CN109570690B - Radioactive source shell opening welding method and radioactive source shell opening structure - Google Patents

Abstract

The invention relates to a method for welding an opening of a radioactive source cladding and an opening structure of a radioactive source cladding. The method includes arranging an opening of a cladding at a welding joint to release pressure during the welding process; the opening of the cladding is welded by welding. The liquid metal flow of the formed molten pool is blocked. The structure includes a cladding formed by splicing two half-shells; the cladding opening is arranged on the splicing edge of one of the half-shells, or the cladding opening is formed by two half-shells arranged on the splicing edge of the two half-shells. Holes are assembled. The beneficial effects of the present invention are as follows: the use of the technical solution of the present invention to weld various radioactive source claddings with a closed inner cavity structure can solve the problem of exhaust and pressure relief in the inner cavity during the welding process of this type of cladding, and at the same time, no additional plugging is required. The hole structure realizes the welding and sealing of the cladding at one time, reduces the welding process steps of the radioactive source cladding, reduces the radiation dose of the operator, and at the same time can effectively ensure the success rate of welding and the quality of the welding seam.

Description

A kind of radioactive source cladding opening welding method and radioactive source cladding opening structure

technical field

The invention relates to the field of radioactivity, in particular to a method for welding a hole in a cladding of a radioactive source and a cladding structure of a radioactive source.

Background technique

A radioactive source is generally composed of a radioactive source core and a single-layer or multi-layer metal cladding that is coated on the outer layer of the source core to protect the safety of the radioactive source core in various operating environments. The preparation process of the radioactive source is required to be carried out in a special chamber isolated from the external environment. After the radioactive source core is put into the metal cladding, the radioactive source core is sealed inside the metal cladding by welding. After the radioactive source cladding is assembled, a closed cavity structure is formed. The high temperature generated during the welding process of this structure causes the air pressure inside the cladding to increase sharply. The high internal pressure acts on the welding pool, causing the inner side of the weld to be arc-shaped, which affects the quality of the weld. , welding defects with perforation in severe cases. The conventional method to solve the internal pressure problem in the welding process of the closed cavity structure is to design a plugging structure, which undertakes the function of exhaust and pressure relief during the welding process, and then plugs and welds the exhaust hole to achieve sealing after the joint welding is completed. The radioactive source cladding adopts the plugging structure method, which requires at least two welding operations to achieve sealing, resulting in two welding seams to form two weak points in the strength of the cladding structure. Radiation dose; for compact radioactive sources, it is unacceptable to increase the volume and mass by adding a plugging structure on the cladding. Therefore, it is necessary to develop a welding method for the cladding of the radioactive source to solve the above problems.

SUMMARY OF THE INVENTION

In view of the defects existing in the prior art, the purpose of the present invention is to provide a method for welding a hole in a radioactive source cladding and a structure for opening a hole in the cladding of a radioactive source. The cladding is welded and sealed and effectively solves the problem of the pressure increase in the inner cavity during the welding process.

The technical scheme of the present invention is as follows:

A cladding hole welding method for a radioactive source. A cladding hole is arranged at a welding joint to release pressure during the welding process; the cladding hole is blocked by the flow of liquid metal in a molten pool formed by welding.

Further, the above-mentioned radiation source cladding welding method, comprising:

(1) Determine the welding starting position and positioning;

(2) Start welding until the welding point reaches the welding starting position again and stop welding.

Further, in the above-mentioned radiation source cladding welding method, the method for determining the welding starting position in the step (1) is:

Rotate the cladding, and determine the position where the welding point just passes through the opening of the cladding as the welding starting position.

Further, in the above-mentioned method for welding the opening of the radioactive source cladding, the method for determining that the welding point just passes through the opening of the cladding is:

A mark corresponding to the position of the opening of the casing is set on the clamping tool for clamping the casing, and the projection of the welding point on the plane where the mark rotates with the casing just passes through the When the above marks are marked, it can be determined that the welding point just passes through the opening of the cladding.

