A fuel assembly water-cooled power reactor

 

Used in construction of fuel assemblies used in water-cooled nuclear power reactors, especially in nuclear reactors VVER-440. In the fuel Assembly water-cooled power reactor mass of uranium dioxide in the beam, outer and inner diameters of the fuel cladding is from 82,24 kg to 190,78 kg, from 6.00·10-3m to 8.00·10-3m and 5,09·10-3m to 6.79·10-3m, respectively, for a beam of (174÷216) fuel elements or mass of uranium dioxide in the beam, outer and inner diameters of the fuel cladding is from 105,44 kg to 179,14 kg, from 7,80·10-3m to 8,79·10-3m and 6,62·10-3m to 7.47·10-3m, respectively, for a beam of (132÷168) fuel elements, and water-to-uranium ratio of a cell selected from 0,69 to 2.69. The technical result is the reduction of linear thermal loads, reducing the likelihood of leaks in the fuel elements, the expansion of the range of control of reactor power and improved fuel consumption. 6 C.p. f-crystals, 5 Il.

The technical field to which the apply adelayda assemblies (FA), of 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 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 five to ten intermediate 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 fuel elements around them th the new ratio in the cross section of the Assembly.

The active zone in water-cooled nuclear power reactors VVER-400 are drawn from the fuel assemblies, containing a bundle of fuel rods located in the casing hexagonal shape (see I. I. Emel'yanov, V. I. Meehan, M. Solonin And. etc. the Construction of nuclear reactors, M., Energoizdat, 1982, S. 76-78).

FA, as a rule, consists of a bundle of fuel rods and frame. The frame of the aircraft provides the integration and consolidation of the fuel rods in the Assembly and their spacing. The frame Assembly consists of the following main parts: a bearing rod end lattices, spacers or guides gratings, the longitudinal connecting elements, different types of distanciation and reference guide rails, and crimp sleeves. Moreover, the fuel assemblies of fuel rods, made of length corresponding to the length of the active zone, coupled by the following details: head Assembly to which is attached the upper part of the frame Assembly; a shaft Assembly that is attached to the lower part of the frame; a suspension Assembly - a device by which FA move, establish and hold in a vertical channel; a shock absorber FA - piece Assembly, which provides reduced impact loading at the fall Assembly on the support, and compensation of vibrations occurring in p is of the medium through the fuel assemblies (see G. N. Ushakov Technological channels and fuel elements of nuclear reactors, M., Energoizdat, 1981, S. 84-86).

To reduce the share of structural material in the core fuel assemblies may not have a cover, so-called Bisceglie FA, in which the bundle of fuel rods of the United spacer grating and the reference grating Assembly are connected by tubes and/or corners, (see I. I. Emel'yanov, V. I. Meehan, Solonin Century. And. and other Construction of nuclear reactors, M., Energoizdat, 1982, S. 77, Fig.3.10).

The cartridge of the WWER-440 reactor consists of a bundle of rod rear, hex housing-cover, a cylindrical shank, head and frame of the cassette, with the latter ensures the fastening of the fuel rods in the cassette. The frame of the cassette includes a hexagonal spacer grid (lower carrier bars, top and middle rails of the lattice of the zirconium alloy), which are mechanically interconnected by the Central tube of zirconium alloy. The lower ends of rods secured in the carrier bars and the upper ends of the fuel rods have the opportunity longitudinal movement in the guide lattice at temperature extensions. The lower supporting bars attached to the cylindrical shank of the cassette, and Verkhovets in the reactor vessel (see G. N. Ushakov Technological channels and fuel elements of nuclear reactors, M., Energoizdat, 1981, S. 89, Fig. 2.8 (a).

Design a truss rods and fuel assemblies for VVER-440 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 contains the frame and the beam core fuel rods of 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 WWER-440 reactor contains (120÷ 126) truss rods, made with an outer diameter 8,80· 10-3m to 9.14· 10-3m and having regrowing the combustion of fuel in the famous FA and well proven during operation of the domestic and foreign nuclear power plants with WWER-440. 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 thermal conductivity of the oxide fuel and reactors VVER-440, 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-440 fuel rods with a maximum heat load for five seconds have design temperature shell 850° 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, the limit t to reduce the maximum linear thermal load, 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-440 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 the initial stage of the accident loss of coolant. In addition, with the development of an advanced active zone of reactor VVER-440, 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 characteristie is the development of a new reactor.

