Reactor core for realizing 18-month circulation of pressurized water reactor with power of over 4000 MW and loading method of reactor core

Abstract

The invention discloses a reactor core for achieving 18-month circulation of a pressurized water reactor with the power exceeding 4000 MW and a loading method of the reactor core, the reactor core is composed of 177 groups of annular fuel assemblies, a 20-month refueling strategy is adopted in the first circulation, each assembly is divided into four areas to be loaded, the enrichment degrees of the assemblies in the four areas are 4.1%, 4.25%, 4.45% and 4.95% respectively, the number of the assemblies is 21, 64, 72 and 20 groups respectively, and the number of the assemblies in the four areas is 4.1%, 4.25%, 4.45% and 4.95% respectively. Placing 4.95% of the components in an outer area of the reactor core, and arranging 4.45% of the components, 4.25% of the components and 4.1% of the components in an inner area of the reactor core according to a checkerboard format; in the second cycle and the third cycle, a low-leakage refueling mode is adopted, and 2 / 3 of the reactor core, namely 108 groups of new assemblies, is loaded into the reactor core during refueling each time; and in the fourth cycle, balanced refueling is achieved, and the reactor core adopts a low-leakage refueling mode. According to the invention, after the annular fuel assembly is adopted by the pressurized water reactor consisting of 177 groups of fuel assemblies, the reactor core power is improved by 30% and reaches 4130MW compared with that when rod-shaped fuel is adopted, and the balance cycle life length still meets 18 months, so that the economical efficiency of the reactor core is obviously improved.

Description

Technical Field

[0001] The invention belongs to the technical field of nuclear engineering, and in particular relates to a core of a pressurized water reactor with a power exceeding 4000MW and using annular fuel to realize an 18-month cycle, and a loading method thereof. Background Art

[0002] At present, the core of a pressurized water reactor consists of 177 fuel assemblies, most of which use 12-foot rod-shaped fuel assemblies. The reactor thermal output power is usually 3050-3180MW, the equilibrium cycle life is about 18 months, the core power is low, the core refueling cycle is short, and the economy is poor.

[0003] Compared with the above-mentioned rod-shaped fuel assemblies, annular fuel makes the pellets into a ring shape, and there are claddings inside and outside the pellets. The fuel pellets can be cooled in both the inner and outer channels at the same time, which can reduce the thickness of the fuel heat conduction, increase the heat transfer area of ​​the fuel, reduce the peak temperature of the pellets, and help improve the safety of the core. In addition, the annular fuel components can increase the core power density by 20% to 50% while maintaining or improving the safety performance of the existing reactor. The increase in reactor core power is conducive to further improving the economy of nuclear power plants. However, although the use of annular fuel can increase the core power density, thereby increasing the reactor output power and the power generation level, the uranium loading of annular fuel is less than that of traditional rod-shaped fuel, which will shorten the core life, that is, the core life no longer meets the 18-month length, which is not conducive to the economy of the core. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a core and a loading method thereof for a pressurized water reactor with a power exceeding 4000MW and realizing an 18-month cycle, so as to ensure that after the pressurized water reactor composed of 177 groups of fuel assemblies adopts annular fuel assemblies, the core power is increased by 30% to 4130MW compared with the case of using rod-shaped fuel, and the balance cycle life length still meets 18 months, thereby significantly improving the core economy.

[0005] The technical solution of the present invention to solve the above technical problems is:

[0006] According to one aspect of the present invention, a core loading method for a pressurized water reactor with a power exceeding 4000 MW to achieve an 18-month cycle is provided, wherein the core is composed of 177 groups of annular fuel assemblies, wherein:

[0007] The first cycle adopts a 20-month refueling strategy, and the annular fuel assemblies are loaded in four areas. The enrichments of the annular fuel assemblies in the four areas are 4.1%, 4.25%, 4.45% and 4.95%, and the number of annular fuel assemblies is 21, 64, 72 and 20 groups, respectively. The annular fuel assemblies with the highest enrichment of 4.95% are placed in the outer core area, and the annular fuel assemblies with relatively low enrichment of 4.45%, 4.25% and 4.1% are arranged in a checkerboard pattern in the inner core area.

