered for the five cycle lengths.

[0080] From the comparison between Example 1 and Comparative Example 1, it can be seen that the core solution obtained in Example 1 is significantly smaller than the traditional core fuel management design method based on cycle coupling (Comparative Example 1).

[0081] In order to evaluate the envelope of Example 1, this paper uses the parameter index M (multiformity) to reflect the power distribution of the loading scheme. The meaning of index M is the F of each fuel assembly in a core loading at the beginning of life and in the equilibrium xenon state. ΔH The distribution of M index reflects the differences between the schemes to a certain extent. The long fuel cycle demonstration of a certain location is selected as the comparison object. The core fuel management includes 3 transition cycles, 1 balance cycle and 4 maneuvering cycles, a total of 8 core schemes. The distribution of its M index is as follows Figure 1 The fuel management design method based on balanced cycle perturbation disclosed in Example 1 selects 18-month refueling plan balanced cycle and perturbs it to obtain 5 core loading plans. The distribution of its M index is shown as follows: Figure 2 shown.

[0082] According to the calculation results, it can be seen that the five core loading schemes obtained by the fuel management design method based on the balanced cycle disturbance are Figure 2 , in F ΔH The proportion of components >1.4 is significantly greater than Figure 2 , F ΔH <1.3 of the components Figure 1 The diversity of its power distribution characteristics is significantly better than the eight scenarios demonstrated in the long fuel cycle demonstration at a certain location. From the perspective of power distribution alone, the set of core loading scenarios derived from the perturbation can completely encompass the original fuel management demonstration.

[0083] In summary, the fuel management design method based on balanced cycle disturbance disclosed in the present invention has the following advantages:

[0084] 1. The cycle coupling between the first cycle, transition cycle and balance cycle is decoupled, greatly reducing the difficulty and workload of fuel management design.

[0085] 2. Decoupled the coupling relationship between the operating requirements and cycles of different nuclear power plants.

[0086] 3. It can effectively consider the high-flexibility operation needs of nuclear power plants, such as long-term low power, extended operation, and alternating long and short operation.

[0087] 4. While ensuring the flexibility of power plant operation, it also effectively improves the efficiency of fuel management design and is worthy of promotion and use.

[0088] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A fuel management design method based on balanced cycle disturbance, characterized in that: The design method includes: Set up multiple balancing cycles according to the cycle length requirements of the nuclear power plant; Determine operational flexibility requirements for nuclear power plants; Designing a core plan for each balancing cycle and determining a final core plan for each balancing cycle, wherein the final core plan is formed by the number of refueling assemblies, the positions of the refueling assemblies, the enrichment of the refueling assemblies, and the positions of the old assemblies; According to the operational flexibility requirements of the nuclear power plant, the burnup model for each equilibrium cycle is branched based on the final core scheme; The fuel consumption model of one balancing cycle is selected, and the type and number of new components of the other balancing cycle are adopted to form a perturbation transition from the fuel consumption model of the former to the fuel consumption model of the latter; Complete perturbation transitions between all equilibration cycles.

2. The fuel management design method based on balanced cycle disturbance according to claim 1, characterized in that: When the cycle length is 14 to 22 months, the balancing cycle includes at least 14 months, 16 months, 18 months, 20 months and 22 months.

3. The fuel management design method based on balanced cycle disturbance according to claim 1, characterized in that: The operational flexibility requirements include normal core operation, long-term low power, extended operation, and end-of-life power reduction.

4. The fuel management design method based on balanced cycle disturbance according to claim 3 is characterized in that: The long-term low power is reflected by a long-term low power operation model.

5. The fuel management design method based on balanced cycle disturbance according to claim 3 is characterized in that: The extended operation is represented by an extended operation model.

6. The fuel management design method based on balanced cycle disturbance according to claim 3, characterized in that: The end-of-life power reduction is reflected by an end-of-life power reduction model.

7. The fuel management design method based on balanced cycle disturbance according to claim 3, characterized in that: The normal core operation is reflected by a normal burnup model.

8. The fuel management design method based on balanced cycle disturbance according to claim 1, characterized in that: The fuel consumption model is an ARO fuel consumption model.

9. The fuel management design method based on balanced cycle disturbance according to claim 1, characterized in that: A fuel consumption model of one balancing cycle is selected, and the new component type and number of another balancing cycle are adopted to form a perturbation transition from the former fuel consumption model to the latter fuel consumption model. Specifically, based on the core loading and fuel consumption information of one cycle, the core loading and fuel consumption design of the next cycle is carried out. The next cycle adopts the loading information of the other balancing cycle. The loading information includes the enrichment, number, and placement of the new components. The position of the old components is adjusted according to safety requirements.

10. The fuel management design method based on balanced cycle disturbance according to claim 1, characterized in that: The type and number of the new components are consistent with the core scheme of the post-disturbance balance cycle.

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