CN85101508A - Improvement to plug for fuel pipe - Google Patents

Abstract

A nuclear reactor fuel pipe close (100) is welded to the compound pipe end of reactor fuel rod [though tungsten electrode blanket gas weldering (ITG) also can] with laser.On the circumference of pipe close (100) outside, a ring-type grooving (126) is arranged, this grooving is radially cut in the barrel portion surface (118) near periphery (118) and shoulder part (120) intersection, and the circumferential weld between pipe close (100) and the complex pipe is just on this position.When using laser to come welding process to carry out circumference butt welding between pipe close (100) and the complex pipe, grooving (126) can avoid producing air blister defect in weld seam.

Description

Improvement to plug for fuel pipe

The present invention relates to the pipe close of nuclear reactor fuel pipe, when manufacturing the used cartridge of nuclear reactor active region (reactor core) fuel-device, be welded in pipe end with pipe close it is sealed.Pipe close of the present invention helps preventing filling in circumference when welding at cartridge, especially when using laser welding process to weld, and structural defective that is occurred and the undesirable feature that exists usually.But under the situation with the welding of tungsten electrode blanket gas weldering (TIG) method, the present invention also can be used for manufacturing of plug for fuel pipe assembly.

As everyone knows, in nuclear power generation technology, the nuclear reactor active region (reactor core) of typical nuclear reactor facility or nuclear power plant minimumly will comprise 100 or more fuel-device, and each fuel-device may be made up of a hundreds of cartridge.A common fuel-device may comprise one 17 * 17 cartridge, and the position of 17 row's cartridges is arranged here, and each row has the position of 17 cartridges again.So each fuel-device will have 264 cartridges, all the other positions are used for installing the sleeve pipe of control usefulness and detect with pipe.Like this, if core section (reactor core) has at least one hundred fuel-devices, this active region just will comprise the cartridge more than 25.000 so.

The nuclear reactor fuel pipe all is to manufacture with thin walled tube or complex pipe usually, adorn with fissile material in the pipe, and in reactor process, whole device is closed.Complex pipe is used for avoiding nuclear fuel and surrounding medium, contacts and produces chemical reaction as the chilled water in the pressurized water type reactor (PWR).

Simultaneously, complex pipe yet is used for limiting radioactive fissile material certainly.In order to reach above-mentioned production purpose, complex pipe just must be corrosion resistant, nullvalent and heat conduction.Be commonly used to make the material of cartridge covering, 304 stainless steels, zirconium-base alloy arranged, as zircaloy 2(Zircaloy-2) or zircaloy 4(Zircaloy-4).In fact, zirconium-base alloy is better than stainless steel, because zircaloy is smaller for the capture cross-section of thermal neutron.

Actual manufacture technology according to general cartridge, the uranium dioxide (UO2) that the nuclear fuel of common cylindrical fritter or U-235 concentrate is loaded in cartridge or the complex pipe, then with pipe close the closed at both ends of pipe is made that nuclear fuel is airtight to be enclosed in the cartridge, this moment, pipe close was that frictionally and cartridge or complex pipe are assembled together temporarily.Then, pipe close with welding method with its be soldered to carry out on the cartridge permanent airtight.During welding, can use an automatic soldering device, this device makes cartridge rotate with respect to an electrode, so that carry out the circumference welding along the interface of cartridge and pipe close, after cartridge and pipe close welded, even if the assembly work of cartridge has been finished.

Up to the present, before the invention of present patent application, all be to carry out on the circumference of the thousands of above-mentioned cartridge-pipe close welding practical work with the method for general tungsten electrode blanket gas weldering (TIG).Certainly, existing a lot of years of tungsten electrode blanket gas weldering (TIG) method, and in a lot of different field and environment, be used for carrying out welding operation.Be very reliable on this welding method practical work, and fault seldom.But, along with the appearance of laser welding technology,, it has been recognized that tungsten electrode blanket gas weldering (TIG) method does not have laser bonding fast like that because its production cycle is shorter.So,, just wish under possible situation in order to make welding job more economically with effective.Adopt laser welding process, replace tungsten electrode blanket gas welding method.Further relate to the special process of nuclear reactor fuel pipe, consider that especially the cartridge radical that the nuclear reactor active region comprised is many, need the position of welding many,, will obtain sizable economic benefit if adopt laser welding process.Regrettably, before the invention of present patent application, replace normally used tungsten electrode blanket gas welding method to carry out existing serious structural defective in cartridge-pipe close circumference welding with method for laser welding.

