JPH08254595A - Welding method for irradiated material - Google Patents

Abstract

PURPOSE: To provide a welding method capable of prevention of intergranular cracking of such a material irradiated by neutron as structure material of reactor structure and in-core components. CONSTITUTION: By analyzing a sample taken at repairing location and the surrounding part and observing the sample after preliminary heat treatment, the preliminary heat treatment conditions properly causing trapsite core on the sample is grasped. The preliminary heat treatment is conducted at the grasped conditions after mechanical treatment is applied to the repairing location of an actual machine. Then, after observing and analyzing the sample taken at the repairing location and the surrounding part of the actual machine and confirming that trapsite core is properly caused on the sample, welding is conducted. The properness of the welding is confirmed and welding is conducted at the repairing location of the actual machine. Inspection is done for the goodness of the welding state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for welding irradiated materials, and more particularly to a method for welding irradiated materials such as irradiation experimental equipment, nuclear reactors and nuclear fusion experimental equipment.

[0002]

2. Description of the Related Art As an example of a material containing an inert gas atom,
Reactor structure containing helium atoms generated by neutron irradiation, constituent materials such as reactor equipment, i.e. irradiation material, irradiation material, by receiving neutron irradiation,
It is generally known that helium atoms are generated inside.

When welding such an irradiated material during repair work of a nuclear reactor, etc., due to heating during welding,
Helium atoms, which are solid-soluted in the irradiated material, diffuse and aggregate at the grain boundaries to form bubbles, which easily causes helium bubbles.

FIG. 9 is a schematic diagram of a heat-affected zone surface structure after conventional welding. Like this, helium bubble 4
8 is less generated in the grain 49 of the crystal grain, and a large number of grains are accumulated on the grain boundary 50, which lowers the strength of the grain boundary 50. Therefore, the tensile stress generated in the heat-affected zone during the solidification process causes grain It is considered that interfacial cracking will occur [WE KANNE, Jr .: Remote React
or Repair: GTA Weld Cracking
Caused by Entrapped Heliu
M., Weld. J., pp. 33-39 (1988)].

Further, in Japanese Patent Laid-Open No. 62-37352, an Fe-based, Ni-based, Cr-based or Co-based alloy material containing boron is used in a recrystallization temperature range, or 50 from the recrystallization temperature.
In the temperature range up to ℃ lower temperature, recrystallization and processing heat treatment including its grain growth process are applied to change the boron content in the material.
Disclosed is a method for preventing He embrittlement of a metal material for neutron irradiation environment, which comprises depositing and dispersing as boron-based precipitates in crystal grains to reduce the amount of boron in the grains.

[0006]

Thus, the irradiation material is
At the time of welding, the helium atoms that form a solid solution inside concentrate on the grain boundaries and form bubbles, which reduces the bonding strength at the grain boundaries. In the case of a material having a large content of helium atoms by receiving a large amount of neutron irradiation, it is difficult to weld, and if a defect should occur, without repairing the welding, It was necessary to take measures such as replacing members.

Further, the above-mentioned Japanese Patent Laid-Open No. 62-37352 discloses that boron is dispersed and held in crystal grains, but helium generated by the (n, α) reaction between boron and neutrons. When the irradiated material has a high temperature during welding, it will flow from inside the crystal grains to the grain boundaries. Therefore, it is impossible to prevent weld cracking by the means as in this known example.

An object of the present invention is to make it possible to provide a welding method capable of preventing intergranular cracking during welding of an irradiation material such as a constituent material of a reactor structure, in-core equipment and the like.

[0009]

The above object can be achieved as follows.

(1) In the method of welding irradiated material, trap site nuclei in which the inert gas atoms are aggregated to form bubbles in the crystals of the irradiated material containing inert gas atoms are preliminarily formed by preheating. Then, the inert gas atoms should be dispersed and retained as bubbles in the crystal grains during the high temperature process during welding.

(2) In (1), when the inert gas atom is a helium atom, 400 to 60 as a pre-heat treatment.
To generate trap site nuclei that turn helium atoms into bubbles by using a heat treatment that raises the temperature of the irradiated material in multiple stages within a temperature range of 0 ° C.

(3) In (1) or (2), before the pre-heat treatment, a machining process is performed to previously generate dislocations in the crystal grains of the irradiated material by water jet peening, shot peening or rolling. Performed and pre-heat treatment,
Use one of a resistance heater, an induction heater, and a laser.

(4) In (2), the temperature of the irradiated material is measured, and the measured temperature is fed back to the condition of the pre-heat treatment to generate trap site nuclei of helium atoms existing in the crystal of the irradiated material. To control the amount of movement of the helium bubble to stably generate trap site nuclei of helium bubbles in the crystal grains of the irradiated material.

