JP2004361113A - Disassembly method for pressure tube of advanced thermal reactor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten a work period, reduce the amount of demolition waste, and simplify a shielding process by rationalizing a disassembly method for pressure tubes when decommissioning of an advanced thermal reactor. <P>SOLUTION: A pressure tube assembly 2 dismantled from a nuclear reactor of an advanced thermal reactor is conveyed to a spent fuel storage pool 19 using an existing fuel handling system and cut finely with a pressure tube cutting machine 41 in the pool. Using the existing fuel handling system to cut pressure tubes in the pool enables to utilize shielding effects due to water. In addition, it does not interfere with other operations unlike a cutting operation in a containment vessel. This process can also reduce the amount of demolition waste compared with the case of preparing a cutting and conveying equipment for a pressure tube assembly 2 after dismantling of the fuel handling system. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for dismantling a decommissioned advanced conversion reactor (ATR), and more particularly to a method for shredding a pressure tube assembly removed from a reactor body.
[0002]
[Prior art]
The new converter is a pressure tube reactor using heavy water as the moderator and light water as the coolant. In Japan, the ATR prototype reactor "Fugen" has been constructed. Is shown in It has already been decided that the Fugen power plant will be shut down soon, and it will be demolished after a predetermined decommissioning preparation period. The reactor is activated even after the fuel is taken out, and its decommissioning requires various technical developments and preparations.This invention was specifically studied for the dismantling of pressure pipe assemblies. is there.
[0003]
FIG. 7 is a conceptual diagram showing a reactor main body portion of the new conversion reactor. In FIG. 7, a large number of pipes (Calandria pipes) 3 for passing the pressure pipe assembly 2 are arranged in a lattice pattern between the upper and lower tube sheets of a cylindrical moderator container (Calandria tank) 1, and The tank 1 is filled with heavy water as a moderator. The upper and lower surfaces and side surfaces of the calandria tank 1 are covered with an iron water shield 4. The pressure pipe assembly 2 is composed of a pressure pipe (main body) 5 and pressure pipe extension pipes 6 and 7 joined to the upper and lower sides thereof. The pressure pipe 5 is housed in the calandria pipe 3, and the upper and lower extension pipes 6, 7 It penetrates the iron water shield 4.
[0004]
The fuel assembly is accommodated in the pressure pipe 5, and primary coolant pipes 8, 9 are connected to the vertical extension pipes 6, 7. Although not shown, a shield plug is attached to the upper and lower extension pipes 6 and 7 to pass the primary coolant but prevent radiation streaming, and the lower end of the lower extension pipe 7 is closed by a seal plug for sealing the primary cooling water. I have. The lower shield plug and the seal plug are connected to the lower extension pipe 7 by a ball latch mechanism so that the lower shield plug and the seal plug can be attached and detached by a fuel exchange device (not shown), and the lower shield plug and the fuel assembly are connected by a collet mechanism. Have been. The cooling water (light water) flowing into the pressure pipe assembly 2 from the lower cooling pipe 9 is heated by the pressure pipe 5 to become steam, and is supplied to the turbine from the upper cooling pipe 8. This reactor main body is stored in a reactor containment vessel (not shown).
[0005]
FIG. 8 is a longitudinal sectional view showing only the pipe of the pressure pipe assembly 2 divided into three parts. As described above, the pressure pipe assembly 2 includes the pressure pipe 5 and the upper extension pipe 6 and the lower extension pipe 7 joined to the upper and lower ends thereof by a roll joint method. , An inlet pipe nozzle 10 and a seal leak type nozzle 11 protrude. The length of each part is about 5 m for the pressure pipe 5, about 2 m for the upper extension pipe 6, about 3 m for the lower extension pipe 7, and the total length is about 10 m. The outer diameter of the pressure pipe 5 is about 130 mm, and the maximum diameter is about 190 mm at the lowermost end of the lower extension pipe 7.
[0006]
[Non-patent document 1]
Japan Society of Mechanical Engineers, Mechanical Engineering Handbook C. Engineering Edition First Edition, 4th Press 1997 The Japan Society of Mechanical Engineers p. C7-78-83
[0007]
[Problems to be solved by the invention]
Now, since the pressure tube assembly 2 has been activated by long-term operation, it is necessary to take measures such as remote control and shielding to perform shredding. In this case, it is conceivable that the shredding operation of the pressure tube assembly 2 is performed in the containment vessel, for example, immediately below the reactor body. FIG. 7 shows such an example. That is, in FIG. 7, a nozzle section cutting machine 12 for cutting the inlet pipe nozzle section and a pressure pipe cutting machine 13 for shredding the pressure pipe assembly 2 are provided below the reactor main body. After the pressure pipe assembly 2 is cut off from the primary coolant pipe 9 at the inlet pipe nozzle portion, the pressure pipe assembly 2 is hung by the pressure pipe shredder 13 through the protective cylinder 15 by the pressure pipe hanger 14 and has an appropriate length. Shredded. The shredded pressure tube assembly 2 is collected in the waste material storage device 16 and transported to the next step.
