JPS6032839B2 - Lift tool for extracting control rods from the core - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION BACKGROUND OF THE INVENTION The present invention relates to a lift device for grasping and lifting control rods from a reactor core.

More specifically, it relates to an IJ lift for simultaneously removing all control rods from a reactor core before refueling or removing fuel from the reactor core. It is common in nuclear power plants to replace at least one-third of the fuel assemblies in the core every year.

This work must be carried out while the furnace is shut down. For this reason, refueling results in considerable operational losses. During this time, not only will you be unable to generate electricity for your own use or for other electricity users, but you will also have to purchase electricity from other power companies and supply it to customers during the outage. There are things that must happen now. All obstructions such as the reactor pressure vessel lid, control shaft drive mechanism, support structure, and, depending on the reactor, protective shroud and calandria must be removed from above the core before the fuel assembly can be pulled out.
And it is not possible to supply new fuel assemblies.

Rapid lift equipment was designed to perform this obstruction removal. It is common practice to remove all control rods from the core after injecting borate into the coolant in the core to prevent criticality and before refueling.

The longer each of these steps takes, the longer refueling will be delayed and the greater the economic loss the power utility will incur. This creates a need for equipment and techniques to quickly complete each step without making errors. When using known equipment using the previous procedure, the operator should either handle the control rods one by one and remove them one by one, or attach the control rods one by one to the fixtures on the bottom plate of the lift. Was.

Not only is this practice time-consuming and labor-intensive, but it also exposes workers to significant amounts of radiation, when radiation exposure to workers should be minimized or even eliminated. This will result in SUMMARY OF THE INVENTION The present invention seeks to address the problems inherent in control sheath removal for refueling by providing a lift device with a plurality of self-actuating mechanisms attached to the plate.

When attempting to remove a control rod using the locking mechanism of the lift tool of the present invention, lower the lift tool until one control rod is inserted into each locking mechanism, and then At that point, each locking mechanism automatically grabs this control rod and raises the lift tool from the core, thereby removing all control rods from the core. The self-latching or self-locking locking mechanism of the lift device of the present invention, which allows for easy removal of the control shaft, allows the operator to easily and remotely unlock the lock only after the scheduled operation is completed. can.

Each locking mechanism consists of a pair of concentrically arranged cylindrical members, one cylindrical member being removably secured by a flange to the upper surface of the plate of the lift device, and the other cylindrical member being removably secured to the upper surface of the plate of the lifting device; It's hanging down. Both cylindrical members are movable relative to each other and their lower ends are bridged by a pair of pivotally fixed latches. These latches can be pivoted from a lower lattice in which the control shank protrudes radially inward to engage a knob on the top of the control shank. The mutual movement between the two cylindrical members causes the cylindrical members to raise the latches from their radially inwardly extended position to a radially retracted disengagement position (in which the control beam is released). and move it.
They were scaled and sometimes provided with means to create relative movement between the two cylindrical members. This means may be a hydraulic, pneumatic, magnetic, or mechanical device capable of remote locking. As the locking mechanism is lowered to the top of the control rod, the upper end of the control rod enters the bottom of each latch, causing the control rod and the inner cylindrical member to momentarily remain vertically stationary. ,
During this time, the external cylindrical member continues to descend. This action pivots the latch to the oblique position in which the inner end of the latch is pulled back radially outwardly, thereby allowing the end of the control rod knob to pass upwardly. After the control rod knob is blocked, the latch is lowered by gravity into its radially inwardly projecting and locking position, and the control rod is automatically gripped.
DESCRIPTION OF THE PREFERRED EMBODIMENTS The nuclear reactor 10 shown in FIG.
It is equipped with a reactor core 12 shown enclosed by a broken line.

As is well known, most nuclear reactors are controlled by introducing and extracting neutron absorbing poisons or control elements 22 from and into the reactor core. Typically, the control fins are bundled together by a connecting spider 24 into a control element assembly 20. In at least one design of the reactor, the individual control rods 22 enter the core through the guide tubes 38 of the individual fuel assemblies, and the control rods exiting above the core are connected to the calandria structure 1.
Protected by 4. That is, the calandria structure has an upper tube sheet and a lower tube sheet connected by intermediate tubes through which the individual control rods 22 pass. Without the calandria structure, the portion of the control rods above the core would be exposed to and subjected to forces from the coolant flowing across it. Control element assembly 20 typically has an extension 28 that terminates in an upper tab 26 that is gripped by a control rod drive mechanism (not shown). The term "control rod" used in this text refers not only to the individual control rod elements 22, but also to joint structures such as spiders 24 and extensions 28 that move together when moving in and out of the core. It is used as including all. The term "control rod" does not refer to the term "control rod" since the extension may actually be connected to the control ram assembly but separate from the control ram. , and is used to include the lid of a pressure vessel and all remaining structures after its removal. As is clear from FIG. 1, the calandria structure 14 must be completely removed in order to gain access to the fuel assemblies that make up the reactor core 12.