This approach leads to some constraints on the choice of the main parameters of the upgraded active zones, which are as follows:

- step (147+/-0,3mm) between the axles FA and the height of the upgraded fuel assemblies in the core must be the same as in the standard design of the VVER-440;

- the size of the "turnkey" and the height of the fuel cores modernized FA compared with the standard design of the VVER-440 should not exceed 1.5% and 2.5%, 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 WWER-440 reactor should not exceed 10%;

- increase of the hydraulic friction losses in the upgraded FA compared with the standard design FA must not exceed the available resources at the head of the main circulation pump (MCP) of VVER-440;

the number, diameter and placement of organs CPS must be the same as in the standard design of the active zone of reactor VVER-440.

With increasing burnup of nuclear fuel, or to stand the first fuel 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 rods 6,0· 10-3m and 6.80· 10-3m (see Beck, E. G., Gorokhov C. F., Dubansky A. S., Kolosovsky Century BC, Lunin, L., Panyushkin A. K., and A. Proshkin A. “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, as the fuel loading in the upgraded FA 3.4% less than regular fuel assemblies for VVER-440, 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 TVs have burnups of the fuel is 2.1% more than regular TVs, it does not compensate fully for the loss in the duration of operation of the fuel load compared to the option with the regular FA. Therefore, the above limitations should also add the following:

- to ensure the design and operation time of the fuel C is to 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 2143144, G 21 3/32, 20.12.1999).

The use of such fuel assemblies in the modernized active zones of the reactor VVER-440 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 WWER-440 (the fuel rod diameter of 9.1· 10-3m) and upgraded fuel assemblies (fuel rods of reduced diameter) showed that the factory cost of the upgraded fuel assemblies for VVER-440 has 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 tesnotu and reliable in operation newly designed and operating reactors, allows you to compensate for the increased 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 spacer grids, 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 217 cells for beam containing from 174 to 216 rod fuel elements with outer and inner diameters of the shell from 6.00· 10-3m to 8.00· 10-3m and 5,09· 10-3m to 6.79· 10-3m, respectively, and the mass dioxide o from 132 to 168 rod fuel elements with outer and inner diameters of the shell from 7,80· 10-3m to 8,79· 10-3m and 6,62· 10-3m to 7.47· 10-3m, respectively, and the mass of uranium dioxide in the beam selected from 105,44 kg to 179,14 kg, and water-to-uranium ratio of a cell selected from 0,69 to 2.69.

A distinctive feature of the present invention is that the spacer grids contain 217 cells for beam containing from 174 to 216 rod fuel elements with outer and inner diameters of the shell from 6.00· 10-3m to 8.00· 10-3m and 5,09· 10-3m to 6.79· 10-3m, respectively, and the mass of uranium dioxide in the beam selected from 82,24 kg to 190,78 kg, or the spacer grids contain 169 cells for beam containing from 132 to 168 rod fuel elements with an outer diameter and inner diameter of the shell from 7,80· 10-3m to 8,79· 10-3m and 6,62· 10-3m to 7.47· 10-3m, respectively, and the mass of uranium dioxide in the beam selected from 105,44 kg to 179,14 kg, and water-to-uranium ratio of a cell selected from 0,69 to 2.69, what characterizes the new concept of fuel assemblies of WWER-440 reactor and, accordingly, the active zones of the reactor VVER-440 with enhanced performance in normal operating conditions and in emergency conditions and is in FA, should be similar to the frame of standard fuel assemblies of WWER-440 reactor, and is water-uranium relationship of the fuel lattice should be close to the value of the regular FA (water-to-uranium ratio of the cell staff FA to 1.47), water-to-uranium ratio of the cell modernized FA selected from 0,69 to 2.69, and the spacer grids are made 217 cells for beam containing from 174 to 216 core rods with the outer and inner diameters of the shell from 6.00· 10-3m to 8.00· 10-3m and 5,09· 10-3m to 6.79· 10-3m, respectively, and the mass of uranium dioxide in the beam from 82,24 kg to 190,78 kg or 169 cells for beam containing from 132 to 168 truss rods with outer and inner diameters of the shell from 7,80· 10-3m to 8,79· 10-3m and 6,62· 10-3m to 7.47· 10-3m, respectively, and the mass of uranium dioxide in the beam from 105,44 kg to 179,14 kg, so the average linear load on the fuel rods upgraded FA decreases 1,20÷ 1.76 times, while maintaining the rated power of the reactor and providing the neutron-physical and thermal-hydraulic characteristics that are close to the standard characteristics of the WWER-440 reactor. Or, as the calculations show, you can increase the heat capacity of the active zone under conditions of increased cost of the upgraded fuel assemblies.

