JPH102991A - Device for welding nuclear fuel rod - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the change of gas pressure inside a nuclear fuel rod from causing a poor weld of it when a clad tube of it is welded to an end plug. SOLUTION: When a clad tube 10 is welded to an end plug 11, the expansion of the gas filling a nuclear fuel rod due to welding heat may cause a poor weld. In order to prevent such a poor weld, the pressure inside an airtight welding chamber 22 is controlled to respond to that inside the nuclear fuel rod by controlling an electric back-pressure control valve 24 with program data Pd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nuclear fuel rod welding apparatus and, more particularly, to a welding portion which does not cause poor welding due to pressure in a nuclear fuel rod when welding a cladding tube and an end plug of the nuclear fuel rod. The present invention relates to a nuclear fuel rod welding apparatus as described above.

[0002]

2. Description of the Related Art Generally, when an end plug is welded to a cladding tube of a nuclear fuel rod to make the inside airtight, as shown in FIG. 3, a fuel is placed in an airtight welding chamber 13 which is an airtight container. After inserting one end of the rod, the inside of the hermetic welding chamber 13 is set to a helium gas atmosphere,
An end plug 11 is attached to the cladding tube 10 of the fuel rod inserted into the fuel rod 3, and the joint between the cladding tube 10 and the end plug 11 is circumferentially welded by an arc using the TIG arc welding electrode 12 while rotating the fuel rod. That is being done.

However, when the cladding tube 10 and the end plug 11 are welded by the arc of the TIG arc welding electrode 12, the helium gas in the nuclear fuel rod is thermally expanded by welding heat, and the weld metal portion is formed into a balloon shape from the inside. Poor welding may occur due to bulging blow holes and the like.

[0004] Therefore, back pressure control valves 16, 17, 18 having solenoid valves 14, 15 are provided in the hermetic welding chamber 13.
Is mounted to control the pressure in the hermetic welding chamber 13.

However, as shown in FIG. 4, the pressure Pr in the nuclear fuel rod due to the welding heat rises and changes in a certain relationship from the start of welding to the end of welding, whereas the pressure Poo in the hermetic welding chamber 13 is controlled by back pressure control. The pressure becomes a step-up pressure controlled in accordance with the opening and closing of the valve 16 and the like.

As a result, the pressure difference Pc between the pressure Pr in the nuclear fuel rod and the pressure Po in the hermetic welding chamber 13 fluctuates, and an imbalance potential may act on the welded portion to cause poor welding.

[0007]

In order to solve this problem, it has been practiced to increase the number of back pressure control valves and reduce variations in the pressure range.

However, no matter how much the number of the back pressure control valves is increased, the control of the back pressure control valves is in a step-up manner. There was a problem to say.

In addition, when the number of back pressure control valves increases, there is a problem that the operation, maintenance and the like become complicated.

Accordingly, the present invention provides a nuclear fuel rod welding apparatus capable of controlling the pressure in an airtight welding chamber so as to correspond to the pressure in the nuclear fuel rod when welding the cladding tube and the end plug of the nuclear fuel rod. The purpose is to obtain.

[0011]

SUMMARY OF THE INVENTION Accordingly, the present invention is directed to an atomic reactor in which an end plug is welded to a cladding tube of a nuclear fuel rod in an airtight welding chamber and an inert gas such as helium gas at a specified pressure is sealed in the nuclear fuel rod. In the fuel rod welding apparatus, in the hermetic welding chamber, the cladding tube and the end plug of the nuclear fuel rod are welded to each other in the hermetic welding chamber in response to a change in pressure in the nuclear fuel rod caused by welding heat. And a pressure control means for controlling the pressure of the pressure.

Further, the pressure control means of the present invention reads a change in pressure in the nuclear fuel rod as pattern data obtained by program patterning, and controls the pressure in the hermetic welding chamber based on the pattern data. And

Further, a pressure signal in the hermetic welding chamber is fed back to the control signal based on the pattern data of the present invention.

Further, the pressure control means of the present invention is an electric back pressure control valve for controlling the pressure in the hermetic welding chamber in accordance with the pressure in the nuclear fuel rod.

