Inspection of the reactor pressure vessel falls into three main areas:

Reactor vessel shell Equipment is provided which is capable of performing ultrasonic examination of the vessel welds from the vessel internal surface (with the reactor internals removed) and the refuelling cavity flooded. The equipment consists typically of a central telescopic support column positioned over the axis of the vessel and supported by three equi-spaced arms mounted on the vessel flange. Attached to the lower end of the central support column is a second tele­scopic arm capable of extension in the vessel radial direction. This second telescopic arm carries an array of ultrasonic transducers, the number and position­ing of wrhich will be determined by the inspection required. The equipment is capable of longitudinal extension sufficient to perform inspection of the low­er head to transition ring weld, and radial extension sufficient to perform inspection of the pipework to nozzle safe-end weld. The equipment control and data acquisition centre is located outside the reactor build­ing, thus minimising dose to operators performing the inspection.

Equipment is also provided to perform external ex­amination of the nozzle to pipework safe-end welds. This equipment takes the form of remotely operated track-mounted devices capable of performing both dye penetrant and ultrasonic scans of the entire weld. Equipment is provided capable of performing an ex­amination of the vessel-to-nozzle welds from the ex­ternal surface. The data acquisition and equipment control systems are located in a low radiation area.

Reactor vessel closure head The vessel head and its associated equipment (studs, nuts and washers) is re­moved prior to refuelling and stored dry on a stand within a shielded area. Ultrasonic examination of the head-to-flange weld is carried out externally using a remotely operated device. Sufficient access is provided to permit ultrasonic or dye penetrant examination of the control rod drive mechanism housing welds. Auto­matic equipment is also provided to perform ultra­sonic inspection of the closure head studs.

Reactor internals The reactor internal structures are removed from the vessel and stored under water in the refuelling cavity. Remotely operated visual inspec­tion equipment (CCTV cameras) is provided to per­form underwater examination of these components.