It is advisable that the mass of uranium dioxide in the beam, outer and inner diameters of the sheath rod fuel element was 131,23 kg to 163,02 kg, from 7.00· 10-3m to 7.50· 10-3m and 5,94· 10-3m to 6,36· 10-3m, respectively, for a bunch of (204÷ 210) rod fuel elements or to the mass of uranium dioxide in the beam, outer and inner diameters of the sheath rod fuel element was 127,82 kg to 157,76 kg, from 7.90· 10-3m to 8.40· 10-3m and from 6,70· 10-3m to 7,13· 10-3m, respectively, for a bunch of (156÷ 162) rod fuel elements, and water-to-uranium ratio of a cell selected from 0.99 to 1.66.

It is also advisable that the mass of uranium dioxide in the beam, outer and inner diameters of the sheath rod fuel element was 130,67 kg to 162,02 kg, 7.20· 10-3m to 7.70· 10-3m and 6,11· 10-3m to 6,53· 10-3m, respectively, for a bunch of (192÷ 198) rod fuel elements or to the mass of uranium dioxide in the beam, outer and inner diameters of the sheath rod fuel element was 124,04 kg to 153,11 kg, 8,10· 10-3m to 8.60· adelayda elements, moreover, water-to-uranium ratio of a cell selected from 0.86 to 1,51.

In addition, it is advisable to weight of uranium dioxide in the beam, outer and inner diameters of the sheath rod fuel element was 129,41 kg to 160,21 kg, from 7,40· 10-3m to 7.90· 10-3m and 6,28· 10-3m to 6.70· 10-3m, respectively, for a bunch of (180÷ 186) rod fuel elements or to the mass of uranium dioxide in the beam, outer and inner diameters of the sheath rod fuel element was 124,81 kg to 144,15 kg, from 8.30· 10-3m to 8.70· 10-3m and? 7.04 baby mortality· 10-3m to 7.38· 10-3m, respectively, for a beam of 138 rod fuel elements, and water-to-uranium ratio of a cell selected from 0.74 to 1,37.

No less appropriate to the mass of uranium dioxide in the beam, outer and inner diameters of the sheath rod fuel element was kzt138.95 kg to 158,86 kg, from 7.00· 10-3M. to 7.30· 10-3m and 5,94· 10-3m up to 6.19· 10-3m, respectively, for beam 216-rod fuel elements or mass of uranium dioxide in the beam, outer and inner diameters of the sheath rod fuel element setzoomfactor for a bunch of 168 rod fuel elements, moreover, water-to-uranium ratio of a cell selected from 1.13 to 1.75.

Most appropriate to the mass of uranium dioxide in the beam, outer and inner diameters of the sheath rod fuel element was 131,95 kg to 153,69 kg, 7,60· 10-3m to 8.00· 10-3m and from 6,45· 10-3m to 6.79· 10-3m, respectively, for a beam of 174 rod fuel elements or to the mass of uranium dioxide in the beam, outer and inner diameters of the sheath rod fuel element was 122,28 kg to 140,75 kg, from 8,40· 10-3m to 8,79· 10-3m and from 7,13· 10-3m to 7.46· 10-3m, respectively, for beam 132 rod fuel elements, and water-to-uranium ratio of a cell selected from 0,69 to 1.30.