Like this, the invention reside in a kind of tube end pipe close in front that is designed to be welded on, this pipe close has one in order to the pipe of packing into, the cylinder faying face part of axially stretching out, and a radially-protruding annulus shoulder part, this shoulder combines with an end of pipe with the form of end face contact, it is characterized in that intersection at the above-mentioned face of cylinder and shoulder, make a circumferential slot on the position near pipe close and pipe end welding, this grooving has certain depth, extends to below the surface of face of cylinder part.

The present invention also comprises a pipe, and this tube end is equipped with a described pipe close of final stage as mentioned, and this pipe close is connected on the pipe end with laser beam or the welding of tungsten electrode blanket gas.

On pipe close of the present invention, above-mentioned habitual in the corner structure place make an otch or groove to replace turning in this effectively.This otch or groove are around the whole circumference of pipe close and be limited between the major diameter part and small diameter portion of pipe close.Because circumferential notch or groove are partly to be limited by annulus shoulder or flange section, this annulus shoulder or flange section are similar to habitual pipe close, and the radially inside degree of depth of the annulus shoulder of pipe close of the present invention is greater than habitual fuel rod tube this degree of depth beyond the Great Wall.In other words, this groove has the following degree of depth of part that extends to the face of cylinder, and the latter does not resemble the habitual interior corner structure and the annulus shoulder intersects vertically and form one 90 ° angle.Desirablely be, make to notch portion a circular conical surface, this circular conical surface outwards reaches face of cylinder part forward from the shoulder part, and angle β approximately is 45 °.This annulus otch or groove that radially inwardly is provided with is to be limited within the sidewall of pipe close, be positioned at the axial intersection of its small diameter portion and major diameter part, it is defective or the defect that is used for eliminating the ring-type weld seam inside that is limited by pipe close and imitation frosted glass rod cladding or pipe that such structure is set, for example at pore or the little pore of nodularization used under the LASER BEAM WELDING situation.

Clearly, replace the very strict horn structure of machining precision of habitually practising at the grooving of a ring-type of weld zone processing, help making the gas of any encirclement or bubble to be run out of according to the present invention.In addition, pipe close of the present invention can also relax when adopting tungsten electrode blanket gas welding method, to the strict demand of machining tolerance.In the manufacturing of nuclear reactor fuel pipe, especially when using laser beam welding process, can obtain the welding operation of surprising effect, although tungsten electrode blanket gas welding method also can be used.

In order to make the present invention say clearlyer, with example and by some accompanying drawings it is specified below, shown corresponding parts among the figure, accompanying drawing comprises:

Fig. 1 is the section of general kernel reactor fuel pipe pipe close.

Fig. 2 is a photo that amplifies 10 times, shows the transversal section of the circumferential weld that nuclear reactor fuel pipe pipe close and complex pipe cooperate, and usefulness is general pipe close shown in Figure 1 here, the welding corresponding laser-beam welding method.Can see gas hole defect in the photo from figure fully aware ofly.

Fig. 3 is a photo that amplifies 50 times, shows the section of weld seam shown in Figure 2, and the gas hole defect here can be seen clearlyer than Fig. 2.

Fig. 4 is similar to Fig. 1, is the sectional drawing of nuclear reactor fuel pipe pipe close of the present invention.

Fig. 5 is the vertical profile of the weld seam of nuclear reactor fuel pipe pipe close-complex pipe, amplifies 3 times.Here usefulness is pipe close among Fig. 4.

Fig. 6 A and Fig. 6 B amplify 50 times photo, in the difference presentation graphs 5, and plug for fuel pipe and the left side weld seam of complex pipe circumference welding and the section of right side weld seam.

Fig. 7 is and half of the similar section of Fig. 2, amplifies 10 times, shows the section of nuclear reactor fuel pipe pipe close-complex pipe circumferential weld among Fig. 5.

Shown in Figure 8 is the elevation drawing of cartridge, and some is a sectional drawing, shows the assembling situation of pipe close in complex pipe among Fig. 4.

