Active zone and a fuel assembly channel uranium - graphite nuclear reactor

 

The invention relates to nuclear engineering and can be used in the active channel zones of uranium-graphite nuclear reactors, formed from the fuel assemblies, the design of which takes into account the previous and subsequent operation of the active zone. The active area includes a technology channels that have fuel assemblies, made in the form of two bundles of fuel elements fixed in the spacer grids. The spacer grids placed at the height of the Assembly between areas of technological channels with weak cross sections. To do this, in the fuel Assembly in each beam end from the first support grid spacer grid is from the end of the support grid in the distance, the value of which lies within certain ranges. The result is increased efficiency of technological channels to scheduled maintenance, reduced the rate of increase of the gap between the graphite blocks, increases the total Energoservice. 2 S. and 2 C.p. f-crystals, 2 Il.

The invention relates to nuclear engineering, in particular to the active channel zones of uranium-graphite nuclear reactors of the RBMK type (reaktorbau and subsequent operation of the active zone.

The prior art nuclear reactors, containing the channels that have the fuel assemblies, made in the form of thin-walled casing, inside of which is vertically arranged packages of fuel elements (SU 665556 A, G 21 3/30, 15.05.85).

To facilitate installation of the casing to the inside of the channel Assembly is provided with a guide pipe, which is connected to the bottom edge with the top edge of the casing and having an outer bearing flange with a tapered lead-in section for the production of packages of fuel elements.

The casing is installed with a gap relative to the channel surface, which prevents their contact and possible abrasion during operation. However, the presence of a solid casing of considerable length significantly reduces the neutron-physical parameters of the active area due to the parasitic capture of neutrons.

The closest to this invention is an active area channel uranium-graphite nuclear reactor containing technological channels that have fuel assemblies, made in the form of two vertical beams of fuel elements fixed in the spacer grids (N. A. Dollezhal, I. Y. Emelianov. Channel nuclear energy is by radial vibration of fuel assemblies within the technological channels due to the interaction of the flow with the structural elements of the Assembly. For this reason, there is an intensive interaction of grid spacers with the inner surface of the technological channel, leading to abrasion of the walls of the technological channel and, consequently, weakening the cross-section of technological channel in contact with the spacer bars. Furthermore, multiple cyclic shock grid spacers on the walls of the channel leads to a decrease of the fatigue strength of the material of the walls of the channel. Therefore, in the course of the campaign continuously monitoring the integrity of the walls of the technological channel, the presence of areas of technological channels with weak cross sections and the degree of weakening.

In case of a critical weakening of any part of the technical channel, make the repair operation which involves the replacement of the entire process channel. All stages of such an operation is rather complicated, time consuming and require a considerable investment of time. In addition, when replacing the technological channel is an increase in the gaps between the blocks of graphite, which also increase due to radiation exposure. As a result, in General, decreases reliability of the governing Assembly of the uranium-graphite nuclear reactor, contains two bundles of fuel elements, some switches which are fixed in the reference lattices, and N grid spacers in each beam, (N-1) of which, starting from the reference lattice, installed along the length of the Assembly at a distance d from each other (N. A. Dollezhal, I. Y. Emelianov. Channel nuclear power reactor, -M: Atomizdat, 1980, S. 95-101).

Known fuel Assembly is designed to form an active area channel uranium-graphite nuclear reactor. After the expiration of its functioning Assembly needs to be uploaded. In its place installed a fresh fuel Assembly is identical to that of the preceding. Naturally, in this case, there is further abrasion technological channel due to the interaction of grid spacers with the walls of the channel, and on the same areas of technological channel.

Summary of the invention the present invention is the creation and development of the active zone of uranium-graphite nuclear reactor generated from fuel assemblies having high reliability and extended life.

The solution of this task, you may receive new technical result decreased the rate of increase of the gaps between the blocks of graphite, increases the total Energoservice.

These technical results are achieved by the fact that in the active channel area of the uranium-graphite nuclear reactor containing technological channels that have fuel assemblies, made in the form of two bundles of fuel elements fixed in the spacer grids of the spacer grid placed at the height of the Assembly between areas of technological channels with weak cross sections.

To do this, in the fuel Assembly uranium-graphite nuclear reactor containing two bundles of fuel elements, some switches which are fixed in the reference lattices, and N grid spacers in each beam, (N-1) of which, starting from the reference lattice, installed along the length of the Assembly at a distance d from each other, each beam end from the first support grid spacer grid is from the end of the support grid on the distance l is not less than 0.25h and not more than (d-2,125h) or at a distance l is not less than (d+2,125h) and not more than (d+2,875h), where h is the height of the spacer grid.

A distinctive feature opisyvayuschih channels with a weakened cross-section prevents further negative interaction grid spacers with the walls of the technological channel, leading to a further decrease of the strength characteristics.

To form this active zone, you must use the fuel assemblies, in which the spacer grids are located along the length of each beam in a certain way, namely, in each beam end from the first support grid spacer grid is from the end of the support grid on the distance l is not less than 0.25h and not more than (d-2,125h) or at a distance l is not less than (d+2,125h) and not more than (d+2,875h), where h is the height of the spacer grid. If the value of the distance l is more than (d-2,125h) or less (d+2,125h), then the spacer grid when the Assembly is installed in the technological channel will be located in areas of the portions of the process channel with a weakened cross-section. The weakening of the cross-sections in areas of the channel due to interaction with the channel walls of the spacer grids of the fuel assemblies used in the active zone previously. If I can get the first spacer bars to the end of the reference grating distance l less than 0.25h) must be installed between the reference grating and the first spacer bars additional lattice. In this case, the first from the reference lattice distantseeruda bars will be an additional spacer grid, the end of which should be installed at a distance l from the end of the support grid, selected from the above ranges.

In addition, the support grid can be installed on the end parts of the fuel Assembly, or in the middle part of the fuel Assembly.

List of figures Fig. 1 shows a fragment of the active zone channel uranium-graphite nuclear reactor of Fig. 2 shows a fuel Assembly channel uranium-graphite reactor.

Information confirming the possibility of carrying out the invention.

The active zone contains graphite stack, consisting of collected columns of blocks 1 with an axial cylindrical hole, which has a production channel 2. In the technological channels 2 installed fuel assemblies 3, made in the form of two vertical beams 4, 5 (top and bottom respectively) of fuel elements 6. Those who t the bending of the fuel elements and reduce vibration. During operation of the active zone due to the intensive interaction of grid spacers 7 with the wall of the technological channel 2 in last may arise sections 8 with a weakened cross-section (with reduced strength characteristics). The emergence of a technological channel 2 stations 8 with a weakened cross-section can be caused not only by the interaction with the walls of the channel grid spacers, but also for other reasons. In particular the emergence of sections 8 may be the result of errors in the manufacturing process of the channel or the impact on the channel graphite when it is swelling, especially in the junction block. To increase the reliability and extend the life of process channel and the active zone can generally due to the fact that the formation of the active zone should identify the sections 8 of the technological channel and positioning the spacer between lattice sites 8 technological channel with a weakened cross-section. To ensure periodic monitoring of technological channels, for example by ultrasonic scanning, it is possible during overloads technological channels. If you find a technological channel sections the following lattices are thus that during normal installation of the fuel Assembly spacer grids 7 are positioned between the sections 8 of the technological channel with a weakened cross-section.

For the formation of the described active zone, it is necessary to manufacture the fuel assemblies, in which the spacer grids 7 are located accordingly. A fuel Assembly uranium-graphite nuclear reactor contains two beams 4 and 5 of the fuel elements 6, some switches which are fixed in the reference gratings 9 and 10 (top and bottom respectively) and N grid spacers 7 in each beam. In each beam end from the first support grid 9 and 10 (top and bottom respectively), the spacer grids 11 and 12 (top and bottom respectively) are located on the ends of these supporting bars on the distance l is not less than 0.25h and not more than (d-2,125h) or at a distance l is not less than (d+2,125h) and not more than (d+2,875h), where h is the height of the spacer grid. The range of distance l is not less than 0.25h and not more than (d-2,125h) corresponds to the symbol "A" in Fig. 2, and the range of the bridge is" in Fig.2.

The choice of the above range of possible distances between the end of the reference grating and the end from her first spacer grid takes into account not only the need to shift the spacer grid by an amount at least equal to the height of the spacer grid, but the factor is exceeded, the section length 8 with reduced strength characteristics values for the height of the spacer grid. Does not meet the section length 8 the height of the spacer grid due to the design features of the mounting grid spacers to the Central rod 13. In the Central rod is made a groove cooperating with the spacer bars and preventing its axial displacement. When the operation of the spacer grid as part of Assembly is moved along the Central rod, resulting in an increased length of the section 8 process channel with a weakened cross-section. Specific values for the above ranges of the distance between the end of the support grid and the end from her first spacer grid is established experimentally.

If the first support grid spacer bars positioned at the minimum possible distance is. is this case, since the distance between (N-1) first spacer grids is equal to d and is constant, the distance between the penultimate spacer bars and the last spacer bars will exceed the maximum allowable value.

When fixing limit switches fuel elements 6 in the reference gratings 9 and 10, located at the end sections of the fuel Assembly, is thermal elongation and radiation extending fuel elements 6 towards the center.

Support grid which set the limit switches fuel elements can be located in the middle part of the fuel Assembly. When one of the reference lattices will still be the upper and the other lower. Fuel elements, in this case, will lengthen and widen towards the terminal region of the fuel Assembly.

A fuel Assembly includes a cylinder 14 and a shaft 15, between which are located the beams 4 and 5 of the fuel elements. Head 14 is connected to the node 16 to install the Assembly into the active zone and its unloading from the active zone. The structural frame of the fuel Assembly is formed by a head 14 and a shank 15, which is connected to the Central startat as follows. Initially, the core form of fuel assemblies that match the prototype. Over time the spacer grid of such assemblies more and more grated wall of the technological channel. If you do not modify in some way the position of the grid spacers, the thinning of the walls of the channel reaches a critical value and technological channel should be replaced. Therefore, when significant wear of the walls of the channel, but less than a critical value, it is necessary to form the active area using the described fuel assemblies. Then the spacer grid will interact with portions of the channel walls that were not previously subjected to abrasion. In case of substantial abrasion of the following sections of the channel walls is necessary to develop a set of fuel assemblies, in which the spacer grid will be located along the assemblies in other places. It is advisable to make the first set described fuel assemblies with the location of the grid spacers corresponding to one range of distances of the end of the first spacer grid from the end of the support grid. The next set of fuel assemblies in this case slnoe lattice, corresponding to a different range.

The described fuel Assembly can be made on the existing well-known equipment with the use of known techniques and does not require any upgrading equipment.

Claims

1. The active channel area of the uranium-graphite nuclear reactor containing technological channels that have fuel assemblies, made in the form of two bundles of fuel elements fixed in the spacer grids, characterized in that the spacer grid placed at the height of the Assembly between areas of technological channels with weak cross sections.

2. A fuel Assembly uranium-graphite nuclear reactor containing two bundles of fuel elements, some switches which are fixed in the reference lattices, and N grid spacers in each beam, (N-1) of which, starting from the reference lattice, installed along the length of the Assembly at a distance of d mm from each other, characterized in that each beam end from the first support grid spacer grid is from the end of the support grid at a distance l mm not less than 0.25h m (d+2,875h) mm, where h is the height of the spacer grid, mm

3. A fuel Assembly uranium-graphite nuclear reactor under item 2, wherein the support grid is installed on the end parts of the fuel Assembly.

4. A fuel Assembly uranium-graphite nuclear reactor under item 2, wherein the support grid is installed in the middle part of the fuel Assembly.

 

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FIELD: nuclear power engineering.

SUBSTANCE: proposed fuel assembly affording supercritical neutron-physical state under normal operating conditions of nuclear reactor and subcritical state of fuel assembly during loss-of-coolant and boiling accident has vertical process channel accommodating fuel elements mounted on supporting blocks which are alternating with absorbing blocks of which at least some of them are provided with cavity communicating with process channel space and filled with absorber in the form of boron powder enriched by boron-10 isotope conveyed in emergency situations by boiling coolant into process channel. Some of absorbing blocks accommodate combustible absorber.

EFFECT: enhanced inherent ability of self-protection and safety of pressurized-tube reactors.

3 cl, 1 dwg

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