It is also advisable that the mass of uranium dioxide in the beam, outer and inner diameters of the sheath rod fuel element was 132,93 kg to 155,04 kg, from 7.50· 10-3m to 7.90· 10-3m and from 6,36· 10-3m to 6.70· 10-3m, respectively, for a beam of 180 rod fuel elements or mass of uranium dioxide in the beam, outer and inner diameters of the sheath rod fuel element was 12 the 138 rod fuel elements, moreover, water-to-uranium ratio of a cell selected from 0.74 to 1,37.

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 the shell 6,8· 10-3m for fuel assemblies of WWER-440 reactor. However, the choice of only a single value 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 a fuel rod, the appropriate range of fuel weight 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 combination of the values of the components marked with a pair of ranges of inner and outer diameters of the rods, without the choice of a value for 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, which allows to solve (while maintaining reactor power) delivered to the backside of the ance with the present invention the fuel assemblies for VVER-440; in Fig.2 shows a variant of the cross section of the spacer grid with a bundle of fuel elements; Fig.3 shows a variant of the longitudinal section of the fuel element for the upgraded fuel assemblies of WWER-440 of Fig.4 shows a cross section of the upgraded fuel Assembly, and Fig presents 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-440 in the accident with rupture of the pipeline DN 500.

Information confirming the possibility of carrying out the invention

A fuel Assembly 1 of the WWER-440 reactor consists of a beam truss rods 2, hex housing-cover 3, a cylindrical shank 4, the head 5 and the frame 6 (see Fig.1). Frame 6 provides fastening of the fuel rods 2 in FA. The frame 6 of the Assembly 1 includes a hexagonal spacer grid (bottom 7 of the carrier bars, the top 8 and average 9 guides lattice of the zirconium alloy), which are mechanically interconnected by a Central pipe 10 of zirconium alloy. The spacer grid 7-9 described for FA have 169 or 217 cell 11 (see ft.2). According to HN cylindrical plungers, burnable absorbers, technological channels, etc., (not shown). The lower ends of the fuel rods 2 rigidly fixed to the carrier 7 the grate and the upper ends of the fuel rods 2 have the opportunity longitudinal movement in the guide 9 lattice at temperature extensions. The bottom 7 of the carrier grating is fixed to a cylindrical shank 4 of the Assembly, and the top 8 guide bars respectively to the cylinder 5 fuel Assembly. With the help of the shank 4 and the head 5, the Assembly is installed in the reactor core.

Fuel element 2 includes a fuel core is made with a diameter of from 5.00· 10-3m to 7,33· 10-3m and consists of separate tablets 12 with a Central hole 13 in diameter from 0.79· 10-3m to 1.35· 10-3m (or solid) or cylindrical rods in length from 6.90· 10-3m to 12.00· 10-3m placed in the shell 14 made with the outer and inner diameters, respectively, from 6.00· 10-3m to 8,79· 10-3m and 5,09· 10-3m to 7.47· 10-3m, which is a structural bearing element and to which are attached end part 14 (see Fig.3 and Fig.4). The shell 14 during operation is experiencing stress due to expansion and rasphone is bleak or rods. The elimination of these negative aspects is carried out by profiling the form of tablets 12 (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 12 the most appropriate use of pressed and sintered uranium dioxide with an average density (10,4· 103÷10,8· 103) 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 82,24 kg to 190,78 kg

