GB2158938A

GB2158938A - Testing of pellets

Info

Publication number: GB2158938A
Application number: GB08412305A
Authority: GB
Inventors: Thomas Gerard Rice; Alan James Billington; Lawrence James Middleton
Original assignee: British Nuclear Fuels PLC
Current assignee: Sellafield Ltd
Priority date: 1984-05-14
Filing date: 1984-05-14
Publication date: 1985-11-20
Also published as: GB2158938B; GB8412305D0

Abstract

Apparatus for testing the orientation of an end face of a pellet to the pellet axis includes a laser 13 which sends a beam 14 of radiation through a beam splitter 16 to apparatus 15. In the apparatus 15 a pellet has a mirror held to an end face and the radiation is reflected by the mirror to form beam 22 leading to sensor 26. If the end face is not at right angles to the pellet axis, the reflected beam is angularly displaced from beam 14, 14a and the beam 22 is divergent, to provide an indication at the sensor. A circular aperture 23 may cut off the beam 22 from sensor 26 at a predetermined angle of divergence to provide an indication of when the pellet end face is at a limit of acceptable orientation. The predetermined angle can be adjusted by changing the aperture diameter. A disc can replace the aperture. <IMAGE>

Description

SPECIFICATION Improvements in or relating to the testing of pellets This invention relates to the testing of pellets.

A pellet has an axis and end faces transverse to the axis.

It is desirable to assess the orientation of an end face to the axis.

According to this invention apparatus for testing the orientation of an end face of a pellet to the pellet axis comprises means for supporting a mirror and engageable with the end face, means for directing radiation onto the mirror, and means for sensing radiation reflected from the mirror.

The radiation directing means may comprise a laser.

The apparatus may comprise limiting means engageable by the reflected radiation for limiting the angle to the axis for which the reflected radiation is sensed by the sensing means.

The limiting means may comprise means defining a circular aperture.

The limiting means may alternatively comprise a circular light-impervious element.

The limiting means may be adjustable to vary said angle.

The apparatus may comprise means mounting the mirror for movement about an axis transverse to the pellet axis, said mounting means comprising spring means.

The mounting means may comprise a plate supported by springs. The springs may extend generally in the plane of the plate.

The mounting means may comprise a cupshaped element having a flat bottom engageable with the end face and supporting the mirror, and spring means supporting the element. The spring means may be helical and generally coaxial with the element in a datum position.

The invention may be performed in various ways and one specific embodiment with possible modifications will now be described by way of example with reference to the accompanying schematic drawings, in which: Fig 1 is a plan view of a pellet end squareness gauge apparatus; Fig 2 is a side view of part of Fig Fig 3 is an end view from the right of Fig 2; Fig 4 is a side view of a modified arrangement; and Fig 5 is a central longitudinal section of part of Fig 4.

Referring to Fig 1, the apparatus 10 comprises an optical beam 11 and a parallel optical beam 1 2. A laser 1 3 is mounted on the beam 11 and a coherent beam 14 of radiation from the laser is directed along the beam 11 to target apparatus 1 5 (see Fig 2) shown diagrammatically in Fig 1. The beam 14 passes through a planar beam splitter 1 6 mounted in the beam 11. A bracket 1 7 supports a sensor 1 8 responsive to radiation 1 9 reflected from the beam splitter 16.

The sensor 1 8 is at an adjustable but desired height and is used to check the correct positioning of the beam splitter 1 6 by adjusting the beam splitter to give maximum radiation 1 9 at sensor 1 8. Sensor 1 8 also checks the presence of the laser beam during normal operation.

Radiation or return beam reflected from apparatus 1 5 is reflected by a dielectric film in beam splitter 16 to a right angle prism 21 mounted on the beam 1 2 which directs the radiation 22 on to or past a circular mask 23, through a plano-convex lens 24 which focusses the radiation 25 which has passed the mask 23 on to a sensor 26.

The circular mask or iris 23 has an adjustable diameter.

As explained below, if the end face of a pellet under test is square to the pellet axis, reflected radiation 30 is a coherent on axis beam and the radiation 22 will therefore pass through the aperture in the mask 23 and will reach the sensor 26.

As the end face progressively departs from square, the radiation beams 30 and 22 become more and more divergent (conical) until, at a certain angle to square of the end face, radiation cannot pass through the aperture in the mask 23 and reach the sensor 26.

