Fuel assembly of water-moderated water-cooled reactor

FIELD: nuclear power engineering.

SUBSTANCE: proposed fuel assembly designed for use in water-moderated water-cooled reactors, primarily those of VVER-1000 type, is characterized in that its uranium dioxide mass in bundle, outer and inner diameters of fuel element cladding are 436.24 to 561.18 kg, 7.00 · 10-3 to 7.50 · 10-3 m, and 5.94 · 10-3 to 6.36 · 10-3 m, respectively, for bundle of 468 to 510 fuel elements, or uranium dioxide mass in bundle, outer and inner diameters of fuel element cladding are 451.37 to 582.17 kg, 7.60 · 10-3 to 8.30 · 10-3 m, and 6.45 · 10-3 to 7.04 · 10-3 m, respectively, for bundle of 390 to 432 fuel elements, or uranium dioxide mass in bundle, outer and inner diameters of fuel element cladding are 442.22 to 544.12 kg, 8.30 · 10-3 to 8.79 · 10-3 m, and 7.04 · 10-3 to 7.46 · 10-3 m, respectively, for bundle of 331 to 367 fuel elements, water-uranium ratio of subchannel being chosen between 1.27 and 1.83.

EFFECT: reduced linear heat loads and fuel element depressurization probability; enlarged reactor power control range, improved fuel utilization.

4 cl, 11 dwg

 

The technical field to which the invention relates.

The invention relates to nuclear engineering and relates to improved designs of fuel assemblies (FA), which is recruited to the active zone of the nuclear reactor in which the coolant and moderator water is used (so-called water-cooled nuclear reactors), used as a heat source for power plants, power plants, etc., especially in reactor thermal power of order (2600-3900) MW.

The level of technology

The fuel loading of the reactor consists of a large number of fuel elements (cartridges), the number of which in the active zone of water-water power reactors (VVER) in tens of thousands. To ensure the necessary rigidity of the truss rods, as well as ease of installation, handling, transportation and maintenance of the required cooling conditions unite them in bunches. Each beam is a uniform design of the fuel Assembly. The number of fuel rods in the fuel Assembly can be from several to several tens or even hundreds. The fuel rods in the fuel assemblies are interconnected by means of two limit and more than fifty grid spacers that are installed at a certain distance from each other along the height of the Assembly that provides a rigid spacing of the heat is widelyused elements around them cooled and compliance gaps between the fuel rods for the passage of fluid and provide the necessary water-to-uranium ratio in the cross section of the Assembly.

A fuel Assembly of the reactor VVER-1000 consists of a beam truss rods and frame Assembly, with the latter ensures the fastening of the fuel rods in the Assembly. The frame Assembly includes a hexagonal spacer grids, which are mechanically interconnected by a Central pipe and 18 of the guide channels, and with the shank and head. Each fuel Assembly contains 312 fuel rods with pellets of uranium dioxide (see Operating modes NPP with VVER-1000, the Library of the operator of the NPP, Issue 12, Moscow, Energoatomizdat, 1992, s-233, 4.3 and 4.4).

Design a truss rods and fuel assemblies for VVER-1000 should provide mechanical stability and strength, including in emergency conditions at high temperatures, which is complicated by the presence of powerful long-term fluxes of neutrons and gamma radiation. Damage to the fuel rod entails radioactive contamination loop fission products. Violation of the original geometric shape of a fuel rod may worsen the conditions of heat transfer from the fuel rod to the coolant. Therefore, in the design of fuel assemblies it is necessary first to consider the possibility of increasing the values of the heat transfer surface of a fuel rod to the active volume occupied by the nuclear fuel.

Known fuel Assembly water-cooled power reactor VVER-1000 soda is separated by the frame and the beam core fuel rods of the nuclear fuel in the form of uranium dioxide (see “Future fuel. - Vattenfall''s new approach,” Nuclear Engineering International, September 1997, p.25-31). In the beam of known fuel assemblies of VVER-1000 reactor contains 312 truss rods, made with an outer diameter 8.90·10-3m to 9.14·10-3m and having an average linear thermal load on the fuel rod from 15,90 kW/m to 16,71 kW/m Such TVEL provides a relatively high level of burnout of the fuel in the famous FA and well proven during operation of the domestic and foreign nuclear power plants with VVER-1000 reactors. However, it should be noted that in case of overheating of the fuel cladding, caused by changing conditions of their cooling may occur depressurization and even the destruction of the fuel rods. The fact that the low conductivity oxide fuel used in the reactors of the VVER-1000, determines its high temperature when operating in the normal operation, a relatively large amount of accumulated heat, and, as a consequence of an accident with blackouts NPP and accident loss of coolant this leads to a considerable heating of the fuel cladding in the first few seconds. Achieved in case of accidents with loss of coolant temperature when using regular fuel largely depends on the initial linear thermal loads on the fuel rod. So, when a large leakage of the primary circuit of the reactor VVER-1000 fuel rods with a maximum heat is howling load for five seconds have design temperature shell ~900° C. At the same time in the same conditions, fuel load, close to the average, heated to 550-600°C.

Experimental and computational studies show that from the point of view to prevent the possibility of leaks in the fuel rods in relation to accidents with loss of coolant temperature limit shells should not exceed ~700-750°C. Therefore, if the core of VVER-1000 reactor to reduce the maximum linear thermal load, it is possible heating of the shells would not exceed the above limit temperature. This essentially solves the problem of possible depressurization of the fuel rods at the initial stage of the accident loss of coolant. In particular, this problem is exacerbated at higher burnup fuel, when the efficiency of the fuel rods even in normal operating conditions close to the maximum allowable.

From the above it follows that to improve the safety of existing and newly designed nuclear power plants with VVER-1000 is a need to develop core fuel container designs of reduced diameter when increased their number in FA (while maintaining the reactor power and is close to the standard fuel assemblies of water-uranium relationship of the fuel lattice), which will fundamentally solve the problem of possible leaks in the fuel rods at a beginning who stage accidents with loss of coolant. In addition, with the development of an advanced active zone of reactor VVER-1000, you must make a choice of the main parameters of the conditions of maximum preservation of core design and nuclear power plants, as well as providing acceptable neutron-physical and thermal-hydraulic characteristics that are close to the standard characteristics of the core of VVER-1000 reactor, since the present invention is the development of a new reactor.

