Another ground-breaking device is leading the way with decommissioning Dounreay’s Prototype Fast Reactor.
The innovative purpose-built drilling probe was designed and tested in-house by DSRL’s specialist design team. It has the combined ability to drill through the reactor roof and capture photographic footage of the sodium deposits in an extreme environment of high radiation levels.
The specialised 6mm diameter exploratory endoscope camera, encased within a stainless steel tube, was inserted over two metres down into the reactor. The camera has allowed the project team to retrieve very clear images of the upper regions of the reactor where the thirty-one stainless steel insulation plates are located, allowing them to survey the sodium residue that has built up on the plates over time.
Appearing like volcanic lava encrusted on the surfaces of the metal plates which once served a crucial part of the reactor roof cooling process, the sodium is clearly visible and the photos and radiation level readings provide the decommissioning team with valuable knowledge and associated risk for planning the safe dismantling of the redundant plant.
Calder Bain, responsible for the design of the equipment, said: “The drilling of the thin plates presented a unique challenge as they are not well supported. Their flexible and flimsy construction meant taking extra care to prevent the drill breaking and being unrecoverable. The design was kept as simple as possible after trials on a test section revealed the intricate nature of the process. Credit is also due to our contractors JGC Engineering & Technical Services and Nuvia who successfully completed the work.”
Mike Brown, fast reactors decommissioning unit manager, said: “The reactor dismantling project is critical to the decommissioning of PFR. To safely take apart the plant we need to inspect all the nooks and crannies within the reactor before we can begin the final phase of work which is to remove the reactor vessel. The design of purpose built equipment such as this is invaluable for successful delivery of our programme of work.”