(5) In (1), (2), (3) or (4), a heater for heating the portion to be welded and the periphery of the portion to be welded during the pre-heat treatment, and the welding scheduled during the pre-heat treatment Temperature sensor for pre-heat treatment that measures the temperature around the weld and the area to be welded, temperature sensor for welding that measures the temperature around the weld and this weld during welding, and remote control for heater temperature control Device, welding planned part and machining processing device for machining the surface around the welding planned part, remote control device for machining processing device, welding device for welding planned welding part, and remote control device for this welding device Use welding repair equipment equipped with at least one of the above.

(6) In (2) or (3), before the pre-heat treatment, a portion to be welded in the irradiated material and a part of the periphery of the portion to be welded are sampled by electric discharge machining, and helium in the irradiated material is sampled. Analyze the atomic concentration in advance and set the pre-heat treatment conditions.

(7) In (3) or (5), before the pre-heat treatment, a portion to be welded in the irradiated material and a part of the periphery of the portion to be welded are sampled by electric discharge machining, and helium in the irradiated material is sampled. To analyze the concentration of atoms in advance and set the conditions for machining processing.

(8) In (5), before the pre-heat treatment, a portion to be welded in the irradiated material and a part of the periphery of the portion to be welded are sampled by electric discharge machining to determine the concentration of helium atoms in the irradiated material. Analyze in advance and set the welding conditions for the planned welding area.

(9) In (5), the welding repair equipment is supported by a crane, and at least any one of an optical device, an acoustic device, and an ultrasonic device for horizontal and vertical positioning, and Equipment for preventing misalignment after fixing must be provided, and the pre-heat treatment equipment, machining equipment, and welding equipment can all be installed so that they can be moved vertically and circumferentially.

(10) In (9), at least one of an optical device, an acoustic device, and an ultrasonic device,
Correct the position of welding repair equipment.

(11) In (5) or (9), the welding repair equipment includes an inspection equipment, a decontamination equipment, a residual stress improvement equipment, a gondola and parts in addition to the pre-heat treatment equipment, the machining equipment and the welding equipment. Equipment that can be used with at least one of the replacement devices installed.

(12) In (11), the gondola has the capability of diving to a water depth of 30 m, and the manipulator,
And a shield that blocks radiation.

[0022]

[Function] When a material containing inert gas atoms is welded, the inert gas atoms accumulate to form bubbles, and large bubbles are generated at the grain boundaries. These bubbles reduce the bonding strength at the grain boundaries. The intergranular cracking occurs due to the tensile stress generated during the solidification shrinkage of the melted portion.

When the inert gas atom is the helium atom contained in the irradiation material, the helium atom is trapped mainly in the vacancies among the irradiation defects caused by the neutron irradiation. When welding the irradiated material in such a state, helium atoms are released to the outside of the material as gas at the welded part,
Large bubbles of helium atoms are generated at grain boundaries in the heat-affected zone where welding does not occur.

That is, at high temperature, helium atoms which are integrated with vacancies and diffused suddenly flow into the grain boundary which is a defect sink, so that helium bubbles are formed along the grain boundaries and are generated in the solidification shrinkage process of the irradiated material. Depending on the tensile stress
Causes grain boundary cracking.

On the other hand, in the present invention, since the pre-heat treatment of heating at a temperature near the hole movement start temperature is performed before welding, the holes are diffused and coalesced to form deep holes for helium atoms. Clusters are formed. Also in this case,
Since the temperature in the preheat treatment and the temperature holding time are properly adjusted, the vacancy diffusion distance is suppressed, and a large number of vacancy clusters are dispersed and formed in the crystal grains.

FIG. 10 is a schematic view of the surface structure of the heat-affected zone when welding is performed after the pre-heat treatment as in the present invention. The helium bulb 48 is not formed at the grain boundary 50, but a large number of small grains are dispersed in the grain 49.

That is, in the present invention, since welding is carried out after such pre-heat treatment is carried out, the helium atoms solid-solved in the irradiated material are trapped in the nearby vacancy clusters during the diffusion process to form bubbles. To do. In this case, since a large number of vacancy clusters are dispersed in the crystal grain as described above, a large number of fine helium bubbles are generated in the crystal grain and are suppressed from flowing into the grain boundary. To be done.

As described above, since many helium bubbles are finely dispersed and confined in the crystal grains,
As compared with the conventional case in which helium bubbles are selectively formed at the crystal grain boundaries, the influence on the strength of the irradiated material is extremely small, and the occurrence of grain boundary cracks during welding can be suppressed.