This approach leads to some constraints on the choice of the main parameters of the upgraded active zone of reactor VVER-1000, which are as follows:

- step (236 mm) between the axles FA and the height of the upgraded fuel assemblies must be the same as in the standard design of the VVER-1000;

- the size of the "turnkey" and the height of the fuel cores modernized FA compared with the standard design of the VVER-1000 should not exceed 1.5 and 2.83%, respectively;

- the diameter of the rods and their number in the upgraded FA should reduce the linear heat loads in the fuel rods modernized active area;

- reduction of fuel loading in the upgraded FA compared with the standard design of the fuel assemblies of VVER-1000 reactor should not exceed 10%;

- increase of the hydraulic friction losses in the modernise without vannoy FA compared with the standard design FA must not exceed the available resources at the head of the main circulation pump (MCP) of VVER-1000 reactor;

- placing agencies of the control system and protection system (CPS) should be the same as in the standard design of the active zone of the reactor VVER-1000.

To increase the burnup of nuclear fuel or to improve the safety of operation at a given load, due to limitations associated with the maximum allowable fuel temperature and the heat sink, strive to increase the ratio of the surface of a fuel rod to its weight, which reduces heat flow by increasing the surface. The decrease of specific heat loads on the fuel rods can be achieved through the use of fuel with a reduced diameter, namely the diameter of the fuel elements 6.0·10-3m and 6.80·10-3m (see Beck Mrs x, Gorokhov V.F., Dubansky A.S., Kolosovsky VG, Lunin GL, Panyushkin A.K. and Proshkin AA “improving the fuel performance of WWER-440 and WWER-1000 reactors by reducing the diameter of the fuel elements,” paper presented at the conference “Top Fuel-97”, Manchester, 1997). However, because fuel loading (U235) u upgraded fuel assemblies of VVER-1000 reactor is not increased, and U235uploaded by 5-6% less, despite the fact that the upgraded fuel assemblies with fuel rods with a diameter of 6.8·10-3m with initial enrichment equal to the enrichment of the fuel in a regular FA, achieved a burnup of fuel more than the regular TV is, it does not compensate fully for the loss in the duration of operation of the fuel load compared with standard TVs. Therefore, the above limitations should also add the following:

- to ensure the design and operation time of the fuel loading fuel assemblies reduce fuel loading in the upgraded FA compared with the standard design of the fuel assemblies must be compensated for by increasing the burnup in the upgraded fuel assemblies in relation to the standard fuel assemblies.

Closest to the technical nature of the described technical solution is a fuel Assembly water-cooled power reactor containing frame, hexagonal spacer grids, cells which are placed in the beam rod fuel elements from the fuel core of uranium dioxide, enclosed in a sheath (EN 2143143, G 21 3/32, 20.12.1999).

The use of such fuel assemblies in the modernized active zones of the reactor VVER-1000 allows for reducing thermal load of the fuel rods to provide the possibility of extending the range of the maneuvering capacity of the reactor, to increase the burnup of the fuel and reduce the likelihood of leaks in the fuel elements.

However, a comparative assessment of the costs of standard fuel assemblies of WWER-1000 (diameter rods 9.1·10-3m) and upgraded fuel assemblies (fuel rods of reduced diameter) on the AZAL, that factory cost of the upgraded fuel assemblies for VVER-1000 reactors increased by 18%, which is one of the reasons why such fuel assemblies have not yet found practical application.

The invention

The present invention is the development and creation of new fuel assemblies of water-cooled power reactor thermal power from 2600 to 3900 MW with improved characteristics, in particular high safety and reliability in the operation of the newly designed and operating reactors, allowing compenstate increased the cost of the upgraded TVs and get the overall increase in economic efficiency.

The solution of this task, the invention can be obtained by technical results, a reduction of thermal loads of fuel elements, reducing the likelihood of leaks in the fuel cladding, reducing the non-uniformity of energy deposition, expanding the range of control of reactor power and improving fuel consumption by increasing the burnup of nuclear fuel.

These technical results are achieved by the fact that in the fuel Assembly water-cooled power reactor containing an armature comprising a hexagonal who Stantsionnaya lattice, in cells which are placed in the beam rod fuel elements from the fuel core of uranium dioxide, enclosed in a shell, the spacer grids contain from 481 to 517 cells for beam containing from 468 to 510 rod fuel elements with outer and inner diameters of the shell from 7.00·10-3m to 7.50·10-3m and from 5.94·10-3m to 6.36·10-3m, respectively, and the mass of uranium dioxide in the beam selected from 436.24 kg to 561.18 kg or spacer grids contain from 403 to 439 cells for beam containing from 390 to 432 rod fuel elements with outer and inner diameters of the shell from 7.60·10-3M. to 8.30·10-3m and from 6.45·10-3m to 7.04·10-3m, respectively, and the mass of uranium dioxide in the beam selected from 451,37 kg to 582,17 kg or spacer grids contain from 331 to 367 cells for beam containing from 318 to 360 rod fuel elements with outer and inner diameters of the shell from 8.30·10-3m to 8.79·10-3m and from 7.04·10-3m to 7.46·10-3m, respectively, and the mass of uranium dioxide in the beam selected from 442,22 kg to 544,12 kg, and water-to-uranium ratio of a cell selected from 1.27 to 1,83.

A distinctive feature of the present invention is that the spacer grids contain from 481 to cells for beam containing from 468 to 510 rod fuel elements with outer and inner diameters of the shell from 7.00·10-3m to 7.50·10-3m and from 5.94·10-3m to 6.36·10-3m, respectively, and the mass of uranium dioxide in the beam selected from 436,24 kg to 561,18 kg or spacer grids contain from 403 to 439 cells for beam containing from 390 to 432 rod fuel elements with outer and inner diameters of the shell from 7.60·10-3M. to 8.30·10-3m and from 6.45·10-3m to 7.04·10-3m, respectively, and the mass of uranium dioxide in the beam selected from 451,37 kg to 582,17 kg or spacer grids contain from 331 to 367 cells for beam containing from 318 to 360 rod fuel elements with outer and inner diameters of the shell from 8.30·10-3m to 8.79·10-3m and from 7.04·103-m to 7.46·10-3m, respectively, and the mass of uranium dioxide in the beam selected from 442,22 kg to 544,12 kg, and water-to-uranium ratio of a cell selected from 1.27 to 1,83 that characterizes the new concept of fuel assemblies of VVER-1000 reactor and, accordingly, the active zones of the VVER-1000 reactor with improved efficiency both in normal conditions and in emergency conditions, and due to the next. Since the frame, which enables the mounting beam sterilisation in FA, should be similar to the frame of standard fuel assemblies of VVER-1000 reactor, and the change in fuel loading in the upgraded FA compared with the standard design shall not exceed 10% (see above conditions), the water-to-uranium ratio of the cell modernized FA selected from 1.27 to 1,83, and the spacer grids contain from 481 to 517 cells for beam containing from 468 to 510 truss rods with outer and inner diameter of sheath from 7.00·10-3m to 7.50·10-3m and from 5.94·10-3m to 6.36·10-3m respectively, and the mass of uranium dioxide in the beam from 436,24 kg to 561.18 kg, or the spacer grids contain from 403 to 439 cells for beam containing from 390 to 432 truss rods with outer and inner diameter of sheath from 7.60·10-3M. to 8.30·10-3m and from 6.45·10-3m to 7.04·10-3m respectively, and the mass of uranium dioxide in the beam from 451,37 kg to 582.17 kg, or the spacer grids contain from 331 to 367 cells for beam containing from 318 to 360 core rods with outer and inner diameter of sheath from 8.30·10-3m to 8.79·10-3m and from 7.04·10-3m to 7.46·10-3m respectively, and the mass of uranium dioxide in the beam from 442,22 kg to 544,12 kg, so the average linear load on the fuel rods upgraded fuel assemblies is reduced to 1.19-1.42 times while maintaining rated the school of reactor power, and ensure the neutron-physical and thermal-hydraulic characteristics, close to the standard characteristics of VVER-1000. Or, as the calculations show, you can increase the heat capacity of the active zone while maintaining the required operational safety of the reactor by up to 2.9%, which is necessary to compensate for the increased cost of the upgraded fuel assemblies.

