GB2173006A - Leak testing nuclear fuel elements - Google Patents
Leak testing nuclear fuel elements Download PDFInfo
- Publication number
- GB2173006A GB2173006A GB08507964A GB8507964A GB2173006A GB 2173006 A GB2173006 A GB 2173006A GB 08507964 A GB08507964 A GB 08507964A GB 8507964 A GB8507964 A GB 8507964A GB 2173006 A GB2173006 A GB 2173006A
- Authority
- GB
- United Kingdom
- Prior art keywords
- testing
- chamber
- welded
- sealing means
- head
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 238000012360 testing method Methods 0.000 title claims abstract description 62
- 239000003758 nuclear fuel Substances 0.000 title abstract description 4
- 239000000446 fuel Substances 0.000 claims abstract description 27
- 238000007789 sealing Methods 0.000 claims abstract description 26
- 238000010998 test method Methods 0.000 claims description 5
- 230000008602 contraction Effects 0.000 claims description 4
- 238000000034 method Methods 0.000 claims description 4
- 230000009471 action Effects 0.000 claims description 2
- 230000002349 favourable effect Effects 0.000 claims description 2
- 230000000007 visual effect Effects 0.000 claims description 2
- 238000001514 detection method Methods 0.000 claims 1
- 230000000694 effects Effects 0.000 claims 1
- 238000004519 manufacturing process Methods 0.000 abstract description 17
- 239000007789 gas Substances 0.000 abstract description 7
- 239000001307 helium Substances 0.000 abstract description 7
- 229910052734 helium Inorganic materials 0.000 abstract description 7
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 abstract description 7
- 238000012544 monitoring process Methods 0.000 abstract description 2
- 239000008188 pellet Substances 0.000 description 3
- 238000003466 welding Methods 0.000 description 3
- 230000008878 coupling Effects 0.000 description 2
- 238000010168 coupling process Methods 0.000 description 2
- 238000005859 coupling reaction Methods 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 230000008439 repair process Effects 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 230000008901 benefit Effects 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 238000011016 integrity testing Methods 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 238000011144 upstream manufacturing Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C17/00—Monitoring; Testing ; Maintaining
- G21C17/06—Devices or arrangements for monitoring or testing fuel or fuel elements outside the reactor core, e.g. for burn-up, for contamination
- G21C17/07—Leak testing
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M3/00—Investigating fluid-tightness of structures
- G01M3/02—Investigating fluid-tightness of structures by using fluid or vacuum
- G01M3/04—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point
- G01M3/20—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point using special tracer materials, e.g. dye, fluorescent material, radioactive material
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E30/00—Energy generation of nuclear origin
- Y02E30/30—Nuclear fission reactors
Landscapes
- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- General Physics & Mathematics (AREA)
- Plasma & Fusion (AREA)
- General Engineering & Computer Science (AREA)
- High Energy & Nuclear Physics (AREA)
- Examining Or Testing Airtightness (AREA)
Abstract
A production line for the manufacture of nuclear fuel elements includes a section for the on-line testing of the end cap welds of the fuel elements by enclosing the ends only in sealed chambers rather than the entire fuel element. Two testing heads (10, 12) are located one on each side of the path of travel (14) of the fuel elements which are transported transversely of the lengths. Each element is loaded on to support rollers (22) and testing heads (10, 12) are advanced towards one another to engage respective welded ends of the element and sealingly enclose the welded portions within chambers and a mass spectrometer testing cycle is initiated which involves evacuation of the chambers and monitoring for coarse and fine leakage of gas (typically helium) from the elements. The side wall of the cans are engaged by sealing rings in each testing head which are axially compressed to cause their internal diameters to be reduced to seal to the side wall. <IMAGE>
Description
SPECIFICATION
Leak testing of fuel elements
This invention relates to the manufacture of fuel elements for nuclear reactors. As used herein, the term "fuel element" is to be understood to refer to an elongated tubular metal can in which the nuclear fuel, eg in the form of pellets, is enclosed. The invention finds application to the manufacture of various types of reactor fuel elements, eg gas cooled reactors, pressurised water reactors and boiling water reactors.
In one known fuel element production method, after end caps have been welded to the cans, the integrity of the welds is tested by removing a batch of fuel elements from the production line, placing them in a chamber, evacuating the chamber and testing for leakage of helium into the chamber from the cans, helium having been introduced into the cans prior to welding of the end caps in place. This suffers from the drawbacks that: the fuel elements have to be taken off line with consequent interruption of production; a large chamber is needed to accommodate the batch of fuel elements to be tested and evacuation is inevitably a slow process; and if a leaky element or elements is detected, further testing is necessary to isolate the faulty element or elements.
