Optics: measuring and testing – Inspection of flaws or impurities – Having predetermined light transmission regions
Patent
1995-01-03
1996-10-15
Pham, Hoa Q.
Optics: measuring and testing
Inspection of flaws or impurities
Having predetermined light transmission regions
356426, 376248, G01N 2148
Patent
active
055659802
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to apparatus for the detection of surface defects especially on cylindrical objects such as nuclear fuel pellets.
2. Discussion of Prior Art
Certain cylindrical objects such as nuclear fuel pellets have to meet very demanding manufacturing quality specifications. Such objects may be manufactured by an automated manufacturing route without handling by human operators and in such a route it will be necessary to inspect the objects for surface defects using automatic apparatus. The objects may for example be sintered cylindrical UO.sub.2 (uranium dioxide) pellets for a so-called "agr" fuel element. Such pellets have an axial hole or bore provided for fuel performance reasons. The sintered pellets are inserted in stainless steel cladding tubes, the tubes being sealed to form a fuel pin and a cluster of pins being assembled to form fuel elements. The pellets require automatic inspection before insertion in the cladding tubes.
SUMMARY OF THE INVENTION
According to the present invention there is provided an apparatus for the detection of surface defects on cylindrical objects which includes means for conveying the objects to be inspected one-by-one each on its end to a first inspection station, means for inspecting the free end of each object as it passes through the first inspection station, means for conveying the objects one-by-one each on its side to a second inspection station the means including means for tipping the objects from their ends to their sides, means for rotating each objects whilst passing it on its side through the second inspection station, means for inspecting the curved surface of each object as it passes through the second inspection station, means for conveying the objects one-by-one to a third inspection station the said means including means for tipping the objects onto their end inspected at the first inspection station and means for inspecting the free end of each object as it passes through the third inspection station.
Unlike prior art systems the apparatus according to the present invention allows all surfaces excepting the surface in the bore if present of the cylindrical objects to be inspected in a continuous operation the objects being presented one-by-one to the apparatus by a conveying means.
The present invention is particularly applicable to the automatic inspection of nuclear fuel pellets. The pellets may comprise well known shapes, e.g. they may be hollow or solid right circular substantially cylindrical bodies. The ends may be flat surfaces or may be convex curves rather than flat surfaces. The pellets may for example be for use in either so called AGR or LWR types of nuclear reactor. The pellets may comprise uranium oxide optionally doped with one or more known additives, e.g. niobia or gadolinia. Alternatively, the pellets may comprise MOX (mixed oxide fuel) e.g. comprising a mixture of uranium and plutonium oxides. In that case, the pellets will normally be within a containment such as a glovebox which confines the plutonium oxide thereby preventing outside contamination. The components of the apparatus according to the invention may be located outside such containment. The containment may include a window, e.g. made of a high quality glass, which allows the optical radiation to pass in and out of the containment to inspect the pellets therein. As only a small number of pellets need to be in the containment for inspection at any one time the window is not required to act as a radiation shield. Conventional neutron and gamma radiation shielding material can be provided around the components of the apparatus located outside the containment containing the pellets being inspected.
The means for tipping the objects between the first and second inspection stations may include a first tipping station comprising a step on the conveying track the step changing the attitude of the axes of the objects from vertical to horizontal. The means for tipping the objects between the second and third
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Davidson Iain S.
Hague Mark
Rice Thomas G.
British Nuclear Fuels PLC
Pham Hoa Q.
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