Further, the pressure control means of the present invention is provided with a filter for removing dust and the like generated inside the hermetic welding chamber when welding the cladding tube and the end plug of the nuclear fuel rod. Features.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the nuclear fuel rod welding apparatus according to the present invention will be described below with reference to FIG.

The nuclear fuel rod welding apparatus A of the present invention has
An airtight welding chamber 22 is installed via a support 21.

The airtight welding chamber 22 is provided with a TIG arc welding electrode 12 for welding the cladding tube 10 of the nuclear fuel rod and the end plug 11 so that the cladding tube 10 and the end plug 11 are welded while rotating. Has become.

The secret welding chamber 22 also includes:
An electric back pressure control valve 24 equipped with a filter 23 and an electric pressure gauge 25
The pressure in the pressure sensor 2 is controlled by the electric back pressure control valve 24 while monitoring and monitoring the internal pressure by the electric pressure gauge 25.

The base 20 is provided with a central processing control unit 26 having a CPU, a RAM, and the like. The RAM (not shown) of the central processing controller 26 has an airtight welding chamber 2
When the cladding tube 10 and the end plug 11 are welded inside the chamber 2, the hermetic welding chamber 22 corresponding to the pressure Pr in the nuclear fuel rod changed by the gas of the nuclear fuel rod due to the welding heat.
The internal pressure Po is read and stored as pattern data Pd in the form of a program pattern.
Command control voltage.

The central processing controller 26 and the electric pressure gauge 25
Is connected to the control unit 27, and controls the pressure Po in the hermetic welding chamber 22 with the monitoring data Sd measured and monitored by the electric manometer 25 from the pattern data Pd received from the central processing control unit 26. Pressure P
The feedback control voltage V at which the pressure difference Pc between the pressure o and the pressure Pr in the fuel rod becomes zero or almost the same value.
Try to get c.

The control unit 27 includes an electric back pressure control valve 24
The airtight welding chamber 2 is connected by an electric back pressure control valve 24 connected to the
The pressure Po in the fuel cell 2 is correspondingly controlled substantially in proportion to the pressure Pr in the fuel rod.

Further, the filter 23 removes dust and smoke generated when welding the cladding tube 10 and the end plug 11 so that the electric back pressure control valve 24 does not impair the dirt performance due to dust and the like.

The operation of the thus constructed nuclear fuel rod welding apparatus A will be described with reference to FIG.

First, a cladding tube 10 and an end plug 11 of a nuclear fuel rod loaded with a pellet and a coil spring (both not shown) are rotatably supported in a hermetic welding chamber 22.

Next, the airtight welding chamber 22 is evacuated and then pressurized helium gas is supplied to the airtight welding chamber 2.
2 and nuclear fuel rods. After that, the end plug 11 is attached to the tip of the cladding tube 10.

When this preliminary operation is completed, the TIG arc welding electrode 12 is energized, and the cladding tube 10 and the end plug 11 are welded while rotating by the arc. Simultaneously with the start of the welding, the electric back pressure control valve 24, the electric manometer 25, the central processing control unit 26, and the control unit 27 are operated.

When welding of the cladding tube 10 and the end plug 11 is started, the pressure Pr in the nuclear fuel rod rises from the start of welding to the end of welding as shown in FIG.

The pattern data Pd is sent from the central processing control unit 26 to the control unit 27 so as to correspond to the increase in the pressure Pr in the nuclear fuel rod. The pattern data Pd is sent to the electric back pressure control valve 24 as a control voltage Vc by the control section 27, and the valve is proportionally controlled.

By the proportional control of this valve, the pressure Po in the hermetic welding chamber 22 is made to correspond to the pressure Pr in the nuclear fuel rod. In such control, when the pressure Po in the hermetic welding chamber 22 is higher or lower than the pressure based on the pattern data Pd, the control voltage Vc is feedback-controlled based on the monitoring data Sd by the electric pressure gauge 25, and the control voltage Vc is constantly controlled. The pressure corresponds to the pressure Pr in the nuclear fuel rod.

The airtight welding chamber 2 is controlled through these controls.
Since the pressure Po in 2 is changed in accordance with the rise in the pressure Pr in the nuclear fuel rod, welding failure due to blow holes or the like does not occur in the welded portion between the cladding tube 10 and the end plug 11. Therefore, the welding quality of the nuclear fuel rods can be improved and the yield can be improved.