By adjusting the diameter of the aperture in the mask 23, the angle of divergence of beam 22 at which radiation stops reaching the sensor 26 can be varied. Thus if it is desired to assess whether the end face of a pellet is more than a desired certain angle to square, the mask diameter is set accordingly and if radiation does not reach the sensor 26 the end face is not within the desired range of angles to square.

Referring now to Figs 2 and 3, apparatus 1 5 includes a block 30 having a V-section cut-out 31 which receives a circular-section nuclear fuel pellet 32 under test. The upper surface of the block 30 has a cut-out 33. A flat gauge or swash plate 34 is rectangular and is supported in a support structure shown at 35 by three springs 36, 37, 38 which extend generally in the plane of the plate.

Spring 36 extends between the structure 35 and the mid-point of the top edge 39 of the plate; and springs 37, 38 respectively extend between the structure 35 and the lower region of the vertical side edges of the plate.

Thus the plate can swing about an axis transverse to the pellet axis.

A plane mirror 40 is fixed to the rear of the plate 34 and is engaged by the curved end 41 of a rod 42 slidably mounted in support 43 fixed on block 30. A fluid-pressure operated actuator indicated at 44 can move the rod 42 as shown by the arrows to bring the end 41 in contact with the mirror 40. The radiation 1 4a passing through the beam splitter falls on the mirror 40 and is reflected-two examples are shown by arrows B, C. If the end face 56 of the pellet 32 is square to the pellet axis 51 the radiation 1 4a is reflected from the mirror 40 on path 1 4a and reaches sensor 26, as mentioned above.

The rod 42 holds the plate 34 against the end face 50 and if this face is inclined to a plane at right angles to the axis 51 (offsquare) the reflected beam 1 4b is angled accordingly. Thus, for example, only pellets producing a beam 1 4b within cone of angles B (radius R at distance Z from mirror 40) will energize sensor 26.

The pellet 32 is held in groove 31 by manually operable clamp 60 and is urged towards plate 34 by manually operable plunger 61.

The pellet may have a flat end face or it may be provided with a circular land indicated at 62-for example if the pellet has an external diameter of 2.1cm the land may be 2/3 of the distance from axis to the periphery and have a radial dimension of 1 mm. The plate 34 engages the land 62. The end face 51 may have an inwardly extending recess but this should not affect the operation of the apparatus. The pellets may be fed in succession to the groove 31 from suitable feed apparatus.

In a modification, instead of the pellets being removed from the groove 31 by hand, they are removed by a device linked to the sensor 26 so that if the sensor 26 indicates the pellet end face is out of square by an unacceptable amount the device directs the pellet to a reject chute.

The use of the pivot 42, 41 reduces vibration (wobble) of plate 34.

The apparatus 1 5 may be enclosed in a sealed bellows, with inlet window for beam 14a, to provide a relative dust-free environment.

Pellets may be fed to groove 31 by a conveyor belt extending laterally to block 30.

Referring now to Figs 4 and 5, this is similar to Figs 1 to 3 but the bar 42 is connected to spaced grooved rollers 80 (only two shown) embracing opposite sides of a horizontal guide slide 81. The unit 1 5 is mounted on the end of the bar 42 and comprises a housing 82 having a stepped bore 83 and externally threaded to engage in a collar 84 fixed to bar 42. The housing is therefore axially adjustable for assembly purposes.

A cup-shaped element 85 has a parallelsided flat bottom 86 the outer face 87 of which is engageable with the end face of the pellet 32 and the other face 88 of which is secured to the mirror 34 having axis 89. A helical spring 90 extends between a flange 70 on element 85 and a shoulder 71 in bore 83.

The mirror-carrying element 85 is thus supported solely on the spring 90. Thus movement of the unit 1 5 to bring element 85 into contact with the pellet 32 is cushioned by spring 90 and the element 85 is given a floating support by the spring 90 and can readily adjust to the orientation of the end face of the pellet. The spring is generally coaxial with element 85 in a datum central position.

In a modification the mask 23 consists of a light-impervious disc of adjustable diameter and the end face is within a desired range of inclination to the pellet axis provided the reflected beam does not reach the sensor 26.

The invention is not restricted to nuclear fuel pellets but could be used with other pellets having an end face.