Further, since the hole migration start temperature of the irradiation material is about 500 ° C., which is a relatively low temperature, the pre-heat treatment for the trap site nucleation of helium bubbles can be easily carried out. Furthermore, by performing a machining process on the irradiated material prior to the pre-heat treatment, it becomes possible to generate dislocations in the crystal grains, which facilitates the generation of trap site nuclei and the grain boundaries of helium bubbles. Can be further suppressed.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS.
Will be explained. FIG. 1 is a flow chart of the present embodiment, and FIG. 2 is a vertical cross-sectional view of a boiling water reactor used for explaining the present embodiment. That is, the present embodiment is a case where the shroud is welded and repaired based on the flowchart shown in FIG.

In this embodiment, as shown in FIG.
A sample of the weld repair area and its periphery is taken, helium concentration analysis is performed for this sample, and after pre-heat treatment, the valve in the sample is observed to see if trap site nuclei have been generated appropriately. After confirming, when it did not occur properly, pre-heat treatment was performed again. Then, if it occurs reasonably, it was decided to perform the pre-heat treatment on the welding repair part of the actual machine under these conditions.

Next, after performing a machining process on the welding repaired portion of the actual machine, a pre-heat treatment was carried out under the conditions determined as described above. After that, a sample of the welding repair part of the actual machine and its peripheral part is taken, helium concentration analysis is performed on this sample, and the valve in the sample is observed to confirm whether trap site nuclei are properly generated and When it did not occur, the pre-heat treatment was performed again. If it is occurring properly, weld the sample and confirm that it is in a proper welding state.If it is not appropriate, perform welding again and determine the welding conditions to weld the welding repaired part of the actual machine. did.

Finally, after welding was carried out at the welding repair portion of the actual machine under these welding conditions, the welded portion and its peripheral portion were inspected and it was confirmed that it was in a good welded state.

Next, the welding repair work of the shroud of this embodiment, which is performed based on the above-mentioned flow chart, will be described with reference to FIG.

As shown in FIG. 2, the boiling water reactor has a reactor pressure vessel 1 as an outer vessel and a shroud 2 as an inner vessel.
And the shroud 2 is fixed to the shroud support leg 3 by welding. A shroud head 4 and a steam separator 5 are fixed to the upper part of the shroud 2 by a shroud head bolt 6.
A fuel assembly 7 is installed inside.

The inner and outer walls of the shroud 2 are normally filled with high-temperature reactor water 8, but the temperature of the reactor water 8 is sufficiently lowered during the periodic inspection. Further, a jet pump 9 for circulating the reactor water 8 is installed between the pressure vessel 1 and the shell 2. The new shroud 2a and the new shroud support leg 3a will be described later in a third embodiment.

In the welding repair work of the shroud 2 of this embodiment, first, in order to reduce exposure to radiation during the work, water is poured so that the upper part of the steam separator 5 is completely covered with the reactor water 8, Using the overhead crane (not shown) of the reactor building, the reactor pressure vessel upper lid 10 joined to the reactor vessel upper flange 11 is removed, and the steam dryer 12 in the reactor pressure vessel 1 is further removed. I removed it.

Next, in order to make radiation exposure reduction more reliable, water was injected so that the inside of a reactor well 22 (see FIG. 3) described later was filled with water, and then the shroud head bolt 6 was removed. After that, the steam separator 5 and the shroud head 4 were removed using an overhead crane, and then the fuel assembly 7, the fuel support fitting 13, the control rod 14, and the control rod guide pipe 15 were sequentially removed. In addition,
The work up to this point is the same as the work performed during the periodic inspection.

Next, after removing the core sparger sparger 16, the water feed sparger 17, and the water feed pipes (not shown) to them, a bolt for fixing the upper lattice plate 18
The restraint and the restraint block (neither shown) were removed, and further the upper lattice plate 18 was removed using an overhead crane.

Finally, after removing a fixing bolt (not shown) for fixing the core support plate 19 to the lower flange of the shroud 2, the core support plate 19 is removed using an overhead crane, and then the ICM guide tube 20 and The ICM stabilizer 21 was removed.

In this embodiment, the welding repair work for the shroud 2 is carried out after the above-mentioned state is set. The contents of this repair work will be described with reference to FIGS. 3 and 4. FIG.
Is an explanatory diagram of each work of decontamination and inspection of the wall surface of the shroud 2 performed in the reactor water in the present embodiment, and FIG. 4 is a sampling process, pre-machining treatment, pre-heat treatment and welding similarly performed in the atmosphere. It is explanatory drawing of each work of.