When choosing the thickness of the shell 14 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 the standard fuel elements of the reactor VVER-440 that maintaining a pressure fill with helium (0,2÷ 0,7) 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 clearance between the pellets 12 of the fuel core and the shell 14 in the described fuel rods was stvie low thermal conductivity material pellets 12 of the fuel core, and considering all of the above conditions, the shell 14 rod fuel elements described TVs upgraded to the active zone of reactor VVER-440 must have outer and inner diameters (6,00· 10-3÷8,00· 10-3) m and (5,09· 10-3÷6,79· 10-3) m, respectively, for beam (174÷ 216) rods or (7,80· 10-3÷8,79· 10-3) m and (6,62· 10-3÷7,47· 10-3) m, respectively, for beam (132÷ 168) 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 Fig.2) must provide water-uranium ratio of the cell 16 (see Fig.3) for the upgraded active zone, close to the water-to-uranium ratio of the cell arrays operating VVER-440. The values of water-to-uranium relationship of the cell to gratings upgraded fuel assemblies are in the range of from 0,69 to 2.69. 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-440 with leakage of the coolant from the primary circuit, they defined the boundaries of the ranges of the main characteristics of the described fuel Assembly for a modernized active zones is t 6,00· 10-3m to 8.00· 10-3m;

- the inner diameter of the sheath of the fuel element selected from 5,09· 10-3m to 6.79· 10-3;

- weight of uranium dioxide selected from 82,24 kg to 190,78 kg;

in the spacer grids are made 217 cells, and for beam containing from 132 to 168 Fe:

- the outer diameter of the sheath of a fuel rod is made from 7,80· 10-3m to 8,79· 10-3m;

- the inner diameter of the sheath of a fuel rod is made from 6,62· 10-3m to 7.47· 10-3m;

- weight of uranium dioxide selected from 105,44 kg to 179,14 kg;

in the spacer grids are made 169 cells, with water-to-uranium ratio of a cell selected from 0,69 to 2.69.

Execution of TVEL described fuel Assembly with the beam from 174 to 216 pieces, of an external diameter less than 6,00· 10-3m, for example 5,90· 10-3m and accordingly the performance of a fuel rod with an inner diameter of the shell is not more 5,08· 10-3m and the mass of fuel in the fuel assemblies of not more than 82,23 kg and failure to follow the above range water-to-uranium ratio (0,69-2,69) 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-440 (which should olnine of a fuel rod outer diameter greater than 8,00· 10-3m (for example, 8,10· 10-3m) and, accordingly, the implementation of a fuel rod with an inner diameter of the shell is not less 6,80· 10-3m and the mass of fuel in the fuel assemblies of not less than 190.79 kg leads to failure to comply with conditions relating to the possible increase of the hydraulic friction losses in the upgraded fuel assemblies of WWER-440 reactor in comparison with the standard design of the VVER-440 (the excess of the value of the relative pressure of the reactor coolant pump more than 19%). Performing the same TVEL described fuel Assembly with the beam from 132 to 168 units, of an external diameter less 7,80· 10-3m, for example 7,70· 10-3m, and accordingly the performance of a fuel rod with an inner diameter of the shell is not more 6,61· 10-3m and the mass of fuel in the fuel assemblies of not more than 105,43 kg and failure to follow the above range water-uranium from wearing also 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-440 (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 outer diameter greater than 8,79· 10-3m (for example, 8,90· 10-3m) and F FA not less 179,15 kg leads to failure conditions, regarding the possible increase of the hydraulic friction losses and upgraded fuel assemblies of WWER-440 reactor in comparison with the standard design of the VVER-440 (the excess of the value of the relative pressure of the reactor coolant pump more than 10%).

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 fuel rod for a modernized active zone of reactor VVER-440, namely:

1) for fuel assemblies with spacer grids containing 217 of cells:

the beam contains from 204 to 210 rods

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

- the inner diameter of the sheath of the fuel element selected from 5,94· 10-3m to 6,36· 10-3m,

the mass of uranium dioxide into fuel assemblies selected from 131,23 kg to 163,02 kg

- water-to-uranium ratio of a cell selected from 0.99 to 1.66 or beam contains 192 to 198 rods

- the outer diameter of the sheath of a fuel rod is made 7.20· 10-3m to 7.70· 10-3m,

- the inner diameter of the sheath of a fuel rod is made from 6,11· 10-3m to 6,53· 10-3m;

- weight of uranium dioxide selected from 130,67 kg to 162,02 kg

- water-to-uranium ratio of a cell selected from 0.86 to 1,51 or

the beam Cyr>m,

- the inner diameter of the sheath of a fuel rod is made from 6,28· 10-3m to 6.70· 10-3m,

- weight of uranium dioxide selected from 129,41 kg to 160,21 kg

- water-to-uranium ratio of a cell selected from 0.74 to 1,37.

