A reactor core and a loading method thereof for realizing 18-month cycle of a power over 4000mw pressurized water reactor

Abstract

The application discloses a reactor core and a loading method for realizing 18-month cycle of a power over 4000MW pressurized water reactor, the reactor core is composed of 177 ring fuel assemblies, 20-month refueling strategy is adopted in the first cycle, each assembly is loaded in four zones, the enrichment of assemblies in the four zones is 4.1%, 4.25%, 4.45% and 4.95% respectively, the number of assemblies is 21, 64, 72 and 20 respectively, the assemblies with the enrichment of 4.95% are arranged in the outer zone of the reactor core, and the assemblies with the enrichment of 4.45%, 4.25% and 4.1% are arranged in the inner zone of the reactor core in a chessboard format; low-leakage refueling mode is adopted in the second cycle and the third cycle, 2 / 3 of the reactor core, namely 108 new assemblies, are loaded into the reactor core during each refueling; balanced refueling is realized in the fourth cycle, and low-leakage refueling mode is adopted for the reactor core. According to the application, after the pressurized water reactor composed of 177 fuel assemblies adopts the ring fuel assembly, the power of the reactor core is increased by 30% compared with the case of adopting the rod fuel, reaches 4130MW, the balanced cycle service life length still satisfies 18 months, and the economy of the reactor core is obviously improved.

Description

Technical Field

[0001] This invention belongs to the field of nuclear engineering technology, specifically relating to a reactor core and its loading method for a pressurized water reactor with a power output of over 4000MW using annular fuel to achieve an 18-month cycle. Background Technology

[0002] Currently, most pressurized water reactor cores, which consist of 177 fuel assemblies, use 12-foot rod fuel assemblies. The reactor output thermal power is typically 3050–3180 MW, the balance cycle life is about 18 months, the core power is relatively low, the core refueling cycle is short, and the economic efficiency is poor.

[0003] Compared to rod-shaped fuel assemblies, annular fuel assemblies use ring-shaped pellets with cladding both inside and outside the pellet. This allows for simultaneous cooling of the fuel pellet through both internal and external channels, reducing the fuel's thermal conductivity thickness and increasing its heat transfer area, thus lowering the peak pellet temperature and improving core safety. Furthermore, annular fuel assemblies can increase core power density by 20% to 50% while maintaining or improving existing reactor safety performance. This increase in reactor core power further enhances the economics of nuclear power plants. However, while annular fuel increases core power density, thereby increasing reactor output power and power generation, the uranium content is lower than that of traditional rod-shaped fuel assemblies. This results in a shorter core lifespan, meaning the core lifespan may no longer meet the 18-month requirement, negatively impacting core economics. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the above-mentioned deficiencies in the existing technology by providing a core and loading method for a pressurized water reactor with a power of over 4000MW that achieves an 18-month cycle. This method can ensure that the core power of the pressurized water reactor composed of 177 fuel assemblies is increased by 30% to 4130MW compared to the use of rod fuel after adopting annular fuel assemblies, while still meeting the 18-month balance cycle life, thereby significantly improving the core economy.

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

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

[0007] The first cycle adopts a 20-month refueling strategy, loading each annular fuel assembly into four zones. The enrichment of the annular fuel assemblies in the four zones are 4.1%, 4.25%, 4.45%, and 4.95%, respectively, with 21, 64, 72, and 20 annular fuel assemblies, respectively. The annular fuel assembly with the highest enrichment of 4.95% is placed in the outer zone of the core, while the annular fuel assemblies with relatively lower enrichment of 4.45%, 4.25%, and 4.1% are arranged in a checkerboard pattern in the inner zone of the core.

[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, or 108 new annular fuel assemblies, are loaded, while 108 fuel assemblies with deep burn-out or low enrichment are removed.

[0009] The fourth cycle achieves balanced refueling. The core adopts a low-leakage refueling method. During each refueling, 2 / 3 of the core, or 108 new annular fuel assemblies, are loaded, while 108 fuel assemblies with deeper burn-out or lower enrichment are removed.

[0010] Optionally, the first cycle core uses gadolinium-loaded fuel rods as a combustible poison, with the gadolinium-loaded fuel rods containing 8.0% Gd2O3 by weight.

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

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

[0013] Optionally, the new annular fuel assembly uses gadolinium-loaded fuel rods as a combustible poison, with the gadolinium-loaded fuel rods containing 8.0% Gd2O3 by weight.