In this embodiment, first, as shown in FIG.
A welding repair facility 23 for performing this work was lowered to a position near the shroud 2 through the reactor well 22 using an overhead crane, and fixed to the reactor pressure vessel 1 by a fixing device 24. Next, the upper flange 1 of the reactor pressure vessel
A reflector 26 for reflecting light from the optical device 25 to
Was attached to the reactor pressure vessel 1 with a fixing bolt.

Next, the optical device 25 measures four points for the distance between the welding repair equipment 23 and the reflector 26,
Using this measurement result, the welding repair facility 23 was leveled by the vertical drive device 27. Further, the optical device 25 similarly performs four-point measurement on the distance between the welding repair facility 23 and the side surface of the reactor pressure vessel 1, and uses the measurement result to measure the welding repair facility by the horizontal drive unit 28. The vertical center axis of 23 was aligned with that of the reactor pressure vessel 1.

After that, the wall surface of the shroud 2 was cleaned using the water jet device 29 attached to the welding repair facility 23, and then the welding repair location was investigated using the inspection device 30. When the repaired part was found, the reactor water 8 was extracted to the lower part of the repaired part so that the repaired part could be repaired in the atmosphere.

The remote control panel 31 is used for the welding repair equipment 2
The high pressure pump 32 is a control panel attached to the remote control unit 3 for remotely controlling the above-mentioned devices.
9 is a facility for sending a high-pressure water stream. The power source 33 is a power source for operating the remote control panel 31 and the high pressure pump 32.

Next, in order to examine the helium concentration in the metal material in advance, the material sample (1-1) near the repaired portion was
As shown in FIG. 4, the sample is collected mechanically using a sample collecting device 34, and then a sample (1-
1) was recovered. Sample (1-1) is 3mmφ x 0.2mm
5 pieces were prepared, and one of them was applied for helium concentration measurement, in which the helium concentration per unit volume in the material was measured by heating.

FIG. 5 is a graph showing the amount of helium released from the sample when the sample is heated so that the temperature of the sample increases linearly.
The amount of helium released was increased in the vicinity, and from this fact, it is clear that the movement of helium atoms is active near 500 ° C. and a trap site nucleus is easily formed.

From this result, the pre-heat treatment condition for forming the trap site nucleus of the helium valve, that is, the temperature condition of the low temperature annealing was set to 400 to 600 ° C. Specifically, low temperature annealing was performed by heating one (1-1) of the samples shaped into 3 mmφ × 0.2 mm at 400 to 600 ° C. for about 120 minutes.

FIG. 6 shows the temperature conditions of the low temperature annealing of this embodiment.
Shown in Up to 400 ° C, the sample (1-1) is heated so that the temperature of the sample (1-1) increases linearly.
After the temperature exceeded 00 ° C, the temperature was raised at intervals of 40 ° C and kept at each temperature for 20 minutes.

Next, the sample (1-1) after the low temperature annealing was electrolytically polished, and the generation state of helium bubbles was observed by a transmission electron microscope. It was sufficient for the helium bubbles to absorb the remaining total amount of helium. Low temperature annealing was repeated until it was determined that the number and diameter of bubbles that could become various trap site nuclei were determined. Then, the obtained low temperature annealing conditions were applied to an actual machine. Before performing the pre-heat treatment on the actual machine, in order to facilitate the generation of trap site nuclei of helium bubbles by the pre-heat treatment, a water jet device 29 (see FIG. 3) is used for the water welding at the planned welding portion and its periphery. Jet peening was performed to generate work dislocations in advance.

Then, from the heat treatment conditions obtained from the sample (1-1), the heat input amount of the laser was set to about 10 by using the laser attached to the preheat treatment device 36 as shown in FIG.
While maintaining the pressure at 30 kJ / cm ² , the welding repaired portion and its periphery were heated to 400 to 600 ° C. to perform low temperature annealing. After that, the sample (1-2) is mechanically collected from the location subjected to the low temperature annealing by using the sample collecting device 34, and then collected by using the crane 35, and the sample (1- The helium concentration in 2) and the state of helium bubbles were examined.

It is considered that the helium bubbles generated in the crystal grains serve as trap site nuclei for the helium atoms released during welding, and consequently grain boundary cracking can be suppressed. Low temperature annealing was repeated until After such repetition, when a sample (1-2) satisfying the above conditions is obtained, by welding this sample (1-2),
After examining the occurrence of intergranular cracks due to the thermal effect of welding and confirming that no intergranular cracks have occurred, the welding device 3
Welding repair was actually performed on shroud 2 using No. 7.