[0008] The second and third cycles are transition cycles. The core adopts a low-leakage refueling method. During each refueling, 2 / 3 of the core, i.e., 108 sets of new annular fuel assemblies, are loaded into the core, and 108 sets of fuel assemblies with higher burnup or lower enrichment are removed at the same time.

[0009] The fourth cycle achieves balanced refueling. The core adopts a low-leakage refueling method. Each time the core is refueled, 2 / 3 of the core, i.e. 108 new annular fuel assemblies, are loaded, and 108 fuel assemblies with deeper burnup or lower enrichment are removed at the same time.

[0010] Optionally, the first cycle core uses gadolinium-loaded fuel rods as burnable poison, and the weight percentage of Gd2O3 in the gadolinium-loaded fuel rods is 8.0%.

[0011] Optionally, the gadolinium-loaded fuel rods used in the first cycle core 235 U enrichment is 2.5%.

[0012] Optionally, the new annular fuel assembly has an enrichment of 4.95%.

[0013] Optionally, the new annular fuel assembly uses gadolinium-loaded fuel rods as burnable poison, and the weight percentage of Gd2O3 in the gadolinium-loaded fuel rods is 8.0%.

[0014] Optionally, the number of burnable poison rods in an annular fuel assembly with an enrichment of 4.1% is 8 or 12; the number of burnable poison rods in an annular fuel assembly with an enrichment of 4.25% is 4 or 12; a part of annular fuel assembly with an enrichment of 4.45% does not contain burnable poison, and the other part contains burnable poison, and the number of burnable poison rods is 4, 8 or 12; a part of annular fuel assembly with an enrichment of 4.95% also does not contain burnable poison, and the other part contains burnable poison, and the number of burnable poison rods is 4, 12 or 16.

[0015] Optionally, the height of the core active section is 426.72 cm and the size of the annular fuel assembly is 14 feet.

[0016] Optionally, the fuel rods of each annular fuel assembly are arranged in a 13×13 manner, including 160 annular fuel rods, 8 guide tubes, and 1 instrument tube.

[0017] According to another aspect of the present invention, there is provided a core of a pressurized water reactor with a power exceeding 4000 MW and capable of achieving an 18-month cycle, which is loaded by the method described above.

[0018] Beneficial effects:

[0019] Compared with the prior art, the core and loading method of the pressurized water reactor with a power exceeding 4000MW and realizing an 18-month cycle can ensure that the core power of the pressurized water reactor composed of 177 fuel assemblies is increased by 30% to 4130MW after the annular fuel assembly is used, compared with the rod-shaped fuel, and the balance cycle life length still meets 18 months, thereby significantly improving the core economy. In addition, the annular fuel can cool the fuel core blocks in the inner and outer channels at the same time, which can reduce the fuel heat conduction thickness, increase the fuel heat transfer area, reduce the core block peak temperature, and further significantly improve the core safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic structural diagram of a core of a pressurized water reactor with a power exceeding 4000 MW that realizes an 18-month cycle according to an embodiment of the present invention. DETAILED DESCRIPTION

[0021] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings in the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0022] In the description of the present invention, it should be noted that the term "upper" and the like to indicate orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience and simplification of description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0023] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0024] In view of the fact that the output thermal power of a pressurized water reactor core composed of 177 groups of fuel assemblies in the prior art is usually 3050-3180MW, the balance cycle life length is about 18 months, and there are problems such as low core power, short core refueling cycle, and poor economy, the present invention discloses a core loading method for a pressurized water reactor with a power exceeding 4000MW to achieve an 18-month cycle, wherein the core is composed of 177 groups of annular fuel assemblies, wherein:

[0025] The first cycle adopts a 20-month refueling strategy, and the annular fuel assemblies are loaded in four areas. The enrichments of the annular fuel assemblies in the four areas are 4.1%, 4.25%, 4.45% and 4.95%, and the number of annular fuel assemblies is 21, 64, 72 and 20 groups, respectively. The annular fuel assemblies with the highest enrichment of 4.95% are placed in the outer core area, and the annular fuel assemblies with relatively low enrichment of 4.45%, 4.25% and 4.1% are arranged in a checkerboard pattern in the inner core area.

