NUCLEAR REACTOR FUEL ASSEMBLY (APPLICATIONS)

Abstract

This invention relates to the field of nuclear engineering, and more specifically to fuel assemblies for VVER-type nuclear reactors. The current fuel assembly consists of a bundle of fuel elements arranged in a regular triangular pattern with a spacing of 12.2–12.3 mm within separator grids connected to a central tube, a hexagonal casing connected to an upper and a lower nozzle, and a residue filter. The outer diameter of the fuel element casing is between 0.720–0.733 µm of the pattern spacing, and the diameter of the fuel pellets is 7.57–7.60 mm. In a second application, the fuel assembly has a reinforcement structure consisting of a regular triangular pattern with a spacing of 12.60–12.75 mm and separator grids connected by longitudinal tubes and corner elements. In this case, the outer diameter of the fuel element casing is between 0.695–0.710 µm of the pattern spacing, and the diameter of the fuel pellets is again 7.57–7.60 mm.This invention makes it possible to increase the water-uranium ratio of fuel bundles, reduce the metal requirements of such bundles, and improve their neutronic properties and energy yields.

Description

1 G21C 3 / 30 TARIFF NUCLEAR REACTOR FUEL ASSEMBLY (APPLICATIONS) TECHNICAL FIELD The invention is beneficial to the field of nuclear engineering, particularly for systems such as the VVER-440, VVER-1000, and VVER-1200. It relates to types of nuclear reactor fuel assemblies. STATE OF THE ART VVER-440 and VVER-1000 nuclear reactor fuel assemblies are well-known and feature 10 different techniques used in previous models. structures (see Kirillov PL, et al. Thermohydraulic Calculation Handbook (Nuclear Reactors, Heat Exchangers, Steam Generators), Energoatomizdat, Moscow, 1990, figure P.8.1, (P.8.3 and P.8.5, pp. 317-319). In the VVER-440 nuclear reactor, the first and second generation fuel assemblies are arranged in a regular triangular pattern. a sub-tube connecting the placed fuel elements to a central tube via separating grids 15 It has a hexagonal housing that connects the nozzle and an upper nozzle. Fuel elements are sealed within a casing by resistance welding of a plug and an end section. It contains pellets and is secured with a 2-stage spring lock to prevent longitudinal movement. A larger spring pitch is the fastening part that rests against the coating with a certain tension, while a thinner one... Step 20: Balancing the lock that rests on the upper fuel pellet by applying pressure on the fuel pile. It is part of the lock. The advantage of the lock is that it prevents the welded joint between the casing and the plug from forming during operation. It is not loading. The outer diameter of the fuel element casing is 9.1 mm, and the outer diameter of the fuel pellets is 7.6-0.03 mm. The fuel element grid spacing in the first-generation VVER-440 reactor was 12.2 mm, for the second generation... and is 12.3 mm. 25 A known disadvantage of the VVER-440 nuclear reactor's fuel assemblies is their low water-uranium ratio. It is having. The water-uranium ratio n for a regular triangular grid pattern of fuel elements is given by the following formula: is calculated (see Skvortsov SA Pressurized water reactors (VVER) in the Soviet Union). Atomic Energy. Volume 5, 3rd edition, 1958, p. 247): 30 𝑛 √ , (1) 2 Here: s - grid spacing of fuel elements, d - outer diameter of the fuel element casing, dt is the outer diameter of the fuel pellet. Formula (1) calculations for the known fuel assemblies of the VVER-440 nuclear reactor, hexagonal 5 water-uranium ratio in containment and fuel elements with a grid spacing of 12.2…12.3 mm It shows that it is 1.41…1.47. From a thermal engineering perspective, the optimum amount of water in the cell for pressurized water VVER reactors is: Including the VVER-440 reactor, the optimum water content for nucleonics is close to practical. It has a value. The corresponding value of the water-uranium ratio, shown by nucleonics calculations, is 10. nopt = 1.9. Due to the low water-uranium ratio of the contained fuel assemblies, the current VVER-440, VVER- Increasing the grid spacing between fuel elements in VVER-1000 and VVER-1200 nuclear reactors. Fuel tank designs without enclosures, which make this possible, have been developed. Fuel assemblies in the VVER-1000 reactor and third-generation fuel in the VVER-440 reactor. In the bundles, the sheathing is excluded. However, in order to ensure their initial horizontal rigidity, Guide channels in the form of longitudinal tubes, separating grids, and connecting upper and lower nozzles. A reinforcement structure consisting of a central tube has been created. Additionally, VVER-1000 and VVER-1200 In the TVS-2M (fuel bundle) design of reactors, separator grids are point-to-point in the guide channels. It is rigidly connected to the source and the TVSA of the VVER-1000 reactor to the VVER-440 20 In the third-generation reactor arrays, the separator grids are rigidly connected by spot welding. There are additional longitudinal corner elements. From a technical standpoint and in terms of the results obtained, it is the closest to the first example of the proposed fuel system. This is the second-generation fuel assemblies of the VVER-440 nuclear reactor; this assemblies consist of fuel elements. It has an outer diameter of 9.1 mm, and the fuel elements are arranged in a regular triangular pattern within a hexagonal housing. and the grid gap between the fuel elements is 12.3 mm (see Bondar Yu.N., et al.). WWER-440 Fuel Design and Technology Improvement. 8th International WWER Fuel Conference. Performance, Modeling and Experimental Support Conference. Sofia, Bulgaria, Nuclear. Research and Nuclear Energy Institute, 2010, pp. 186-190). From a technical standpoint and in terms of the results obtained, the 30 closest to the second example of the proposed fuel bundle. This is a third-generation fuel assembly for the VVER-440 reactor (RU2728894, dated 03.08.2020). G21C3 / 30); this bundle has a support structure consisting of a central tube and 6 longitudinal corner elements. It has separator grids fixed to these elements using spot welding, and the fuel The outer diameter of the elements is 9.1 mm, and the fuel elements are arranged in a regular triangular pattern. The grill gap is 12.6 mm. 35 The value of 9.1 mm was selected as a single value for the outer diameter of the fuel element casing, and the fuel the required ranges of the outer diameters of the elements, the grid spacing of the separating grids and Their relationships (combinations of specific values ​​they contain) are not specified. This situation, The water-uranium ratio of the fuel assemblies of the VVER-440 and VVER-1000 nuclear reactors. It does not allow for increasing or decreasing metal consumption. Known fuel assemblies, 40 It has a water-uranium ratio ranging between 1.45 and 1.61, which is significantly below the optimum value. It is lower. 3 EXPLANATION OF THE INVENTION The aim of the present invention is to produce fuel for the VVER-440, VVER-1000 and VVER-1200 nuclear reactors. The goal is to increase the energy efficiency of the bundles. The technical result of the invention is to reduce the outer diameter of the fuel element coating, thereby decreasing metal consumption. by reducing and ultimately improving the neutronic properties and energy efficiency of VVER-440 and 5 The goal is to increase the water-uranium ratio of the fuel assemblies in VVER-1000 nuclear reactors. A BRIEF DESCRIPTION OF THE INVENTION The desired technical result is achieved with the invention in the following way: • Axial via a two-stage spring lock based on the fuel element coating. a resistance butt weld 10 having a bundle fuel element containing oriented compressed fuel pellets. 12.2...12.3 in separating grids connected to a central tube, closed with one end and one plug. Connected by an upper nozzle and a lower nozzle, arranged in a regular triangular pattern at mm intervals. The outer diameter of the fuel element housing, which includes a hexagonal housing and a waste filter, is the pattern. a nuclear reactor with a fuel element range of 0.720...0.733 mm and a fuel pellet diameter of 7.57...7.60 mm fuel bundle. 15 • Axial via a two-stage spring lock based on the fuel element coating. a resistance butt weld having a bundle of fuel elements containing oriented compressed fuel pellets. 12.60...12.75 in separating grids connected to a central tube, closed with one end and one plug. Tubes and corner elements are placed in a regular triangular pattern at mm intervals, leading to an upper nozzle, Fuel elements 20 include a load-bearing frame to which the lower nozzle is connected, and a waste filter. the outer diameter of the casing is 695...0.710 of the fuel element spacing in the pattern and fuel pellet A nuclear reactor fuel assembly characterized by having a diameter of 7.57-7.60 mm. • The separating grids are made of E110 zirconium alloy, and the cells are point-type. They are connected to each other using the same source. • The fuel elements are welded to the supporting grid, lower nozzle with collet joints. 25 • The casing, fuel element plug and tip are made of E110 zirconium alloy. • The spring lock of the pellets in the fuel elements is made of chrome-nickel alloy or stainless steel. It is made of steel. This entire set of features enables the achievement of the intended purpose of the invention and the new techniques mentioned above. It enables the achievement of results. 30 DESCRIPTION OF THE FIGURES Figure 1 shows the recommended fuel bundle (including the casing) according to the first example. Figure 2 shows the recommended fuel bundle (excluding the casing) according to the second example. Figure 3 shows the fuel element of the proposed fuel assembly. Figure 4 shows the cellular separator grid. 35 4 DETAILED DESCRIPTION OF THE INVENTION According to the first application, the nuclear reactor fuel bundle (including containment) is placed on the lower grid (5) two-stage spring lock (11) which is fixed, resting on the casing (13) of the fuel elements (2) by means of axially compressed fuel pellets (12) using resistance butt welding 5 in separating grids (4) connected to a central tube (3) closed with one end (14) and a plug (10) A bundle of fuel elements placed in a regular triangular pattern (15) at a range of 12.2...12.3 mm. (2), a hexagonal housing (6) connected with an upper nozzle (1) and a lower nozzle (8) and a waste filter (7), outer diameter of the housing of the fuel elements (2), spacing of the grid (15) 0.720...0.733 and contains fuel pellets (12) with a diameter between 7.57...7.60 mm. According to the second application, the (containerless) nuclear reactor fuel bundle is placed on the lower grid (5) 10 two-stage spring lock (11) which is fixed, resting on the casing (13) of the fuel elements (2) By means of axially compressed fuel pellets (12), one end was welded using resistance butt welding. (14) and closed with a plug (10), in separating grids (4) connected to a central tube (3) 12.60...12.75 a bundle of fuel elements (2) placed in a regular triangular pattern (15) at mm intervals; 15 by connecting longitudinal tubes (17) or corner elements (9) with longitudinal tubes (17) a reinforcement structure formed and connected with the upper nozzle (1) and the lower nozzle (8); lower nozzle (8) a waste filter (7) placed inside; the outer diameter of the housing of the fuel elements (2), placement the grid spacing (15) is between 0.695…0.710 and the diameter of the fuel pellets (12) is between 7.57…7.60 mm It includes the following: The casing (13), plug (10), tip (14) and separator grid (4) are made of Zirconium alloy E110 and 20 The separating grid (4) cells (16) are connected by spot welding. Spring lock (11), EK173-ID type chrome-nickel alloy or 12X18N10T type stainless steel It is made in a two-stage, spring-shaped form. The fuel elements are connected to the end (14) and the lower support grid (5) by a collet connection. As an example of fuel bundle design according to the first application, the fuel element spacing is 25 In VVER type nuclear reactor fuel assemblies with a thickness of 12.2…12.3 mm, the fuel element lining to reduce the outer diameter to 8.784…9.0159 mm, preferably 8.9 mm, and the uranium dioxide pellet outer It is recommended to keep the diameter the same, leaving it at 7.6-0.03 mm. Fuel element coating. The fact that the outer diameter is in the range of 8,784…9,016 mm means that the recommended fuel bundles are suitable for both VVER-440 30 nuclear reactors, as well as for VVER-1000 and VVER-1200 nuclear reactors. This ensures its feasibility. The analyses performed show that with known fuel assemblies... compared to a fuel element cladding with an outer diameter of 8.784…9.016 mm, preferably 8.9 mm. According to the first example, the proposed fuel bundle increased the water-uranium ratio to 1.54, metal that it reduces its consumption and ultimately improves its neutronic properties and energy efficiency It shows. 35 As an example of fuel bundle design according to the second application, the spacing of fuel elements. In VVER type nuclear reactor fuel assemblies with a thickness of 12.6...12.75 mm, the fuel element lining... to reduce the outer diameter to 8.757…9.0525 mm, preferably 8.9 mm, and the uranium dioxide pellet outer It is recommended to keep the diameter the same, leaving it at 7.6-0.03 mm. Fuel element coatings. The outer diameter being in the range of 8.757…9.052 mm, the recommended fuel bundles are both VVER-440 40 nuclear reactor, as well as for VVER-1000 and VVER-1200 nuclear reactors in practice This ensures its feasibility. The analyses performed show that with known fuel assemblies... In comparison, fuel element with an outer diameter of 8.9 mm, preferably in the range of 8.757…9.052 mm. According to the second example with its coating, the proposed fuel assembly has an optimal water-uranium ratio of 1.9. that it increased to 1.76, which is quite close to the value, reduced metal consumption, and ultimately It has been shown to improve neutronic properties and energy efficiency. For the practical application of the proposed design, the technology has been improved and a coating with an outer diameter of 8.9 mm has been produced. tubes (13) produced, separator grids (4), fuel elements (2) and fuel bundle production 5 technology has been improved and consists of fuel assemblies with a 12.3 mm fuel element spacing. A pilot batch has been produced and trial operations have commenced at Paks NPP. Compared to known designs, the proposed fuel bundle has a significantly higher water- It has a uranium content, with reduced metal consumption, and ultimately neutron properties and energy. Efficiency has been improved. 10

Claims

9 REQUESTS 1. Via a two-stage spring lock based on the coating of the fuel elements. an end containing axially compressed fuel pellets, welded using resistance butt welding. and 12.2...12.3 mm separating grids connected to a central tube, sealed with a plug. a bundle of fuel elements arranged in a regular triangular pattern between them, an upper 5 a nuclear nozzle and a hexagonal housing connected to a sub-nozzle, containing a waste filter. reactor fuel bundle, the pattern of the outer diameter of the fuel element casing of the fuel with a component spacing of 0.720...0.733 mm and a fuel pellet diameter of 7.57...7.60 mm It is characterized.

2. According to Claim 1, the nuclear reactor fuel assembly has separator gratings E110 10 It is made of zirconium alloy and the cells are joined together by resistance butt welding. It is characterized by its connection.

3. According to Claim 1, the nuclear reactor fuel assembly consists of fuel elements that reach the end nozzle. by connecting to the supporting grid which is welded with a collet joint It is characterized. 15 4. According to Claim 1, a nuclear reactor fuel assembly is defined as a reactor fuel tank, fuel The components, including the coating, plug, and tip, are made of E110 zirconium alloy. It is characterized by...

5. According to Claim 1, a nuclear reactor fuel assembly is defined as the fuel elements. The spring lock of the pellets should be made of chrome-nickel alloy or stainless steel. 20 It is characterized by...

6. Axial via a two-stage spring lock based on the fuel element coating. a plug and a stopper containing compressed fuel pellets in one direction, formed by resistance butt welding. enclosed with a regular triangular pattern on the separating grids at intervals of 12.60...12.75 mm. A bundle of fuel elements is installed, with an upper nozzle connected to a lower nozzle, 25 The booster structure is a nuclear reactor fuel assembly that includes a tailings filter, and fuel the outer diameter of the coating elements is 695...0.710 of the pattern spacing and the fuel pellet diameter It is characterized by having a diameter of 7.57...7.60 mm.

7. According to Claim 6, the nuclear reactor fuel assembly is located on the E110 separator grating. Made of zirconium alloy and the cells are joined together by resistance butt welding 30 It is characterized by its connection.

8. According to Claim 6, the nuclear reactor fuel assembly consists of fuel elements that reach the end nozzle. by connecting to the supporting grid which is welded with a collet joint It is characterized.

9. According to Claim 6, the nuclear reactor fuel assembly consists of 35 fuel elements. with its coating, stopper and tip being made of E110 zirconium alloy It is characterized.

10. According to Claim 6, a nuclear reactor fuel assembly is defined as the fuel elements. The pellet spring lock should be made of chrome-nickel alloy or stainless steel. It is characterized by 40.

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