With reference to Fig. 1, shown in be a rectangular pipe close 10 that is commonly used to sealed fuel pipe or complex pipe pipe end, this cartridge is used for 17 * 17 active regions (reactor core) fuel-device.The shape of pipe close 10 is a right cylinder substantially, comprises slightly little one section 14 of diameter bigger a section 12 and diameter.The front end 16 that a band tapering is arranged on one section 14 of minor diameter, cone angle 2 can be about 10 °, and the cone angle of pipe close 10 front ends is to go for the ease of pipe close 10 is inserted in cartridge or the complex pipe, and cartridge is not expressed in the drawings.One section 18 of extending back of the reduced diameter section 14 of pipe close 10 is cylindrical, when pipe close 10 inserts in the cartridges, can borrow friction match with the inside surface of cartridge, does not express on the figure.Because two section 12 and 14 of pipe close has different diameters, therefore a round flange or shoulder 20 must be arranged therebetween, simultaneously, a hole 22 must be arranged on pipe close 10, so that the inert gas of high pressure feeds in cartridge or the complex pipe, so just form the cartridge of a band pipe close.A concentric hole 24 that diameter is bigger is arranged, so that at inert gas entrance, promptly carry out the exchange of fluid between hole 22 and the cartridge internal diameter, as everybody knows, after high-pressure inert gas feeds in the cartridge, perforate 22 will be sealed with a kind of suitable welding method.

When manufacturing plug for fuel pipe 10, must carry out strict quality, to the machining tolerance of flange or shoulder 20 and surface of contact 18, especially to be strict with, the angle of cut that makes these two orthogonal planes is sharp-pointed corner.Equally, the end face that matches in corresponding surface with pipe close of cartridge or complex pipe and turning is accurately processing also, to avoid the producing gap that surpasses allowable tolerance between these surface of contact.It is very harsh that such machining tolerance has been proved to be in fact, and this is because if do not reach this tolerance, will produce various inherent vices in the welding of tungsten electrode blanket gas weldering (TIG) method.Such as, pore can appear in the molten bath of weld seam.And pore can cause the problem on structural intergrity and the intensity, equally, as produce inside surface undercut defective, near cartridge or the complex pipe thickness weld seam is reduced, this defective might enlarge, it can cause the problem on structural intergrity and the intensity equally, and what pay particular attention to is that the cartridge inside that seals has pressure, so exist structural weak link will avoid especially in cartridge body and weld seam.Owing to adhere to the strict quality standard, on the practical work, when using tungsten electrode blanket gas weldering (TIG) method to manufacture general cartridge, the defective on the said structure has reduced.

Research laser welding process and technology are used go in the sort of plug for fuel pipe structure of saying the front in; having been found that in the weld zone metal that inside surface undercut defective does not show falls into, but has increased when welding with tungsten electrode blanket gas weldering (TIG) method on the gas hole defect practical work.In Fig. 2 and Fig. 3, can see this gas hole defect, expose some spherical pores on the photo.In other words be a string gas hole defect, photo is to absorb from the laser welded seam mid-plane, and amplify 10 times and 50 times respectively, these defectives appear at when welding under the general plug for fuel pipe situation of (as shown in Figure 1) with laser welding process, and this pipe close matches with general cartridge or complex pipe.The above-mentioned clear and definite reason that exists for the disadvantageous phenomenon of welding line structure performance, though also do not have and to put forward, if but near the wedge angle of pipe close or corner, just having gas to exist at shoulder 20 and barrel portion 18 will be when using LASER BEAM WELDING, because various evaporations, solidify and the contraction of plug for fuel pipe and composite pipe etc. is former thus accumulate in the metal pool significantly and weld seam in.Therefore,, adopt laser beam welding process, just must prevent from weld seam, to exist above-mentioned this gas hole defect if when manufacturing nuclear reactor fuel pipe-pipe close assembly.

As shown in Figure 4, nuclear reactor fuel pipe pipe close generally should be designed to 100 such shapes.As can be seen, all parts or design feature, 100 designs all are similar or identical for the pipe close among the general pipe close 10 among Fig. 1 and Fig. 4, but all structural members of pipe close 100 have the characteristic of 100 series.