[0026] The second and third cycles are transition cycles. The core adopts a low-leakage refueling method. During each refueling, 2 / 3 of the core, i.e., 108 sets of new annular fuel assemblies, are loaded into the core, and 108 sets of fuel assemblies with higher burnup or lower enrichment are removed at the same time.

[0027] The fourth cycle achieves balanced refueling. The core adopts a low-leakage refueling method. Each time the core is refueled, 2 / 3 of the core, i.e. 108 new annular fuel assemblies, are loaded, and 108 fuel assemblies with deeper burnup or lower enrichment are removed at the same time.

[0028] Correspondingly, the present invention also discloses a core of a pressurized water reactor with a power exceeding 4000MW and capable of achieving an 18-month cycle, which is loaded by the method described above.

[0029] Compared with the prior art, the present invention can ensure that after a pressurized water reactor consisting of 177 fuel assemblies adopts annular fuel assemblies, the core power is increased by 30% to 4130MW compared with when rod-shaped fuel is used, and the balance cycle life length still meets 18 months, thereby significantly improving the core economy.

[0030] Example 1

[0031] This embodiment discloses a core loading method for a pressurized water reactor with a power exceeding 4000MW to achieve an 18-month cycle, wherein the core is composed of 177 groups of annular fuel assemblies.

[0032] The first cycle adopts a 20-month refueling strategy, and the annular fuel assemblies (referred to as assemblies) are loaded in four areas. The enrichments of the annular fuel assemblies in the four areas are 4.1%, 4.25%, 4.45% and 4.95%, respectively. The number of annular fuel assemblies is 21, 64, 72 and 20 groups, respectively. The annular fuel assemblies with the highest enrichment of 4.95% are placed in the outer core area, and the annular fuel assemblies with relatively low enrichment of 4.45%, 4.25% and 4.1% are arranged in a checkerboard pattern in the inner core area.

[0033] The second and third cycles are transition cycles. The core adopts a low-leakage refueling method. Each time the core is refueled, 2 / 3 of the core, i.e., 108 sets of new annular fuel assemblies (also called new fuel assemblies or new assemblies) are loaded into the core, and 108 sets of fuel assemblies with higher burnup or lower enrichment are removed at the same time.

[0034] The fourth cycle achieves balanced refueling. The core adopts a low-leakage refueling method. Each time the core is refueled, 2 / 3 of the core, i.e. 108 new annular fuel assemblies, are loaded, and 108 fuel assemblies with deeper burnup or lower enrichment are removed at the same time.

[0035] Specifically, the height of the core active section is 426.72 cm, and the size of the annular fuel assembly is 14 feet. The annular fuel assembly includes a number of fuel rods, guide tubes and instrument tubes. In this embodiment, the annular fuel assembly includes 160 fuel rods, 8 guide tubes and 1 instrument tube. The fuel rods in each annular fuel assembly are arranged in a 13×13 manner.

[0036] In the method of this embodiment, starting from the second cycle, the reactor undergoes two material changes, and reaches a balanced material change in the fourth cycle.

[0037] In this embodiment, the low leakage fuel replacement method is: placing the new annular fuel assembly as close to the core as possible.

[0038] In some embodiments, the first cycle core uses gadolinium-loaded fuel rods as burnable poison, and the weight percentage of Gd2O3 in the gadolinium-loaded fuel rods is 8.0%.

[0039] In some embodiments, the 235U enrichment in the gadolinium-loaded fuel rod is 2.5%.

[0040] In some embodiments, the enrichment of the new annular fuel assembly is 4.95%.

