Nuclear experts have come up with an innovative solution to the challenge of removing radioactive sludge from the world’s biggest open-air nuclear pond. Using a petrol-pump style design, the Drum Filling Plant (DFP) will export the sludge from the Pile Fuel Storage Pond (PFSP) at a fraction of the original estimated cost.
PFSP was the very first nuclear fuel storage pond constructed at Sellafield back in the 1940s and to this day remains the largest open air nuclear storage pond in the world. It is currently being decommissioned and part of this work involves emptying the pond of its radioactive sludge.
Dorothy Gradden, Head of PFSP explained: “The pond was built in 1948 and contains more than 300 cubic metres of radioactive sludge, which is made up of fuel corrosion products and algae, which have been accumulating in this open air pond. It poses one of the most challenging decommissioning projects on the Sellafield site.
“The plan is to decommission and empty the PFSP to make this historic plant safer sooner. However, before the pond water can be drained, the radioactive sludge has to be removed. This sludge is similar in consistency to tomato ketchup and lies at the bottom of the seven-metre-deep pond. We’ve already started hoovering this up and pumping it in an in-pond corral and we need the Drum Filling Plant to export the sludge for treatment.”
The pond stored nuclear fuel and isotopes from the Windscale Reactors that were designed and built in an incredibly short timescale to produce nuclear materials for the defence industry. The Windscales Piles as they are better known never actually generated electricity, but were the precursor to our Calder Hall reactor – the first commercial reactor in the world.
Today, the Sellafield Ltd project team has echoed this innovative spirit and come up with a revolutionary design for the DFP in less than twelve months.
Project Manager Chris Plane said: “Well over 60 years after the PFSP was built, we’ve developed a new concept plant to package and transfer the radioactive sludge to a modern waste treatment plan. The DFP will be operational by mid 2015 and provides a cost effective solution saving the UK taxpayer money and reducing the sludge hazard.
“The original planned encapsulation export facility was estimated to cost well over £70 million, but we’ve come up with some innovative ideas using technology borrowed from other industries and will build a fit-for-purpose plant which is simpler and will instead cost in the region of £20 million.
“We’ve thrown out the original idea of a high capacity nuclear crane, shielded concrete operating cells and substantially reinforced foundations. Instead we have designed a building skeleton containing what is effectively a large-scale petrol filling pump which we’ve proved using a test rig and it does what it says on the tin – it fills drums.”
The drums will sit inside a 40 tonne transport flask on the back of a transport wagon which is already used on the site for moving waste between plants. The filling system is lowered onto the flask using locomotive lifts from the rail industry and the drum filled without ever leaving the flask. A new lid is being designed for the existing flask using 3D scanning technology to introduce a filling port to allow the sludge to be metered into the drum.
Dorothy Gradden added: “The Nuclear Decommissioning Authority (NDA) has approved the plant build and we’ve recently placed a contract with Nuvia to construct the DFP.
“The plant will be built as separate modules to allow it to be assembled and fully tested off site in a controlled environment before being unplugged and shipped to site. This reduces the work required to be done in the more restrictive Sellafield site environment and further accelerates the delivery schedule.”