On pipe close 100, the corner structure of pipe close 10 required accurate processing has replaced with the otch or the groove 126 of processing among Fig. 1, and this grooving along pipe close 100 ringwise.Can see, constitute otch or groove 126 one is annular shoulder 120 radially, another is a taper surface 128, this taper surface extends cylindrical surperficial 118 from the inside outward radial of shoulder 120, it is one 45 ° β angle that taper surface 128 intersects with shoulder or plane 120, and stretches to the front end 116 of the band tapering of pipe close 100.

Can see from above; the characteristics of general nuclear reactor fuel pipe pipe close 10 are interior corner structures that limited by annular shoulder plane 20 and periphery 18 of its tolerance strictness; when using tungsten electrode blanket gas weldering (TIG) method to carry out the circumference welding; although this pipe close 10 has made the circumference welding of the plug for fuel pipe-complex pipe of no inherent vice produce progress has been arranged; but when adopting general pipe close 10; fact table pit-ted skin defective still is apparent in the circumferential weld of plug for fuel pipe-complex pipe; and when using laser beam welding process and equipment, such defective can be seen in Fig. 2 and Fig. 3.As in pipe close-composite pipe sections zoarium, using new improved nuclear reactor fuel pipe pipe close 100 proposed by the invention, weld with laser beam welding process and equipment equally, formed weld seam between pipe close and complex pipe, there is not above-mentioned gas hole defect fully, shown in Fig. 5 and Fig. 6 A-6B.From these photos, can be clear that especially, between the annular shoulder 120 of complex pipe tube wall and pipe close, form desirable fillet weld, and there is not air blister defect in whole welding line.The similar photo that is to use pipe close 100 of the present invention resulting zero defect welding under the condition of LASER BEAM WELDING shown in Figure 7.

Above-described nuclear reactor fuel pipe pipe close-composite pipe sections zoarium in fact all is to weld with this laser means of RA-YTHEON 550 YAG.Otch or groove 126 are to process on the sidewall of pipe close 100, if reach 0.100 inch from its radial depth of right cylinder 118 outer surface measurings, but this grooving finally becomes the weld seam of complete penetration on the practical work, in addition, if the working depth of ring-type grooving 126 has only the 0.05-0.07 inch, so also can obtain suitable heat-affected zone.Also can see simultaneously, in actual production, can obtain satisfied welding at present with plug for fuel pipe of the present invention and cartridge.Another benefit that adopts pipe close 100 of the present invention to bring is owing to processed a grooving 126 on pipe close 100, can avoid the only about half of of pipe close available heat loss.So also find, when adopting corresponding laser-beam welding method to carry out the welding of pipe close-complex pipe, be under the situation of standard in other parameter, in order to obtain satisfied welding, laser-beam welding machine is turned round with 400W power.According to the used welding method of pipe close of the present invention 100, owing to can obtain sufficient through welding, just might use rated power only to be the laser welder equipment of 340W.Manufacturing pipe close-composite pipe sections when fit, can obtain good effect, because laser welder equipment need not turn round, thereby can prolong its serviceable life under its peak power.

At last; pipe close of the present invention is proposed; be in order to overcome nuclear reactor fuel pipe pipe close-complex pipe and to weld on the practical work with laser beam welding process; existing various shortcoming; can eliminate defective or structural defective in the production; the pipe close of special construction of the present invention also can weld with tungsten electrode blanket gas weldering (TIG) welding technology.Should remember; tungsten electrode blanket gas welding technology up to the present; can be successfully used in the welding production of nuclear reactor fuel pipe-composite pipe sections zoarium; only be because in the processing of pipe close and the complex pipe that is mated; strict control of quality; but after adopting the present invention, or else above-mentioned stringent condition or machining tolerance just must be carried out.So, when the pipe close of processing pipe close-composite pipe sections zoarium and complex pipe, the cost of machining may significantly descend.Be higher than these characteristics of LASER BEAM WELDING from tungsten electrode blanket gas welding method required input power; grooving 126 on the pipe close 100 of the present invention may need to widen intensification; perhaps also need to change; make it have different geometric configuratioies; such as adopting square cross-section, and do not resemble the sort of leg-of-mutton grooving that with laser beam welding process the time, has adopted effectively shown in Fig. 4.