It is advisable that the spacer grids contained 481 box beam containing from 468 to 474 rod fuel elements with outer and inner diameters of the shell from 7.00·10-3m to 7.40·10-3m and from 5.94·10-3m to 6.28·10-3m, respectively, and the mass of uranium dioxide in the beam selected from 441.83 kg to 501,50 kg or 403 cells for beam containing from 390 to 396 rod fuel elements with outer and inner diameters of the shell from 7.70·10-3m to 8.10·10-3m and from 6.53·10-3m to 6.87·10-3m, respectively, and the mass of uranium dioxide in the beam selected from 446,64 kg to 508,25 kg or contained 331 cell for beam containing from 318 to 324 rod fuel elements with outer and inner diameters of the shell from 8.50·10-3m to 8.70·10-3m and 7.21·10-3m to 7.38·10-3m, respectively, and the mass of uranium dioxide in the beam selected from 442,22 kg to 479,89 kg, and water-to-uranium ratio of a cell selected from 1,41 up to 1.83.

It is also advisable mo is if the spacer grid contained 496 cells for beam containing 489 rod fuel elements with outer and inner diameters of the shell from 7.00·10-3m to 7.30·10-3m and from 5.94·10-3m to 6.19·10-3m, respectively, and the mass of uranium dioxide in the beam selected from 455,81 kg to 509,94 kg or 418 cells for beam containing 411 rod fuel elements with outer and inner diameters of the shell from 7.70·10-3m to 8.00·10-3m and from 6.53·10-3m to 6.79·10-3m, respectively, and the mass of uranium dioxide in the beam selected from 463,56 kg to 514,56 kg or 346 cells for beam containing 339 rod fuel elements with outer and inner diameters of the shell from 8.40·10-3m to 8.70·10-3m and 7.13·10-3m to 7.38·10-3m, respectively, and the mass of uranium dioxide in the beam selected from 455,03 kg to 502.11 kg, and water-to-uranium ratio of a cell selected from 1.48 to 1.83.

In addition, it is advisable that the spacer grids contained 517 cells for beam containing from 468 to 510 rod fuel elements with outer and inner diameters of the shell from 7.00·10-3m to 7.40·10-3m and from 5.94·10-3m to 6.28·10-3m, respectively, and the mass of uranium dioxide in the beam selected from 448.79 kg to 531.83 kg or 439 cells for beam containing from 390 to 432 rod fuel the x elements with outer and inner diameters of the shell from 7.60· 10-3m to 8.10·10-3m and from 6.45·10-3m to 6.87·10-3m, respectively, and the mass of uranium dioxide in the beam selected from 451.37 kg to 540.85 kg or 367 cells for beam containing from 318 to 360 rod fuel elements with outer and inner diameters of the shell from 8.30·10-3m to 8.79·10-3m and from 7.04·10-3m to 7.46·10-3m, respectively, and the mass of uranium dioxide in the beam selected from 442.22 kg to 521.03 kg, and water-to-uranium ratio of a cell selected from 1.41 to 1.83.

It should be emphasized that only the whole set of essential features provides a solution to the problem of the invention and obtaining the above-mentioned new technical results. Indeed, the known fuel rods with an outer diameter of sheath 6.0·10-3or 6.8·10-3m for fuel assemblies of VVER-1000 reactor. However, selecting only the values of the outer diameter of the sheath of the fuel element without specifying the ranges of the values of the inner and outer diameters of the sheath of the fuel element, the corresponding range of the mass of fuel, amount of fuel and cells in the spacer grids and their relationship, and without specifying the range of values of water-uranium relationship of the fuel lattice (which involves a combination of their constituent specific values) does not allow to implement new technical results. In addition, the Combi is the situation of the values components marked with a pair of ranges of inner and outer diameters of the rods, as well as the number of cells and the fuel rods in the beam without selecting a value of the mass of fuel (uranium dioxide) leads to the possibility of non-compliance allowable change the value of the water-to-uranium relationship of the fuel lattice and/or heating surface of the fuel rods, as well as the desired loading of nuclear fuel, which allows to solve (while maintaining reactor power) the task.

List of figures

1 shows a variant of the longitudinal incision modernized in accordance with the present invention the fuel assemblies for VVER-1000 reactor, figure 2 shows a variant of the cross section of the spacer grid with a bundle of fuel elements and displacers, figure 3 shows a variant of a fragment of the cross-section of the beam, containing 318 fuel elements, figure 4 shows a variant of a fragment of the cross-section of the beam, containing 360 fuel elements, figure 5 shows a variant of a fragment of the cross-section of the beam, containing 390 fuel elements, figure 6 shows a variant of a fragment of the cross-section of the beam, containing 432 fuel elements, figure 7 shows a variant of a fragment of the cross-section of the beam, containing 468 fuel elem is now, on Fig depicts a variant of a fragment of the cross-section of the beam containing 510 fuel elements, figure 9 shows a variant of the longitudinal section of the fuel element for the upgraded fuel assemblies of VVER-1000 reactor, figure 10 presents the curves characterizing the change of the maximum temperature of the shell most energonapryazhennosti staff and upgraded fuel rod used in the described fuel assemblies for VVER-1000 reactor during the accident with rupture of the pipeline DN 850, figure 11 presents the curves characterizing the change of the maximum temperature of the shell srednenapryazhennyh staff and described TVEL VVER-1000 in the accident with rupture of the pipeline DN 850.

