JPS6045838B2 - Reactor fuel inlet/outlet guide tube hole plug support device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hole plug support device for a reactor fuel inlet/outlet guide cylinder in a nuclear reactor facility.

As is well known, for example, when loading and unloading fuel from a reactor vessel using a fuel handling machine, a fuel inlet/outlet guide cylinder (hereinafter simply referred to as A fuel handling machine is connected to the upper end door valve of the guide tube, and the fuel and grippers are guided up and down through the guide tube.

On the other hand, a reactor building may have a downstairs room partitioned off between the room where the fuel handling machine is installed and the reactor vessel and where various equipment is installed.

In this case, it goes without saying that the guide tube described above will pass through the downstairs room and be pulled out upwards. If maintenance personnel need to enter the room for maintenance of equipment installed in the downstairs room, they will need to newly prevent radiation from entering the room and the reactor. The need arises. In other words, although the guide tube is equipped with a door valve that has a radiation shielding function at the upper end, the area below the door valve is directly connected to the primary gas system in the furnace, and as it is, the guide tube has a relatively thin wall. Radiation leaks into the room downstairs through the wall of the tube. For this reason, some attempts have been made to surround the entire circumference of the guide tube that penetrates the downstairs room with thick lead or other materials, but due to spatial constraints, this is not practical. This is difficult and requires high equipment costs. As a countermeasure for this, conventionally, a long hole plug with a radiation shielding function whose tip reaches inside the reactor is poured into the guide tube from the top end, and the hole plug is inserted into the guide tube when the fuel is not being handled. A radiation shielding method has also been adopted in which the support step is held at the shoulder of the support step formed at the upper end. However, in this method, the hole plug is longer than the fuel, so a large dedicated plug handling machine is required to handle it. The reason why the hole plug is so long is as follows. In other words, when withdrawing fuel, especially spent fuel, from inside the reactor, it is necessary to directly cool the fuel by flowing cooling gas during the process of pulling it out of the guide cylinder, as the fuel has a high level of decay heat. be. In order to maintain a constant flow rate of the cooling gas in this case, it is necessary that the gap between the inner surface of the guide tube and the fuel or gripper be constant over the entire guide tube. Therefore, it is not preferable to form a step part in the middle of the guide tube to support the hole plug, and if there is a room downstairs, it is unavoidable to add an extra step for the height of the room. A support method is adopted in which the hole plug is provided in a long dimension at the upper end of the guide tube and supported at the engagement stage. However, if the hole plug suspended from the upper end of the guide tube can be supported in the middle of the guide tube without forming a locking step for supporting the hole plug in the middle of the guide tube, then the hole plug can be supported in the middle of the guide tube. Instead of using a long hole plug as in the past, it is possible to use a short hole plug that provides a slight radiation shield between the downstairs room and the inside of the furnace.
Moreover, with such a short hole plug, it is possible to insert and remove the hole plug using a fuel handling machine without using a large dedicated plug handling machine, and the equipment can be simplified. The present invention has been made in view of the above points, and includes a short hole plug inserted from the upper end of the guide cylinder and suspended at a predetermined comfortable position between the downstairs room and the primary gas system space of the reactor. It is an object of the present invention to provide a hole plug support device that can skillfully support a hole plug without forming a locking step in the middle of a guide tube.

Hereinafter, the configuration and operation of the present invention will be described in detail based on illustrated embodiments.

First, in Fig. 1, numeral 1 is a guide tube, the upper end of which faces the room where a fuel handling machine (not shown) is installed, and is connected to a door valve 3 installed at the point where it penetrates the thin concrete wall 2 of the building. has been done.

On the other hand, the guide tube 1 is installed so that it penetrates the downstairs room 4 divided below the room, and further penetrates the upper shield plug 5 of the reactor so that its lower end protrudes into the primary gas system space 6 in the reactor. has been done. Note that 7 indicates the primary coolant inside the furnace.
Connect the fuel handling machine to the door valve 3 with the configuration so far,
The flow of fuel into and out of the reactor vessel through the guide tube 1 as shown by arrow A is similar to the conventional method. By the way, in order to allow maintenance personnel to enter the downstairs room 4, except when handling fuel as mentioned above, there is a space between the room 4 and the in-furnace primary gas system space 6 that prevents radiation from entering the guide tube 1. A hole plug 8 having a shielding function is inserted and supported to provide radiation shielding between the room 4 and the primary gas system space.

The hole plug 8 is a cylindrical body whose outer diameter is selected to match the inner diameter of the hole plug 8, and is provided with a handling portion at its top for engagement with gripper pawls. In addition, the length of the hole plug 8 is much shorter than the conventional long dimension described above, and at the predetermined shrinkage position shown in FIG. It is made as a short hole plug that protrudes slightly upward, and is locked and supported in the illustrated position by a hole plug support device 9, which will be described in detail later. Next, the detailed structure of the hole plug support device of the present invention will be described with reference to FIG.