CLAIMS 1. Apparatus for testing the orientation of an end face of a pellet to the pellet axis comprising means for supporting a mirror and engageable with the end face, means for directing radiation onto the mirror, and means for sensing radiation reflected from the mirror.

2. Apparatus as claimed in Claim 1, in which the radiation directing means comprises a laser.

3. Apparatus as claimed in Claim 1 or Claim 2, comprising limiting means engageable by the reflected radiation for limiting the angle to the axis for which the reflected radiation is sensed by the sensing means.

4. Apparatus as claimed in Claim 3, in which the limiting means is adjustable to vary said angle.

5. Apparatus as claimed in Claim 3 or Claim 4, in which the limiting means com prises means defining a circular aperture for the reflected radiation.

6. Apparatus as claimed in Claim 3 or Claim 4, in which the limiting means com prises a circular light-impervious disc for inter rupting the reflected radiation.

7. Apparatus as claimed in any preceding claim, comprising means mounting the mirror for movement about an axis transverse to the pellet axis, said mounting means comprising spring means.

8. Apparatus as claimed in Claim 7, in which the mounting means comprises a plate supported by springs.

9. Apparatus as claimed in Claim 8, in which the springs extend generally in the plane of the plate.

10. Apparatus as claimed in Claim 7, in which the mounting means comprises a cup shaped element having a flat bottom engage able with the end face and supporting the mirror, and spring means supporting the ele ment.

11. Apparatus as claimed in Claim 10, in which the spring means is helical and gener ally coaxial with the element in a datum position.

1 2. Apparatus as claimed in Claim 1, in which the sensing means is arranged to provide an indication when the end face is not at right angles to the axis.

1 3. Apparatus as claimed in Claim 1, in which the sensing means is arranged to prowide an indication when the end face is inclined at more than a predetermined angle to a plane at right angles to the axis.

14. Apparatus for testing the orientation of an end face of a pellet to the pellet axis substantially as hereinbefore described with reference to and as shown in Figs. 1 to 3, or Figs. 4 and 5, of the accompanying drawings.

Claims

CLAIMS New claims or amendments to claims filed on 2 July 1985 Superseded claims 1-4 New or amended claims:

1. Apparatus for testing the orientation of an end face of a pellet to the pellet axis comprising means for supporting a pellet, means for mounting a mirror structure for movement about two orthogonal axes at right angles to the pellet axis for engagement of the mirror structure with the pellet end face, means for directing radiation onto the mirror, and means for sensing radiation reflected from the mirror.

5. Apparatus as claimed in Claim 3 or Claim 4, in which the limiting means comprises means defining a circular aperture for the reflected radiation.

6. Apparatus as claimed in Claim 3 or Claim 4, in which the limiting means comprises a circular light-impervious disc for interrupting the reflected radiation.

7. Apparatus as claimed in any preceding claim, in which the mounting means enables the mirror structure to move along the pellet axis.

8. Apparatus as claimed in Claim 7, in which said mounting means is such that the mirror structure is constrained solely by spring means.

9. Apparatus as claimed in Claim 8, in which the mounting means comprises a plate supported by springs.

10. Apparatus as claimed in Claim 9, in which the springs extend generally in the plane of the plate.

11. Apparatus as claimed in Claim 8, in which the mounting means comprises a cupshaped element having a flat bottom engageable with the end face and supporting the mirror, said spring means supporting the element.

1 2. Apparatus as claimed in Claim 11, in which the spring means is helical and generally coaxial with the element in a datum position.

1 3. Apparatus as claimed in Claim 1, in which the sensing means is arranged to provide an indication when the end face is not at right angles to the axis.

14. Apparatus as claimed in Claim 1, in which the sensing means is arranged to provide an indication when the end face is inclined at more than a predetermined angle to a plane at right angles to the axis.

1 5. Apparatus as claimed in any preceding claim, comprising means for moving a pellet on said support to bring an end face of the pellet into engagement with the mirror structure.

1 6. Apparatus as claimed in any preceding claim, in which one side of the mirror structure is adapted for engagement with the pellet end face, said one side facing in one direction, said mirror facing in the opposite direction.

1 7. Apparatus for testing the orientation of an end face of a pellet to the pellet axis substantially as hereinbefore described with reference to and as shown in Figs. 1 to 3, or Figs. 4 and 5, of the accompanying drawings.