A long-cycle fuel management method for pressurized water reactor core refueling and its application

Abstract

The present invention discloses a long-cycle fuel management method for core refueling of a pressurized water reactor. New fuel assemblies with an enrichment of more than 5% are used for each refueling in a balanced cycle, and the number of new fuel assemblies used for each refueling is less than or equal to 1 / 2 of the number of core assemblies; the balanced cycle is a 24-month refueling cycle. By using new fuel assemblies with an enrichment of more than 5% for refueling, and the number of assemblies used for each refueling does not exceed 1 / 2 of the number of core assemblies, fuel economy can be effectively improved, a fuel management method with a 24-month refueling cycle with good fuel economy can be realized, and a wide application of the 24-month refueling method for pressurized water reactors of various types in large nuclear power plants can be realized.

Description

Technical Field

[0001] The invention relates to the technical field of pressurized water reactor nuclear power plant reactors, and in particular to a long-cycle fuel management method for pressurized water reactor core refueling and an application thereof. Background Art

[0002] Nuclear PWR core fuel management generally refers to the core from the first cycle to the balance cycle, determining the fuel enrichment used in the core, the type of burnable poisons, and the arrangement of various components and poisons in the core, so that the design results of the PWR core meet the nuclear design criteria and the overall requirements of the power plant. The quality of core fuel management directly affects the economy and safety of nuclear power plants and is the basis for subsequent safety analysis or evaluation.

[0003] At present, the mainstream cycle length of nuclear power plants in operation around the world is about 18 months. There are a few nuclear power plants in the United States that have applied the 24-month refueling strategy. They are all nuclear power plants with relatively low reactor power that were put into use in the 1970s. Their linear power density is generally between 145 and 170W / cm. However, for the core of a pressurized water reactor of a nuclear power plant with a power of one million kilowatts, due to the high linear power density and enrichment limit, the cost of the 24-month refueling strategy is high, and the fuel economy index of the 24-month refueling method is not as good as the 18-month refueling method. Summary of the invention

[0004] The technical problem to be solved by the present invention is that the existing long-cycle fuel management method for core refueling of pressurized water reactors is high in cost and low in economic efficiency, which results in that the long-cycle refueling method cannot be widely used for the core of pressurized water reactors in large nuclear power plants. The purpose is to provide a long-cycle fuel management method for core refueling of pressurized water reactors and its application, so as to achieve a balanced cycle of 24-month refueling cycle, and after the core reaches equilibrium, the average batch unloading fuel consumption of each batch of fuel assemblies is greatly improved compared with the current 18-month fuel design of the same type of power plant, and the fuel utilization rate is significantly improved.

[0005] The present invention is achieved through the following technical solutions:

[0006] The first object of the present invention is to provide a long-cycle fuel management method for pressurized water reactor core refueling, in which balanced cycle refueling uses new fuel assemblies with an enrichment degree exceeding 5%, and the number of new fuel assemblies in each refueling is less than or equal to 1 / 2 of the number of core assemblies; the balanced cycle is a 24-month refueling cycle.

[0007] Optionally, the core is cooled and moderated by light water, the coolant containing soluble boron.

[0008] Optionally, the core balance cycle adopts an extremely low leakage loading method.

[0009] Optionally, during refueling, the new fuel assemblies and the fuel assemblies with less burnup are placed in the inner area of ​​the core and arranged crosswise, and the fuel assemblies with greater burnup are placed in the outermost circle of the core.

[0010] Optionally, the new fuel assembly has one or more enrichment levels.

[0011] Optionally, the enrichment of the new fuel assembly may be 5.45% and / or 5.95%.

[0012] Optionally, each of the new fuel assemblies is arranged in a 17×17 array, containing 264 fuel rods, 24 guide tubes and one in-pile measuring instrument tube;

[0013] The number of gadolinium-loaded fuel rods in the new fuel assembly is 4, 8, 12, 16, 20 or 24.

[0014] Optionally, the U-235 enrichment in the UO2-Gd2O3 fuel pellets in the new fuel assembly is 2.5%, and the weight percentage of Gd2O3 is 10%.