The object of the present invention is to provide an improved weld integrity testing method and apparatus which avoid the foregoing drawbacks.
According to a first aspect of the invention a method of testing the integrity of welded ends of fuel element cans comprises enclosing a welded end of a can within a chamber which makes sealing engagement with the outer surface of the can at a position close to the end of the can, evacuating the can and testing for the leakage of gas from the can into the chamber.
Thus, the size of the chamber in which the welded end of the can is enclosed may be smaller, by several orders of magnitude, than the batch-receiving chamber used in the known method. This enables rapid leak testing of the cans individually with the advantage that leak testing of the welded ends may be carried out on-line thereby speeding production. Moreover, faulty cans may be identified immediately when tested individually.
According to a second aspect of the invention a method of testing the integrity of welds at or adjacent the ends of fuel element cans comprises: locating each of a plurality of fuel elements, one at a time, at a testing station; effecting relative movement between at least one testing head and the so located can to enclose a welded end of the can within a chamber of the testing head; effecting evacuation of the chamber; testing for the leakage of gas from the welded end of the can; and, in the event of a favourable test result, effecting disengagement of the testing head and the can to allow the can to be removed from the testing station.
Preferably both ends of each can are tested at the same time by a pair of testing heads engageable with respective welded ends of the can.
If a leak is detected during testing, a visual and/or audible signal may be generated and the arrangement may be such that automatic advance of the can out of the testing station is prevented, thus making it necessary for the failed can to be manually removed for off-line repair of the can. Alternatively, the arrangement may be such that a failed can is automatically transferred to a reject station for subsequent repair.
According to another aspect of the invention there is provided apparatus for on-line testing of gas-containing fuel element cans with welded ends, the apparatus comprising: at least one testing head which is displaceable along a predetermined axis, the testing head including a chamber with an entry port presented axially and encircled by sealing means; means for locating a fuel element can with a welded end thereof in registry with said entry port whereby relative axial movement between the can and the testing head enables the welded end to be enclosed within the chamber with the can sealingly engaged by the sealing means; means for evacuating the chamber; and means for testing for leakage of gas from the can into the chamber.
Preferably the apparatus comprises a pair of testing heads which are relatively displaceable towards and away from one another in the axial direction to engage and disengage respective welded ends of a can.
The sealing means in the or each testing head may be designed so as to automatically make sealing engagement with the can during the aforesaid relative axial movement, ie each sealing means may be an interference type fit with the can so that as the can enters the chamber of each testing head, the sealing means is placed under radial stress to provide the sealing action.
Preferably however the sealing means is arranged to afford clearance during entry of the can and means is provided for effecting radial contraction of the sealing means into sealing engagement with the can. Such radial contraction may be effected by means for axially compressing the sealing means.
To promote further understanding of the invention, one embodiment thereof will now be described by way of example only with reference to the accompanying drawings, in which:
Figure 1 is an isometric view of on-line leak testing of fuel elements, certain parts of the apparatus being omitted for the sake of clarity;
Figure 2 is a side view, partly-sectioned and cut-away, of a testing head; and
Figure 3 is a front view, partly sectioned and cut-away of the testing head.
The following description will refer to stages involved in the production of fuel elements for advanced gas cooled (AGR) reactors but it is to be understood that the ambit of the invention is not restricted to this particular type of fuel element. The production route currently used by the Applicants for AGR fuel elements includes the follow steps: open-ended, cylindrical stainless steel cans are loaded with sintered pellets of UO2 fuel; the cans are filled with helium at atmospheric pressure and cupshaped end caps are inserted into the open ends of the cans; the end caps are welded in position by a circumferential weld so as to seal the interior of the can; a batch of cans are accumulated and are taken off the production line to enable the integrity of the end cap welds to be tested in the manner previously described involving evacuation of a large chamber and testing for helium leakage by means of a mass spectrometer; the tested cans are brought back on to the production line, trimmed to length, fitted with extension pieces by welding; and then passed to a pressurising chamber to deform the can at localised points into grooves in the pellet stack.It will be noted that the step involving leak testing of the welded end caps constitutes a significant interruption to the continuity of the production process.