A lift device 3 shown in FIG. 1 provided for this purpose has a plate 32 suspended from a support 34. The coin holder mechanism 40 is slidably inserted into the multiple circular holes 36 (best shown in FIGS. 3 and 5) of the plate 32. Each locking mechanism has a pair of downwardly extending concentric first and second cylindrical members 50, 60, the first cylindrical member 50 being the second
is attached to the outside of the cylindrical member 60.

The diameter of the upper flange 58 of the first cylindrical member 50 is larger than the circular hole 36 in the plate 32, and the upper flange 58 is secured to the plate 32 by shoulder bolts 42. The diameter of the upper flange 68 of the second cylindrical member 60 is larger than the diameter of the circular hole 36 in the plate 32 and is also larger than the diameter of the upper flange 58 of the first cylindrical member. The shoulder bolts 42 pass through a number of positioning holes 62 in the upper flange 68. Shoulder bolts 42 align second cylindrical member 60 and its upper flange 68 with first cylindrical member 50 and its upper flange 58. These shoulder bolts are attached to the second cylindrical member 6
0 and its upper flange 68 are moved up and down in the direction of the ball, and the highest position in the axial direction is determined by the height of the head of the shoulder bolt 42. Turning now to the description of the lower end of the coin holder mechanism 40 (best shown in Figures 3, 4, 5 and 6).

Passage 80 of the annular ring 51 at the lower end of the first cylindrical village 50
The diameter of the control rod 22 is somewhat larger than the diameter of the control rod 26. The inwardly upwardly chamfered surface 48 of the annular ring 51 guides the knob 26 of the extension of the control twill into the passageway 80 of the coin mechanism 40. The annular ring 51 includes an upwardly directed support shoulder 52 for supporting the control lever engagement latch 70 in a horizontal position (see FIG. 3). A plurality of holes spaced a central angle through the cylindrical wall of the cylindrical member 50 receive one end of the elongated latch 70. An elongated latch 70 is rotatably secured to the cylindrical member 50 by a tenon pin 72 which is connected to the hole 54 in the first cylindrical member 50.
(best shown in Figure 6)
. With this configuration, the latch 70 rises upward from the horizontal position (in this horizontal position, the end of the latch is in the passage 80) and moves back to the laterally retracted position (in this position, the latch 70 The other end of 70 can be pivoted into the passageway 80. As shown in FIGS. 3, 4 and 5, the second cylindrical member 60 inside the first cylindrical member 50 has a head of reduced diameter, which head is connected to the tenon pin 7.
It fits into the constriction of the cylindrical member 50 in the position 2.

Latch 70 is inserted through latch slot 66 in cylindrical member 60.
extends into the passageway 80. As with the first cylindrical member 50, the retaining pin 74 of the second cylindrical member 60 is mounted within the latch slot 66 and loosely engages the elongated slot 76 at the end of the latch 70. Due to the vertical upward movement of the cylindrical member 60 configured in this way, the mounting pin 74
moves within the slot 76 of the latch 70 and around the pin 72 so as to raise the end of the latch 70 and swing the other end of the latch 70 out of the horizontally extended position in the passageway 80 and into the semi-vertically retracted position. Rotate it. As can be seen from the description above, as the lift plate 32 is lowered into the control rod engagement position, the knob 26 on the upper end of the control rod 22 is guided by the chamfered surface 48 and enters the passageway 80 of the locking mechanism 40.

