Littleham and nuclear waste disposal
23 September 2012
What is the connection?
Littleham, a small village on the outskirts of Exmouth, gives its name to the geological formation the Littleham Mudstone on which it is situated. Where the mudstones crop out in the cliffs at Littleham Cove they can be seen to have some curious features. The reddish brown mudstones were laid down in short-lived fresh water lakes. Near their base they contain oval nodules, some containing unusual minerals – try getting your tongue round metatyuyamunite (a calcium, uranium, vanadium mineral) for instance. Some of the nodules containing uranium are slightly radioactive. They also contain the metals cobalt, nickel, arsenic, lead, silver and gold. Native or metallic copper also occurs as concretions in the Littleham Mudstone. Specimens of this copper have recently been donated to RAMM by Mr Ron Harrison, formerly of the British Geological Survey.
The source of these metals is uncertain but they may be related in some way to the formation of the mineral lodes associated with the Dartmoor Granite which were forming at about the same time as the mudstones were laid down, perhaps with metal-rich water flowing into the lakes.
The particular interest is the occurrence of the copper that occurs as thin plates, 5 to 10 centimetres in diameter. It is believed to have formed when the mudstones were laid down in the Permian some 270-280 million years ago. The copper has survived as relatively unaltered metal for this immense length of time.
The study of the long term stability of copper in underground conditions is leading recent research by the British Geological Survey and a Swedish waste management company in the development of copper canisters for the storage and deep underground disposal of radioactive waste.
For this purpose the target requirement for survival of the storage canisters is a mere100,000 years compared with the millions of years over which the Littleham copper has survived.