[0014] Optionally, the number of combustible poison rods in the annular fuel assembly with an enrichment of 4.1% is 8 or 12; the number of combustible poison rods in the annular fuel assembly with an enrichment of 4.25% is 4 or 12; a portion of the annular fuel assembly with an enrichment of 4.45% contains no combustible poison and another portion contains combustible poison, and the number of combustible poison rods is 4, 8 or 12; a portion of the annular fuel assembly with an enrichment of 4.95% also contains no combustible poison and another portion contains combustible poison, and the number of combustible poison rods is 4, 12 or 16.

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

[0016] Optionally, each annular fuel assembly has fuel rods arranged in a 13×13 pattern, comprising 160 annular fuel rods, 8 guide tubes, and 1 instrument tube.

[0017] According to another aspect of the present invention, a core for a pressurized water reactor with a power output exceeding 4000MW that achieves 18-month cycles is provided, which is loaded using the method described above.

[0018] Beneficial effects:

[0019] The present invention relates to a pressurized water reactor (PWR) with a power output exceeding 4000MW that achieves an 18-month cycle and its loading method. Compared to existing technologies, this invention ensures that the PWR composed of 177 fuel assemblies, when using annular fuel assemblies, achieves a 30% increase in core power, reaching 4130MW, while maintaining the 18-month equilibrium cycle life, thus significantly improving core economics. Furthermore, the annular fuel assemblies allow for simultaneous cooling of fuel pellets through both internal and external channels, reducing fuel thermal conductivity thickness and increasing heat transfer area, thereby lowering peak pellet temperature and significantly improving core safety. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the core structure of a pressurized water reactor with a power output exceeding 4000MW that achieves an 18-month cycle, according to an embodiment of the present invention. Detailed Implementation

[0021] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0022] In the description of this invention, it should be noted that the terms "above" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience and simplification of the description and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0023] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0024] The existing pressurized water reactor (PWR) core, composed of 177 fuel assemblies, typically has an output thermal power of 3050–3180 MW and a balance cycle life of approximately 18 months. This results in low core power, short refueling cycles, and poor economic efficiency. This invention discloses a core loading method for a 4000 MW+ PWR achieving an 18-month cycle. The core consists of 177 annular fuel assemblies, wherein:

[0025] The first cycle adopts a 20-month refueling strategy, loading each annular fuel assembly into four zones. The enrichment of the annular fuel assemblies in the four zones are 4.1%, 4.25%, 4.45%, and 4.95%, respectively, with 21, 64, 72, and 20 annular fuel assemblies, respectively. The annular fuel assembly with the highest enrichment of 4.95% is placed in the outer zone of the core, while the annular fuel assemblies with relatively lower enrichment of 4.45%, 4.25%, and 4.1% are arranged in a checkerboard pattern in the inner zone of the core.

[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, or 108 new annular fuel assemblies, are loaded, while 108 fuel assemblies with deep burn-out or low enrichment are removed.

[0027] The fourth cycle achieves balanced refueling. The core adopts a low-leakage refueling method. During each refueling, 2 / 3 of the core, or 108 new annular fuel assemblies, are loaded, while 108 fuel assemblies with deeper burn-out or lower enrichment are removed.

[0028] Accordingly, the present invention also discloses a reactor core for a pressurized water reactor with a power output exceeding 4000MW that achieves 18-month cycles, which is loaded using the method described above.

[0029] Compared to existing technologies, this invention can ensure that the core power of a pressurized water reactor consisting of 177 fuel assemblies is increased by 30% to 4130MW when using annular fuel assemblies, while the balance cycle life still meets the requirement of 18 months, thus significantly improving the core economy.

[0030] Example 1

[0031] This embodiment discloses a core loading method for a pressurized water reactor with a power output exceeding 4000MW to achieve an 18-month cycle. The core consists of 177 annular fuel assemblies.

[0032] The first cycle adopts a 20-month refueling strategy, loading each annular fuel assembly (hereinafter referred to as assembly) into four zones. The enrichment of the annular fuel assemblies in the four zones are 4.1%, 4.25%, 4.45%, and 4.95%, respectively, and the number of annular fuel assemblies is 21, 64, 72, and 20, respectively. The annular fuel assembly with the highest enrichment of 4.95% is placed in the outer zone of the core, while the annular fuel assemblies with relatively lower enrichment of 4.45%, 4.25%, and 4.1% are arranged in a checkerboard pattern in the inner zone of the core.

[0033] The second and third cycles are transition cycles. The core adopts a low-leakage refueling method. During each refueling, 2 / 3 of the core, namely 108 new annular fuel assemblies (also known as new fuel assemblies or new assemblies), is loaded, while 108 fuel assemblies with deeper burn-out or lower enrichment are removed.

[0034] The fourth cycle achieves balanced refueling. The core adopts a low-leakage refueling method. During each refueling, 2 / 3 of the core, or 108 new annular fuel assemblies, are loaded, while 108 fuel assemblies with deeper burn-out or lower enrichment are removed.

