[Guardian] They look like grotesque open-air swimming pools – and they contain some of the UK’s biggest problems regarding nuclear waste.Built 50 years ago at Sellafield, the “ponds” were part of the cooling process on the nuclear bomb development programme and then the Magnox reactors, built in the 1960s, to generate electricity.

After the UK moved to better reactor technology, these ponds – two uncovered, one covered – were half forgotten. Records were mislaid and even birds flying overhead would add their contribution to the 100 metre long, 20 metre deep, 40 metre wide constructions.

But lurking in the water (officially described as “sludge”) are vast quantities of old machinery and equipment from the reactors – such as the Magnox cladding.

Now, however, the ponds – these three and another three closed pools which were built to better standards more recently – are top of the Nuclear Decommissioning Agency’s (NDA) agenda.

The NDA is spending a third of its £1bn budget this year on Sellafield, including work on the ponds and an assessment of how much they have leaked their radioactive contents into the soil around them.

The costs of processing the waste could well be greater than was first imagined – especially since the scale of the problem and how much land is contaminated is not known. For instance, the NDA recently increased its cost projections for cleaning up the UK’s nuclear total legacy by 12% to £63bn.

The NDA’s duties at Sellafield are deemed so important that they were spelled out in the Energy Act 2004 – and must be completed by April 2007. more