[0015] The second object of the present invention is to provide an application of the above-mentioned fuel management method for use in the long-cycle fuel management design of pressurized water reactors of various mainstream reactor types.

[0016] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0017] The present invention provides a long-cycle fuel management method for core refueling of a pressurized water reactor. In the balancing cycle, new fuel assemblies with an enrichment degree exceeding 5% are used for refueling, and the number of assemblies replaced each time does not exceed 1 / 2 of the number of core assemblies. The balancing cycle adopts a 24-month refueling cycle, which can effectively improve fuel economy, realize a fuel management method with a 24-month refueling cycle with good fuel economy, and realize the wide application of the 24-month refueling method for large pressurized water reactor nuclear power plants of various mainstream reactor types. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments. The illustrative embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0019] In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it is apparent to one of ordinary skill in the art that these specific details are not necessarily employed to practice the present invention. In other embodiments, in order to avoid obscuring the present invention, well-known structures, circuits, materials, or methods are not specifically described.

[0020] Throughout the specification, references to "one embodiment," "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment of the present invention. Therefore, the phrases "one embodiment," "an embodiment," "an example," or "an example" appearing in various places throughout the specification do not necessarily all refer to the same embodiment or example. Furthermore, particular features, structures, or characteristics may be combined in one or more embodiments or examples in any appropriate combinations and / or subcombinations.

[0021] Example

[0022] Due to the high cost and low economic efficiency of the current long-cycle fuel management method for pressurized water reactor core refueling, the long-cycle refueling method cannot be widely used for pressurized water reactor cores of large nuclear power plants.

[0023] In order to solve the above problems, an embodiment of the present invention provides a long-cycle fuel management method for core refueling in a pressurized water reactor, adopting the following technical scheme: a long-cycle fuel management method for core refueling in a pressurized water reactor, wherein the balanced cycle refueling uses new fuel assemblies with an enrichment degree exceeding 5%, and the number of new fuel assemblies for each refueling is less than or equal to 1 / 2 of the number of core assemblies; the balanced cycle is a refueling cycle of 24 months.

[0024] For the core of a pressurized water reactor, the use of new fuel assemblies with an enrichment degree of more than 5% can effectively improve fuel economy, and the number of assemblies replaced each time shall not exceed 1 / 2 of the number of core assemblies. The balanced cycle adopts a 24-month refueling period to achieve a fuel management method with a 24-month refueling period with good fuel economy, and realize the widespread application of the 24-month refueling method for large nuclear power plants.

[0025] Furthermore, the core is cooled and moderated by light water, and the coolant contains soluble boron.

[0026] Furthermore, the transition cycle and balance cycle of the core adopt an extremely low leakage loading method.

[0027] Furthermore, during refueling, the new fuel assembly and the fuel assembly with less burnup are placed in the inner area of ​​the core and arranged crosswise, and the fuel assembly with greater burnup is placed in the outermost circle of the core.

[0028] Furthermore, the enrichment degree of the new fuel assembly is one or more.

[0029] Furthermore, the new fuel assembly has various enrichment levels. Preferably, the new fuel assembly has an enrichment level of 5.45% and / or 5.95%.

[0030] Furthermore, each of the new fuel assemblies is arranged in a 17×17 array and contains 264 fuel rods, 24 guide tubes and an in-pile measuring instrument tube.

[0031] Furthermore, the number of gadolinium-loaded fuel rods in the new fuel assembly is 4, 8, 12, 16, 20 or 24.

[0032] Furthermore, the U-235 enrichment in the UO2-Gd2O3 fuel pellets in the new fuel assembly is 2.5%, and the weight percentage of Gd2O3 is 10%.

[0033] The embodiment of the present invention provides a long-cycle fuel management method for core refueling of a pressurized water reactor. During refueling, new fuel assemblies with an enrichment greater than 5% are used, and the refueling assemblies do not exceed 1 / 2 of the whole stack assembly. The loading method of the core, the enrichment of the new fuel assemblies, the arrangement of the fuel rods in the new fuel assemblies, the enrichment of UO2-Gd2O3 fuel core blocks in the new fuel assemblies and the weight of poisons are reasonably designed. The method is applied to large pressurized water reactor nuclear power plants, overcoming the limitations of high online power density and enrichment of pressurized water reactor cores in large nuclear power plants, and reducing the cost of a 24-month refueling cycle. The average batch unloading fuel consumption of each batch of fuel assemblies is greatly improved compared with the current 18-month fuel design of the same type of power plant, the fuel utilization rate is significantly improved, and the availability of the power plant is significantly increased.

