ENVIRONMENTAL RADIOACTIVITY MONITORING

DML carries out regular surveys of radioactivity in the environment in accordance with the requirements of its Authorisation for the discharge of radioactive waste, which was issued by the Environment Agency and came into force in March 2002.

Monitoring for radioactivity in the marine environment is carried out at various locations along the banks of the Rivers Tamar, Lyner, Tavy and Plym. Measurements are made of environmental gamma dose rates and samples are taken of the sediment along the low waterline, and of seaweed, mussels and river water at various points. The monitoring points and arrangements for monitoring, sampling and analysis have been agreed with the Environment Agency.

DML's marine environmental radioactivity monitoring and sampling programme is carried out quarterly in January, April, July and October every year. On each occasion the survey takes place over two days and includes four points on each side of the Hamoaze. Additional points at Calstock, Bovisand Bay, the top of the River Lyner (at St. Germans) and the River Plym are included in the July survey. Samples of fish are also taken in July. The results from these quarterly surveys are forwarded to the Environment Agency and the Food Standards Agency.

In 2002, DML's environmental radiation monitoring regime was further developed to include an airborne radioactivity monitoring programme. This involves the sampling of air, using a High Volume Air Sampler (HVAS) and the collection, sampling and analysis of rainwater.

All the results obtained from the marine and airborne radioactivity monitoring programmes are included in DML's Annual Environmental Radioactivity Monitoring Report, the most recent one of which (2004) can be accessed via the link to the left of this page. The Annual Report is sent to a number of organisations including the regulator and the local authorities, which place a copy on the Public Register.
The Ministry of Defence's Dstl Radiological Protection Services (DRPS) carries out similar annual surveys at all nuclear submarine berths. Its Devonport and Plymouth area survey is carried out in conjunction with DML. Results from this joint survey are published annually by DML, and by MoD through Her Majesty's Stationary Office (HMSO).

Government Agencies (including The Environment Agencyy and the Centre for Environment Fisheries and Aquaculture Science (CEFAS) on behalf of the Food Standards Agency) and Local Authorities carry out surveys of radioactivity in the environment across the country, including the area around Plymouth. These results are also published once a year and are consistent with the results published by DML.

To facilitate comparison of the various surveys carried out in the Plymouth area, results from the Local Authority, Environment Agency/Food Standards Agency/CEFAS, MoD's DRPS and DML surveys can be seen by following the links on the left of this page. These pages are shown with kind permission of the respective authors and publishers, and are taken from the published reports for 2004. These will be updated for 2005 when all of the reports are available for that year. Some differences between the results are to be expected because of the statistical uncertainties inherent in the measurement of radioactivity at the low levels present in the environment.

The results of DML's marine environmental monitoring programme, and the other surveys mentioned above, demonstrate that the impact of radioactive liquid discharges from the dockyard on the local marine environment is so low that its contribution to the natural background radiation dose rate is indistinguishable. DML therefore has to assess the impact using theoretical models into which data from radiochemical analysis of the samples collected during the quarterly surveys is used. For the year 2005 the dose to the most exposed members of the public (usually referred to as the 'critical group') as a result of DML's discharges was assessed to be no greater than 0.002 mSv. This dose is well below the statutory limit and constraints for members of the public and is over 1300 times less than the UK average background radiation dose of 2.6 mSv per year.