[0008]
However, shredding in the storage container has the following problems.
(1) When the shredding operation is performed in the containment vessel, the radioactivity level in the surrounding atmosphere increases, and other operations cannot be performed in parallel. Incidentally, there are a large number (224) of pressure pipe aggregates, and the shredding work and the transport work after the shredding work take a long time, and as a result, the critical work period of the reactor dismantling work becomes long.
(2) Since the pressure tube shredder is a newly manufactured device, after dismantling the reactor, the device itself becomes waste and secondary waste increases.
(3) Since the shredding operation is performed in the atmosphere, the amount of material required for shielding the device increases.
[0009]
An object of the present invention is to rationally proceed with pressure pipe dismantling work accompanying decommissioning of a new type of converter, to shorten the construction period, reduce dismantling waste, and simplify shielding procedures.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, the present invention conveys the pressure pipe assembly removed from the reactor body of the new converter which has been decommissioned to the spent fuel storage pool using the existing fuel handling equipment, This pressure pipe assembly is shredded in the pool (claim 1).
[0011]
Considering that the pressure tube assembly is cylindrical and has a large number, the handling operation can be a simple and repetitive operation. Therefore, if this transport operation is performed using fuel handling equipment that originally handles fuel in water, the effects of automation and labor saving are great. Further, since the shredding work of the pressure pipe assembly can be performed in the pool water, the shielding effect by water can be utilized and other work in the containment vessel is not hindered. Furthermore, it is possible to reduce the amount of dismantling waste as compared with the case where a cutting and transferring device for the pressure pipe assembly is installed after removing the fuel handling equipment.
[0012]
The pressure pipe assembly is about 10 m long as described above, and a cooling water inlet pipe nozzle or the like protrudes to the side. Therefore, it is necessary to cut the pressure pipe assembly into an appropriate length that is easy to handle before transporting, and cut off the inlet pipe nozzle and the like. Therefore, a cutting device for the pressure tube assembly is installed at the head of the refueling device, and the pressure tube assembly is cut into a shape and size that can be easily handled by this cutting device, and then transported. Good (claim 2).
[0013]
By the way, the pressure tube assembly originally designed to accommodate the fuel assembly has a larger diameter than the fuel assembly, and the transfer path of the fuel handling equipment has a neck at the point of the maximum passage diameter. First, the pressure tube assembly cannot be accommodated in the magazine tube of the refueling apparatus. Therefore, in the refueling device, it is preferable to abolish the magazine unit and newly install a guide tube capable of accommodating the maximum diameter of the pressure tube assembly. As a result, it is possible to increase the maximum passage diameter of the refueling device (claim 3).
[0014]
Also, the transfer container of the transfer chute cannot accommodate most of the diameter of the pressure tube assembly. Therefore, in the transfer chute, it is preferable that the transfer container be replaced with a new container capable of accommodating the maximum diameter of the pressure tube assembly so as to enlarge the maximum passage diameter.
[0015]
On the other hand, it is preferable that the pressure pipe assembly transported to the spent fuel storage pool is temporarily placed on a temporary storage rack in the pool, and then shredded (claim 5). Thus, the work of removing and transferring the pressure tube assembly from the reactor body can be performed independently of the shredding work.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 3 is an overall configuration diagram of the fuel handling facility. In FIG. 3, the fuel handling equipment includes a fuel exchange device 17 for loading and unloading the fuel assembly to and from the pressure tube assembly, and a fuel transfer device for transferring the fuel assembly between the storage container 18 and the fuel storage pool 19. It consists of 20. The refueling device 17 is movably disposed below the reactor body formed in the calandria tank 1, takes out the fuel assembly in the pressure pipe assembly from the lower part of the reactor at the time of refueling, and Move down. The fuel assembly in the refueling device 17 is lifted by the fuel accessor 23 through the transfer port 22 and then discharged to the fuel storage pool 19 outside the storage container through the upper swing device 24 and the transfer chute 25. This fuel assembly is lifted by the fuel transfer device 27 via the lower swing device 26 and transported to the spent fuel rack. The new fuel is carried into the storage container 18 in the reverse order to the above, and is loaded into the pressure tube assembly by the fuel exchange device 17.