[0034] Example 1

[0035] This embodiment is directed to a reactor core of a 1 million kilowatt nuclear power plant, which is composed of 157 fuel assemblies. The core is cooled and moderated by light water, and the coolant contains soluble boron.

[0036] This scheme loads 72 new fuel assemblies with an enrichment of 5.95% per cycle and arranges them inside the core. The outermost ring of the core is placed with old fuel assemblies that have been burned up for multiple cycles, and the old fuel assemblies that have been burned up and have a shallower burnup are placed crosswise with the new fuel assemblies in the inner ring of the core, forming an extremely low leakage loading method.

[0037] Each new fuel assembly is arranged in a 17×17 array, containing 264 fuel rods, 24 guide tubes and an in-pile measuring instrument tube. The solid burnable poison uses gadolinium, and the U-235 enrichment in the UO2-Gd2O3 fuel pellets is 2.5% and the weight percentage of Gd2O3 is 10%. The typical number of gadolinium-loaded fuel rods in the new fuel assembly is 4, 8, 12, 16, 20 or 24.

[0038] Table 1 below is a comparison of the fuel management schemes for the balancing cycle of the 157 core of the 1 million kilowatt unit in the 18-month and 24-month refueling cycles. It can be seen that the core fuel management method described in this embodiment can achieve a 24-month long-cycle refueling design for the balancing cycle, the cycle length of the balancing cycle is greater than 649 equivalent full power days, and the power plant availability rate is more than 93%; the fuel assembly batch unloading fuel consumption is more than 12GWd / tU higher than the highest batch unloading fuel consumption of the same core with 18-month refueling, and the average fuel consumption of the largest unloading assembly is less than 62GWd / tU.

[0039] Table 1 Comparison of fuel management schemes for different refueling cycles of 157 cores of 1 million kW unit

[0040]

[0041] Example 2

[0042] This embodiment is directed to a reactor core of a 600,000-kilowatt nuclear power plant, which is composed of 121 fuel assemblies. The core is cooled and moderated by light water, and the coolant contains soluble boron.

[0043] This scheme loads 56 new fuel assemblies with an enrichment of 5.45% per cycle and arranges them inside the core. The outermost ring of the core is placed with old fuel assemblies that have been burned through multiple cycles. The old fuel assemblies that have been burned through and have a shallower burnup in the inner ring of the core are placed crosswise with the new fuel assemblies, forming an extremely low leakage loading method.

[0044] Each new fuel assembly is arranged in a 17×17 array, containing 264 fuel rods, 24 guide tubes and an in-pile measuring instrument tube. The solid burnable poison uses gadolinium, and the U-235 enrichment in the UO2-Gd2O3 fuel pellets is 2.5% and the weight percentage of Gd2O3 is 10%. The typical number of gadolinium-loaded fuel rods in the new fuel assembly is 4, 8, 12, 16, 20 or 24.

[0045] Table 2 below is a comparison of the fuel management schemes for the balancing cycle of 18 months and 24 months refueling cycle of the core of 121 fuel assemblies of a 600,000-kilowatt unit. As can be seen from Table 2, the core fuel management method described in this embodiment can achieve a 24-month long-cycle refueling design, the cycle length of the balancing cycle is 692 equivalent full-power days, and the power plant availability rate is more than 93%; the fuel assembly batch unloading fuel consumption is about 52GWd / tU, which is about 5GWd / tU higher than the highest batch unloading fuel consumption of the same core with 18 months refueling, and the average fuel consumption of the largest unloading assembly is less than 58GWd / tU.

[0046] Table 2 Comparison of fuel management schemes for different refueling cycles of 121 core of 600MW unit

[0047]

[0048]

[0049] Example 3

[0050] This embodiment is directed to a reactor core of a million-kilowatt nuclear power plant, which is composed of 177 fuel assemblies. The core is cooled and moderated by light water, and the coolant contains soluble boron.