As can be seen, pipe close of the present invention has very big advantage than nuclear reactor fuel pipe pipe close in the past.Owing on pipe close 100 of the present invention, processed a grooving 126,, can eliminate gas hole defect or structural defective in the weld seam no matter with tungsten electrode blanket gas (TIG) welding method or use corresponding laser-beam welding method.Require emphasis and point out, initial the present invention mainly is the problem that defective manifests when solving nuclear reactor fuel pipe pipe close-composite pipe sections zoarium with LASER BEAM WELDING.But the present invention can use tungsten electrode blanket gas (TIG) welding method too on the practical work, and its reason as mentioned above.But need lay special stress on here once, in the development of the fit process of nuclear reactor fuel pipe pipe close-composite pipe sections, the present invention must be considered to a kind of surprising notion different from the past according to tungsten electrode blanket gas welding method.At nuclear reactor fuel pipe pipe close-composite pipe sections zoarium, when manufacturing with tungsten electrode blanket gas welding technology, gas hole defect in fact manifests, if but strict control machining tolerance just might make these defectives controlled so that avoid effectively.If so in pipe close-composite pipe sections zoarium with the laser beam welding process welding, the problem that also has similar defective to manifest, just must continue the control machining tolerance or when machining tolerance is stricter, can solve the problem that there is gas hole defect in the LASER BEAM WELDING district.But, verifiedly there is not a this situation.Therefore, the present invention has been proposed, developed in the present invention and a kind of and the antipodal technical matters of method that know in the past, replace improve that accurate to dimension requires and the situation of strict control of quality under, loosened the requirement of this respect on the practical work of the present invention effectively.

When introducing the specific (special) requirements of pipe close of the present invention aspect angle and size, should think such angle and size be recommended with general, in addition, as shown in Figure 8, typical nuclear reactor fuel pipe 200(nuclear fuel bead 204 of packing into) comprises a sort of pipe close 100 shown in Figure 4, this pipe close is soldered to an end of complex pipe 202, also has a pipe close 100(as shown in Figure 4) hole 122 and 124(in the middle of not having that is to say that this is a solid pipe close) be soldered to the other end of complex pipe 202.At last, in the outside 206 of center pit 122 its weldering is lived again, seal.

Claims (8)

1, a pipe close is used for being welded on the pipe end, this pipe close has a barrel portion and is used for packing in the above-mentioned pipe end, also have an annular shoulder partly to be used for docking with above-mentioned pipe end, the feature of pipe close is to process a circumferential slot on the position of the intersection of above-mentioned periphery and shoulder, close above-mentioned pipe close and the welding of above-mentioned pipe end, this grooving has certain degree of depth, below the surface of barrel portion.

2, according to the pipe close that proposes in the claim 1, the one side that it is characterized in that grooving is to be made of a taper surface, and taper surface is from the shoulder part periphery part of outwards extending forward.

3, according to the pipe close that proposes in the claim 2, it is characterized in that taper surface is with respect to shoulder part angle at 45.

4, according to claim 1,2 or 3 pipe closes that propose, it is characterized in that its grooving is in the degree of depth that radially is cut into 0.100 inch.

5,, it is characterized in that pipe close made by stainless steel or zircaloy according to the pipe close that any one is manufactured in the claim 1～4.

6, the body that cooperates with pipe close of an end, pipe close and this pipe end is characterized in that with laser beam or the welding of tungsten electrode blanket gas (TIG) welding method above-mentioned pipe close is by any one is manufactured in the claim of front.

7, pipe close of each end welding at nuclear reactor fuel pipe complex pipe, pipe close is made of a less right cylinder and the bigger right cylinder of diameter of diameter, both are coaxial to be connected, the less part of above-mentioned diameter and above-mentioned body by friction mandrel to cooperating, the part that above-mentioned diameter is bigger has the free end of a chamfered edge and from having certain diameter than minor diameter with than major diameter part intersection to the free end of above-mentioned chamfered edge, it is characterized in that having a circumferential slot of inwardly extending at above-mentioned intersection, grooving has certain degree of depth, below the surface of smaller diameter portion.

8, nuclear reactor fuel Guan Youyi complex pipe is formed, and many nuclear fuel beads are packed in this pipe, has a pipe close to be soldered to each end of above-mentioned cartridge, it is characterized in that above-mentioned pipe close manufactures by claim 7.

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