The second of two operators to win demonstration contracts from site contractor UKAEA is in the midst of testing out its system.

Merseyside firm Land and Marine Project Engineering Ltd is waiting for a break in the weather to put its bespoke remote-control operation through its paces on the seabed within a kilometre of the defunct fast-reactor complex.

It is to work in an area polluted by the most active hot-spots to leach from the plant as a result of historic unauthorised discharges.

Rival firm Fathoms, which has a base in Wick, successfully deployed its system in December.

The object of the exercise for the UKAEA is to have confidence in a set-up to do the job for real in the summer.

Land and Marine is working as part of a consortium with Cheshire-based Nukem Ltd, one of the biggest contractors at the site.

A 30-metre-long surface vessel and support craft arrived at Scrabster at the weekend, with the detection-and-recovery device being launched into the waters off the port on Monday.

Land and Marine aims to carry out three full days of trials in the seabed off Dounreay by the end of next week.

Once the second trial is completed, the UKAEA will evaluate both systems before awarding one or more contracts for the clean-up.

Earlier this year the UKAEA firmed up its preferred option of seeking out and recovering the higher-active particles on the seabed. The target zone is a 60-hectare tract near the disused subsea diffuser, which is the suspected source of the contamination.

It is thought the area could contain about 2500 of the higher-active particles, which experts say pose a danger.

With an activity level of one million becquerels (Bq) or more, they are judged significant. Those over 100,000 Bq are classed as relevant and those under that level deemed minor.

Phil Cartwright, particles and land contamination manager, said yesterday: "Seabed mapping surveys have, since 2004, improved our understanding of the extent of the particle population.

"The results of these surveys indicate a limited spread of significant particles and a wider, more diffuse spread of relevant and minor particles to the west into Sandside Bay and eastwards to Brims. Taken together with the information from years of beach monitoring and diver surveys, the contaminated area offshore is now reasonably well understood and has allowed us to initially target a specific area for particle recovery."

The UKAEA's clean-up plan is awaiting the go-ahead from the Scottish Environment Protection Agency, the Nuclear Decommissioning Authority and the Scottish Government. The seven-year programme, which includes the ongoing monitoring of public beaches, has a £18 million to £25m price tag.

Mr Cartwright said the programme will be kept under constant review. He again underlined that the UKAEA has ruled out recapturing all the hundreds of thousands of particles of reprocessed reactor fuel which have ended up in the Pentland Firth. He said: "We recognise that detection and recovery of all particles on the seabed will not be possible. But targeting the area where the highest-activity particles reside, the risk of relevant particles arriving onshore will be much reduced."

The offshore survey carried out by Fathoms on behalf of the UKAEA last summer tracked down 26 particles – none in the significant category – between the old diffuser outfall and Sandside Bay.

This has led the UKAEA to believe that between 400 and 500 particles are "in transit" to Sandside.

Mr Cartwright said: "These could gradually arrive over many years and show the importance of continuing the beach monitoring programme."

iain-grant@ukf.net

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