[0051] This scheme loads 80 new fuel assemblies per cycle, of which the new fuel assemblies include two enrichments, 5.45% and 5.95%, 4 new fuel assemblies with an enrichment of 5.45%, and 76 new fuel assemblies with an enrichment of 5.95%. The new fuel assemblies are arranged inside the core. The outermost circle of the core is placed with old fuel assemblies that have been burned through multiple cycles. The old fuel assemblies with shallower burnup in the inner circle of the core are placed crosswise with the new fuel assemblies, forming an extremely low leakage loading method.

[0052] Each new fuel assembly is arranged in a 17×17 array, containing 264 fuel rods, 24 guide tubes and an in-pile measuring instrument tube. The solid burnable poison uses gadolinium, and the U-235 enrichment in the UO2-Gd2O3 fuel pellets is 2.5% and the weight percentage of Gd2O3 is 10%. The typical number of gadolinium-loaded fuel rods in the new fuel assembly is 4, 8, 12, 16, 20 or 24.

[0053] Table 3 below is a comparison of the fuel management schemes for the 18-month and 24-month refueling cycles of the core of 177 fuel assemblies of a 1 million kilowatt unit. As can be seen from Table 3, the core fuel management method described in this embodiment can achieve a 24-month long-cycle refueling design, the cycle length of the balancing cycle is 665 equivalent full-power days, and the power plant availability rate reaches more than 93%; the fuel assembly batch unloading fuel consumption is about 58GWd / tU, which is about 10GWd / tU higher than the highest batch unloading fuel consumption of the same core with 18-month refueling, and the average fuel consumption of the largest unloading assembly is less than 62GWd / tU.

[0054] Table 3 Comparison of fuel management schemes for different refueling cycles of 177 cores of 1 million kW unit

[0055]

[0056] Among them, the power plant availability in each table is converted according to "cycle length / (cycle length+overhaul time)".

[0057] It can be seen from the above embodiments that the fuel management method provided by the present invention greatly improves the utilization rate of nuclear fuel and the operating economy of the power plant.

[0058] Methods, processes, equipment, etc. not mentioned in this patent application are all based on existing methods in the art and will not be described in detail here.

[0059] 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 long-cycle fuel management method for core refueling of a pressurized water reactor, characterized in that: The balancing cycle refueling adopts new fuel assemblies with an enrichment of (5%~5.95%), and the number of new fuel assemblies for each refueling is less than or equal to 1 / 2 of the number of core assemblies; the balancing cycle is a 24-month refueling period, and the batch unloading burnup of the assemblies after balancing is ≥52GWd / tU; the core is cooled and moderated by light water, and the coolant contains soluble boron; the balancing cycle of the core adopts an extremely low leakage loading method; during refueling, the new fuel assemblies and the fuel assemblies with lighter burnup are placed in the inner area of ​​the core and placed crosswise, and the fuel assemblies with deeper burnup are placed in the outermost circle of the core; the enrichment of the new fuel assemblies is one or more.

2. A method for long-cycle fuel management of a pressurized water reactor core refueling according to claim 1, characterized in that: The enrichment of the new fuel assembly may be 5.45% and / or 5.95%.

3. A method for long-cycle fuel management of a pressurized water reactor core refueling according to claim 1, characterized in that: Each of the new fuel assemblies is arranged in a 17×17 array and contains 264 fuel rods, 24 guide tubes and one in-piles instrument tube; The number of gadolinium-loaded fuel rods in the new fuel assembly is 4, 8, 12, 16, 20 or 24.

4. The method for long-cycle fuel management of a pressurized water reactor core refueling according to claim 1, characterized in that: The UO2-Gd2O3 fuel pellets in the new fuel assembly have a U-235 enrichment of 2.5% and a Gd2O3 weight percentage of 10%.

5. The application of the long-cycle fuel management method for core refueling of a pressurized water reactor according to claim 1, characterized in that: Long-cycle fuel management design for pressurized water reactors of various mainstream reactor types.

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