Further, in the above-mentioned radioactive source cladding welding method, a welding current upslope time of not longer than 0.5s is set to form a molten pool after starting welding; The liquid metal flow closes the cladding openings.

Further, in the above-mentioned method for welding the opening of the radioactive source cladding, the downslope time of the welding current is set to be no longer than 5s to prevent the welding seam from protruding or perforating due to the increase of the internal pressure due to the excessively long downslope time of the welding.

Further, the above-mentioned radiation source cladding welding method also includes:

(3) Carry out welding quality inspection.

Further, in the above-mentioned method for welding the opening of the radioactive source cladding, the welding quality inspection includes the inspection of appearance, size and tightness.

The present invention also provides a radioactive source cladding opening structure, comprising a cladding formed by splicing two half-shells; the cladding opening is arranged on the spliced edge of one of the half-shells, or the cladding opening is formed by setting It is formed by splicing the two half-openings on the splicing edges of the two half-shells.

Further, the above-mentioned radioactive source cladding opening structure further includes a mark for determining the opening position of the cladding; the mark is provided on a clamping tool for clamping the cladding.

The beneficial effects of the present invention are as follows:

Using the technical solution of the present invention to weld the radioactive source cladding to form a closed inner cavity structure after various assemblies can solve the problem of exhaust and pressure relief in the inner cavity during the welding process of this type of cladding, and at the same time, there is no need to add an additional hole blocking structure to achieve one-time The welding and sealing of the cladding is completed, the process steps of the cladding welding of the radioactive source are reduced, the radiation dose of the operator is reduced, and the welding success rate and the quality of the welding seam can be effectively guaranteed.

Description of drawings

FIG. 1 is a flow chart of the high temperature radioactive source welding method of the present invention.

FIG. 2 is a schematic structural diagram of a half-shell with cladding openings in an embodiment of the present invention.

FIG. 3 is a schematic structural diagram of a cladding of the same embodiment as that of FIG. 2 .

FIG. 4 is a schematic diagram of a welding structure for welding using the cladding structure of the present invention.

In the above drawings, 1. the cladding; 2. the cladding opening; 3. the clamping tool; 4. the mark; 5. the tungsten needle.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and embodiments.

As shown in FIG. 1 , the present invention provides a method for welding a radioactive source cladding opening, wherein a cladding opening is provided at a welding joint to release pressure during the welding process; the cladding opening is formed by welding. The liquid metal flow of the pool is blocked. Specifically include:

S1 determines the welding starting position;

S2 starts welding until the welding point reaches the welding starting position again and stops welding;

S3 performs welding quality inspection.

The above welding point is the position where the tungsten needle of the welding gun is aligned.

The method for determining the welding starting position in step S1 is: rotating the cladding, and determining the position where the welding point just passes through the opening of the cladding is the welding starting position.

In the above steps, in order to make full use of the exhaust and pressure relief function of the cladding opening structure during the welding process, it is necessary to realize the filling and plugging of the openings before the lap sealing near the weld seam through process control. It will cause the problem of increased internal pressure due to the poor ventilation of the inner cavity.

The welding of the radioactive source cladding is carried out in a radioactive special operation box with a glass observation window. Due to the small opening size of the cladding, it is difficult to identify the opening position when the cladding is rotated during the welding process. In the embodiment, the method for determining that the welding point just passes through the opening of the cladding is as follows: setting a mark corresponding to the position of the opening of the cladding on the clamping tool used for clamping the cladding, and the welding When the projection of the point on the plane in which the mark rotates with the cladding just passes the mark, it can be determined that the welding point just passes through the opening of the cladding. In this way, an obvious sign that can be seen visually is designed on the mold of the radioactive source cladding. After the cladding is assembled, it is clamped into the welding mold. The position of the cladding is adjusted so that the opening is aligned with the marking position of the mold. The welding process When the middle cladding is rotated, the welding arc starting and arc extinguishing are controlled by observing the marks on the tire. This facilitates the control of welding.