[0041] In some embodiments, the new annular fuel assembly uses a gadolinium-loaded fuel rod as a burnable poison, wherein the weight percentage of Gd2O3 in the gadolinium-loaded fuel rod is 8.0%, and the weight percentage of Gd2O3 in the gadolinium-loaded fuel rod is 8.0%. 235 U enrichment is 2.5%.

[0042] The method strictly controls the Gd2O3 weight percentage and 235U enrichment in the gadolinium-loaded fuel rods, so that the power flattening effect of the core can be optimized, which is beneficial to the core safety. In addition, the release of poisons under this ratio during the entire life cycle can best match the changes in the core reactivity and can better control the reactivity.

[0043] In some embodiments, the number of burnable poison rods in the annular fuel assembly with an enrichment level of 4.1% is 8 or 12;

[0044] The number of burnable poison rods in an annular fuel assembly with an enrichment of 4.25% is 4 or 12;

[0045] A portion of the annular fuel assembly with an enrichment degree of 4.45% does not contain burnable poison, and another portion contains burnable poison, and the number of rods containing burnable poison is 4, 8 or 12;

[0046] A portion of the annular fuel assembly with an enrichment degree of 4.95% also contains no burnable poison, while another portion contains burnable poison, and the number of the burnable poison rods is 4, 12 or 16.

[0047] In some more specific embodiments, the number of fuel assemblies in each batch in seven cycles from the first cycle to the seventh cycle is as shown in Table 1, where:

[0048] The fuel assemblies in the first cycle core include: 12 new assemblies with an enrichment of 4.1%, containing 8 burnable poison rods; 9 new assemblies with an enrichment of 4.1%, containing 12 burnable poison rods; 24 new assemblies with an enrichment of 4.25%, containing 4 burnable poison rods; 40 new assemblies with an enrichment of 4.25%, containing 12 burnable poison rods; 24 new assemblies with an enrichment of 4.45%, without burnable poison rods; 16 new assemblies with an enrichment of 4.45%, containing 4 burnable poison rods; 20 new assemblies with an enrichment of 4.45%, containing 8 burnable poison rods; 12 new assemblies with an enrichment of 4.45%, containing 12 burnable poison rods; 20 new assemblies with an enrichment of 4.95%, without burnable poison rods.

[0049] The fuel assemblies in the second cycle core include: 20 groups of old assemblies with an enrichment of 4.45% and no burnable poison rods; 9 groups of old assemblies with an enrichment of 4.45% and containing 4 burnable poison rods; 8 groups of old assemblies with an enrichment of 4.45% and containing 8 burnable poison rods; 12 groups of old assemblies with an enrichment of 4.45% and containing 12 burnable poison rods; 20 groups of old assemblies with an enrichment of 4.95% and no burnable poison rods; 8 groups of new assemblies with an enrichment of 4.95% and no burnable poison rods; 28 groups of new assemblies with an enrichment of 4.95% and containing 4 burnable poison rods; 40 groups of new assemblies with an enrichment of 4.95% and containing 12 burnable poison rods; 32 groups of new assemblies with an enrichment of 4.95% and containing 16 burnable poison rods.

[0050] The fuel assemblies in the third cycle core include: 8 groups of old assemblies with an enrichment of 4.95% and no burnable poison rods; 28 groups of old assemblies with an enrichment of 4.95% and containing 4 burnable poison rods; 13 groups of old assemblies with an enrichment of 4.95% and containing 12 burnable poison rods; 20 groups of old assemblies with an enrichment of 4.95% and containing 16 burnable poison rods; 8 groups of new assemblies with an enrichment of 4.95% and no burnable poison rods; 20 groups of new assemblies with an enrichment of 4.95% and containing 4 burnable poison rods; 44 groups of new assemblies with an enrichment of 4.95% and containing 12 burnable poison rods; 36 groups of new assemblies with an enrichment of 4.95% and containing 16 burnable poison rods.

[0051] The core reaches equilibrium in the fourth cycle, at which time the fuel assemblies in the core include: 8 groups of old assemblies with an enrichment of 4.95% and no burnable poison rods; 20 groups of old assemblies with an enrichment of 4.95% and containing 4 burnable poison rods; 28 groups of old assemblies with an enrichment of 4.95% and containing 12 burnable poison rods; 13 groups of old assemblies with an enrichment of 4.95% and containing 16 burnable poison rods; 8 groups of new assemblies with an enrichment of 4.95% and no burnable poison rods; 20 groups of new assemblies with an enrichment of 4.95% and containing 4 burnable poison rods; 44 groups of new assemblies with an enrichment of 4.95% and containing 12 burnable poison rods; 36 groups of new assemblies with an enrichment of 4.95% and containing 16 burnable poison rods.

[0052] Table 1

[0053]

[0054]

[0055] This embodiment also discloses a core of a pressurized water reactor with a power exceeding 4000MW and achieving an 18-month cycle, which is obtained by the above method. The specific structure of the core is as described in the above method and will not be repeated here.

[0056] The core loading method of the pressurized water reactor with a power exceeding 4000MW in this embodiment realizes an 18-month cycle. Compared with the prior art, it can ensure that the core power of the pressurized water reactor composed of 177 fuel assemblies is increased by 30% to 4130MW after the annular fuel assembly is used compared with the rod-shaped fuel, and the balance cycle life length still meets 18 months, thereby significantly improving the core economy. In addition, the annular fuel can cool the fuel pellets in the inner and outer channels at the same time, which can reduce the fuel heat conduction thickness, increase the fuel heat transfer area, reduce the pellet peak temperature, and thus significantly improve the core safety.

[0057] Example 2

[0058] This embodiment discloses a core loading method for a pressurized water reactor with a power exceeding 4000MW to achieve an 18-month cycle. The reactor output thermal power is 4130MW. The method is basically the same as the method described in Example 1, except that:

[0059] In the method of this embodiment, after reaching the equilibrium cycle, the arrangement of the core fuel assembly is as follows: Figure 1 As shown, the horizontal axis is arranged from right to left by AR, and the vertical axis is arranged from top to bottom by 1-15, in the core L3, E3, J2, G2, P8, L2, E2, H2, P7, M7, K2, H5, F2, G4, B7, J4, J1, G1, D7, N5, P6, N4, H1, D3, B6, C5, P5, R7, M3, C4, A7, B5, L8, R8 , E10, A8, E8, P11, R9, N12, D13, A9, B11, N11, P10, M13, H15, C12, B10, C11, M9, J15, G15, G12, P9, J12, K14, H11, F14, D9, B9, H14, L14, E14, B8, J14, G14, L13, E13 Position arrangement runs a cycle 235 The component with U enrichment of 4.95% is loaded in the remaining positions 235 New annular fuel assembly with U enrichment of 4.95%.

[0060] It should be noted that Figure 1 A combination of letters and numbers is used to indicate the position of the irradiated fuel assembly in the previous cycle. For example, L3 indicates that the position of the irradiated fuel assembly in the previous cycle is L3.

[0061] This embodiment also discloses a core of a pressurized water reactor with a power exceeding 4000MW and achieving an 18-month cycle, which is obtained by the above method. The specific structure of the core is as described in the above method and will not be repeated here.

[0062] After calculation, the main parameters of the first cycle of the pressurized water reactor core of this embodiment are as shown in Table 2.

[0063] Table 2

[0064]

[0065]

[0066] At present, there is no clear safety criterion for the core parameters of a pressurized water reactor using an annular fuel assembly. Referring to the existing design criteria for the pressurized water reactor core of the 177 assembly, the core design criteria in this embodiment are as follows:

[0067] 1) Core fuel assembly 235 U enrichment ≤4.95%;

[0068] 2) The maximum core nuclear enthalpy rise factor ≤ 1.49 and the maximum hot spot factor ≤ 2.60 are used as design criteria;

[0069] 3) Core moderator temperature coefficient ≤ 0pcm / ℃;

[0070] 4) The maximum fuel consumption value of the component is ≤52000MWd / tU.

[0071] According to the calculation results of the main core parameters in Table 2, it can be determined that the core parameters meet the design criteria requirements.

[0072] Furthermore, a core loading method for a PWR with a power exceeding 4000MW using annular fuel to achieve an 18-month cycle can be determined. The annular fuel can be applied to a PWR core with 177 components. While the core power is increased by 30%, the balanced cycle can still meet the 18-month life span.

[0073] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, but the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A core loading method for a pressurized water reactor with a power exceeding 4000MW to achieve an 18-month cycle, characterized in that: The core consists of 177 annular fuel assemblies. The first cycle adopts a 20-month refueling strategy, and the annular fuel assemblies are loaded in four areas. The enrichments of the annular fuel assemblies in the four areas are 4.1%, 4.25%, 4.45% and 4.95%, and the number of annular fuel assemblies is 21, 64, 72 and 20 groups, respectively. The annular fuel assemblies with the highest enrichment of 4.95% are placed in the outer core area, and the annular fuel assemblies with relatively low enrichment of 4.45%, 4.25% and 4.1% are arranged in a checkerboard pattern in the inner core area. The second and third cycles are transition cycles. The core adopts a low-leakage refueling method. During each refueling, 2 / 3 of the core, i.e., 108 sets of new annular fuel assemblies, are loaded into the core, and 108 sets of fuel assemblies with higher burnup or lower enrichment are removed at the same time. The fourth cycle achieves balanced refueling. The core adopts a low-leakage refueling method. Each time the core is refueled, 2 / 3 of the core, i.e. 108 new annular fuel assemblies, are loaded, and 108 fuel assemblies with deeper burnup or lower enrichment are removed at the same time.

2. The core loading method for a pressurized water reactor with a power exceeding 4000 MW to achieve an 18-month cycle according to claim 1, characterized in that: The first cycle core uses gadolinium-loaded fuel rods as burnable poison, and the weight percentage of Gd2O3 in the gadolinium-loaded fuel rods is 8.0%.

3. The core loading method for a PWR with a power exceeding 4000 MW to achieve an 18-month cycle according to claim 1, characterized in that: Gadolinium-loaded fuel rods 235 U enrichment is 2.5%.

4. The core loading method for a PWR with a power exceeding 4000 MW to achieve an 18-month cycle according to claim 1, characterized in that: The enrichment of the new annular fuel assembly is 4.95%.

5. The core loading method for a pressurized water reactor with a power exceeding 4000 MW to achieve an 18-month cycle according to claim 1, characterized in that: The new annular fuel assembly uses gadolinium-loaded fuel rods as burnable poison, with a Gd2O3 weight percentage of 8.0%.

6. The core loading method for a PWR with a power exceeding 4000 MW to achieve an 18-month cycle according to claim 2 or 5, characterized in that: The number of burnable poison rods in annular fuel assemblies with an enrichment of 4.1% is 8 or 12; The number of burnable poison rods in an annular fuel assembly with an enrichment of 4.25% is 4 or 12; A portion of the annular fuel assembly with an enrichment degree of 4.45% does not contain burnable poison, and another portion contains burnable poison, and the number of rods containing burnable poison is 4, 8 or 12; A portion of the annular fuel assembly with an enrichment degree of 4.95% also contains no burnable poison, while another portion contains burnable poison, and the number of the burnable poison rods is 4, 12 or 16.

7. The core loading method for a pressurized water reactor with a power exceeding 4000 MW to achieve an 18-month cycle according to claim 1, characterized in that: The height of the core active section is 426.72 cm and the size of the annular fuel assembly is 14 feet.

8. The core loading method for a pressurized water reactor with a power exceeding 4000 MW to achieve an 18-month cycle according to claim 1, characterized in that: The fuel rods of each annular fuel assembly are arranged in a 13×13 pattern, including 160 annular fuel rods, 8 guide tubes and 1 instrument tube.

9. A core of a pressurized water reactor with a power exceeding 4000MW and achieving an 18-month cycle, characterized in that: The method according to any one of claims 1 to 8 is used for loading.

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