2) for fuel assemblies with spacer grids containing 169 of cells:

the beam contains from 156 to 162 of the fuel rods,

- the outer diameter of the sheath of the fuel element selected from 7.90· 10-3m to 8.40· 10-3m,

- the inner diameter of the sheath of the fuel element selected from 6,70· 10-3m to 7,13· 10-3m,

the mass of uranium dioxide into fuel assemblies selected from 127,82 kg to 157,76 kg

- water-to-uranium ratio of a cell selected from 0.99 to 1.66 or

the beam contains from 144 to 150 of the fuel rods,

- the outer diameter of the sheath of a fuel rod is made from 8,10· 10-3m to 8.60· 10-3m,

- the inner diameter of the sheath of a fuel rod is made from 6,87· 10-3M. to 7.30· 10-3m,

- weight of uranium dioxide selected from 124,04 kg to 153,11 kg

- water-to-uranium ratio of a cell selected from 0.86 to 1,51 or

the beam contains rods 138,

- the outer diameter of the sheath of a fuel rod is made from 8.30· 10-3m to 8.70· 10-3m,

- the inner diameter of the sheath of a fuel rod is made from? 7.04 baby mortality· 10-3m to 7.38· 10-3m,

- weight of uranium dioxide selected Poslednij two of the above conditions should that modernized the active zone of reactor VVER-440 is the most appropriate execution of fuel assemblies with the following characteristics, namely:

1) for fuel assemblies with distantsioniruyuschih lattices containing 217 of cells:

the beam contains rods 216,

- 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 up to 6.19· 10-3,

- weight of uranium dioxide selected from kzt138.95 kg to 158,86 kg

- water-to-uranium ratio of a cell selected from 1.13 to 1.75 or

the beam contains rods 174,

- the outer diameter of the sheath of the fuel element selected from 7,60· 10-3m to 8.00· 10-3,

- the inner diameter of the sheath of the fuel element selected from 6,45· 10-3m to 6.79· 10-3,

- weight of uranium dioxide selected from 131,95 kg to 153,69 kg

- water-to-uranium ratio of a cell selected from 0.69 to 1.30 or

the beam contains 180 rods

- the outer diameter of the sheath of the fuel element selected from 7.50· 10-3m to 7.90· 10-3m,

- the inner diameter of the sheath of the fuel element selected from 6,36· 10-3m to 6.70· 10-3m,

- weight of uranium dioxide selected from 132,93 kg to 155,04 kg

- water-to-uranium ratio of a cell selected from 0.7 which contains rods 168,

- 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· 10-3m to 6.87· 10-3m,

- weight of uranium dioxide selected from 134,19 kg to 152,12 kg

- water-to-uranium ratio of a cell selected from 1.13 to 1.75 or

the beam contains 132 vel,

- the outer diameter of the sheath of the fuel element selected from 8,40· 10-3m to 8,79· 10-3m,

- the inner diameter of the sheath of the fuel element selected from 7,13· 10-3m to 7.46· 10-3m,

- weight of uranium dioxide selected from 122,28 kg to 140,75 kg

- water-to-uranium ratio of a cell selected from 0.69 to 1.30 or

the beam contains rods 138,

- the outer diameter of the sheath of the fuel element selected from 8.30· 10-3m to 8.70· 10-3m,

- the inner diameter of the sheath of the fuel element selected from? 7.04 baby mortality· 10-3m to 7.38· 10-3m,

- weight of uranium dioxide selected from 124,81 kg 144,15 to kg

- water-to-uranium ratio of a cell selected from 0.74 to 1,37.