In the specific welding process, after the cladding is installed, turn on the tire and turn on the tire. After visually observing that the mark (opening position) on the tire passes through the tungsten needle, start the arc welding immediately, and set a short current upslope time (usually No more than 0.5s), after passing the tungsten needle at the opening of the cladding, the metal of the cladding joint forms a molten pool in a short time, and after the arc passes through the opening again, the liquid metal flows through the molten pool to complete the filling and plugging of the hole to fully Exhaust pressure relief function using the opening. The process parameters such as welding current and welding speed are determined according to the specific structure of the cladding. During the welding process, observe the marking position of the rotating mold, and after the marking (opening position mark) passes through the tungsten needle again, the arc is extinguished to complete the welding. In this process, it is necessary to set an appropriate current downslope time. Because the pressure relief hole has been plugged before the arc ends downhill, it is difficult to discharge the gas in the inner cavity at this time. Too long downslope time will cause the internal pressure to increase and cause welds. Convex or perforation; and too short downslope time will lead to insufficient weld penetration in the arc starting section due to the short overlap length of the weld. Generally speaking, set the welding current downslope time to ≤5s.

Welding quality inspection includes appearance, size and tightness inspection. Appearance inspection mainly detects external welding defects such as dislocation, cracks, pores, and undercuts. The dimensional inspection mainly measures the height of the cladding after welding and the diameter of the weld zone, and uses calipers to measure multiple positions/angles, and takes the maximum measurement value of height and diameter. There may be radioactive contamination on the surface of the welded radioactive source cladding, which cannot be tested by helium mass spectrometry. According to GB15849-1995 "Leak Test Method for Sealed Radioactive Sources", use the hot liquid bubbling method to test the tightness of the radioactive special operation box: put the cladding in a water bath of 90-95 ℃ at room temperature, and the top of the cladding At least at a depth of 5cm below the water surface, observe for more than 1min to see if there are air bubbles escaping from the sealing source. If no air bubbles escape, it can be determined that the cladding is in a sealed state.

As shown in FIG. 4 , the open-hole structure of the radioactive source cladding according to the present invention and the above-mentioned method includes a cladding 1 (refer to FIG. 2 and FIG. 3 ) that is assembled by two half-shells; the cladding aperture 2 is provided in The combined edge of one of the half-shells (see FIG. 2 ), or, the opening of the cladding is formed by combining two half-openings provided on the combined edges of the two half-shells. In addition, it also includes a mark for determining the position of the opening of the cladding; the mark 4 is provided on the clamping tool 3 for clamping the casing. The tungsten needle 5 of the welding torch is aimed at the welded seam of the two half shells.

Using the technical solution of the present invention to weld various radioactive source claddings with a closed inner cavity structure can solve the problem of exhaust and pressure relief in the inner cavity during the welding of this type of cladding, and at the same time, it is not necessary to add an additional hole blocking structure to complete the cladding at one time. The shell is welded and sealed, which reduces the welding process steps of the radioactive source shell, reduces the radiation dose of the operator, and can effectively ensure the welding success rate and weld quality.

Example

Argon arc welding of stainless steel radioactive source cladding with a closed inner cavity structure after butt assembly:

Stainless steel radioactive source cladding structure

壁厚0.8mm，封闭端底厚0.8mm。Example The radioactive source cladding material is 316L stainless steel. The two half-shells with the same structure are assembled at the open ends of the half-shell to form a sealed cladding shell by argon arc welding. The half-shell is a structure with one end open and one end closed.

The wall thickness is 0.8mm, and the thickness of the closed end bottom is 0.8mm.

Shell opening

A 0.2mm×0.2mm open groove with a wall thickness of 0.8mm is machined at any position of the open end joint of one of the half shells, and the edge of the open groove is cleaned from burrs so as not to affect the next assembly. The perforated half-shell and the unopened half-shell are cleaned and transferred to the special box for radioactive operation.

