Patent Number: 047956062
Section: claims

1. Apparatus for inspecting the surface of a structure comprising a track extending around an upper region of the structure, an elongated flexible carrier engageable along its length with the track and movable lengthwise along the track, means for leading the flexible carrier insertably into engagement with the track, and retractably out of engagement with the track, at at least one position along the length of the track, and inspection means carried by the carrier for selective downward extension and upward retraction relative to the carrier and relative to the track. 2. Apparatus as claimed in claim 1 in which the inspection means is connected to a cable which extends lengthwise through the carrier and is capable of being used to push or pull the inspection device relative to the carrier. 3. Apparatus as claimed in claim 2 in which said cable is extendable through an opening in said carrier and, when so extended, depends downwardly from the carrier whereby selective extension and retraction of the cable is effective to move the inspection means downwardly and upwardly over the surface to be inspected. 4. Apparatus as claimed in claim 1 in which said flexible carrier comprises a series of units connected end-to-end with some degree of freedom whereby adjacent units can articulate relative to each other in following the contour of the track. 5. Apparatus as claimed in claim 4 in which said units are of tubular configuration and are connected end-to-end by flexible bellows couplings to form a continuous flexible tube through which said inspection means can be moved. 6. Apparatus as claimed in claim 1 in which the track includes a slot extending lengthwise thereof and through which said inspection means can be extended. 7. In combination: (a) a nuclear reactor installation including a primary vessel surrounded externally by a guard vessel and defining an annular space therebetween, and (b) apparatus as claimed in claim 1, said track extending around the top of said primary and guard vessels and said inspection means being extendable into and retractable from said annular space. 8. The combination of claim 7 in which each of said means for leading extends between a respective position along said track and a respective access aperture in roof structure disposed above said vessels. 9. The combination of claim 7 in which said flexible carrier is withdrawable in its entirety through each access aperture in said roof structure and re-insertable via a different access aperture. 10. The combination of claim 7 in which the track includes a slot extending lengthwise of the track and through which said inspection means can be extended, said slot in the track overlying said annular space.