Sellafield Making Headway on Sludge Plants
After decades of having radioactive sludge sitting in unlined open air ponds at Sellafield, the site is commissioning two new plants aimed at removing and processing the material. Site license company Sellafield Ltd. recently completed construction of the £240 million ($412 million) Sludge Packaging Plant to remove material from the highly radioactive First Generation Magnox Storage Pond. Sellafield hopes to begin test retrievals at the end of this year. “The idea of the SPP facility, which is a new building with giant tanks in it, is that the most important safety consideration is to get the fuel … out because that’s where the risk is,” Sellafield Ltd. Chief Decommissioning Officer Jack DeVine said in an interview with WC Monitor this month. “That concrete pool has a significant number of cracks and it certainly has potential for leakage over time. It is certainly vulnerable to external events. We want to get it in a secure place. So the plan is to get the fuel out and get the sludge out.”
Spent fuel has been stored since the 1950s at the Magnox Storage Pond and the Windscale Pile Fuel Storage Pond. Over the decades, corroded fuel and equipment, along with organic material blown into the open-air pools, accumulated to form a heavy sludge in the ponds, which is estimated to total 1,500 cubic meters in the Magnox pond and lay up to one meter deep. In order to take out the spent fuel in the ponds and eventually drain them, the sludge must first be removed, which has proven challenging in the past.
‘We Are Essentially Attacking the Risk First’
The new Sludge Packing Plant essentially vacuums up the sludge and transfers it from the Magnox pond to the plant through a 31-meter-long pipe bridge. In the plant, the material ends up in three large tanks equipped with 11 pulse jet mixers, which prevent the sludge from settling and forming a crust within the vessels. It will be stored there in the interim until it can be prepared for storage. “It is going from a facility of unknown design to one that is very well designed, very firm, properly shielded, properly instrumented and properly isolated from the environment. You are taking that material and putting it in a much safer place where you can deal with it later,” DeVine said. “We are essentially attacking the risk first and then we will attack the disposal as a second bite for the whole approach.”
Sellafield has an “aggressive program” to begin test retrievals at the end of this year using portable equipment, with a full-bore start scheduled for 2016, DeVine said. “We want to test drive this whole system and be able to move material out of the pond, through the transport system into the SPP-1 tanks and really validate and verify that whole process and learn from it,” he said, adding later, “I think we are going to learn a lot. One of the big philosophical things we are trying to do here is as much as possible move fast and learn by doing and not spend years analyzing things.”
Efficiencies Added to Pile Fuel Storage Pond Drum Filling Plant
Meanwhile, to address sludge in the Windscale Pile Fuel Storage Pond, design efficiencies are being incorporated into a planned Drum Filling Plant, which is expected to be operational by mid-2015. The site says that the new design will save more than £50 million ($88 million) from the original cost estimate. The pond is estimated to have more than 300 cubic meters of sludge. The Drum Filling Plant will accept waste from the pond that has been processed at the Local Sludge Treatment plant, which was completed in 2012. It will then be sent to the Waste Encapsulation Plant, a treatment facility.
The material will be transferred between the plants using a “petrol-pump style design,” according to a Sellafield release. “The original planned encapsulation export facility was estimated to cost well over £70 million ($120 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 ($34 million),” Project Manager Chris Plane said in a statement, adding, “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.”
Fuel Retrievals Restart
Meanwhile, retrievals of canned fuel has resumed at the Pile Fuel Storage Pond after a two-year pause. “In 2012 we accelerated the retrieval of the first sixteen cans of fuel to allow us to prove our retrieval techniques and underpin the treatment route; while this work was successful we had to pause the retrieval programme while a scheduled upgrade of the Windscale Laboratory was carried out,” Dorothy Gradden, Head of PFSP said in a statement. “This is now complete and we are very pleased to be able to start moving canned fuel from the pond and reducing the hazard associated with the facility.”