2006 Seabed Survey For Particles Completed

7th September 2006

UKAEA has completed a three-month programme of offshore monitoring surveys to improve understanding of the location of irradiated fuel particles in off-shore sediments using a remotely-operated monitoring device.

The results are being compiled and a preliminary report has been sent to the Dounreay Particles Advisory Group and Scottish Environment Protection Agency.

The surveys were undertaken by a remotely-operated vehicle deployed from a surface vessel, developed and operated by Fathoms, a Caithness-based contractor, working with UKAEA. The system was shown during trials in 2005 to have a high particle detection efficiency when compared to divers who had previously undertaken manual surveys of the seabed.

Enhancements made to the system this year enabled improved estimates to be made of the particle activity and depth of burial, though without particle retrieval. The system operated wholly as intended, as demonstrated by the variety of sensor readings recorded.

The aims of the surveys were to test a computer model which predicted concentrations of particles in certain areas of the seabed, to survey in deeper water beyond the capability of divers and to find the northward edge of the main particle plume. The main plume, where the largest concentrations are found, extends a short distance westwards and a distance of 2km to the east of Dounreay.

During the 51 days of mapping, approximately 145,000 m2 of seabed was surveyed in eight targeted areas: Strathy Point, Melvich Bay, Red Point/Sandside Head, Dounreay, Crosskirk, Brims Ness, Thurso Bay and Dunnet Bay.

A total of sixteen buried particles were detected, with the higher activity particles being found in the main plume. The locations that particles were detected were: one at Red Point/Sandside, nine at the outer regions (seaward) of the main plume and six at East Brims.

Dr Joe Toole, UKAEA's particles monitoring manager, said: "The surveys did not provide any evidence of accumulations of particles off Strathy point, as had been predicted by the model, and no particles were detected off Melvich. The western-most particle was found near Red point/Sandside head close to Sandside Beach where particles of a similar activity have been found. There was some evidence of particle accumulation eastwards from the main plume, at Brims Ness, although they were not found in the region predicted by the model- they were closer inshore and at the low end of particle activity range."

"At the main plume area off Dounreay, surveys in deeper water showed a pattern of particle locations which is consistent with the edge of the plume being limited to the nearshore zone - no particles were found in any of the areas surveyed beyond the 30m water depth contour."

"Surveys in Thurso Bay and Dunnet Bay (16 km and 22 km respectively from Dounreay) did not detect any particles."

Phil Cartwright, UKAEA's Particles and Contaminated Land Department Manager, said "The data from the survey has certainly moved us forward. From the area covered - it would appear the extent of detectable particles in the marine environment is less than predicted by the computer model which is good news. We are reviewing all the data to ensure we make efficient use of this new information. We've sent a preliminary report to DPAG and SEPA and we'll ensure that all our findings are communicated to both bodies for their consideration."

"We are committed to finding the best practical environmental option for dealing with this legacy. The data gathered from these surveys is an important step forward in our understanding and will help to inform full public consultation on the options early next year."

Background Information
Particles were generated during the dismantling and preparation for reprocessing at Dounreay of spent nuclear fuel. There is evidence from the 1960s and 1970s of some of these particles entering the drainage systems at Dounreay and being discharged to sea.

Lower activity particles have been detected during routine monitoring of the beaches used by the public at Sandside and Dunnet. Other, higher activity particles have been detected on the foreshore at Dounreay and in the sediment offshore. Restrictions on fishing are in place in this area.

UKAEA is required to monitor a number of local beaches to criteria regulated by SEPA, when access is available to do so.

In March, SEPA published research into the potential health effects of particles typically found at Sandside. While there is potential for short-term visible effects to occur through skin contact, the chances of coming in to contact with a particle are extremely low.
See - http://www.sepa.org.uk/news/releases/view.asp?id=349&y=2006

UKAEA is carrying out a study to determine if there is a better option to reduce the risk from particles than the current strategy of monitoring beaches. Full public consultation on the options is scheduled for early 2007.
See Here