FIG. 7 is an explanatory diagram of welding repair of the shroud 2 in this embodiment. That is, in the unlikely event that a crack 39 is present on the surface of the pre-heat treatment section 38 of the shroud 2, the location where the crack 39 is generated is polished by using a polishing device (not shown) and built up. Weld or crack 39
Apply the backing plate 40 so as to cover the
As shown in the welded portion 41, all the edges of the pad plate 40 were welded to the shroud 2.

When there are a plurality of welding repair points,
This repair work was divided into multiple steps up to the lower part of the shroud 2 and carried out in sequence, and after the welding repair was completed, the parts removed for this repair were attached. In addition, also in this attachment, if welding is necessary and there is a risk of occurrence of intergranular cracks during welding, a sample is taken, and by the same operation as described above, intergranular cracks do not occur,
After confirming that welding was possible, welding was performed.

A second embodiment of the present invention will be described with reference to FIGS. 3, 4 and 7. The present embodiment is a case where the present invention is applied to the welding repair of the upper lattice plate and the core support plate. In addition, FIG. 3, FIG. 4 and FIG.
It has already been used.

In this embodiment, similarly to the first embodiment, the upper lattice plate 18 and the core support plate 19 are removed from the shroud 2. Next, the upper grid plate 18 and the core support plate 19 were immersed in decontamination water for decontamination, and then inspected in the atmosphere to confirm the weld repaired portion. Then, when the welding repair is difficult, when the welding repair cost is high, or when the strength is deteriorated by the welding repair, the entire repair is performed, but in other cases, the welding repair is performed.

In this embodiment, as described above, the upper grid plate 1
8 and the core support plate 19 are repaired by welding, but both are performed in the same manner, and therefore the core support plate 19 will be described below as an example.

In this example, first, the sample (2-1) was taken out from the vicinity of the weld repaired portion by a mechanical method. For the evaluation of the sample and the pre-heat treatment, the same method as in the first embodiment was used. That is, the welding repaired portion was machined before the low-temperature annealing to generate work dislocations. Then, from the heat treatment conditions obtained from the sample (2-1), a laser was used to measure the welding repair location and its periphery in 400 to 6
It was heated to 00 ° C. and low temperature annealing was performed.

After that, from the place where low temperature annealing was performed,
The sample (2-2) was mechanically collected, and the helium concentration and the state of the helium bubble in the sample (2-2) were inspected by using the same method as in the first example. Then, based on the data obtained from the sample (2-2), the helium bubble generated in the grain becomes the trap site nucleus of the helium atom released during welding, and the helium concentration considered to be able to suppress intergranular cracking, and Low temperature annealing was performed until the number and diameter of bubbles were reached. Then, after that, welding repair was performed.

If a crack has been generated after the low temperature annealing, the place where the crack is generated is polished and welded by welding, as in the case of the first embodiment. The plate was applied and welding was performed.

Then, the core support plate 19 repaired by welding as described above was fixed to the shroud 2 by welding. In the case of this embodiment, the preheat treatment of the shroud 2 is the same as that of the first embodiment. As in the case, welding repair equipment 23
This was performed using The fixing method of the welding repair equipment 23 is also the first
This is similar to the case of the embodiment. That is, the core support plate 19
After returning to the original position, the water jet device 29 attached to the welding repair equipment 23 is used to clean the welded portion of the wall surface of the shroud 2 with the core support plate 19 and its vicinity, and The reactor water 8 was extracted until the water surface of the reactor water 8 is below the core support plate 19 so that the welding repair can be carried out.

Subsequently, from the shroud 2 on the core support plate 19 and the welded portion and the vicinity thereof, the sampling device 3
After taking sample (2-3) using
The sample (2-3) was collected by. And the sample (2-
This sample (2-3) was evaluated after pre-heat treatment of (3). Each of these pre-heat treatment and evaluation methods is
This is similar to the case of the embodiment.

That is, according to the heat treatment conditions obtained from the sample (2-3), a laser attached to the heat treatment apparatus 36 was used to measure the welded portion between the core support plate 19 and the shroud 2 and its vicinity in the range of 400 to 600. It was heated to ℃ and low temperature annealing was performed. After that, a sample (2-4) is collected from the low-temperature annealed portion using the sample collecting device 34, and then collected using the crane 35, and the sample (2-4) is collected using the same method as in the first embodiment. The helium concentration in) and the state of helium bubbles were examined.

Based on the data obtained from the sample (2-4), it is considered that the helium bubbles generated in the grains serve as trap site nuclei for the helium atoms released during welding and can suppress grain boundary cracking. Repeated low temperature annealing was performed until the concentration and the number and diameter of bubbles were reached. After that, samples (2-4) were welded, and it was confirmed that grain boundary cracking due to the heat effect of welding did not occur.