Packaging card and hole alignment

Assemble the radioactive source core into the non-perforated half-shell in the special box for radioactive operation, and then cover the perforated half-shell to complete the assembly of the cladding and the source core. After assembly, the cladding is clamped into a special tire with obvious marks, and the cladding is rotated so that the openings are aligned with the markings of the tire.

arc

Set the uphill time to 0.5s. Turn on the welding station and rotate, the cladding installed in the mold begins to rotate, and the position of the mark on the tire is visually observed. When the mark passes through the tungsten needle, the arc starts to start welding immediately.

Process parameters

The welding process parameters of stainless steel cladding of this structural size are set as follows:

Tungsten needle diameter working distance Nozzle diameter Argon flow Welding current Welding speed 1.6mm 0.8mm 8mm 9L/min 80A 4.5mm/s

end arc

Set the downhill time to 4s. During the welding rotation process, the position of the tire mark is observed in real time. When the mark passes through the tungsten needle again, the arc is stopped immediately, and the arc is extinguished after the welding current goes downhill to complete the welding.

Weld quality inspection

The macroscopic appearance of the weld was observed by visual inspection. The opening of the original cladding was completely filled and covered, the weld at this position was smooth and smooth, and no external welding defects such as dislocation, cracks, pores, and undercuts were observed on the appearance of the entire weld.

Use calipers to measure the height of the cladding and the diameter of the weld area, and measure the height values of three positions and the diameter of the weld area at three angles respectively to meet the subsequent assembly size requirements.

Put the cladding into a water bath at 90-95°C at room temperature, and observe for more than 1 minute that no bubbles escape, so it can be determined that the cladding is in a sealed state.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention. Thus, provided that these modifications and variations of the present invention fall within the scope of the claims of the present invention and their technical equivalents, the present invention is also intended to include such modifications and variations.

Claims (10)

1. a radiation source cladding opening welding method, it is characterized in that, cladding openings are provided at welding joints to vent pressure during welding; the cladding openings are formed by welding the liquid metal of the molten pool flow blockage; The cladding is formed by splicing two half-shells; the cladding opening is arranged on the splicing edge of one of the half-shells, or the cladding opening is assembled by two half-openings arranged on the splicing edge of the two half-shells made. 2. The method for welding a hole in a radiation source cladding as claimed in claim 1, wherein the method comprises: (1) Determine the welding starting position and positioning; (2) Start welding until the welding point reaches the welding starting position again and stop welding. 3. The radioactive source cladding hole welding method as claimed in claim 2, wherein the method for determining the welding starting position in the step (1) is: Rotate the cladding, and determine the position where the welding point just passes through the opening of the cladding as the welding starting position. 4. The radiation source cladding hole welding method as claimed in claim 3, wherein the method for determining that the welding point just passes through the cladding hole is: A mark corresponding to the position of the opening of the casing is set on the clamping tool for clamping the casing, and the projection of the welding point on the plane where the mark rotates with the casing just passes through the When the above marks are marked, it can be determined that the welding point just passes through the opening of the cladding. 5. The radioactive source cladding welding method according to any one of claims 2-4, characterized in that: setting a welding current upslope time not longer than 0.5s so that a molten pool is formed after starting welding; the welding point is again After reaching the welding starting position, the liquid metal flow through the molten pool seals the cladding openings. 6. The radioactive source cladding welding method according to any one of claims 2-4, wherein the welding current downslope time of not longer than 5s is set to avoid that the welding downslope time is too long and causes the internal pressure to increase. Cause weld bulge or perforation. 7. The method for welding a hole in a radioactive source cladding as described in any one of claims 2-4, further comprising: (3) Carry out welding quality inspection. 8 . The method for welding a hole in a radioactive source cladding according to claim 7 , wherein the welding quality inspection includes inspection of appearance, size and tightness. 9 . 9. A radioactive source cladding opening structure, characterized in that: it comprises a cladding formed by splicing two half-shells; the cladding opening is arranged on the spliced edge of one of the half-shells, or the cladding opening is It is formed by splicing two half-opening holes arranged on the splicing edges of the two half-shells. 10. The radioactive source cladding opening structure according to claim 9, characterized in that: it further comprises a mark for determining the opening position of the cladding; Install the card on the tire.

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