Referring now to Figure 1, there is shown an on-line testing machine by means of which the cans, following welding of the end caps, can be tested for helium leakage individually rather than batchwise, thus enabling the cans to be leak tested on-line without interrupting the production line flow. The machine comprises two testing heads 10, 12 located one on each side of the path of travel (indicated by arrow 14) of the cans along the production line, the cans being transported with their axes generally horizontal and perpendicular to the path of travel. The machine includes a pair of spaced, entry tracks 16 (one only of which is shown) on to which the cans are fed from the upstream side of the production line.Stop pins 18 on the entry tracks 16 arrest the leading can in a predetermined position and the tracks 16 may be slightly inclined to ensure that the leading can engages the pins 18 and is thereby properly located for pick-up and transfer by arms 20 (one only illustrated) on to V-shaped rollers 22 associated with each testing head.
The arms 20 are mounted for pivotal movement with a shaft 24 which can be rotated by means of a piston and cylinder-operated crank mechanism 26. As shown in Figure 1, the arms occupy a neutral position but are movable by the crank mechanism between a raised position and a lowered position. In the lowered position, steps 28 on the arms will underlie the can supported by the rollers 22 so that when the arms rise they lift the can off the rollers and deposit it on a pair of exit tracks 30 for subsequent transfer downstream of the production line by a trolley 32 with support tracks 34. As the arms 20 rise, their ends 36 are arranged to engage behind the leading can on the entry tracks 16 and raise it past the stops 18.The leading can rolls down sloping surfaces 38 and comes to rest at the junctions 40 which are so positioned that when the arms are lowered again the can is deposited on the rollers 22. Each raising and lowering operation of the arms 20 is therefore operative to transfer a tested can to the exit tracks 30 and position a new can in the testing station defined by the rollers 22.
Referring now to figures 2 and 3, each testing head 10, 12 is mounted on a slide 42 supported on each side by grooved cylinders 44 for movement relative to base structure 46 in a direction transverse to the path of travel (arrow 14) and hence parallel to the longitudinal axes of the cans. Such movement is effected by means of double acting piston and cylinder arrangement 48 connected to the slide 42 by a coupling 50. Each testing head comprises a housing 52 which is fixed with respect to the slide 42 and defines a small chamber 54 connected via coupling 56 to a vacuum valve 58. The chamber 54 houses a stop 60 and the entry to the chamber includes a plate 62 providing a lead-in port 64 with sealing means, the eg an O-ring, located between the plate 62 and the face 68 of the housing 52.
The plate 62 is displaceable towards the face 68 by means of a piston and cylinder arrangement comprising a fixed piston 70 and a movable cylinder 72 which is coupled to the plate via connecting pins 74 supported in bearings 76 mounted by the housing 52. As shown in figure 2, the seal 66 is unstressed and in this condition its inside diameter is greater than the outside diameter of the cans.
When piston snd cylinder 70, 72 is operated, the seal 66 is axially compressed with consequent reduction of its inside diameter so that a good seal may be made with the end portion of a can inserted through the port 64 and into the chamber 54.
In operation, when a can has been loaded onto the rollers 22 so as to be in registry with the ports 64, the testing heads are advanced sequentially over the end portions of the can and the seals 66 are sealingly engaged with the can inboard of the welds. A mass spectrometer testing cycle is then activated, involving evacuation of the chambers 54 and monitoring for coarse and fine helium leakage. If the can is leak tight, the seals 66 are disengaged, the heads 10, 12 are retracted and arms 20 are operated to transfer the tested can to the exit tracks and located a new can on the rollers 22. If a leaking can is detected or if the system cannot detect a calibrated leak, these conditions may be indicated on a control panel. In this event, the can in question has to be removed manually (or can be transferred to a reject station) before testing can be resumed.
Claims (12)
1. A method of testing the integrity of welded ends of fuel element cans comprises enclosing a welded end of a can within a chamber which makes sealing engagement with the outer surface of the can at a position close to the end of the can, evacuating the can and testing for the leakage of gas from the can into the chamber.
2. A method of testing the integrity of welds at or adjacent the ends of fuel element cans comprises: locating each of a plurality of fuel elements, one at a time, at a testing station; effecting relative movement between at least one testing head and the so located can to enclose a welded end of the can within a chamber of the testing head; effecting evacuation of the chamber; testing for the leakage of gas from the welded end of the can; and, in the event of a favourable test result, effecting disengagement of the testing head and the can to allow the can to be removed from the testing station.
3. A method as claimed in Claim 1 or 2 in which both ends of each can are tested at the same time by a pair of testing heads engageable with respective welded ends of the can.