Information confirming the possibility of carrying out the invention

A fuel Assembly 1 of the VVER-1000 reactor consists of a beam truss rods 2, shank 3, head 4 and frame 5. Using the frame 5 is secured fastening of the fuel rods 6 in the fuel Assembly 1. The frame 5 of the Assembly 1 includes a hexagonal spacer grid 7, which is mechanically connected to the Central pipe 8 and the guide channels 9 (for sinks). Central coarse 8 in the fuel Assembly 1 is intended for fixation of grid spacers 7 and for placement of in-core detectors. With the help of the shank 3 and the head 4 of the fuel Assembly octanal who live in the reactor core (see 1). In distantierului lattices 7 described TVs upgraded the core of VVER-1000 reactor contains from 331 to 367 cells 10 (see figure 2) for beam 2, containing from 318 to 360 rods 6 (see figure 3 and figure 4) or 403 to 439 cells 10 for beam 2, containing from 390 to 432 rods 6 (see figure 5 and 6) or from 481 to 517 cells 10 for beam 2, containing from 468 to 510 rods 6 (see Fig.7 and Fig). Depending on the selected number of fuel rods 6 in beam 2 in free cells 10 grid spacers 7 can be installed channels 11 for displacers or burnable absorbers 12 and has a production channels and the like (not shown).

The fuel element 6 includes a fuel core, consisting of separate tablets 13 with a Central hole 14 with a diameter of from 1.15·10-3m to 1.45·10-3m (or solid) or cylindrical rods ranging in length from 6.90·10-3m to 12.00·10-3m placed in the shell 15 made with the outer and inner diameters, respectively, from 7.00·10-3m to 8.79·10-3m and from 5.94·10-3m to 7.46·10-3m, which is a structural bearing element and to which are attached end part 16 (see figure 2 and figure 9). The shell 15 during operation experiences stress due to expansion and fuel swelling, and also due to Gazovye the value of the fuel, especially in places corresponding to the boundary of the tablets 13 or rods. The elimination of these negative aspects is carried out by profiling the form of tablets 13 (or rods), in particular by performing their ends concave or conical shape of the side surface near the ends (not shown).

As the material of the tablets 13 the most appropriate use of pressed and sintered uranium dioxide with an average density (10.4-103-10.8·10-3) kg/m3but can also be used oxides of plutonium, thorium and carbides of uranium or a mixture of these fissile materials. The mass of uranium dioxide in the fuel Assembly is 428,52 kg to 582,17 kg

When choosing the thickness of the shell 15 of a fuel rod modernized active zone is most appropriate to maintain the ratio of shell thickness to the outer diameter of the described fuel rod is the same as in a regular fuel of VVER-1000 reactor that maintaining a pressure filling with helium 2.0 MPa helps to ensure stability of shells of TVEL modernized active zone, no less than for regular fuel. In addition, one must also consider the requirement that the radial gap between the tablets 13 of the fuel core and the shell 15 in the described fuel rods was not less than 0.05·10-3M. This condition is due to their technological difficulties in the Assembly of fuel elements.

Due to the low thermal conductivity of the material of the tablets 13 of the fuel core, and taking into account all the above conditions, the shell 15 of a rod fuel elements described TVs upgraded to the active zone of the reactor VVER-1000 must have outer and inner diameters (7.00·10-3-7.50·10-3) m and (5.94·10-3-6.36·10-3) m, respectively, for beam (468-510) fuel rods, or (7.60·10-3-8.30·10-3) m and (6.45·10-3-7.04·10-3) m, respectively, for beam (390-432) rods or (8.30·10-3-8.79·10-3) m and (7.04·10-3-7.46·10-3) m, respectively, for beam (331-367) fuel rods. The fact that the first three of the above conditions, it follows that the relative step h the location of the fuel rods (see figure 2) must provide water-uranium ratio of the cell 10 for the upgraded active zone, close to the water-to-uranium ratio of the cell arrays operating VVER-1000. The values of water-to-uranium relationship of the cell to gratings upgraded fuel assemblies are in the range from 1.27 to 1.83. Taking into account all the above conditions, and the results of neutronic, thermal-hydraulic and thermo-mechanical calculations and, above all, the results of the analysis of accidents VVER-1000 leakage of the coolant from the primary circuit, they defined the boundaries of the ranges of the main characteristics describe emeu FA upgraded to the active zone of the reactor VVER-1000. So, for a beam containing from 468 to 510 Fe:

- the outer diameter of the sheath of the fuel element selected from 7.00·10-3m to 7.50·10-3;

- the inner diameter of the sheath of the fuel element selected from 5.94·10-3m to 6.36·10-3m;

- weight of uranium dioxide selected from 436,24 kg to 561,18 kg;

in the spacer grids are made from 481 to 517 cells for beam containing from 390 to 432 Fe:

- the outer diameter of the sheath of a fuel rod is made from 7.60·10-3M. to 8.30·10-3;

- the inner diameter of the sheath of a fuel rod is made from 6.45·10-3m to 7.04·10-3;

- weight of uranium dioxide selected from 451,37 kg to 582,17 kg;

in the spacer grids are made from 403 to 439 of cells, and for beam containing from 318 to 360 Fe:

- the outer diameter of the sheath of a fuel rod is made from 8.30·10-3m to 8.79·10-3;

- the inner diameter of the sheath of a fuel rod is made from 7.04·10-3m to 7.46·10-3m;

- weight of uranium dioxide selected from 442,22 kg to 544,12 kg;

in the spacer grids are made from 331 to 367 cells, with water-to-uranium ratio of a cell selected from 1.27 to 1,83.

