RU2357304C2 - Withdrawal method of deformed process channel from active zone of graphite-uranium nuclear reactor - Google Patents

Abstract

FIELD: power engineering.

SUBSTANCE: invention refers to nuclear power engineering, and deals with operation of nuclear reactors, and namely with withdrawal of defective process channels from active zone of graphite-uranium reactor. Withdrawal method of deformed process channel from active zone of graphite-uranium nuclear reactor consists in locating of a cutting tool in the channel, and cutting and withdrawal of the channel. By means of the measuring tool introduced into the channel there determined are sections with value of channel transverse deformation, which exceeds the allowable one. In the deformed sections revealed, by means of cutting tool moved in the channel there made are longitudinal unloading cuts in the channel wall and the channel is withdrawn from reactor. Unloading cuts are mainly made across the length exceeding the limits of deformed section by 0.4÷0.5 m. When the number of unloading cuts is more than one, it is expedient to make cuts symmetrically relative to channel axis.

EFFECT: invention allows improving processability and ecological safety of withdrawal method of deformed process channels and considerably reducing time required for reactor maintenance.

3 cl, 3 dwg

Description

The invention relates to nuclear energy, relates to the operation of nuclear reactors, in particular the extraction of defective process channels from the core of a uranium-graphite reactor.

The prior art has not been identified analogues methods aimed at solving the problem of extracting the deformed technological channels of a uranium-graphite reactor (UTR). However, there are patents that describe devices for extracting undeformed channels in the process of solving standard technological problems (RF patents No. 2098871 and No. 2086014). During the operation of the UTR under the influence of radiation-thermal factors and dynamic influences, the geometric dimensions of the graphite of the active zone of the channel and technological channels change. As a result of these effects, the gap between the graphite masonry and the pipe of the process channel is reduced, the minimum value of which is determined from the condition of inadmissibility of jamming of the process channel in the core cell.

As the closest analogue, RF patent No. 2086014 was selected, priority date 05/07/1996, IPC G21C 19/26, because the description describes the operations present in the claimed invention: the operation of cutting and moving the tool and fuel assembly with a lifting mechanism.

The disadvantage of a technical solution known from the analogue is the inability to extract deformed technological channels.

The problem solved by the invention is to develop a technologically advanced, environmentally friendly method for extracting deformed technological channels.

The essence of the claimed invention lies in the fact that in the method of extracting a deformed technological channel from the core of a nuclear uranium-graphite reactor using cutting operations by a remotely controlled cutting tool and extracting the technological channel by a lifting mechanism, it is proposed by means of a measuring tool introduced into the channel to determine sections with a transverse value channel deformation exceeding permissible, and in the identified deformed areas with a cutting tool, per was placed in a channel, perform longitudinal cuts in the unloading channel wall, and then removing it from the reactor. In addition, it was proposed that discharge sections be made at a length exceeding the boundaries of the deformed section by 0.4–0.5 m. When the number of discharge sections is more than one, sections are proposed to be performed symmetrically to the channel axis.

The implementation of the steps indicated in the claimed method allows one to technologically solve the problems of extracting a defective technological channel (TC) from the core of a nuclear uranium-graphite reactor with a minimum level of environmental radiation pollution. To ensure reliable TC removal, it is preferable to carry out the discharge section with the boundaries of the deformed section exceeding 0.4–0.5 m. The lower limit was determined experimentally based on the conditions for ensuring reliable compression of the deformed channel. The upper limit of the cut is determined on the basis of the conditions for saving the operating time of cutting and the volume of generated radiation-contaminated shavings. With the number of discharge sections more than one section is performed symmetrically to the axis of the channel, which facilitates a more uniform compression of the deformed technological channel.

Figure 1, 2, 3 illustrates the process according to the claimed invention.

Figure 1 shows the location of the measuring tool in the technological channel in the area of the deformed section. Figure 2 presents a fragment of a deformed section of the technological channel with a cutting tool installed in its original position. Figure 3 shows a fragment of the deformed section after performing a longitudinal discharge section.

Fragments of the design of the reactor (figure 1, 2, 3): graphite masonry 1, graphite bushings 2, process channel 3, rod 7 (figure 2, 3). Positions 8, 9, 10 show the supporting elements of the reactor: slab flooring 8, the upper metal structure 9, the lower metal structure 10. A cutting tool (or measuring tool) 4 with a milling cutter 5 is installed in the technological channel 3 (Fig. 1). In Fig. 2, 3, 6 denotes a deformed section, 11 denotes a crane with a hook.

A method of extracting a deformed technological channel 3 is as follows. Using the measuring tool 4 of figure 1, placed in the technological channel 3, identify areas where the transverse strain of the technological channel 3 exceeds the permissible. Then, in the identified deformed section 6 (Fig. 2), using a hook of a crane 11 connected to a dynamometer 12, a cutting tool 4 is provided with a cutter 5. Using a pneumatic drive (not shown) placed on the rod 7, the cutter 5 is brought into rotation, placing it in the technological channel 3 at the initial moment above the deformed defective section 6, drill a hole, and then allow the cutter 5 to lower under the influence of its own weight down the channel 3. After passing the deformed section 6, the cutter 5 os They are removed, removed inside the cutting tool 4 and removed from the channel 3. Next, the technological channel 3 is removed by means of a crane 11. During the movement, the technological channel 3 is crimped at the locations of the vertical cuts, decreasing in diameter, which ensures the extractability of the deformed technological channel 3.

The proposed method allows to solve a very important practical problem of replacing deformed technological channels of the core of a nuclear uranium-graphite reactor with a high-tech environmentally friendly method that can significantly reduce the time it takes to repair the reactor.

Claims (3)

1. The method of extracting a deformed technological channel from the active zone of a nuclear uranium-graphite reactor, which consists in placing a cutting tool in the channel, cutting and removing the channel, characterized in that by means of a measuring tool introduced into the channel, sections with a channel transverse strain greater than permissible, and in the identified deformed areas with a cutting tool moved in the channel, longitudinal unloading cuts are made in the channel wall, and then it is removed and from the reactor. 2. The method according to claim 1, characterized in that the discharge sections are performed at a length exceeding the boundaries of the deformed section by 0.4 ÷ 0.5 m. 3. The method according to claim 1, characterized in that when the number of discharge sections more than one section is performed symmetrically to the axis of the channel.

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