British Energy taps Babcock's nuclear tool design

London – Babcock has won a competitively tendered £1.3-million contract from British Energy to develop a new hybrid trepanning tool for sampling the graphite of nuclear reactors. Eventually, there will be four such tools, which Babcock claims will offer more refinement and operational flexibility than any predecessor.

“We recognised that it was important for us to have a tool that reliably breaks the sample or our data would cease to be as reliable,” said Alan Greenaway, British Energy team leader. “Graphite friability changes over time and it is important we are able to measure this process accurately as it occurs. However, the cutting mechanism is just part of the story. Our six strong graphite core inspection equipment team developed a list of scored criteria for the optioneering process.”

The tool design can cut 40 to 75 mm samples, rotate within the reactor to sample at any selected angle and jack tightly up to the face of the sample area. Other features include a highly engineered precision mechanism for cutting and the ability to view the trepanning area via integral camera.

John Holt graphite inspection project manager at Babcock, explained: “Prior to tendering, Babcock built a prototype Hybrid Tool Cutter and with our knowledge of graphite densities, we were able to experiment on bonded samples to simulate irradiated graphite and prove our design.

“Our prototype got close to the final design very quickly and we were able to deliver for inspection all 50 samples the prototype cut prior to contract award. With delivery scheduled for May 2011, the programme is tight. However with an 18 strong, experienced team working on the project, both sides are confident that this ambitious deadline will be met.”

Since Babcock won this contract, further refinements have been made, such as making the hybrid trepanning tool both lighter and narrower. These improvements mean that even if the graphite channels were to bow slightly or the graphite was to expand, narrowing the channels, the Tool would always be removable.

Babcock has also designed a control console to drive the tool and monitor the camera output. The control console works with British Energy’s existing contained hoist, thus negating the need for additional equipment to be commissioned.

The tool’s dust extract system features an air mover that sucks graphite dust through the cutter and blows it out of the bottom of the Tool. Additionally, an inflatable seal closes off the channel bore to prevent any flow past the tool.

“Not only will the Hybrid Trepanning Tool deliver longer samples”, said Greenaway, “but we will also benefit from the on board camera, as well as a marginally quicker operation time.”