Execution of TVEL described fuel Assembly with the beam from 468 to 510 units with an outer diameter of less than 7.00·10-3m, for example 6.90·10-3m, and, therefore, execution of a fuel rod with an inner diameter of shell less 5.94·10-3m and weighing Oliva in FA less 436,24 kg, noncompliance with the above range of water-to-uranium ratio (1,27-1,83) leads to failure to comply with conditions relating to the provision of the project the duration of the operation of the fuel load due to reduction of fuel loading in the upgraded FA, compared with the standard design of the VVER-1000 (which must be compensated for by increasing the burnup in the upgraded fuel assemblies in relation to the standard FA), and the implementation of a fuel rod with an outer diameter greater than 7.50·10-3m (for example, 7.60·10-3m) and, therefore, execution of a fuel rod with an inner diameter of the shell more 6.36·10-3m and the mass of fuel in the fuel assemblies more 561,18 kg leads to failure to comply with conditions relating to the possible increase of the hydraulic friction losses in the upgraded fuel assemblies of VVER-1000 reactor in comparison with the standard design of the VVER-1000. Execution of TVEL described fuel Assembly with the beam from 390 to 432 piece with an outer diameter less 7.60·10-3m, for example 7.50·10-3m, and, therefore, execution of a fuel rod with an inner diameter of shell less than 6.45·10-3m and the mass of fuel in the fuel assemblies is less 451,37 kg and failure to follow the above range water-uranium relationship also leads to the failure to comply with conditions relating to the provision of the project the duration of the operation of the fuel load due to the decrease is the group of fuel loading in the upgraded FA compared with the standard design of the VVER-1000 (which must be compensated for by increasing the burnup in the upgraded fuel assemblies in relation to the standard FA) and execution of a fuel rod with an outer diameter greater than 8.30·10-3m (for example, 8.40·10-3m) and, therefore, execution of a fuel rod with an inner diameter of the shell more 7.04·10-3m and the mass of fuel in the fuel assemblies more 582,17 kg leads to failure to comply with conditions relating to the possible increase of the hydraulic friction losses in the upgraded fuel assemblies of VVER-1000 reactor in comparison with the standard design of the VVER-1000. Performing the same TVEL described fuel Assembly with the beam from 331 to 367 piece with an outer diameter less than 8.30·10-3m (for example, 8.20·10-3m) and, therefore, execution of a fuel rod with an inner diameter of shell less 7.04·10-3m and the mass of fuel in the fuel assemblies is less 442,22 kg and failure to follow the above range water-uranium relationship also leads to the failure to comply with conditions relating to the provision of the project the duration of the operation of the fuel load due to reduction of fuel loading in the upgraded FA compared with the standard design of the VVER-1000 (which must be compensated for by increasing the burnup in the upgraded fuel assemblies in relation to the standard FA), and the implementation of a fuel rod with an outer diameter greater than 8.79·10-3m (for example, 8.90·10-3m) and, therefore, execution of a fuel rod with an inner diameter of the shell more 7.46·10-3m and the mass of fuel in the aircraft 544,12 kg leads to failure conditions, regarding the possible increase of the hydraulic friction losses in the upgraded fuel assemblies of VVER-1000 reactor in comparison with the standard design of the VVER-1000.

It should be noted that the first four of the above conditions allow you to specify the preferred bounds of the ranges of the main characteristics of the described upgraded the core of VVER-1000 reactor, namely:

1. for fuel assemblies with spacer grids containing 517 of cells:

the beam contains 468 rods,

- the outer diameter of the sheath of the fuel element selected from 7.10·10-3m to 7.40·10-3m,

- the inner diameter of the sheath of the fuel element selected from 6.02·10-3m to 6.28·10-3,

the mass of uranium dioxide into fuel assemblies selected from 448,79 kg to 501,50 kg

- water-to-uranium ratio of a cell selected from 1.48 to 1,74;

2. for fuel assemblies with spacer grids containing 517 of cells:

the beam 510 contains the fuel rods

- the outer diameter of the sheath of the fuel element selected from 7.00·10-3m to 7.30·10-3m,

- the inner diameter of the sheath of the fuel element selected from 5.94·10-3m to 6.19·10-3m,

the mass of uranium dioxide into fuel assemblies selected from 475,83 kg to 531,83 kg

- water-to-uranium ratio of a cell selected from 1.55V to 1,83;

3. for fuel assemblies with spacer grids containing 496 cells:

the beam contains 89 Fe,

- the outer diameter of the sheath of the fuel element selected from 7.00·10-3m to 7.30·10-3m,

- the inner diameter of the sheath of the fuel element selected from 5.94·10-3m to 6.19·10-3m,

the mass of uranium dioxide into fuel assemblies selected from 455,81 kg to 509,94 kg

- water-to-uranium ratio of a cell selected from 1.55V to 1,83;

4. for fuel assemblies with spacer grids containing 481 cell:

the beam contains 468 rods,

- the outer diameter of the sheath of the fuel element selected from 7.10·10-3m to 7.40·10-3m,

- the inner diameter of the sheath of the fuel element selected from 6.02·10-3m to 6.28·10-3m,

the mass of uranium dioxide into fuel assemblies selected from 448,79 kg to 501,50 kg

- water-to-uranium ratio of a cell selected from about 1.47 to 1,74;

5. for fuel assemblies with spacer grids containing 481 cell:

the beam contains 474 rods,

- the outer diameter of the sheath of the fuel element selected from 7.00·10-3m to 7.30·10-3m,

- the inner diameter of the sheath of the fuel element selected from 5.94·10-3m to 6.19·10-3m,

the mass of uranium dioxide into fuel assemblies selected from 441,83 kg to 494,29 kg

- water-to-uranium ratio of a cell selected from 1.55V to 1,83;

6. for fuel assemblies with spacer grids containing 439 of cells:

the beam contains 390 Fe,

- the outer diameter of the sheath of the fuel element selected from 7.60·10-3m to 8.0· 10-3m,

- the inner diameter of the sheath of the fuel element selected from 6.45·10-3m to 6.87·10-3m,

the mass of uranium dioxide into fuel assemblies selected from 451.37 kg to 500.72 kg

- water-to-uranium ratio of a cell selected from 1.41 to 1.82;

7. for fuel assemblies with spacer grids containing 439 of cells:

the beam contains 432 vel,

- the outer diameter of the sheath of the fuel element selected from 7.60·10-3m to 8.00·10-3m,

- the inner diameter of the sheath of the fuel element selected from 6.45·10-3m to 6.79·10-3m,

the mass of uranium dioxide into fuel assemblies selected from 474.67 kg to 540.85 kg

- water-to-uranium ratio of a cell selected from 1.48 to 1.82;

8. for fuel assemblies with spacer grids containing 418 of cells:

the beam contains rods 411,

- the outer diameter of the sheath of the fuel element selected from 7.70·10-3m to 8.00·10-3m,

- the inner diameter of the sheath of the fuel element selected from 6.53·10-3m to 6.79·10-3m,

the mass of uranium dioxide into fuel assemblies selected from 463.56 kg to 514.56 kg

- water-to-uranium ratio of a cell selected from 1.48 to 1.73;

9. for fuel assemblies with spacer grids containing 403 cell:

the beam contains 390 Fe,

- the outer diameter of the sheath of the fuel element selected from 7.80·10-3m to 8.10·10-3m,