At the time of this welding, the hermetic welding chamber 2
2 is removed by the filter 11 and the electric back pressure control valve 28 is not stained.
8 does not degrade.

Therefore, the electric back pressure control valve 28 can be operated stably for a long time.

[0034]

The present invention relates to a nuclear fuel rod welding apparatus in which an end plug is welded to a cladding tube of a nuclear fuel rod in an airtight welding chamber and an inert gas such as helium gas at a specified pressure is sealed in the nuclear fuel rod. Controlling the pressure in the hermetic welding chamber in response to a change in pressure in the nuclear fuel rod caused by welding heat when welding the cladding tube and the end plug of the nuclear fuel rod to the hermetic welding chamber. Since the pressure control means is provided, the pressure in the hermetic welding chamber is increased in proportion to the pressure in the nuclear fuel rod, thereby preventing the occurrence of welding defects due to blow holes due to pressure variations in the weld between the cladding tube and the end plug. be able to.

Further, the pressure control means of the present invention reads a change in pressure in the nuclear fuel rod as pattern data in the form of a program pattern, and controls the pressure in the hermetic welding chamber according to the pattern data. Therefore, the pressure control means can be favorably controlled by the pattern data.

Further, since the pressure signal in the hermetic welding chamber is fed back to the control signal based on the pattern data of the present invention, even if the pressure in the hermetic welding chamber is different from the pattern data, the pressure in the hermetic welding chamber may be different. Can be controlled in proportion to the pressure in the nuclear fuel rod.

Further, the pressure control means of the present invention is an electric back pressure control valve for controlling the pressure in the hermetic welding chamber in accordance with the pressure in the nuclear fuel rod, so that the pressure in the hermetic welding chamber is reduced. The pressure in the nuclear fuel rod can be controlled correspondingly electrically proportionally.

Further, the pressure control means of the present invention is provided with a filter for removing dust and the like generated inside the hermetic welding chamber when welding the cladding tube and the end plug of the nuclear fuel rod. The means is not contaminated by dust or the like.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an outline of a nuclear fuel rod welding apparatus of the present invention.

FIG. 2 is a characteristic curve diagram showing a pressure in a secure welding chamber and a pressure in a nuclear fuel rod according to the present invention.

FIG. 3 is an explanatory view showing an outline of a conventional nuclear fuel rod welding apparatus.

FIG. 4 is a characteristic curve diagram showing a pressure inside a conventional secure welding chamber and a pressure inside a nuclear fuel rod.

[Explanation of symbols]

 A, Nuclear fuel rod welding device 10 Clad tube of nuclear fuel rod 11 End plug 12 TIG arc welding electrode 13, 22 Airtight welding chamber 14, 15 Electromagnetic valve 16, 17, 18 Back pressure control valve 23 Filter 24 Electric back pressure control valve 25 Electric pressure gauge 26 Central processing control unit 27 Pressure control unit

Claims (5)

[Claims] 1. A nuclear fuel rod welding apparatus for welding an end plug to a cladding tube of a nuclear fuel rod in an airtight welding chamber and enclosing an inert gas such as helium gas at a specified pressure in the nuclear fuel rod. Pressure control means for controlling the pressure in the hermetic welding chamber in response to a change in pressure in the nuclear fuel rod caused by welding heat when welding the cladding tube and the end plug of the nuclear fuel rod to a welding chamber. A nuclear fuel rod welding apparatus characterized by comprising: 2. The pressure control means reads a change in pressure in the nuclear fuel rod as pattern data obtained by program patterning, and controls the pressure in the hermetic welding chamber based on the pattern data. Item 8. A nuclear fuel rod welding apparatus according to Item 1. 3. The apparatus according to claim 2, wherein a pressure signal in the hermetic welding chamber is fed back to the control signal based on the pattern data. 4. The valve according to claim 1, wherein said pressure control means is an electric back pressure control valve for controlling a pressure in said hermetic welding chamber in accordance with a pressure in said nuclear fuel rod. The nuclear fuel rod welding apparatus according to any one of the above. 5. The pressure control means is provided with a filter for removing dust and the like generated inside the hermetic welding chamber when welding the cladding tube and the end plug of the nuclear fuel rod. The nuclear fuel rod welding apparatus according to claim 1.