Further lowering causes the top of the /b 26 to contact the bottom surface of the latch 70, swinging the latch 70' upwardly and outwardly to the retracted position, allowing the /b 26 to pass. Due to such movement of the latch 70, the second cylindrical member 60
As the first cylindrical portion 50 begins to descend, it temporarily stops. After the knob 26 has completely passed the latch 70, the weight of the second cylindrical member 60 causes the first cylindrical member 60 to
and latch 70 fall to their lowest horizontal position, in which position latch 70 is again exposed to passage 80, as shown in FIG.
rush into. When the lift tool 30 is then raised, the horizontally projecting upward support surface 78 of the latch 70 moves into contact with the lower engagement surface of the knob 26. In this control lever engagement and straightening, the upward supporting eyebrows 52 of the annular ring 51 support the latch 70, and as the lift tool is further raised, the control levers 22 are raised. Occasionally, after the control rod 22 has been grabbed and removed from the core, individual control rods have been removed from the lift mechanism in order to inspect or replace them. Furthermore,
After refueling is completed and the control rod is inserted into the reactor core, the locking mechanism 40 is removed from the control rod.
It is necessary to leave the control rod in the core so that the lift tool 30 can be removed. To perform both of these functions, the second cylindrical member 60 is allowed to move vertically relative to the first cylindrical member 50', thereby controlling the latch 70 from its laterally projecting position. Allow the comb to move to a laterally retracted position for release. Although suitable mechanisms for creating relative movement between the cylindrical members 50 and 60 may be provided, in the preferred embodiment shown in the accompanying figures, the plate 32 and the upper flange 68 are moved around the upper flange 58. It has an inflatable torus 44 in between. The expandable torus 44 is selectively expanded by an inlet tube 46 through which compressed air passes. Therefore, this configuration allows all locking mechanisms 4 to be removed from control pocket 22 by inflating all toruses 44 at the same time.
Detach 0. Moreover, the toric body 4 of the arbitrarily selected coin purse mechanism 40
It is also possible to separate only the locking mechanism 40 from the control rod 22 by inflating the locking mechanism 4. The lift 30 shown in the accompanying figures and described above includes a self-locking mechanism that automatically locks the control rod to the lift when the lift is lowered.

This self-locking is accomplished solely by the action of gravity, so no external power source is required. Additionally, the latch is positioned and sized to automatically center the control latches within the locking mechanism 40 so that the latch 70 will not become jammed or damaged during operation. The locking mechanism 40 can be secured in either the locked position or the locked position by simple locking means such as toggle clamps or bolts. Finally, a simple switch or mechanical indicating device may be provided to reliably indicate the locked or unlocked state of the locking mechanism.

[Brief explanation of the drawing]

FIG. 1 is a side view of the reactor vessel with a portion cut away to reveal the top of the control beam and the lift tool of the present invention about to engage the control beam; FIG. 2 is a partially cutaway end view of the coin holder mechanism taken along line 2--2 of FIG. Figures 3, 4 and 5 are side sectional views of the locking mechanism of the lift device of the present invention, with Figure 3 showing the locking mechanism about to engage the control lever, and Figure 4 showing the locking mechanism fully engaged. FIG. 5 shows the separated state. FIG. 6 is a cross-sectional view of the coin stop mechanism taken along line 6--6 in FIG. 4. 10... Nuclear reactor, 12... Core, 14... Calandria structure, 20...
... Control element assembly, 22 ... Control rod, 24 ... Spider, 26 ... Knob, 28 ... Extension part, 30 ... Lift odor, 32 ... ...Plate, 34... Branch village, 36... Circular hole, 38.
... Guide tube, 40 ... Locking mechanism, 42.
...Shoulder bolt, 44...Inflatable torus, 46...
...Inlet pipe, 48... Chamfered surface, 50... First
cylindrical member, 51... annular ring, 52...
- Support shoulder, 54... hole, 58... upper flange, 60... second cylindrical member, 62...
...Log hole, 66...Latch slot, 68...Upper flange, 70...・Latch, 72...Tonon pin, 74...Mounting pin, 76. ．．・．． ．． - Slot, 78...Upward support surface, 80. ．． ．． ．． ．． ．． aisle. Lots of ^. ．． Yu ZZ・、Zo＾Magota... Yuyu Yu, 6, -ZZ Hakama. Z Minu, Z

Claims (1)

[Scope of Claims] 1. A lift tool for extracting a plurality of vertically extending control rods 22, each having a knob 26 for gripping, from a reactor core before refueling, comprising: (a) said control rods; (b) a plurality of locking mechanisms 40 fixed to and depending from the plate, each locking mechanism being attached to the plate; a vertically disposed first cylindrical member 50;
an elongated latch 70 having a surface 78 pivotally mounted at one end to the cylindrical member of the control rod and engaging the knob of the control rod at the other end; a second cylindrical member 60;
A cylindrical member is provided with a latch slot 66 through which the other end of the latch passes toward the internal passageway 80, and a mounting pin 74 loosely fitted into a slot 76 formed in the other end of the latch connects the latch to the second A lift tool characterized by being connected to a cylindrical member. 2. The lifting device of claim 1, wherein the second cylindrical member is provided with a vertical movement, thereby moving the latch from the laterally extended position to the laterally retracted position. Expandable torus 44
A lift device characterized by being provided with. 3. The lifting device according to claim 1, wherein the latch is pivotally mounted to rotate in a vertical plane,
A lifting device characterized in that said second cylindrical member has a support shoulder 52 consisting of a substantially horizontal surface facing upwardly to support said latch in a laterally projecting position thereof.