The Nuclear Decommissioning Authority

 

A unique piece of Dungeness plant that dissolves intermediate-level waste could generate a predicted lifetime saving to the taxpayer of at least £35 million *.

The site's Magnox dissolution (MXD) plant programme dramatically reduces the volume of metal Fuel Element Debris (FED), leading to significant savings on long-term storage costs.

The knowledge is now being shared with a view to building such plants at other Magnox South sites – a team from Hinkley has already paid a visit - while Magnox North sites could also benefit. At Dungeness alone, savings are expected to reach £25 million.

The material is dissolved in magnesium hydroxide (an antacid often used to treat heartburn and indigestion) and carbon dioxide to produce magnesium bicarbonate which can be safely discharged to sea. The process is not suitable for all kinds of intermediate-level waste.

 

The Nuclear Installations Inspectorate and Environment Agency have both assessed the project as having negligible environmental impact.

MXD plant manager Ian Cuthbert said:

"The team has built up a wealth of knowledge which we are sharing across the Magnox estate and we are expecting to process all the remaining fuel element debris at Dungeness by the end of 2011."

Rob Goodwill from the Hinkley group added:

"From in-house experience we knew details about the plant, however, it was great to see that with a pragmatic design and operating approach, you can safely progress FED recovery and processing at realistic costs. We found the visit very useful."

The MXD plant is currently used to process the waste in two storage vaults containing fuel element debris, predominantly in the form of solid metallic lugs. Lugs are the fin-shaped parts on the outside of the fuel element casing. They were shaved off to allow the rest of the casing to be tightly packed into flasks for transport and reprocessing at Sellafield.

The two vaults, next to the fuel cooling ponds on Reactor 1 and Reactor 2 respectively, originally contained about 30 tonnes of lugs and so far about 15 tonnes have been dissolved.

The MXD plant, which recently completed another major milestone with the emptying of the reactor 1 lug vault, was constructed in the mid-80s and refurbished and returned to service in 1999.

 

It was originally designed to process the corroded sludge and debris that accumulated in the splitter storage vaults. Splitters are a different type of FED and with a different metallic make-up. This waste, representing about 60 tonnes of magnesium, has been successfully processed and the original splitter vaults are now empty.

* Savings are calculated by estimating the disposal, storage and packaging costs of the original volume before the dissolution process and subtracting the estimated packaging and disposal costs of treated waste.