Performance analysis 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 stavraki tablets with a Central hole. This decision is caused, on the one hand, a relatively small decrease in the temperature of fuel through the Central hole at low heat loads on the fuel elements and the increased safety margin but against the melting of the fuel, and possible technological difficulties in the manufacture of tablets of reduced diameter with a Central hole less than 1.5· 10-3m

Case-case 3 inside the fuel rods 2, integrates all parts of the fuel assemblies and provides the necessary direction of flow of the coolant within the fuel Assembly between the individual fuel rods 2 in the Assembly and between the fuel assemblies in the reactor core. Case-case 3 assemblies unloaded from the internal pressure of the fluid, caused by flow of coolant through the fuel Assembly. 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 of the coolant in the fuel Assembly (not shown).

The manufacturing techniques described constructions of fuel elements and fuel assemblies produced by known standard equipment is estaline curves, characterizing the change in the maximum design basis accident (MPA) temperature of the fuel cladding to the maximum load for the staff (the outer diameter of the sheath of standard fuel elements 9,10· 10-3m) and upgraded (the outer diameter of the sheath of the fuel element described FA 7,00· 10-3m) of the active zone of reactor VVER-440. From analysis of fuel elements in the specified mode can be seen (Fig.5) that the fuel elements in the described fuel Assembly has a significantly lower maximum temperature of the shell. For hot fuel rod, the fuel rod with the maximum linear heat load) lowering the maximum temperature is 278° C, and for fuel rods with an average load of 150° 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-440. Primarily, this is due to the strong dependence of the mechanical properties of the sheath material temperature in the T>550° C 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° With good size fuel claddings.

It should also be noted that the fuel rods described FA modernized the active zone of reactor VVER-440, 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 reactor VVER-440 real achievement average fuel burn-up (55÷ 60 MW· d./kg

The 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 "STN load. Therefore, the reduction of linear thermal loads of the fuel rods is one of the most effective ways of solving this problem. Reducing the maximum linear thermal loads from 40 kW/m up to 23 kW/m is almost limitless in power change for modernized designs of fuel assemblies. The average linear load of TVEL described TVs upgraded to the active zone of reactor VVER-440 with an outer diameter from 7.00· 10-3m to 8.00· 10-3m is (was 7.36÷ 7,54) CVG/m and (9,46÷ RS 9.69) kW/m for fuel rods with a diameter of sheath from 7,8· 10-3m to 8,79· 10-3m (for regular fuel rod with a diameter of 9.1· 10-3m average linear load equal 12,82 kW/m). Therefore, the transition to reduced thermal stresses in the fuel element described FA modernized the active zone of reactor VVER-440 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 maximum (25÷ 30) Eph. days, or the increasing power of 3.6%. Assess the potential of the upgraded active zone opererator upgraded fuel assemblies with a more profound decrease in the leakage of neutrons, that is doable on the VVER-440 with the increase of thermal reserves in the transition to the reduced diameter of the fuel rods. Thermal-hydraulic calculations modernized the active zone of reactor VVER-440 confirm the potential of 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 (3.6%) to compensate for the increased cost of the upgraded fuel assemblies. Thus the above-described design of the upgraded fuel assemblies for VVER-440 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-440 makes it possible to lower thermal load on the fuel rod in (1,33÷ 1,76) times. Such a significant reduction of linear thermal loads in fuel elements described FA modernized the active zone of reactor VVER-440 allows you to:

- to increase the safety of power plants with VVER-440;

- to ensure the possibility of solving the problems associated with the maneuvering capacity of the reactor VVER-440;

- increase the efficiency of topliva in fuel elements (55-60) MW· day/kg

It should be noted that the described fuel assemblies can be used not only in the VVER-440 and other pressurized water reactors pressurized water (PWR) and boiling-water reactors (BWR) and pressurized heavy water reactors.