[0017]
1 and 2 show the flow of dismantling processing of a pressure pipe assembly using existing fuel handling equipment at the time of reactor facility decommissioning, and FIG. 2 is a cross-sectional view taken along the line II-II in FIG. FIG. The fuel handling equipment originally handles the fuel assembly housed in the pressure tube assembly, and the pressure tube assembly is naturally larger in size than the fuel assembly. For this reason, there is a part in the fuel handling equipment that cannot handle the pressure pipe assembly as it is because of the maximum diameter of passage, and it is necessary to modify this part. Hereinafter, including the modification, the processing flow shown in FIGS. 1 and 2 will be described in accordance with the procedures (1) to (8). Note that the same reference numerals are used for the portions corresponding to the conventional example.
[0018]
{Circle around (1)} First, the fuel exchange device 17 is positioned at the lower part of the furnace, and the pressure pipe assembly 2 is received. At this time, the inlet pipe nozzle 10 and the seal leak diameter nozzle 12 (see FIG. 8) protrude sideways and are cut off because they hinder handling. Further, since the pressure pipe assembly 2 is too long as it is, it is cut into an appropriate length, for example, 1/3 to 1/4. These cuts are performed by a pressure pipe cutting device 28 installed at the head of the refueling device 17 as a pre-operation.
[0019]
FIG. 4 shows an example of the pressure tube cutting device 28. In FIG. 4, a pair of front and rear metal saw type cutting mechanisms 31 and 32 are supported on a water ring type elevating and rotating drive unit 29 via a front and rear movement drive unit 30, and a metal saw 33 on the right side of FIG. The left metal saw 33 is mounted horizontally. The illustrated pressure pipe cutting device 28 is attached to the trace from which the snout provided to connect the pressure pipe 13 and the fuel exchange device 17 in a watertight manner at the time of refueling has been removed. In order to cut the pressure pipe assembly 2, the nozzle part is cut off by the cutting mechanism 31 while the pressure pipe assembly 2 is hung and supported by the pressure pipe hanger 14 (FIG. 1) having the same structure as the overhead crane. Then, the tube portion is cut by the cutting mechanism 32. As the pressure tube cutting device 28, other methods such as a plasma cutting method and an abrasive cutting method can be adopted.
[0020]
On the other hand, a magazine unit is provided in the pressure vessel of the refueling device 17, and the magazine unit has four magazine tubes, each of which accommodates a fuel assembly, on a magazine support cylinder so as to sequentially rotate around the center of the snout. Supported. However, a pressure tube assembly cannot be accommodated in a magazine tube having an inner diameter as it is. Therefore, the magazine tube is replaced with a tube having a larger inner diameter, or the magazine unit is removed and a new guide tube is installed, so that the pressure tube assembly can be accommodated. The pressure tube assembly 2 cut by the cutting mechanism 32 as described above is lowered and stored in its own weight in the fuel exchange device 17 thus modified. The inside of the refueling device 17 is filled with water, and the pressure tube assembly 2 is shielded by this water.
[0021]
{Circle around (2)} After the pressure pipe assembly 2 is accommodated in the fuel exchange device 17, the fuel exchange device 17 is moved by the traversing carriage and positioned with respect to the transfer port 22.
[0022]
{Circle around (3)} The pressure pipe assembly 2 is gripped by the fuel inlet / outlet device 23 and suspended from the fuel exchange pool 21. Here, the original gripper 34 of the fuel access unit 23 has a structure in which the fuel assembly is grasped from the outside, but this gripper 34 cannot be used for the pressure tube assembly 2. Therefore, the gripper 34 is modified so that the pressure pipe assembly 2 whose inner peripheral surface is exposed by the round cutting is gripped from the inside.
[0023]
FIGS. 5 and 6 show a configuration example of the gripper that grips the pressure tube assembly 2. (A) of each figure shows a state in which the gripper is suspended in the pressure tube assembly, and (B) shows a state in which the pressure tube assembly is gripped. FIG. 5 shows a structure in which the elevating operation of the camshaft 35 is changed to the in / out operation of the claw 36. After the claw 36 is inserted into the pressure tube assembly 2, the claw 36 is protruded to the outer peripheral side, and the inner peripheral surface of the pressure tube assembly 2 is exposed. Hold by friction. FIG. 6 shows a structure in which a ring-shaped balloon (air picker) 37 is inflated by air pressure and held similarly.
[0024]
(4) The fuel inlet / outlet machine 23 is moved, and the pressure tube assembly 2 is set on the upper swing device 24.
[0025]
(5) The pressure pipe assembly 2 is transferred to the fuel transfer pool 38 by the transfer chute 25. At this time, since it is difficult to handle the pressure pipe assembly alone, it is necessary to store the pressure pipe assembly in a storage cylinder such as a transfer container, but the original transfer container is formed with an inner diameter that does not cause rattling with the fuel assembly. Replace it with a new transfer container with an enlarged inner diameter.
[0026]
(6) The pressure pipe assembly 2 is lifted from the lower swing device 26 by the fuel transfer device 27. Also in the fuel transfer machine 27, the same gripper as the fuel access machine 23 is used.
[0027]
{Circle around (7)} The pressure pipe assembly 2 is transferred to the spent fuel storage pool 19, and the pressure pipe assembly 2 is temporarily placed on the pressure pipe temporary storage rack 39. In addition, the pressure pipe temporary storage rack 39 is installed at the mark where the spent fuel rack has been removed.
[0028]
{Circle around (8)} The pressure pipe assembly 2 is transferred from the pressure pipe temporary storage rack 39 to the spent fuel discharge chamber 40 by the fuel transfer device 27, and the pressure pipe assembly 2 is shredded by the pressure pipe shredding device 41 installed there. I do. The shredded waste material is transferred to another space and stored in a waste container.
[0029]
The transfer / shredding of the pressure pipe assembly using the fuel handling equipment described above has the following advantages.
(1) Most handling operations can be performed underwater and remotely. Therefore, exposure associated with the dismantling operation can be minimized.
(2) The work can be visually monitored by installing the processing apparatus underwater. Further, scattering of chips and dross generated at the time of cutting is suppressed, and a measure for collecting secondary waste is easy.
(3) Since the shredding operation can be performed after the pressure pipe assembly is carried out of the containment vessel, the high-dose work inside the containment vessel can be reduced.
(4) By temporarily placing the pressure tube assembly in the spent fuel storage pool, the removal and transfer of the pressure tube assembly from the reactor body and the subsequent storage in the shredder / waste container are independent. It is possible to plan and remove and transfer the pressure tube assembly without waiting for shredding, thereby increasing the process allowance for the work in the containment vessel. In addition, as a result, the influence on other working steps in the storage container is reduced.
(5) Since the pressure tube assembly can be transferred using the existing transfer chute, a new passage for penetrating the storage container is not required.
(6) Existing equipment is effectively used, and the generation of new waste such as equipment dedicated to decommissioning work is reduced. As a result, the cost of dismantling processing can be reduced.
[0030]
【The invention's effect】
As described above, according to the present invention, the pressure pipe assembly removed from the reactor body is transported to the spent fuel storage pool by the existing fuel handling equipment, and the pressure pipe assembly is shredded in the pool. Thus, it is possible to reduce the exposure at the time of dismantling and shredding by utilizing the pool water shielding effect and to reduce the dismantling waste by effectively utilizing the existing facilities, only by modifying a part of the existing facilities.
[Brief description of the drawings]
FIG. 1 is a flow chart of conveying a pressure tube assembly showing an embodiment of the present invention.
FIG. 2 is a sectional view taken along the line II-II in FIG.
FIG. 3 is a diagram illustrating an overall configuration of a fuel handling facility.
FIG. 4 is a side view showing a schematic configuration of a pressure tube cutting device.
5A and 5B show a configuration of a gripper of the fuel access device, wherein FIG. 5A shows an open state and FIG. 5B shows a gripping state.
FIGS. 6A and 6B show different configurations of the gripper of the fuel access device, wherein FIG. 6A shows an open state and FIG.
FIG. 7 is a diagram showing a method of dismantling and shredding a pressure tube assembly in a reactor containment vessel.
FIG. 8 is a longitudinal sectional view showing a pressure pipe assembly divided into three parts.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 calandria tank 2 pressure pipe assembly 17 fuel exchange device 19 fuel storage pool 20 fuel transfer device 21 fuel exchange pool 22 transfer port 23 fuel access device 24 upper swing device 25 transfer chute 26 lower swing device 27 fuel transfer device 28 pressure pipe Cutting device 38 Fuel delivery pool 39 Pressure pipe temporary storage rack 40 Spent fuel discharge chamber 41 Pressure pipe shredding device

Claims (5)

The pressure pipe assembly removed from the reactor body of the decommissioned new conversion reactor is transported to the spent fuel storage pool using the existing fuel handling equipment, and this pressure pipe assembly is shredded in the pool A pressure tube disassembly method for a new type converter. A cutting device for the pressure tube assembly is installed at the head of the refueling device, and the pressure tube assembly is cut into a shape and size that can be easily handled by the cutting device, and then transported. A method for dismantling a pressure tube of a new type conversion furnace according to claim 1. The guide tube capable of accommodating the maximum diameter of the pressure pipe assembly is newly installed in place of the magazine unit of the refueling device, and the maximum passage diameter of the refueling device is enlarged. Pressure tube disassembly method for new type of converter. 2. The pressure of a new converter according to claim 1, wherein the transfer container of the transfer chute is replaced with a new container capable of accommodating the maximum diameter of the pressure tube assembly, and the maximum diameter of the transfer chute passing therethrough is enlarged. Pipe dismantling method. 2. The pressure pipe disassembly method for a new type converter according to claim 1, wherein the pressure pipe assembly transported to the spent fuel storage pool is temporarily placed on a temporary rack in the pool and then cut.

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