Vistas has performed over 200 Steam Generator FOSAR (Foreign Object Search and Retrieval) tube sheet inspections at major utilities during the last 11 years. The Steam Generator FOSAR is broken down into three distinctive parts: the annulus, or shell to tube bundle outer surface; the tube lane area, the area adjacent to the blow-down pipe or divider plate, and the tube bundle area between the tubes inside the bundle. These areas are each unique because of the different sets of tooling required to inspect and retrieve foreign objects. This is not to say that Vistas charges separately for each area. On the contrary, we inspect and retrieve at the same time where possible and advantageous to dose. We inspect per a daily rate and do not add on charges for the different areas discussed. Vistas pioneered in-bundle inspection and the tools to perform retrieval there.
Vistas invented and patented AMOS (Annulus Monitoring Optical System) to use in the annulus because of the numerous retrievals we were performing there and to cut down on the use of costly video-probes. AMOS is a high resolution waterproof remote camera, with variable intensity spot and flood lighting, remote focusing up to 1/8″, and 270 degree horizontal articulation. It is 20 ft long and has the ability to retrieve as it inspects. It is inserted manually into the S/G hand-hole or port through a directional guide tube. Dose is cut down by the use of RAD-Vent-Loc hand-hole plugs. These are a Vistas patented hole plugs used during FOSAR that cuts the Gamma dose down. Actual working readings have been measured at 1000Mr at the plane reduced to 40Mr/hr. AMOS can also be turned on its side to look up at wrapper to shell braces or brackets. Vistas also has an arsenal of waterproof video-probes, retrieval tools and articulating guide tubes including several electro-mechanical grippers and samplers.
The tubelane area is performed with a video-probe because of the small space constraints. Retrievals are accomplished with small grippers, pliers, magnets, snares, or other tools as the situation necessitates.
In square-pitch steam generators, 6mm video-probes are utilized. In the larger tri-pitch 3.9mm probes are used. When the smaller tri-pitch replacement steam generator requires it, tiny 1-2mm fiber-scopes can be used. These yield a smaller round picture that is less resolute than the video probes. Vistas has a large array of in-bundle retrieval tools also sized to the particular in-bundle S/G dimensions to fit the task at hand. Tools such as tiny screwdrivers, magnets, nudgers, snares, pliers, fork & tines can be used to dislodge and push or pull foreign objects out of the tube bundle to be retrieved in the annulus or directly from the bundle.
Vistas also has performed numerous S/G Upper Secondary Inspections. These range from a general visual of the secondary components (digitally videotaped to DVDs), U-bend inspection through swirl vanes, retrievals, U-Bend and quatrefoil inspections through transition ports to informational UT of the feed ring. Top-down inspection through support plate openings can be accomplished through a transitional or other penetration from the highest support plate down to the tubesheet (depending on S/G design). J-Nozzle visual inspection is also performed with a 180 degree articulating, patented J-Nozzle camera. The inside of the feedwater pipe can also be inspected for backing rings or general integrity.
Vistas provides all documentation before leaving site so there is no waiting for a report, DVD, Tapes, or pictures. We make high resolution color contact picture sheets 6 or 8 pictures to a page usually two pages per S/G inspection. Our DVDs have custom menus setup to highlight the important areas of the inspection so that our customers can go directly to a point of interest.