Claims

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 217 cells for beam containing from 174 to 216 rod fuel elements with outer and inner diameters of the shell from 6.00·10-3to 8.00·10-3m and 5,09·10-3to 6.79·10-3m, respectively, and the mass of uranium dioxide in the beam selected from 82,24 to 190,78 kg or spacer grids contain 169 cells for beam containing from 132 to 168 rod fuel elements with outer and inner diameters of the shell from 7,80·10-3to 8,79·10-3m and 6,62·10-3to 7.47·10-3m, respectively, and the mass of uranium dioxide in the beam selected from 105,44 to 179,14 energeticheskogo reactor under item 1, characterized in that the mass of uranium dioxide in the beam, outer and inner diameters of the sheath rod fuel element is from 131,23 to 163,02 kg, from 7.00·10-3to 7.50·10-3m and 5,94·10-3to 6,36·10-3m, respectively, for the beam from 204÷210 rod fuel elements or mass of uranium dioxide in the beam, outer and inner diameters of the sheath rod fuel element is from 127,82 to 157,76 kg, from 7.90·10-3to 8.40·10-3m and from 6,70·10-3before 7,13·10-3m, respectively, for beam 156÷162 rod fuel elements, and water-to-uranium ratio of a cell selected from 0.99 to 1.66.

3. A fuel Assembly water-cooled power reactor under item 1, characterized in that the mass of uranium dioxide in the beam, outer and inner diameters of the sheath rod fuel element is from 130,67 to 162,02 kg, 7.20·10-3to 7.70·10-3m and 6,11·10-3to 6,53·10-3m, respectively, for a beam of 192÷198 rod fuel elements or mass of uranium dioxide in the beam, outer and inner diameters of the sheath rod fuel element is from 124,04 to 153,11 kg, 8,10· nevah fuel elements, moreover, water-to-uranium ratio of a cell selected from 0.86 to 1,51.

4. A fuel Assembly water-cooled power reactor under item 1, characterized in that the mass of uranium dioxide in the beam, outer and inner diameters of the sheath rod fuel element is from 129,41 to 160,21 kg, from 7,40·10-3to 7.90·10-3m and 6,28·10-3to 6.70·10-3m, respectively, for a beam of 180÷186 rod fuel elements or mass of uranium dioxide in the beam, outer and inner diameters of the sheath rod fuel element is from 124,81 to 144,15 kg, from 8.30·10-3to 8.70·10-3m and? 7.04 baby mortality·10-3to 7.38·10-3m, respectively, for a beam of 138 rod fuel elements, and water-to-uranium ratio of a cell selected from 0.74 to 1,37.

5. A fuel Assembly water-cooled power reactor under item 1, characterized in that the mass of uranium dioxide in the beam, outer and inner diameters of the sheath rod fuel element is from kzt138.95 to 158,86 kg, from 7.00·10-3to 7.30·10-3m and 5,94·10-3up to 6.19·10-3m, respectively, for beam 216-rod fuel elements or mass of uranium dioxide 152,12 kg, from 7,80·10-3to 8.10·10-3m and 6,62·10-3to 6.87·10-3m, respectively, for a beam of 168 rod fuel elements, and water-to-uranium ratio of a cell selected from 1.13 to 1.75.

6. A fuel Assembly water-cooled power reactor under item 1, characterized in that the mass of uranium dioxide in the beam, outer and inner diameters of the sheath rod fuel element is from 131,95 to 153,69 kg, 7,60·10-3to 8.00·10-3m and from 6,45·10-3to 6.79·10-3m, respectively, for a beam of 174 rod fuel elements or mass of uranium dioxide in the beam, outer and inner diameters of the sheath rod fuel element is from 122,28 to 140,75 kg, from 8,40·10-3to 8,79·10-3m and from 7,13·10-3to 7.46·10-3m, respectively, for beam 132 rod fuel elements, and water-to-uranium ratio of a cell selected from 0,69 to 1.30.

7. A fuel Assembly water-cooled power reactor under item 1 or 4, characterized in that the mass of uranium dioxide in the beam, outer and inner diameters of the sheath rod fuel element is from 132,93 to 155,04 kg, from 7.50·10-3to 7.9 operating elements or mass of uranium dioxide in the beam, outer and inner diameters of the sheath rod fuel element consists of 124.1 from 144,15 to kg, from 8.30·10-3to 8.70·10-3m and? 7.04 baby mortality·10-3to 7.38·10-3m, respectively, for a beam of 138 rod fuel elements, and water-to-uranium ratio of a cell selected from 0.74 to 1,37.



 

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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.

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FIELD: nuclear power engineering.

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4 cl, 11 dwg

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