- the inner diameter of the sheath of the fuel element selected from 6.62·1 -3m to 6.87·10-3m,

the mass of uranium dioxide into fuel assemblies selected from 451.37 kg to 500.55 kg

- water-to-uranium ratio of a cell selected from 1.41 to 1.65;

10. for fuel assemblies with spacer grids containing 403 cell:

the beam contains 396 rods,

- the outer diameter of the sheath of the fuel element selected from 7.70·10-3m to 8.10·10-3m,

- the inner diameter of the sheath of the fuel element selected from 6.53·10-3m to 6.87·10-3m,

the mass of uranium dioxide into fuel assemblies selected from 456.64 kg to 508.25 kg

- water-to-uranium ratio of a cell selected from 1.41 to 1.73;

11. for fuel assemblies with spacer grids containing 367 cells:

the beam contains 318 rods,

- the outer diameter of the sheath of the fuel element selected from 8.55·10-3m to 8.79·10-3m,

- the inner diameter of the sheath of the fuel element selected from 7.25·10-3m to 7.46·10-3m,

the mass of uranium dioxide into fuel assemblies selected from 442.22 kg to 480.80 kg

- water-to-uranium ratio of a cell selected from USD 1.43 to 1.60;

12. for fuel assemblies with spacer grids containing 367 cells:

the beam contains 360 rods

- the outer diameter of the sheath of the fuel element selected from 8.30·10-3m to 8.60·10-3m,

- the inner diameter of the sheath of the fuel element selected from 7.04·10-3m to 7.30·10-3m,

- weight of uranium dioxide in FA select the and from 471,78 kg to 521,03 kg

- water-to-uranium ratio of a cell selected from 1.56 to 1.79;

13. for fuel assemblies with spacer grids containing 346 of cells:

the beam contains 339 rods,

- the outer diameter of the sheath of the fuel element selected from 8.40·10-3m to 8.70·10-3m,

- the inner diameter of the sheath of the fuel element selected from 7.13·10-3m to 7.38·10-3m,

the mass of uranium dioxide into fuel assemblies selected from 455,03 kg to 502,11 kg

- water-to-uranium ratio of a cell selected from 1.49 to 1.72;

14. for fuel assemblies with spacer grids containing 331 cell:

the beam contains 318 rods,

- the outer diameter of the sheath of the fuel element selected from 8.55·10-3m to 8.70·10-3m,

- the inner diameter of the sheath of the fuel element selected from 7.25·10-3m to 7.38·10-3m,

the mass of uranium dioxide into fuel assemblies selected from 442,22 kg to 471,01 kg

- water-to-uranium ratio of a cell selected from 1.49 to 1.60;

15. for fuel assemblies with spacer grids containing 331 cell:

the beam contains rods 324,

- the outer diameter of the sheath of the fuel element selected from 8.50·10-3m to 8.70·10-3m,

- the inner diameter of the sheath of the fuel element selected from 7.21·10-3m to 7.38·10-3m,

the mass of uranium dioxide into fuel assemblies selected from 445,31 kg to 479,89 kg

- water-to-uranium ratio of a cell selected from 1.49 to 1.64.

Review of the health and thermomechanical state of the fuel rods helped to clarify some basic design parameters of the fuel rods described TVs. As shown by computational studies, a significant reduction in heat load on the fuel rod eliminates traditional for VVER-type reactors and is not found in the foreign PWR design fuel pellets 13 with a Central hole 14 (see figure 2 and figure 9). This decision is caused, on the one hand, a relatively small decrease in the temperature of fuel through the Central hole 14 at low heat loads on the fuel rod 6 and the increased safety margin in relation to the melting of the fuel, and possible technological difficulties in the manufacture of the tablets 13 of reduced diameter with a Central hole 14 is less than 1.5·10-3m

The coolant water in the reactor (as in FA) moves upward, which provides cooling of fuel assemblies, including the mode of natural circulation. To obtain the same temperature of the coolant at the outlet of the fuel Assembly coolant flow through the Assembly may be shaped in accordance with the distribution of heat along the radius of the reactor by installing a throttle washers at the entrance to the FA (not shown). Heated in the reactor water is directed into a steam generator where it transfers its heat to the water of the secondary circuit, and then returns to the active zone.

The manufacturing techniques described design the components of fuel elements and fuel assemblies produced by known standard equipment and has no differences from the point of view of production of similar products.

Figure 10 and 11 as an example, presents the curves characterizing the change in the maximum design basis accident (MPA) temperature of fuel cladding with maximum and average load for the staff (the outer diameter of the shell regular TVEL 9.1·10-3m) and upgraded (the outer diameter of the shell of the described fuel elements 7.0·10-3m) active zones of the VVER-1000 reactor. The analysis of the condition of the fuel rods shows that for the hot fuel rod, the fuel rod with the maximum linear heat load) lowering the maximum temperature is 278°and for fuel rods with an average load 142°C. Such values reduce the temperature of the fuel cladding would fundamentally alter the level of efficiency of the fuel rods and the predicted degree of safety of VVER-1000 reactor. Primarily, this is due to the strong dependence of the mechanical properties of the sheath material temperature in the T>550°and intensively increasing contribution of heat prociconia reactions in the development of an emergency at temperatures T>700°C. Therefore, the transition to a modernized area and, accordingly, reduction of the maximum temperature at MPA 900°below 600°largely eliminates the influence of prociconia response to changes in material properties and geometric dimensions of the fuel claddings.

