The Nuclear Decommissioning Authority

Despite high levels of radioactivity, Sellafield's open-air spent fuel ponds appear to be a welcoming environment for a surprising range of micro-organisms that inhabit and sporadically cloud the water, reducing visibility and hampering retrieval operations.

Years ago, it was thought that such environments would be sterile but there is now intense interest in understanding the precise nature of the pond life, and how, ultimately, measures can be developed to inhibit its growth.

Doctoral research student Victoria Evans has spent six months at the National Nuclear Laboratory (NNL) on the Sellafield site, examining the DNA of microbes extracted from water in three of the oldest open-air ponds.

"The ponds are an extreme environment but they are teeming with bug life, which doesn't need much to survive, however, it's difficult to devise measures for decontamination until you know exactly what is in there," said Victoria, whose first degree in Environmental Geosciences was followed by a Masters in Applied Environmental Geology, both at Cardiff University, where she became interested in the disposal of nuclear waste.

She is now studying for a PhD at Manchester University's School of Earth, Atmospheric and Environmental Sciences, co-supervised by Prof Jon Lloyd, who specialises in the microbiology of the nuclear fuel cycle, radiochemist Prof Katherine Morris, and algal biologist Dr David Sigee.

Her research forms part of the work being undertaken by students associated with a consortium of six universities collaborating on Decommissioning Immobilisation and Management of Nuclear Waste for Disposal (DIAMOND). The consortium is funded by the Engineering and Physical Sciences Research Council (EPSRC). Victoria's research at Sellafield is sponsored by the NDA's R&D programme, which has provided additional funding to the consortium to enhance its research and develop key technical skills essential to the delivery of the NDA decommissioning mission.

Victoria, from Bridgend, South Wales, has been studying three of Sellafield's open-air ponds, including the historic First Generation Magnox Fuel Storage Pond, which pose some of the site's greatest decommissioning challenges.

Organic material is deposited in the demineralised water from wind-blown agricultural residues, from the rain, the sea and overflying birds. Noticeable algal blooms tend to arise in the demineralised water between May and October, similar to the effect seen in lakes and ponds around the country, causing visibility issues.

Water samples are collected from the ponds on a regular basis but Victoria only needs the DNA from the microbes for her studies. She has been carrying out this extraction process at the NNL laboratories on the Sellafield site before sending the DNA to the University of Manchester labs, where she subjects the samples to detailed forensic analysis.

"The algal growth can generate sludge and our work will assist in identifying more precisely what species are present, and potentially supporting measures to control their growth," added Victoria.

Such detailed analysis of the microorganisms in the pond water has not been carried out previously and the results of the research may enable a better understanding of how organisms contend with radioactivity.

"One of the organisms we have identified is a close relative of a fresh-water algal species that usually collects in shallow pools ofwater, such as bird baths, turning the water slightly pink. The reddish pigment seems to be a defence mechanism against high ultra-violet intensity. It's unusual to find it in such deep water and we are at the early stages of exploring whether it could be linked to a protective mechanism against ionising radiation from spent fuel," said Victoria.

Her studies will continue for a further 18 months and the outcomes will be published, with the likelihood that it will stimulate further research into ponds decommissioning and clean-up.

Following completion of her PhD research, Victoria hopes to progress to post-doctoral research and, ultimately, a career in nuclear, focusing on public and political perception of the industry. Her Sellafield experience has already provided an insight into some of the major challenges facing the decommissioning sector.