A leading scientist has said that Cumbria is sitting on a stockpile of what could be thousands of years of energy in the bank. 

Professor of nuclear fuel technology at the University of Manchester, Tim Abraham, made the comments earlier this month at a briefing to discuss the fate of the UK's plutonium. 

It is estimated that Sellafield has a has around 140 tonnes of the material, now the largest stockpile of civil plutonium in the world. 

The government hasn’t decided what to do with the stockpile yet, but in 2013 the Department of Energy and Climate Change (DECC) indicated that it would prefer to reuse it as fuel rather than just dispose of it. 

This would require new reactors that are able to use plutonium as fuel to be built, a complex and expensive process. 

Professor Abram said: "Having [a store of] separated plutonium without a declared end use represents a poor international example.

"We should at least keep the process moving forward and not give the impression to the world that we have stalled." 

Plutonium can extracted from reprocessed nuclear waste and was originally stockpiled as a source of fuel for a new breed of experimental nuclear reactors. 

In the 1990s, the government-backed programme of research to develop these new reactors was cancelled, on both cost and safety grounds, so Sellafield has been left storing plutonium with no long-term plan for it. 

DECC tasked the Nuclear Decommissioning Authority (NDA) with assessing the technical, safety and economic pros and cons of the three "credible" types of new generation nuclear reactor that would allow the plutonium to be used as fuel. 

The NDA says it is "in the middle" of this complicated consultation. 

The NDA said: "A decision is expected to be made by ministers on how to proceed during 2015/16. 

"However, only when the Government is confident that its preferred option could be implemented safely and securely, in a way that is affordable, deliverable and offers value for money, will it be in a position to proceed."