4. Apparatus for on-line testing of gas-containing fuel element cans with welded ends, the apparatus comprising: at least one testing head which is displaceable along a predetermined axis, the testing head including a chamber with an entry port presented axially and encircled by sealing means; means for locating a fuel element can with a welded end thereof in registry with said entry port whereby relative axial movement between the can and the testing head enables the welded end to be enclosed within the chamber with the can sealingly engaged by the sealing means; means for evacuating the chamber; and means for testing for leakage of gas from the can into the chamber.
5. Apparatus as claimed in Claim 4 including a pair of testing heads which are relatively displaceable towards and away from one another in the axial direction to engage snd disengage respective welded ends of a can.
6. Apparatus as claimed in Claim 4 or 5 in which the sealing means in the or each test head is arranged to automatically make sealing engagement with the can during the aforesaid relative axial movement.
7. Apparatus as claimed in Claim 6 in which each sealing means is an interference type fit with the can so that as the can enters the chamber of each testing head, the sealing means is placed under radial stress to provide the sealing action.
8. Apparatus as claimed in Claim 6 in which the sealing means is arranged to afford clearance during entry of the can and means is provided for effecting radial contraction of the sealing means into sealing engagement with the can.
9. Apparatus as claimed in Claim 8 including means for axially compressing the sealing means so as to effect said radial contraction.
10. Apparatus as claimed in any one of
Claims 5-9 including means for producing a visual and/or audible signal in response to leak detection.
11. A method of testing the integrity of welds at or adjacent the ends of fuel element cans, substantially as hereinbefore described with reference to the accompanying drawings.
12. Apparatus for on-line testing of gascontaining fuel element cans, substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08507964A GB2173006A (en) | 1985-03-27 | 1985-03-27 | Leak testing nuclear fuel elements |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08507964A GB2173006A (en) | 1985-03-27 | 1985-03-27 | Leak testing nuclear fuel elements |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB8507964D0 GB8507964D0 (en) | 1985-05-30 |
| GB2173006A true GB2173006A (en) | 1986-10-01 |
Family
ID=10576728
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08507964A Withdrawn GB2173006A (en) | 1985-03-27 | 1985-03-27 | Leak testing nuclear fuel elements |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2173006A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0379946A2 (en) * | 1989-01-25 | 1990-08-01 | Westinghouse Electric Corporation | Nuclear fuel rod helium leak inspection apparatus and method |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB815706A (en) * | 1956-10-11 | 1959-07-01 | Canadian Ind | Apparatus and method for testing tubes closed at one end |
| US3595065A (en) * | 1969-09-17 | 1971-07-27 | Harry E Scribner | Differential pressure crown inspector |
| GB1265349A (en) * | 1969-02-21 | 1972-03-01 | ||
| US3776025A (en) * | 1971-01-04 | 1973-12-04 | Gen Electric | Exhaust machine leak detector and shut off |
| US3793876A (en) * | 1972-08-10 | 1974-02-26 | Gould Inc | Battery terminal leak detector |
| GB1409079A (en) * | 1971-12-30 | 1975-10-08 | Pont A Mousson | Apparatus for testing the helium-tightness of tubular bodies |
| US3949596A (en) * | 1974-12-11 | 1976-04-13 | The United States Of America As Represented By The United States Energy Research And Development Administration | Leak test fixture and method for using same |
-
1985
- 1985-03-27 GB GB08507964A patent/GB2173006A/en not_active Withdrawn
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB815706A (en) * | 1956-10-11 | 1959-07-01 | Canadian Ind | Apparatus and method for testing tubes closed at one end |
| GB1265349A (en) * | 1969-02-21 | 1972-03-01 | ||
| US3595065A (en) * | 1969-09-17 | 1971-07-27 | Harry E Scribner | Differential pressure crown inspector |
| US3776025A (en) * | 1971-01-04 | 1973-12-04 | Gen Electric | Exhaust machine leak detector and shut off |
| GB1409079A (en) * | 1971-12-30 | 1975-10-08 | Pont A Mousson | Apparatus for testing the helium-tightness of tubular bodies |
| US3793876A (en) * | 1972-08-10 | 1974-02-26 | Gould Inc | Battery terminal leak detector |
| US3949596A (en) * | 1974-12-11 | 1976-04-13 | The United States Of America As Represented By The United States Energy Research And Development Administration | Leak test fixture and method for using same |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0379946A2 (en) * | 1989-01-25 | 1990-08-01 | Westinghouse Electric Corporation | Nuclear fuel rod helium leak inspection apparatus and method |
| EP0379946A3 (en) * | 1989-01-25 | 1991-11-21 | Westinghouse Electric Corporation | Nuclear fuel rod helium leak inspection apparatus and method |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8507964D0 (en) | 1985-05-30 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |