WO2003017286A2

WO2003017286A2 - Improvements in and relating to inspection systems

Info

Publication number: WO2003017286A2
Application number: PCT/GB2002/003836
Authority: WO
Inventors: Philip Dean Greenwood; Edward Taylor
Original assignee: Bnfl (Ip) Ltd
Priority date: 2001-08-20
Filing date: 2002-08-19
Publication date: 2003-02-27
Also published as: WO2003017286A3; GB0120220D0; AU2002321509A1

Abstract

An inspection unit, inspection system and method of inspecting an item provided with a view to accurately checking the level of loose contaminated material upon an item, particularly nuclear fuel rods following their manufacture. The inspection unit, inspection system and method of inspection are aimed at automated handling which is consistent and accurate in its level of inspection.

Description

IMPRONEMENTS IN AND RELATING TO INSPECTION SYSTEMS

The present invention concerns improvements in and relating to inspection systems, particularly, but not exclusively, systems for inspecting loose contamination on nuclear fuel rods.

Nuclear fuel rods are subjected to a range of checks and inspections during and after their production. One such inspection seeks to determine the level of loose material on a fuel rod, and more specifically the level of loose radioactive material contaminating the fuel rod. In existing systems the fuel rod is cleaned and then a paper swab is manually used to wipe the surface of the fuel rod and pick up a representation of the loose contamination remaining. The level is then inspected by placing the swab under a radiation detecting counter.

The present invention aims to provide an inspection system and units for use in such a system which offers a number of advantages over existing systems and/or which is suitable for use on mixed oxide fuel rods, fuel rods containing plutonium and uranium oxides.

According to a first aspect of the invention we provide an inspection unit, the unit including a first component provided with a through aperture and a second component provided with a through aperture, the second component through aperture being of reduced dimension compared with the first component through aperture, at least part of the second component through aperture being expandable.

The second component may be, at least in part, formed of swabbing material.

According to a second aspect of the invention we provide an inspection unit, the unit including a first component provided with a through aperture and a second component provided with a through aperture, the second component through aperture being of reduced dimension compared with the first component through aperture, the second component being at least in part formed of swabbing material.

At least part of the second component through aperture maybe expandable. The first and/or second aspects of the invention may include one or more of the following features, options or possibilities.

Preferably the first component is planar. The first component may be provided with opposing, preferably parallel, planar faces. The first component may be rectilinear, preferably square. The first component may be provided with rounded corners. A notch may be provided in one edge of the first component. Preferably the first component is made of plastics, ideally uPNC.

Preferably the first component through aperture is circular in cross section. Preferably the first component through aperture has a constant diameter along the length of the central axis of the through aperture. Preferably the first component through aperture has a diameter of between 3 and 6 times the diameter of the item to be inspected. The first component through aperture may have a diameter of between 4.25 and 5 times the diameter of the item to be inspected.

Preferably the second component is planar. The second component may be provided with opposing, preferably planar faces. The second component may be rectilinear, preferably square. The second component may be provided with rounded corners. A notch may be provided in one edge of the first component. Preferably the second component is made of plastics, ideally nylon. Preferably the second component is a fabric, ideally a knitted material.

Preferably the second component through aperture is circular in cross section. Preferably the second component through aperture has a constant diameter along the length of the centre axis of the through aperture. Preferably the second component through aperture has a diameter of between 0.6 and 0.95 times the diameter of the item to be inspected, more preferably between 0.65 and 0.8 times the diameter of the item to be inspected and ideally between 0.7 and 0.75 times the diameter of the item to be inspected. These values represent increasing levels of optimisation with regard to ensuring that the correct pressure is applied to the exterior of the fuel rod to achieve loose contamination removal and to ensure that the same level of performance is achieved whatever the rod diameter is under consideration. Preferably the first and second components are of corresponding planar extent. Preferably the notch in the edge of the first component matches the notch on the second component. Preferably the second component through aperture is entirely provided within the profile of the first component through aperture. Preferably the first and second component through apertures have a common axis.

Preferably the second component through aperture can be expanded in all radial directions. The expansion may involve displacement of the material defining the second component through aperture radially and / or axially or a mixture thereof. It is preferred that the second component through aperture expand evenly in all radial directions. This is important in ensuring that equivalent levels of loose contamination material removal are achieved for the entire circumference of the fuel rod. The second component through aperture may be expanded by stretching the material forming at least part of the second component.

Preferably at least the portion of the second component defining the perimeter of the second component through aperture is of swabbing material. The material may be a plastics material, for instance a knitted plastics material or fabric plastics material. It is preferred that a nylon knit is used. The second component may be formed of one material. Preferably at least the portion of the second component defining the perimeter of the second component through aperture is an absorbent and / or lint free and / or elastic material.

It is preferred that the unit include a third component. Preferably the third component is planar. The third component may be provided with opposing, preferably parallel, planar faces. The third component may be rectilinear, preferably square. The third component may be provided with rounded corners. A notch may be provided in one edge of the third component. Preferably the third component is made of plastics, ideally uPNC.

Preferably the third component is provided with a through aperture. Preferably the third component through aperture is circular in cross section. Preferably the component through aperture has a constant diameter along the length of the centre axis of the through aperture. Preferably the third component through aperture has a diameter of between 1.2 and 1.6 times the diameter of the item to be inspected, more preferably between 1.3 and 1.45 times the diameter of the item to be inspected and ideally between 1.35 and 1.4 times the diameter of the item to be inspected. Preferably the third component is of corresponding planar extent to the first and / or second components. Preferably the notch in the edge of the third component matches the notch in the edge of the second and / or first component.

Preferably the third component through aperture is entirely within the profile of the first component through aperture. Preferably the second component through aperture is entirely within the profile of the third component through aperture. Preferably the first, second and third component through apertures are axially aligned.

Preferably the third component through aperture is at least 1.6 times the diameter of the second component through aperture. Preferably the third component through aperture is less than 3 times the diameter of the second component through aperture. Preferably the third component through aperture is between 1.75 and 2.25 times the diameter of the second component through aperture. More preferably the third component through aperture is between 1.8 and 2.05 times the diameter of the second component through aperture.

Preferably the second component through aperture is at least 1mm less in diameter than the diameter of the item to be inspected, and more preferably is between 2.75 and 3.25mm less. More preferably the second component through aperture is at least 2mm and preferably between 2.75 and 3.25mm less than the diameter of the item to be inspected.

Preferably the third component through aperture is at least 2mm more in diameter than the item to be inspected. Preferably the third component through aperture is at least 3mm and more preferably between 3.75 and 4.25mm larger in diameter than the item to be inspected.

According to a third aspect of the invention we provide an inspection system, the inspection system including a mount for an inspection unit, a drive unit for moving the inspection unit between an item inspecting position and an inspection unit inspecting position, the inspection unit being provided according to the first and/or second aspects of the invention.

The mount may releasably retain the inspection unit. Preferably the positioning of the inspection unit in the mount involves cooperation of an element on the mount with the notch or keyway on the inspection unit. The mount may retain the inspection unit in position at the item inspecting position. The inspection unit may be released from the mount at the inspection unit inspecting position.

The drive unit may include one or more actuators and / or one or more supports, preferably for achieving the desired movement and relative position of the inspection unit at the item inspecting position and at the inspection unit inspecting position. Preferably the system includes means for supporting and / or moving the item through the inspection unit at the item inspecting position. The inspecting unit is preferably stationary during the passage of the item through the inspecting unit. The item is preferably a nuclear fuel rod.

Preferably the inspection unit inspecting position includes a radiation detector, most preferably together with an electronic processing unit for converting the radiation detections into an indication of the level of loose radiative material on the item.

The third aspect of the invention may include one or more of the features, options or possibilities set out above in relation to the first and / or second aspects of the invention, particularly as these effect the inspection unit involved in the third aspect of the invention.

According to a fourth aspect of the invention we provide a method of inspecting an item, the method including positioning an inspection unit on a mount at an item inspecting position, introducing an item to the inspection unit and passing the item through the inspection unit, the inspection unit then being moved from the item inspecting position to an inspection unit inspecting position by a drive unit, the level of radiation emitted by the inspection unit being determined at the inspection unit inspecting position.

Preferably the item is a nuclear fuel rod. Preferably the item is manoeuvred into position relative to the inspection unit. Preferably the item is moved through the inspection unit in a uniform manner. Preferably the item is supported on one, or more preferably both sides of the inspection unit during at least part of the inspection method.

Preferably the level of radiation emitted by the inspection unit is converted into a level of loose contamination material on the outside of the item. Preferably the item advances to a further processing stage if the level of loose contaminated material is below a predetermined threshold. Preferably the item returns to a cleaning stage if the level of loose contaminated material is above a predetermined threshold value. Preferably the item is inspected according to the fourth aspect of the invention a further time after further cleaning.

The fourth aspect of the invention may include any of the features, options or possibilities set out above in relation to the first and / or second and / or third aspects of the invention.

Embodiments of the invention will now be described, by way of example only, and with reference to the accompanying drawings in which :-

Figure 1 illustrates a first component of the apparatus; Figure 2 illustrates a second component of the apparatus; Figure 3 illustrates a third component of the apparatus; Figure 4 illustrates a front view of the assembled apparatus; and Figure 5 illustrates a side view of the assembled apparatus.

For a number of reasons it is desirable to have low levels of loose radioactive material on manufactured fuel rods. As a consequence such fuel rods are inspected in existing techniques. The present system uses a paper swab which is held by an operator and passed along the fuel rod. The swab, together with any material picked up, is then placed in front of a radiation detector and the reading obtained can be equated to a level of loose material. If necessary further cleaning of the rod can be implemented if the level is not met.

The applicant has identified that such an inspection system is impaired in its repeatability due to the manual nature of the process, a factor which needs to be accounted for in a pessimistic conversion of the detected radiation on the swab into a loose radioactive material level for comparison with customer specifications. Additionally manual systems introduce the possibility of operator error in conducting the measurement or recording the result. Finally, manual inspection of some fuel rod types, in particular mixed oxide fuel rods (which contain plutonium oxides as well as uranium oxides), is undesirable due to the dose to which this exposes the operators.

To address these issues the applicant has developed an automated inspection system which includes as a key component, a swabbing unit. The unit is provided from three principal components illustrated in Figures 1, 2 and 3. The size of the holes in the three components will vary depending upon the fuel rod being inspected, but in this embodiment are exemplified by swabbing units suitable for use on a 0.75mm diameter fuel rod.

The first component 1, Figure 1, is a uPNC plate 3 with a hole 5 centrally provided. The diameter of the hole 5 is 50mm and as such is larger than the fuel rod which will pass through during inspection. The plate 5 is provided with a keyway 7 for mounting and alignment purposes.

The second component 9, Figure 2, is a single faced thermoplastic polyurethane coated 100% nylon knit 10 which acts as the loose material collecting component in use. The nylon knit side is placed against the rear surface of the first component 1 in the assembled form. The second component 9 also has a hole 11 which is axially aligned with the hole 5 in the first component 1. The hole 11 is 7.75mm in diameter and as such is intended to be 3mm less in diameter than the fuel rod to be inspected. The elastic nature of this material allows it to stretch in a reliable manner as the fuel rod passes through. Other materials can be used for the swabbing component, but it is preferred that they are lint free

The third component 13, Figure 3, is also a uPNC plate 15 with a hole 17 provided in it. The hole 15 is axially aligned with holes 5 and 11. The diameter of the hole 15 is 14.75mm in diameter and as such is intended to be 4mm greater in diameter than the fuel rod being inspected. The third component 13 is placed against the rear surface of the second component 9. The exposed rear surface of the third component 13 carries a unique identifier code.

As can be seen in Figure 4, when viewed from the front the hole 5 and hole 11 can be seen. The overall unit has a thin depth, 2.9mm, due to the 1mm thick first component 1 and third component 13, and the 0.9mm thick second component 9, Figure 5.

In use, the unit is placed in the desired position relative to the fuel rod path using an automated handler. The fuel rod is then advanced through the unit, passing through the first component hole 5, then the second component hole 11 and then the third component hole 15. Due to the lower diameter of the second component hole 11 the swab material 10 is stretched by the profile of the fuel rod as it passes and is thus maintained in even, intimate contact with the entire circumference/profile of the fuel rod. The fuel rod does not touch either the first component 1 or third component 13 as it passes, the fuel rod being supported at other locations. The third component 13 is important in supporting the swabbing second component 9 and hence maintaining the position and profile of the second component hole 11.

Once the fuel rod has passed through the unit, the collection process is completed and the automated handler transfers the unit to a measuring station where a radiation detector is used to measure the level of radioactive material picked up. As full contact with the fuel rod profile is achieved throughout the length of the rod a thorough investigation is provided. Furthermore, as a consistent unit is used and presented in a consistent manner a reproducible investigation is provided. The removal of manual manipulation and provision of unit suited to use in an automated system allows the investigation to be performed without exposing operators to dose.

Claims

CLAIMS:

1. An inspection unit, the unit including a first component provided with a through aperture and a second component provided with a through aperture, the second component through aperture being of reduced dimension compared with the first component through aperture, at least part of the second component through aperture being expandable.

2. An inspection unit according to claim 1 in which the second component through aperture has a diameter of between 0.6 and 0.95 times the diameter of the item to be inspected.

3. An inspection unit according to claim 1 in which the second component through aperture has a diameter of between 0.7 and 0.75 times the diameter of the item to be inspected.

4. An inspection unit according to any preceding claim in which the second component through aperture expands evenly in all radial directions.

5. An inspection unit according to any preceding claim in which the second component through aperture expands by stretching the material forming the bounds of the through aperture.

6. An inspection unit according to any preceding claim in which the second component is, at least in part, formed of swabbing material.

7. An inspection unit according to any preceding claim in which a third component is provided with a through aperture and the third component through aperture is entirely within the profile of the first component through aperture.

8. An inspection unit according to any preceding claim in which the first, second and third component through apertures are axially aligned.

9. An inspection unit according to any preceding claim in which the first component is planar, rectilinear and is made of plastics, ideally uPNC.

10. An inspection unit according to any preceding claim in which the second component is planar, rectilinear and is made of a fabric, ideally a knitted material.

11. An inspection unit according to any preceding claim in which the third component is planar, rectilinear and is made of plastics, ideally pNC.

12. An inspection system, the inspection system including a mount for an inspection unit, a drive unit for moving the inspection unit between an item inspecting position and an inspection unit inspecting position, the inspection unit being provided according to any of the claims 1 to 11.

13. A method of inspecting an item, the method including positioning an inspection unit on a mount at an item inspecting position, introducing an item to the inspection unit and passing the item through the inspection unit, the inspection unit then being moved from the item inspecting position to an inspection unit inspecting position by a drive unit, the level of radiation emitted by the inspection unit being determined at the inspection unit inspecting position.

14. A method according to prior claim 13 in which the item advances to a further processing stage if the level of loose contaminated material is below a pre-determined threshold.

15. A method according to claim 13 and claim 14 in which the item returns to a cleaning stage if the level of loose contaminated material is above a pre-determined threshold.