[0035] Specifically, the height of the active section of the reactor core is 426.72 cm, and the size of the annular fuel assembly is 14 feet. The annular fuel assembly includes several 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 within each annular fuel assembly are arranged in a 13×13 configuration.

[0036] In this embodiment, starting from the second cycle, the reactor undergoes two refueling cycles, and by the fourth cycle, a balanced refueling is achieved.

[0037] In this embodiment, the low-leakage refueling method is to place the new annular fuel assembly as close to the inner part of the reactor core as possible.

[0038] In some implementations, the first cycle core uses gadolinium-loaded fuel rods as a combustible poison, with the gadolinium-loaded fuel rods containing 8.0% Gd2O3 by weight.

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

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

[0041] In some embodiments, the novel annular fuel assembly uses gadolinium-loaded fuel rods as a combustible poison, wherein the gadolinium-loaded fuel rods contain 8.0% Gd₂O₃ by weight, and the gadolinium-loaded fuel rods contain... 235 The U enrichment level is 2.5%.

[0042] This method achieves optimal power flattening of the reactor core by strictly controlling the weight percentage of Gd2O3 and the enrichment of 235U in the gadolinium-loaded fuel rods, which is beneficial to core safety. Furthermore, the release of poisons at this ratio throughout the entire lifespan can best match the changes in core reactivity, thus enabling better control of reactivity.

[0043] In some implementations, the number of combustible poison rods in the annular fuel assembly with an enrichment of 4.1% is 8 or 12.

[0044] The number of combustible poison rods in annular fuel assemblies with an enrichment of 4.25% is 4 or 12.

[0045] The annular fuel assembly with an enrichment of 4.45% contains a portion of flammable poison and another portion of flammable poison, with the number of flammable poison rods being 4, 8, or 12.

[0046] The annular fuel assembly with an enrichment of 4.95% also includes a portion that does not contain flammable poison and another portion that does contain flammable poison, with the number of flammable poison rods being 4, 12, or 16.

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

[0048] The fuel assemblies in the first cycle core include: 12 new assemblies with 8 combustible poison rods each, enriched at 4.1%; 9 new assemblies with 12 combustible poison rods each, enriched at 4.1%; 24 new assemblies with 4 combustible poison rods each, enriched at 4.25%; 40 new assemblies with 12 combustible poison rods each, enriched at 4.25%; 24 new assemblies without combustible poison rods each, enriched at 4.45%; 16 new assemblies with 4 combustible poison rods each, enriched at 4.45%; 20 new assemblies with 8 combustible poison rods each, enriched at 4.45%; 12 new assemblies with 12 combustible poison rods each, enriched at 4.45%; and 20 new assemblies without combustible poison rods each, enriched at 4.95%.

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

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

[0051] The reactor core reaches equilibrium in the fourth cycle. At this point, the fuel assemblies in the core include: 8 sets of old assemblies with an enrichment level of 4.95% and no combustible poison rods; 20 sets of old assemblies with an enrichment level of 4.95% and 4 combustible poison rods; 28 sets of old assemblies with an enrichment level of 4.95% and 12 combustible poison rods; 13 sets of old assemblies with an enrichment level of 4.95% and 16 combustible poison rods; 8 sets of new assemblies with an enrichment level of 4.95% and no combustible poison rods; 20 sets of new assemblies with an enrichment level of 4.95% and 4 combustible poison rods; 44 sets of new assemblies with an enrichment level of 4.95% and 12 combustible poison rods; and 36 sets of new assemblies with an enrichment level of 4.95% and 16 combustible poison rods.

[0052] Table 1

[0053]

[0054]

[0055] This embodiment also discloses a reactor core for a pressurized water reactor with a power output exceeding 4000MW that achieves an 18-month cycle using the above method. Its specific structure is as described in the above method and will not be repeated here.

[0056] The core loading method for a pressurized water reactor (PWR) with a power output exceeding 4000MW, achieving an 18-month cycle, compared to existing technologies, ensures that the core power of a PWR consisting of 177 fuel assemblies using annular fuel assemblies is increased by 30% to 4130MW compared to using rod fuel, while still meeting the 18-month equilibrium cycle life requirement, thus significantly improving core economics. Furthermore, the annular fuel assemblies can simultaneously cool the fuel pellets through both inner and outer channels, reducing the fuel's thermal conductivity thickness and increasing its heat transfer area, thereby lowering the peak pellet temperature and significantly improving core safety.

[0057] Example 2

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

[0059] In this embodiment, the core fuel assembly arrangement after achieving a balanced cycle is as follows: Figure 1 As shown, the horizontal axis is arranged from right to left as AR, and the vertical axis is arranged from top to bottom as 1-15. The numbers in the reactor core are 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, and R8. The positions 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, and E13 are arranged in one cycle. 235 The component with a U enrichment of 4.95% is loaded in the remaining positions. 235 A new annular fuel assembly with a U enrichment of 4.95%.

[0060] It should be noted that, Figure 1 The position of the irradiated fuel assembly in the previous cycle is indicated by a combination of letters and numbers. For example, L3 indicates that the position of the irradiated fuel assembly in the previous cycle is L3.

[0061] This embodiment also discloses a reactor core for a pressurized water reactor with a power output exceeding 4000MW that achieves an 18-month cycle using the above method. Its specific structure is as described in the above method and will not be repeated here.

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

[0063] Table 2

[0064]

[0065]

[0066] Currently, there are no clear safety guidelines for the core parameters of pressurized water reactors using annular fuel assemblies. Referring to the existing design guidelines for pressurized water reactor cores with 177 assemblies, the core design guidelines in this embodiment are as follows:

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

[0068] 2) The design criteria are: maximum nuclear enthalpy rise factor ≤ 1.49 and maximum hot spot factor ≤ 2.60.

[0069] 3) The temperature coefficient of the reactor core moderator is ≤0 pcm / ℃;

[0070] 4) Maximum fuel consumption of the component ≤ 52000MWd / tU.

[0071] Based on 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 pressurized water reactors with a power output exceeding 4000MW using annular fuel to achieve an 18-month cycle can be determined. Annular fuel can be applied to a pressurized water reactor core with 177 assemblies. While increasing the core power by 30%, the balanced cycle can still meet the 18-month lifespan requirement.

[0073] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled 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 output exceeding 4000MW to achieve an 18-month cycle, characterized in that, The reactor core consists of 177 annular fuel assemblies. The first cycle adopts a 20-month refueling strategy, loading each annular fuel assembly into four zones. The enrichment of the annular fuel assemblies in the four zones are 4.1%, 4.25%, 4.45%, and 4.95%, respectively, with 21, 64, 72, and 20 annular fuel assemblies, respectively. The annular fuel assembly with the highest enrichment of 4.95% is placed in the outer zone of the core, while the annular fuel assemblies with relatively lower enrichment of 4.45%, 4.25%, and 4.1% are arranged in a checkerboard pattern in the inner zone of the core. The second and third cycles are transition cycles. The core adopts a low-leakage refueling method. During each refueling, 2 / 3 of the core, or 108 new annular fuel assemblies, are loaded, while 108 fuel assemblies with deep burn-out or low enrichment are removed. The fourth cycle achieves balanced refueling. The core adopts a low-leakage refueling method. During each refueling, 2 / 3 of the core, or 108 new annular fuel assemblies, are loaded, while 108 fuel assemblies with deeper burn-out or lower enrichment are removed.

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

3. The core loading method for achieving an 18-month cycle in a pressurized water reactor with a power output exceeding 4000MW according to claim 1, characterized in that, In gadolinium fuel rods 235 The U enrichment level is 2.5%.

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

5. The core loading method for achieving an 18-month cycle in a pressurized water reactor with a power output exceeding 4000MW according to claim 1, characterized in that, The new annular fuel assembly uses gadolinium-loaded fuel rods as a combustible poison, with the gadolinium-loaded fuel rods containing 8.0% Gd2O3 by weight.

6. The core loading method for achieving an 18-month cycle in a pressurized water reactor with a power output exceeding 4000MW according to claim 2 or 5, characterized in that, The number of combustible poison rods in annular fuel assemblies with an enrichment of 4.1% is 8 or 12. The number of combustible poison rods in annular fuel assemblies with an enrichment of 4.25% is 4 or 12. The annular fuel assembly with an enrichment of 4.45% contains a portion of flammable poison and another portion of flammable poison, with the number of flammable poison rods being 4, 8, or 12. The annular fuel assembly with an enrichment of 4.95% also includes a portion that does not contain flammable poison and another portion that does contain flammable poison, with the number of flammable poison rods being 4, 12, or 16.

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

8. The core loading method for achieving an 18-month cycle in a pressurized water reactor with a power output exceeding 4000MW according to claim 1, characterized in that, Each annular fuel assembly has fuel rods arranged in a 13×13 pattern, containing 160 annular fuel rods, 8 guide tubes, and 1 instrument tube.

9. A reactor core for a pressurized water reactor with a power output exceeding 4000MW that achieves 18 months of cycle time, characterized in that: It is loaded using the method described in any one of claims 1-8.

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