Remote surface sampling of a Bradwell reactor pressure vessel

This paper describes the design, development and application of remotely operated equipment to obtain metal samples from welds in the high temperature zone of a reactor pressure vessel (RPV) at Bradwell Power Station. In-service embrittlement of the weld metal made it desirable to obtain small saucer-shaped samples from two selected welds, in order that predictions of the state of the material could be substantiated. To achieve this an electrically driven ''scoop'' sampler was incorporated in a specially designed work package and deployed inside the pressure vessel on a SNAKES hydraulic manipulator. Prior to metal sampling, the weld surfaces had to be cleaned with a flex hone tool to remove loose oxide before the weld volume could be inspected ultrasonically, to confirm the absence of significant defects. As the outside of the RPV is covered with insulating material, access to the welds had to be gained by entry down refuelling or control rod standpipes to the inside of the vessel. As a consequence of this the sampling work package was constrained in diameter to 200mm. (Author)