It should also be noted that the fuel rods described FA modernized the active zone of the reactor VVER-1000 due to the decrease of the specific heat loads have significantly lower fuel temperature and have a high efficiency due to the reduction of the impact on shell fuel pressure gaseous fission products. Reduced their output in the fuel rods modernized active zone also leads to less corrosion on the shell side of fuel. This gives reason to believe (design rationale)that the fuel rods described FA modernized the active zone of the reactor VVER-1000 actually achieving average burnup of 55-60 MW·day/kg efficiency of the fuel elements in the transient operation modes associated with the required maneuvering capacity, due to many factors: the level of thermal loads, the background work, the speed and magnitude of change of capacity, corrosion on the shell side of the fuel core, etc. To avoid depressurization of the fuel rods in the maneuvering mode restrictions are imposed on the speed and range of lifting capacities standard reactor, which leads to economic losses. Valid values "step" lifting power is most sharply decreased with the increase of fuel burnup, and initial linear load is I. Therefore, the reduction of linear thermal loads of the fuel rods is one of the most effective ways in solving this problem. Reducing the maximum linear thermal loads from 40 kW/m up to 20 kW/m is almost limitless in power change for existing designs of fuel assemblies. The average linear load of TVEL described TVs upgraded to the active zone of the reactor VVER-1000 with an outer diameter 7.00·10-3m to 7.50·10-3m is respectively 9,94 kW/m to 10,83 kW/m, for rods with an outer diameter 7.60·10-3M. to 8.30·10-3m is respectively 11,74 kW/m to 13.00 kW/m and from 14,08 kW/m to 15,94 kW/m, respectively, for fuel rods with an outer diameter of sheath from 8.30·10-3m to 8.79·10-3m (for regular fuel rod diameter 9.10·10-3m average linear load equal 16,71 kW/m). Therefore, the transition to reduced thermal stresses in the fuel element described FA modernized the active zone of the VVER-1000 expands the range of the maneuvering capacity of the reactor with high speed. It should also be noted that according to economic calculations to compensate for the increased cost of the upgraded FA enough or extension of the fuel cycle to a maximum of 25-30 Eph. days, or the increasing power of 2.9%. Evaluation sweat the social capabilities of the upgraded active zone show the extension of the fuel cycles of 30 Eph. the day is achieved with the implementation of the scheme overloads upgraded fuel assemblies with a more profound decrease in the leakage of neutrons, which is feasible on the VVER-1000 reactors with consideration of thermal growth stocks during the transition to reduced diameter fuel rods. Thermal-hydraulic calculations modernized the active zone of the reactor VVER-1000 acknowledge the potential for increasing the heating capacity of the active zone when using rods of reduced diameter on the value (up to 15%) significantly more than the requirement (2.9 percent) to compensate for the increased cost of the upgraded fuel assemblies. Thus, the above-described design of the upgraded fuel assemblies for VVER-1000 reactor allows not only to compensate for the increased cost, but also increase economic efficiency. Based on the above it can be stated that the transition to a modernized active zone with the described fuel assemblies in reactors VVER-1000 makes it possible to lower thermal load on the fuel rod 1.2-1.7 times. Such a significant reduction of linear thermal loads in fuel elements described FA modernized the active zone of the reactor VVER-1000 allows you to:

- to improve the safety of power units with VVER-1000 reactor;

- to ensure the possibility of solving the problem of maneuvering the power of the VVER-1000 reactor;

- increase the efficiency of the fuel rods under normal operating conditions, which gives grounds to consider the real achievement of the average burnup of the fuel elements 55-60 MW·day/kg

It should be noted that the described fuel assemblies can be used not only in the VVER-1000 reactors, and other pressurized water reactors pressurized water (PWR)water water boiling-water reactors (BWR) and pressurized heavy water reactors.

1. A fuel Assembly water-cooled power reactor containing an armature comprising a hexagonal spacer grids, cells which are placed in the beam rod fuel elements from the fuel core of uranium dioxide, enclosed in a shell, characterized in that the spacer grids contain from 481 to 517 cells for beam containing from 468 to 510 rod fuel elements with outer and inner diameters of the shell from 7.00·10-3to 7.50·10-3m and 5,94·10-3to 6,36·10-3m, respectively, and the mass of uranium dioxide in the beam selected from 436,24 to 561,18 kg, or the spacer grids contain from 403 to 439 cells for beam containing from 390 to 432 rod fuel elements with outer and inner diameters of the shell from 7,60·10-3to 8.30·10-3m and from 6,45·10-3to 7.04·10-3m tuberculosis is estwenno, and the mass of uranium dioxide in the beam selected from 451,37 kg to 582,17 kg, or the spacer grids contain from 331 to 367 cells for beam containing from 318 to 360 rod fuel elements with outer and inner diameters of the shell from 8.30·10-3to 8,79·10-3m and? 7.04 baby mortality·10-3to 7.46·10-3m, respectively, and the mass of uranium dioxide in the beam selected from 442,22 to 544,12 kg, and Vodorezova the ratio of cells selected from 1.27 to 1,83.

2. A fuel Assembly of a pressurized water reactor according to claim 1, characterized in that the spacer grids contain 481 box beam containing from 468 to 474 rod fuel elements with outer and inner diameters of the shell from 7.00·10-3to 7.40·10-3m and 5,94·10-3to 6,28·10-3m, respectively, and the mass of uranium dioxide in the beam selected from 441,83 to 501,50 kg, or the spacer grids contain 403 cells for beam containing from 390 to 396 rod fuel elements with outer and inner diameters of the shell from 7,70·10-3to 8.10·10-3m and 6,53·10-3to 6.87·10-3m, respectively, and the mass of uranium dioxide in the beam selected from 446,64 to 508,25 kg, or the spacer grids contain 331 cell for beam containing from 318 to 324 rod fuel elements with outer and inner diameters of the shell from 8.50· 10-3to 8.70·10-3m and from 7,21·10-3to 7.38·10-3m, respectively, and the mass of uranium dioxide in the beam selected from 442,22 to 479,89 kg, and Vodorezova the ratio of cells selected from 1,41 up to 1.83.

3. A fuel Assembly of a pressurized water reactor according to claim 1, characterized in that the spacer grids contain 496 cells for beam containing from 489 rod fuel elements with outer and inner diameters of the shell from 7.00·10-3to 7.30·10-3m and 5,94·10-3up to 6.19·10-3m, respectively, and the mass of uranium dioxide in the beam selected from 455,81 to 509,94 kg, or the spacer grids contain 418 cells for beam containing 411 rod fuel elements with outer and inner diameters of the shell from 7,70·10-3to 8.00·10-3m and 6,53·10-3to 6.79·10-3m, respectively, and the mass of uranium dioxide in the beam selected from 463,56 to 514,56 kg, or the spacer grids contain 346 cells for beam containing 339 rod fuel elements with outer and inner diameters of the shell from 8,40·10-3to 8.70·10-3m and from 7,13·10-3to 7.38·10-3m, respectively, and the mass of uranium dioxide in the beam selected from 455,03 to 502,11 kg, and Vodorezova the ratio of cells selected from 1.48 to 1,83.

4. Teplovi the determinant Assembly water-cooled power reactor according to claim 1, characterized in that the spacer grids contain 517 cells for beam containing from 468 to 510 rod fuel elements with outer and inner diameters of the shell from 7.00·10-3to 7.40·10-3m and 5,94·10-3to 6,28·10-3m, respectively, and the mass of uranium dioxide in the beam selected from 448,79 to 531,83 kg, or the spacer grids contain 439 cells for beam containing from 390 to 432 rod fuel elements with outer and inner diameters of the shell from 7,60·10-3to 8.10·10-3m and from 6,45·10-3to 6.87·10-3m, respectively, and the mass of uranium dioxide in the beam selected from 428,52 to 540,85 kg, or the spacer grids contain 367 cells for beam containing from 318 to 360 rod fuel elements with outer and inner diameters of the shell from 8.30·10-3to 8,79·10-3m and? 7.04 baby mortality·10-3to 7.46·10-3m, respectively, and the mass of uranium dioxide in the beam selected from 442,22 to 521,03 kg, and Vodorezova the ratio of cells selected from 1,41 up to 1.83.



 

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The invention relates to nuclear energy, and more particularly to fuel assemblies for nuclear reactors with pressurized water

The invention relates to nuclear engineering and involves the development of designs of fuel assemblies (TBS), which is typed in the active zone of the nuclear reactor in which the coolant and moderator water is used (so-called water-cooled nuclear reactors), used as a heat source for power plants, power plants, etc., especially in reactor thermal power of order (1150 - 1700) MW

The invention relates to nuclear engineering and involves the development of designs of fuel assemblies (FA), which is recruited to the active zone of the nuclear reactor in which the coolant and moderator water is used (so-called water-cooled nuclear reactors), used as a heat source for power plants, power plants, etc., especially in reactor thermal power of about 2600 - 3900 MW

The invention relates to nuclear engineering and relates to improved constructions of fuel elements (cartridges), members of the upgraded fuel assemblies (FA), of which recruited upgraded active area and can find application in various types of water-cooled housing nuclear reactors using fuel rods mounted parallel to each other, especially in water-cooled nuclear power reactors (VVER-440 or VVER-1000)

The pumping section // 2066486
The invention relates to the pumping sections of the fuel assemblies and can be used in high temperature gas cooled reactors, in particular in the reactors of nuclear rocket engines (YARD) with hydrogen carrier

FIELD: nuclear power engineering; fuel assembly manufacture.

SUBSTANCE: proposed fuel assembly has hexahedral spacer grid with coolant passage holes made in the form of equilateral triangles with rounded-off angles symmetrically disposed relative to holes for bottom plugs of fuel elements or tubular channels in the amount of six ones around each of them, their rounded-off angles being directed toward them; it also has similarly designed round holes for coolant passage.

EFFECT: enhanced flow section of holes for coolant passage through bottom support grid at same desired stiffness; reduced labor consumption and metal input.

2 cl, 7 dwg

FIELD: nuclear power engineering; fuel assemblies for pressurized-water reactors.

SUBSTANCE: proposed fuel assembly manufactured using prior-art technology and characterized in enhanced in-service bending stiffness has fuel element bundle, spacer grids disposed through height of fuel assembly, top and bottom nozzles joined together by means of added-stiffness elements connected to spacer grids and bottom nozzle. Added-stiffness elements are made in the form of tubes or cylindrical rods and substitute at least one fuel element in other-than-peripheral line of fuel element bundle. As an alternative, fuel element may have added-stiffness elements made in the form of tubes or cylindrical rods substituting one of fuel elements on each edge of peripheral line of fuel element bundle. There is still another alternative in which added-stiffness elements substitute central fuel element on each other-than-adjacent edge of fuel element bundle. Added-stiffness elements may be joined with top nozzle for longitudinal displacement.

EFFECT: enhanced stability of thermomechanical behavior of reactor core in promising cycles, facilitated transport and in-process handling.

4 cl, 7 dwg

The invention relates to fuel assemblies (FA) channel water cooled with boiling nuclear reactor, including reactors (RBMK)

The invention relates to fuel assemblies used for dual functions: energy production and regulation of the neutron flux in water-cooled nuclear power reactors, especially in nuclear reactors VVER-440

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The invention relates to nuclear reactors, and in particular to a fuel Assembly for a nuclear reactor

The invention relates to nuclear energy, and more specifically to the active zones of nuclear reactors with pressurized water

FIELD: nuclear power engineering; fuel assemblies for pressurized-water reactors.

SUBSTANCE: proposed fuel assembly manufactured using prior-art technology and characterized in enhanced in-service bending stiffness has fuel element bundle, spacer grids disposed through height of fuel assembly, top and bottom nozzles joined together by means of added-stiffness elements connected to spacer grids and bottom nozzle. Added-stiffness elements are made in the form of tubes or cylindrical rods and substitute at least one fuel element in other-than-peripheral line of fuel element bundle. As an alternative, fuel element may have added-stiffness elements made in the form of tubes or cylindrical rods substituting one of fuel elements on each edge of peripheral line of fuel element bundle. There is still another alternative in which added-stiffness elements substitute central fuel element on each other-than-adjacent edge of fuel element bundle. Added-stiffness elements may be joined with top nozzle for longitudinal displacement.

EFFECT: enhanced stability of thermomechanical behavior of reactor core in promising cycles, facilitated transport and in-process handling.

4 cl, 7 dwg

FIELD: nuclear power engineering; fuel assembly manufacture.

SUBSTANCE: proposed fuel assembly has hexahedral spacer grid with coolant passage holes made in the form of equilateral triangles with rounded-off angles symmetrically disposed relative to holes for bottom plugs of fuel elements or tubular channels in the amount of six ones around each of them, their rounded-off angles being directed toward them; it also has similarly designed round holes for coolant passage.

EFFECT: enhanced flow section of holes for coolant passage through bottom support grid at same desired stiffness; reduced labor consumption and metal input.

2 cl, 7 dwg

FIELD: nuclear power engineering.

SUBSTANCE: proposed fuel assembly designed for use in water-moderated water-cooled reactors, primarily those of VVER-1000 type, is characterized in that its uranium dioxide mass in bundle, outer and inner diameters of fuel element cladding are 436.24 to 561.18 kg, 7.00 · 10-3 to 7.50 · 10-3 m, and 5.94 · 10-3 to 6.36 · 10-3 m, respectively, for bundle of 468 to 510 fuel elements, or uranium dioxide mass in bundle, outer and inner diameters of fuel element cladding are 451.37 to 582.17 kg, 7.60 · 10-3 to 8.30 · 10-3 m, and 6.45 · 10-3 to 7.04 · 10-3 m, respectively, for bundle of 390 to 432 fuel elements, or uranium dioxide mass in bundle, outer and inner diameters of fuel element cladding are 442.22 to 544.12 kg, 8.30 · 10-3 to 8.79 · 10-3 m, and 7.04 · 10-3 to 7.46 · 10-3 m, respectively, for bundle of 331 to 367 fuel elements, water-uranium ratio of subchannel being chosen between 1.27 and 1.83.

EFFECT: reduced linear heat loads and fuel element depressurization probability; enlarged reactor power control range, improved fuel utilization.

4 cl, 11 dwg

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