First, the hole plug 8 has the gripper claw 1 of the fuel handling machine on its top.
0, and an engagement groove 82 is formed on the outer circumferential surface of the upper region, in which a hole plug support shaft to be described later engages. A support device 9 consisting of a combination structure of a hole plug support shaft 91 and a support shaft operating mechanism 92 is installed on the shield plug 5 in the downstairs room 4 facing the hole plug 8 . The support shaft 91 projects laterally from the operating mechanism 92, and its tip is disposed so as to penetrate the guide cylinder 1 and project into the cylinder. Also, guide tube 1
A bellows 93 is provided across the support shaft 91 and forms an airtight boundary inside and outside the guide cylinder. The operating mechanism 92 incorporates a suitable drive unit such as a hydraulic cylinder, and moves the support shaft 91 forward or backward into the cylinder as shown by arrow B based on an operating command. In addition, especially the support shaft 9
The retracted position of No. 1 is set such that the tip end surface of the support shaft 91 is flush with the inner surface of the guide tube 1, as shown by the chain line. Next, the operation of the hole plug support device will be explained.

When handling fuel, the support shaft 91 is retreated to the chain line position and stands by, and the gap between the fuel that enters and exits through the guide tube 1 or the gripper and the guide tube does not change due to the support shaft 91 and is kept at a constant value. Good gas cooling of fuel can be performed. When not handling fuel, the lower area of the guide tube 1 is sealed with a hole plug 8 to provide radiation shielding between the primary gas system space in the furnace and the downstairs room 4. The hole plug 8 is suspended from the guide tube 1 through the door valve 3 shown in FIG. 1 by operating a gripper of a fuel handling machine. When the hole plug 8 eventually reaches a predetermined lower position and the engagement groove 82 matches the level at which the support shaft 91 is located, a command is given to the operating mechanism 92 to move the support shaft 91 forward. Therefore, the support shaft 91 engages the engagement groove 82 and supports the hole plug 8 in that position. Thereafter, the gripper claws 10 of the fuel handling machine are removed from the handling portion 81 of the hole plug 8 and pulled upward. To remove the hole plug 8 from the guide tube 1, the above-mentioned operation is reversed. According to the above-mentioned hole plug support device of the present invention, the hole plug can be supported at a predetermined flexible position in the middle of the guide tube without providing the guide tube with an engagement step that engages with the hole plug as in the conventional case. can.

Therefore, the inner diameter of the guide cylinder is constant over the entire area, and the flow rate of the cooling gas flowing into the guide cylinder can be maintained at a predetermined value during the process of drawing out fuel from the inside of the furnace. In particular, by aligning the retracted position of the support shaft with the inner surface of the guide tube, the inner diameter of the guide tube does not change, making it more effective. In addition, since the hole plug can be supported midway through the guide tube, there is no longer a need for it to be long as in the past, and the minimum required for radiation shielding between the primary gas system space in the furnace and the downstairs room is eliminated. As a result, the hole plug can be handled by a fuel handling machine, and a special plug handling machine can be omitted, which is a practical benefit. The present invention applies not only to the fuel inlet/outlet guide cylinder directly pulled out from the reactor vessel, but also to transfer equipment on the fuel transfer line,
Alternatively, the present invention can be similarly applied to a guide tube pulled out from a spent fuel storage facility.

[Brief explanation of the drawing]

Each figure shows one embodiment of the present invention, and FIG. 1 is a cross-sectional view of the entire structure of the fuel inlet/outlet guide cylinder in a state in which the hole plug is supported, and FIG. 2 is an enlarged view of the main parts in FIG. 1. . 1: Guide cylinder, 3: Door valve, 4: Downstairs room, 5: Upper reactor plug, 6: Next gas system space, 8:
Hole plug, 81: Handling part, 82: Engagement groove, 9:
Hole plug support device, 91: Hole plug support shaft, 92: Support shaft operating mechanism, 93: Airtight sealing bellows, 10: Gripper claw of fuel handling machine, A: Direction of entry and exit of fuel or hole plug in guide cylinder.

Claims (1)

[Scope of Claims] 1. For a fuel inlet/outlet guide tube that is provided with a door valve at the upper end and is installed with the lower end protruding into the primary gas system space of the nuclear reactor through a room on the lower floor, a predetermined position within the guide tube is provided from the upper end. This is a support device for a hole plug that has a radiation shielding function and is suspended up to a level that provides radiation shielding between the downstairs room and the primary gas system space, and has an outer diameter that matches the inner diameter of the guide tube. An engaging groove is provided on the outer circumferential surface of the upper region of a cylindrical hole plug selected from
At the lower position in the downstairs room, there is a hole plug support shaft that passes through the guide tube in an airtight manner and protrudes into the tube to engage the engagement groove of the hole plug to support the hole plug, and the support shaft is moved forward. A hole plug support device for a nuclear reactor fuel inlet/outlet guide cylinder, characterized in that it is equipped with a support shaft operating mechanism for moving backward. 2. The hole plug support device according to claim 1, characterized in that the hole plug support shaft is set in a backward movement position with its shaft end surface aligned with the inner surface of the guide tube. A hole plug support device for the reactor fuel inlet/outlet guide cylinder.