UK Magnox Ltd, on behalf of the Hinkley Point A NPP has asked, Steve Vick International (SVI) to design and supply an effective method for sealing and decommissioning radioactive pipework. Hinkley Point A in Somerset, with two Magnox reactors, operated from 1965 to 2000 and is now being decommissioned. The UK Office of Nuclear Regulation said the focus is on the safe and secure retrieval, packaging and storing of legacy waste. Priorities for the site include completing the build and commissioning of the intermediate level waste store and installing the modular active effluent treatment plant.
Magnox is looking to decommission 1.2km of pipework housed in an Active Drains Trench (ADT) where access is very restricted.
SVI said on 30 June that its FOAMBAG system “offers the ideal solution whereby contamination in the pipes could be immobilised using expanding Polyurethane (PU) Foam, allowing the pipes to be cut safely”. This solves the issue of access as the PU foam can be deployed from a remote location. Using SVI’s technique, the project was completed with just 50 injection points and took 20 days to complete.
Mike Gladwyn, Project Engineer at Magnox commented: “SVI’s FOAMBAG system helped to improve safety by encapsulating contamination prior to cutting but also significantly reduced the timescale of the project and therefore helped to reduce our overall costs.”
The semi porous FOAMBAG creates a permanent plug inside the pipe without the loss of pipe integrity. It uses an expanding PU resin foam, comprising a resin base and hardener which is mixed prior to application and then injected into the bag via an injection tube. The expanding foam fills the bag and then a measured volume of foam seeps through the FOAMBAG material to adhere to the pipe wall.
The foam encapsulates loose debris and contamination as it expands and cures. Once cured hard, it is then possible to section the pipe into 800mm lengths for disposal without contamination becoming airborne.
Graham Steer, project manager, noted that this technology has not only reduced the programme and cost, it has also resulted in significant safety improvements. SVI Technicians were trained by Magnox to enable them to work on site and SVI Technicians in turn trained Magnox Technicians in the installation of Foambags and pipe drilling operations.
Photo courtesy of Steve Vick International