Then, after the overhead crane is pulled up and the welding repair equipment 23 is recovered, the core support plate 19 is attached to the shroud 2 while adjusting the adjusting pins (not shown) using the overhead crane. It was placed in the place where the After that, using the overhead crane, welding repair equipment 23
Was lowered to the vicinity of the core support plate 19 and fixed in the same manner as in the first embodiment, and then welding was performed using the welding device 37 to fix the core support plate 19 to the shroud 2.

In the case of the upper lattice plate 18,
Although not described, each method of welding repair and fixing to the shroud 2 after the welding repair was performed in the same manner as in the case of the core support plate 19 described above. Further, after the welding is completed, in each case of the upper lattice plate 18 and the core support plate 19, the detached one is attached by a process reverse to the process of removing the reactor pressure vessel upper lid 10 to the control rod guide pipe 15. went.

A third embodiment of the present invention will be described with reference to FIGS. 8 and 4. In this embodiment, when replacing the shroud, shroud support leg, shroud support cylinder and shroud support plate with a new one,
This is a case where the present invention is applied.

FIG. 8 is an explanatory diagram of work contents by the gondola with a manipulator of this embodiment. Further, FIG. 4 has already been used in the description of the first and second embodiments described above.

In this embodiment, as in the case of the first embodiment, the reactor pressure vessel upper lid 4 to the ICM guide tubes 20 and I are connected.
The CM stabilizer 21 was removed, the shroud 2 was separated from the reactor pressure vessel 1 using a cutting device 42 as shown in FIG. 4, and the shroud 2 was taken out in multiple stages using an overhead crane.

Next, after cleaning the inner surface of the reactor pressure vessel 1 by using the welding repair equipment 23, a gondola with a manipulator 43 is attached to the welding repair equipment 23, and the jet pump 9
I lowered it to the vicinity of. In addition, the gondola 43 with a manipulator has a capability of diving to a water depth of 30 m, and includes a manipulator and a shield that shields radiation.

After that, as in the case of the first embodiment,
The welding repair facility 23 was fixed, and the jet pump 9 was removed in the reactor water 8 by using the manipulator 44 and a cutting tool (not shown) attached thereto. Then, using a separately installed crane (not shown), the jet pump 9 was pulled up, and then the welding repair equipment 23 was lowered to the vicinity of the shroud support cylinder 45 and fixed.

Next, the gondola with manipulator 43 was operated to cut and remove the shroud support cylinder 45 from the shroud support plate 46 and the shroud support leg 3 using the above-mentioned cutting tool.
After that, the welding repair facility 23 was once pulled up, and the shroud support cylinder 45 was pulled up using an overhead crane.

Thereafter, the welding repair equipment 23 is lowered to a position near the shroud support leg 3 and fixed, and the reactor pressure vessel 1 to the shroud support plate 46, the shroud support leg 3 and the jet pump riser brace 4 are fixed.
After removing 7, the welding repair equipment 23 was pulled up, and the shroud support plate 46, the shroud support leg 3, and the jet pump riser brace 47 were pulled up using an overhead crane.

Then, after the reactor water 8 has been completely drained, the preheat treatment device 36 is attached to the welding repair equipment 23, and the welding repair equipment 23 is lowered to the vicinity of the lower part of the reactor pressure vessel 1.
After fixing, the cut portion was ground and shaped using a grinder (not shown).

Thereafter, the new shroud support leg 3a
Further, in order to attach the new shroud support cylinder 45a, the pre-heat treatment similar to that in the first embodiment was performed on the planned welding portion of the reactor pressure vessel 1 and its peripheral portion to generate trap site nuclei in advance. Then, the welding repair facility 23 was pulled up, and the new shroud support leg 3a was positioned at the welded portion with the reactor pressure vessel 1 using the overhead crane.

Subsequently, the welding repair equipment 23 is lowered to the lower part of the reactor pressure vessel 1 by using an overhead crane, and the reactor pressure vessel 1 and a new shroud are installed using the welding device 37 attached to the welding repair equipment 23. The welded portion with the support leg 3a was welded, and the new shroud support leg 3a was fixed to the reactor pressure vessel 1. Further, the new shroud support leg 3a is provided with a new shroud support cylinder 45.
a is fixed by welding, and the new shroud support plate 4 is attached to the new shroud support cylinder 45a.
6a was fixed by welding. In the case of welding the above-mentioned new ones, the pre-heat treatment was omitted because the welded member has not been subjected to neutron irradiation.

Subsequently, preheat treatment was performed on the portion of the reactor pressure vessel 1 to be welded to the new jet pump riser brace 47a. After that, the welding repair equipment 23 is temporarily pulled up, the gondola 43 with a manipulator is attached to the welding repair equipment 23, and it is lowered to the vicinity of the jet pump 9.
It was fixed to the reactor pressure vessel 1.

After that, the jet pump 9 is lowered using the crane 35, the jet pump 9 is installed using the manipulator 44, and then the new jet pump riser brace 47a is fixed to the reactor pressure vessel 1 by the welding device 37. did. After fixing the jet pump 9, the welding repair equipment 23 was pulled up.

Then, after using the overhead crane to position the new shroud 2 (see FIG. 2) so that the weld portion with the new shroud support cylinder 45a comes into contact,
The welding repair equipment 23 equipped with the remote control type heat treatment device 36 and the welding device 37 is lowered to the vicinity of the lower part of the shroud 2a, and the welded portion between the new shroud 2a and the new shroud support cylinder 45a is welded to the new shroud support cylinder 45a. Against new shroud 2
a was fixed. After that, the welding repair equipment 23 is pulled up,
Then, the core support plate 19 and the upper grid plate 18 were attached as in the case of the second embodiment. Subsequently, each structure was attached in a step opposite to the step of removing the reactor pressure vessel upper lid 10 to the control rod guide tube 15, and the attaching operation of this example was completed.

That is, in this embodiment, the preheat treatment is performed by the reactor pressure vessel 1 and the new shroud support leg 3.
The portion to be welded to a and the portion to be welded to the new jet pump riser brace 47a in the reactor pressure vessel 1 are shrouds, shroud support legs, shroud support cylinders, shrouds by performing such preheat treatment. It was possible to suppress the decrease in the strength of the welded portion of the structure of the boiling water reactor, which is likely to occur when the support plate and the jet pump riser brace are replaced with new ones.

Further, in each of the above-mentioned embodiments, since the device which is attached to the welding repair facility 23 as required is operated by remote control, it is safe and the work can be performed efficiently. .

[0082]

According to the present invention, the irradiation material containing the inert gas atoms is subjected to the pre-heat treatment by annealing at a relatively low temperature, and the inert gas atoms are dispersed as bubbles in the grains to form grain boundaries. By reducing the amount of the inert gas flowing into, it is possible to suppress the generation of bubbles at the grain boundaries during welding and prevent grain boundary cracking caused by welding.

Therefore, in the repair of the components of the boiling water reactor, it is possible to weld the neutron irradiation material such as the reactor structural material or the material having a large helium content, which has been difficult to weld and repair in the past. Maintenance measures for the reactor will be significantly improved.

[Brief description of drawings]

FIG. 1 is a flowchart of a work process according to a first embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view of a boiling water reactor for explaining the work process of FIG.

FIG. 3 is a vertical cross-sectional view of the boiling water nuclear reactor for explaining the first half of the work process of FIG. 1.

FIG. 4 is a vertical cross-sectional view of a boiling water reactor for explaining the latter half of the work process of FIG.

FIG. 5 is a diagram showing the relationship between sample temperature and helium emission amount.

FIG. 6 is a diagram showing a temperature condition of preheat treatment in FIG. 1.

FIG. 7 is an explanatory diagram of a shroud welding repair process in FIG. 1.

FIG. 8 is a vertical sectional view of a boiling water reactor for explaining a third embodiment of the present invention.

FIG. 9 is a schematic diagram of a neutron irradiation material structure after welding.

FIG. 10 is a schematic diagram of a neutron irradiation material structure welded after the preheat treatment of the present invention.

[Explanation of symbols]

1 ... Reactor pressure vessel, 2 ... Shroud, 2a ... New shroud, 3 ... Shroud support leg, 3a ... New shroud support leg, 4 ... Shroud head, 5 ... Steam separator, 6 ... Shroud head bolt, 7 ... Fuel Assembly, 8 ... Reactor water, 9 ... Jet pump, 10 ... Reactor pressure vessel upper lid, 11 ... Reactor pressure vessel upper flange, 12 ...
... Steam dryer, 13 ... Fuel support metal fitting, 14 ... Control rod, 1
5 ... control rod guide tube, 16 ... core sparger purger, 1
7 ... Water supply sparger, 18 ... Upper lattice plate, 19 ... Core support plate, 20 ... ICM guide tube, 21 ... ICM stabilizer, 22 ... Reactor well, 23 ... Welding repair equipment, 24 ...
Fixing device, 25 ... Optical device, 26 ... Reflector, 27 ... Vertical drive device, 28 ... Horizontal drive device, 29 ... Water jet device, 30 ... Inspection device, 31 ... Remote control panel, 32 ... High pressure pump, 33 ... Power supply , 34 ... Sampling device, 35
… Crane, 36… Pre-heat treatment device, 37… Welding device, 3
8 ... Pre-heat treatment part, 39 ... Crack, 40 ... Patch plate, 41 ... Welding part, 42 ... Cutting device, 43 ... Gondola with manipulator, 44 ... Manipulator, 45 ... Shroud support cylinder, 45a ... New shroud support cylinder, 46 ... Shroud support plate, 46a ... New shroud support plate, 47 ... Jet pump riser brace, 47a ... New jet pump riser brace, 48 ... Helium valve, 49 ... Intragranular, 50 ... Grain boundary.

Claims (12)

[Claims] 1. A pre-heat treatment is performed to previously generate trap site nuclei in which the inert gas atoms are aggregated to form bubbles in the crystal of the irradiated material containing the inert gas atoms, and then the inert gas is generated. A method for welding an irradiating material, characterized in that gas atoms are dispersed and held as bubbles in crystal grains during a high temperature process during welding. 2. When the inert gas atom is a helium atom, the helium is obtained by using, as the pre-heat treatment, a heat treatment for raising the temperature of the irradiation material in multiple stages within a temperature range of 400 to 600 ° C. The method for welding an irradiating material according to claim 1, wherein the trap site nuclei that atomize atoms are generated. 3. Prior to performing the pre-heat treatment, water jet peening, shot peening, or rolling is performed to perform a machining process for generating dislocations in the crystal grains of the irradiated material in advance. The method for welding irradiation material according to claim 1 or 2, wherein any one of a heater, an induction heater, and a laser is used. 4. The temperature of the irradiated material is measured, and the measured temperature is fed back to the conditions of the pre-heat treatment to generate the trap site nuclei of helium atoms present in the crystal of the irradiated material. Control the amount of movement of
The method for welding an irradiating material according to claim 2, wherein the trap site nuclei of the helium bubble are stably generated in the crystal grains of the irradiating material. 5. A heater for heating a welded portion and the periphery of the welded portion during the pre-heat treatment, and a pre-heat treatment for measuring each temperature of the welded portion and the periphery of the welded portion during the pre-heat treatment. Temperature sensor for welding, temperature sensor for welding that measures the temperature of the weld and the surroundings of this weld during welding, remote control device for controlling the temperature of the heater, surface to be welded and the area around this weld Processing equipment for machining processing, a remote operation device for the machining processing device, a welding device for welding the welding planned portion, and a welding repair facility including at least one of the remote operation device for the welding device The method for welding an irradiating material according to claim 1, 2, 3, or 4. 6. Prior to the pre-heat treatment, a portion to be welded in the irradiated material and a part of the periphery of the portion to be welded are sampled by electric discharge machining, and the concentration of helium atoms in the irradiated material is analyzed in advance. 3. The conditions for the preheat treatment are set according to claim 2.
Alternatively, the method for welding the irradiation material according to the item 3. 7. Prior to the pre-heat treatment, a portion to be welded in the irradiated material and a part of the periphery of the portion to be welded are sampled by electric discharge machining, and the concentration of helium atoms in the irradiated material is analyzed in advance. The welding method for an irradiating material according to claim 3 or 5, wherein the conditions of the machining process are set. 8. Before the pre-heat treatment, a portion to be welded in the irradiated material and a part of the periphery of the portion to be welded are sampled by electric discharge machining, and the concentration of helium atoms in the irradiated material is analyzed in advance. The welding method for the irradiated material according to claim 5, wherein the welding conditions for the portion to be welded are set. 9. The welding repair facility is supported by a crane, and for preventing horizontal and vertical positioning, at least one of an optical device, an acoustic device, and an ultrasonic device, and displacement prevention after fixing. The irradiation material welding according to claim 5, wherein tools are respectively provided, and the pre-heat treatment apparatus, the machining processing apparatus, and the welding apparatus are all attachable so as to be movable in the vertical direction and the circumferential direction. Method. 10. The welding method for an irradiating material according to claim 9, wherein the position of the welding repair facility is corrected by at least one of the optical device, the acoustic device, and the ultrasonic device. 11. The welding repair facility includes, in addition to the preheat treatment device, the machining processing device, and the welding device,
The irradiation material welding method according to claim 5 or 9, wherein the irradiation material is a facility capable of mounting and using at least one of an inspection device, a decontamination device, a residual stress improvement device, a gondola, and a component replacement device. 12. The welding method for irradiating material according to claim 11, wherein the gondola has a capability of diving to a water depth of 30 m, and is provided with a manipulator and a shield for shielding radiation.