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Caithness News Bulletins March 2005
|February 2005||January 2005 Index|
|Dounreay News||Dounreay Web Site|
DUNNET BEACH Update On Contaminated
UKAEA Will Assist Highland Council To
Remove Storm Rubbish At Dunnet
‘NEW’ COURT CASE
UKAEA Briefing Note
The object was found in a bundle of
seaweed and other detritus and the location of the find is marked on the
enclosed maps. The object is not a Particle, which are fragments of
metallic irradiated nuclear fuel. Preliminary analysis of the find at
UKAEA’s particle analysis laboratory on the Dounreay site showed
Caesium-137 to be present at around 20,000 Bq and suggested the presence
of a minor isotope Niobium-94.This level of Caesium-137 is equivalent to
that contained in the least active Particles found
Further non-destructive tests have been carried out, as agreed with SEPA, who have formally used their pollution control powers to take possession of this find. A longer count of the find in UKAEA’s low-level environmental laboratory confirmed the initial Caesium-137 result (2nd result 23,000 ± 2,600 Bq) and confirmed the presence of tiny traces of Niobium-94 (1.2 ± 0.3 Bq) and of Americium-241 (3.4 ± 0.6 Bq). The activity levels of these two minor isotopes, relative to the Caesium-137 present, are a factor of between about ten to one hundred times lower than typically found for DFR-derived material and on this basis does not match the signature for DFR particles from Dounreay.
Further examination of the object by a qualified geologist has indicated the find is made up of quartz and feldspar, both naturally occurring minerals. The object is fragile and appears to have been damaged by corrosion of some sort. These minerals are found in outcropping rocks in the Melvich area but not around Dunnet or the Dounreay site. The mechanism by which this object was transported to Dunnet beach is not yet clear but it may be related to flotsam driven ashore during storms in January 2005.
Caesium-137 is widely found in the environment as a result of fallout from weapons testing, the Chernobyl accident and discharges made under authorisation from the nuclear industry. Tests carried out so far by UKAEA would discount the activity arising on this object as being related to the Chernobyl accident. Caesium-137 is also used widely in sealed radioactive sources, which have many industrial uses. At present it is not possible to determine the source of the contamination on this object.
Further destructive testing of this object can only be carried out with the permission of SEPA and are likely to have to take place at a specialist laboratory given the nature and fragility of the find. Surveys of Dunnet beach will continue during 2005 as shown on the enclosed indicative schedule. The exact dates of surveying can be affected by operational and environmental factors and may not always match that scheduled.
From measurements of dose rates made on the find, it would have to remain in direct and static contact with the skin for about 1 day to deliver the skin dose limit for a member of the public of 50 mSv/yr. Contact would have to persist for about 1 month to present any visible skin effects.
A visual inspection of the seaweed and other material found in association has been undertaken and found:
The package of this flotsam type detritus has now been collected by SEPA. The package contents were checked with a heath physics probe in trays and no counts above background were identified. This detritus does not contain any radioactive particles.