By Tim Hirsch
BBC News environment correspondent
As ministers ponder the future of Britain's nuclear power industry, one plant in the mountains of Snowdonia has never been busier.
Decommissioning at Trawsfynydd employs over 500 staff
Every day more than 500 staff and contractors turn off the scenic A470 trunk road linking north and south Wales, to pass through the gates of Trawsfynydd power station.
The place is a hive of activity, including major construction work to create a new building alongside the two giant cube-shaped 51m high reactor towers, which stand out starkly against the stunningly beautiful landscape.
Nothing unusual in this - except that Trawsfynydd has not generated a Watt of electricity in nearly fifteen years.
The labour, energy and taxpayers' money (about £45m this year) being devoted to this site are all part of the decommissioning process which will continue here for nearly another century.
A visit to the plant vividly illustrates the dilemma facing the government as it squares up to two key decisions in the coming months: whether to approve a new generation of nuclear power stations, and what to do with the legacy of waste bequeathed to us and our descendants by the last generation.
Operators were watching a closed-circuit TV image of a metal probe smoothing out the debris in preparation for the next scoop
The dilemma is that the two decisions, although separate, are inextricably linked through a basic ethical question: regardless of the merits of nuclear power as a future energy source, is it right to commit the UK to creating more radioactive waste while society has yet to find an acceptable long-term option for handling the material already in existence?
The Committee on Radioactive Waste Management (CORWM), after an exhaustive public consultation exercise, will soon publish draft recommendations on what should be done with some 470,000 cubic metres of waste - enough to fill the Royal Albert Hall five times over.
This is the estimated quantity of waste material from existing nuclear plants, including those like Trawsfynydd which are being dismantled, for which there is still no long-term disposal plan.
It excludes a large quantity of mildly radioactive material such as gloves and laboratory equipment, which is disposed of at a special site at Drigg in Cumbria.
Reprocessing fuel rods
The heavy workload at Trawsfynydd - employing a larger workforce than when it was generating electricity before 1991 - is centred around converting waste material into a form suitable for long-term storage, and starting to return the site to the way it was before the plant was built in the early 1960s.
That process is only projected to be completed by the end of this century, as it is not considered safe to start dismantling the highly radioactive core until the 2080s - although this may be brought forward due to technological advances in decommissioning techniques.
The nuclear fuel rods themselves which powered the reactors have already been sent to Sellafield in Cumbria for reprocessing.
This recycles uranium for use in other plants, but leaves highly irradiated nitric acid which must be cooled and encased in glass, remaining radioactive for thousands of years.
The bulk of the waste produced at Trawsfynydd is debris of various materials not radioactive in themselves, but which were in prolonged contact with nuclear fuels.
So, for example, before the fuel rods could be removed from the site, the steel fins which encased them had to be sheared off, leaving 380 cubic metres of metal shards in temporary vaults at the plant, where they are now being scooped up and transferred to specially-reinforced steel and concrete casings for long-term storage.
Although carried out under strict safety procedures, this can appear a curiously low-tech activity.
In a control room above these vaults, operators were watching a closed-circuit TV image of a metal probe smoothing out the debris in preparation for the next scoop.
I assumed this was being done by remote action until I was told there was actually a man beneath us in protective gear doing it all by hand.
Another key component of the Trawsfynydd waste is the sludge and resin extracted from the water ponds adjacent to the reactors, used to cool spent nuclear fuel before it was removed for re-processing. It's all messy stuff, and needs to be solidified before being packed into steel and concrete drums.
This is the kind of material, known collectively as Intermediate Level Waste, which forms the biggest part in terms of volume of the waste for which solutions are now being sought - although most of the radioactivity is concentrated in the High Level Waste from Sellafield.
While this long-term answer is awaited, foundations are just being completed for a building behind the Trawsfynydd reactors, 90m long and 20m high, which will act as a temporary store for the waste containers, probably for around 30-40 years.
The claim of the nuclear industry is new reactor designs would produce very much smaller quantities of waste from future stations
This building and the reactor towers themselves, whose height will be reduced, will be clad in local Welsh slate designed to make them blend better into the landscape.
Watching the heavy trucks depositing great quantities of concrete into this building site, it was impossible to avoid reflecting on the description of nuclear power as "carbon-free electricity".
Certainly the process of generating electricity by this method avoids releasing significant quantities of greenhouse gases, but the transport and construction emissions involved here long after the useful life of the station must surely also be taken into account.
For the long-term storage of this waste, CORWM is looking at four main options:
- keeping it above or just below ground
- locking it away forever in deep geological rock layers
- burying it in deep vaults but in a way where it can be retrieved in future
- splitting the waste between different stores according to how long it remains radioactive
Whichever of these solutions is recommended in the final report in July, the committee will not be suggesting a particular site - that unenviable task will be left to ministers.
But the chairman of the committee, Professor Gordon Mackerron, has another concern: he does not wish his recommendation for the disposal of existing waste to be interpreted by the government as a green light for building new nuclear stations.
"We think it is important that there is a full review of the waste implications of any new-build programme, and not to take our report as somehow having managed the entire problem - because the politics and ethics are different, even if the technology is not," said Prof Mackerron.
The claim of the nuclear industry is new reactor designs would produce very much smaller quantities of waste from future stations, and therefore this is more a historic problem than one which should influence current energy decisions.
Fuel rods are taken to Sellafield for reprocessing
But Britain is by no means alone in taking many years to grapple with this issue.
In Belgium, for example, decades have been spent investigating the possibility of storing waste in underground clay formations, with research centred on the delightfully-named High Activity Disposal Experimental Site (Hades).
Regardless of whether it is considered an acceptable cost for the energy produced during the three decades of its useful life, the waste now piling up at Trawsfynydd and other stations is there, and must be dealt with somehow.
Eventually, some community or other is going to be asked to have it nearby.
Even if ministers do, as widely expected, signal a new era for nuclear power, the political and financial legacy of the last one will be with us for decades to come.