|
Radioactivity has always been a part of our environment. The substances in the world around us all contain unstable atoms that emit energy as radiation when they decay to more stable atoms. Such radioactive atoms are also called radionuclides. The air that we breathe, the water we drink, the food we eat, and our own bodies all contain radionuclides. Many radionuclides were formed long before our own solar system came into existence, while some are continually being created in the Earth’s atmosphere by the action of cosmic rays.
Around 85 per cent of our average annual radiation dose comes from natural sources, with 14 per cent from medical procedures. The remaining 1% comes from a combination of man-made sources, e.g. weapons test fallout, Chernobyl fallout and radioactive discharges.
SEPA’s main responsibility is to ensure that public exposure to sources of radioactivity in food and the environment from authorised discharges (e.g. from nuclear power stations) does not go above international limits.
SEPA is not responsible for public exposure to radiation from natural sources or medical treatment.
SEPA’s approach to this is two-fold:
- we monitor levels of radioactivity in food and the environment
- we identify people who are most likely to come into contact with radioactivity from discharges.
For more information, see:
Regulation
Sources of radiation to members of the public from nuclear sites are regulated. There are three main sources:
- discharges to water
- discharges to air, and
- direct radiation.
SEPA regulates discharges to water and air, under the Radioactive Substances Act 1993. We aim to protect the environment and the public, by encouraging users to minimise the production of radioactive waste, and by setting limits on the quantities of radionuclides that may be discharged from authorised premises.
The Health and Safety Executive regulates sources of direct radiation. It is also responsible for the exposure of workers to radiation (e.g. staff at nuclear power stations).
The Food Standards Agency is responsible for protecting the public from radioactivity in food.
SEPA works closely with all of these organisations to protect the public.
Doses
When living tissue is exposed to ionising radiation, it will absorb some of the radiation’s energy and may become damaged. The amount of radiation energy absorbed by the body is measured in terms of a quantity called effective dose. This quantity takes into account the effects of different types of radiation and the sensitivities of different organs and tissues.
Effective dose is often referred to simply as dose. The unit of effective dose is the sievert (Sv). One sievert is actually a large quantity, and doses are often reported in units of thousandths of a sievert, or millisieverts (mSv). The average dose to members of the public from all sources of radioactivity is estimated by the National Radiological Protection Board to be 2.6 mSv per year. Exposure to natural radioactivity accounts for 85 per cent of the total dose and medical procedures account for 14 per cent. Doses due to discharges from nuclear sites contribute less than 0.1 percent.
It is important to remember that this is an average exposure. Individual doses may differ widely from the average depending upon many factors such as age, diet, the area lived in, occupation and medical history.
A dose limit of 1 millisievert each year is embodied in UK law. This limit does not include exposure to accidental releases, naturally occurring radiation or medical exposure. It is SEPA’s duty to make sure that the public is protected to this standard.
A sievert is a measure of radiation dose. A millisievert is one thousandth of a sievert.
Environmental monitoring
SEPA arranges for more than 1000 samples to be taken from around Scotland every year. The particular materials sampled are chosen for several reasons:
- they may be eaten or used in food preparation for humans
- they may be used in agriculture
- they may be a good indicator of radiation in the environment.
The results are published in an annual study known as the RIFE report and you can view copies here.
The programme focuses on areas where concentrations of man-made radioactivity may be elevated by discharges from sites both within and beyond Scotland’s borders. SEPA pays special attention to the areas around the following nuclear sites:
- Chapelcross, Hunterston, and Torness nuclear power stations
- Dounreay nuclear research facility
- Holy Loch (now closed) and Faslane submarine bases and the naval dockyards at Rosyth.
Monitoring is also carried out along the Dumfries and Galloway coastline and in the Solway Firth, to assess the effects of radioactive waste discharges from BNFL Sellafield nuclear fuel reprocessing plant into the Irish Sea.
SEPA also requires all major sites to carry out comprehensive monitoring programmes locally. These results are held by the sites but are available for SEPA to audit. The sites are required to notify SEPA of any abnormal results.
Critical groups
To protect the public from radiation, SEPA and other organisations use ‘critical groups’. A critical group is a group of people who are likely to receive the highest radiation dose from a site because of where they live and what they do.
For example, someone living near a nuclear site who eats local shellfish may be part of a critical group. In other words, those people who are most likely to receive the highest radiation dose of any member of the public.
SEPA assesses the dose received by the critical group and compares it with statutory dose limits. If the dose to the critical group is within statutory limits, it follows that the doses to other members of the public will also be within these limits.
In order to find out which people are in a critical group SEPA pays for research to be carried out. This research is known as a habits survey and covers most, if not all, of the following factors:
- angling, commercial fishing (netting and creeling) and mollusc collection
- production, use and destination of local produce
- types, seasonality and consumption of local wild foods
- land use and soil types
- occupancy near the site
- local food consumption rates
- extraordinary practices.
SEPA’s researchers use a range of techniques to investigate these factors:
- interviewing local residents, farmers, gardeners etc
- interviewing food retailers, fishery managers etc
- observing habits at particular locations (eg beach use)
- taking measurements of radioactivity.
SEPA staff also have a direct input into this process by using their knowledge about the locality and the sites they regulate.
Environmental Radioactivity Monitoring Task Team (ERMTT)
Monitoring for environmental radioactivity by the environmental regulator and the Food Standards Agency in Scotland takes a different approach than that in England & Wales. It is the desire of Scottish Ministers’ to have a ‘one-stop shop’ in Scotland for monitoring of environmental (anthropogenic) radioactivity. To this end ERMTT was formed to allow all agencies to work in partnership to ensure that the environment and public are adequately protected from authorised radioactive discharges. The ERMTT is the national forum that brings together the technical expertise and relevant authorities to assess issues of environmental radioactivity. In undertaking co-ordinated working, efficiencies of scale can be developed.
Membership
ERMTT consists of representation from SEPA’s Radioactive Substances Policy Unit, SEPA’s Radioactive Substances Regulatory Group, SEPA’s Science Directorate, the Food Standards Agency, the Scottish Executive, the Health Protection Agency and Scottish Natural Heritage. Representatives may be invited from other organisations as the ERMTT deem necessary.
Role
ERMTT has oversight of the monitoring programme for radioactivity undertaken in Scotland by SEPA on behalf of the Agency, Scottish Ministers and the Food Standards Agency. The Group also peer review specific assessments and ensure that monitoring programmes for radioactivity are ‘fit for purpose’.
Terms of Reference
The terms of reference for the group can be viewed – here (13k pdf)
Minutes of Meetings
Radiological Monitoring Standards Working Group
Status
This group is a sub-group of the Nuclear Industry Liaison Group. NILG is a discussion group between nuclear site operators and the UK’s environment agencies.
Objective
To develop and promote Best Practicable Means in radiological monitoring of the environment, including releases to air, land and water.
Terms of Reference of Working Group
- To review the adequacy of radiological monitoring.
- To identify which types of existing and future radiological monitoring will benefit the most from the development of technical standards (e.g. MCERTS) and guidance; and to prioritise their development.
- To identify the most appropriate means for improving the adequacy of radiological monitoring (for example, standards or guidance).
- To develop and maintain links with other relevant national and international groups (e.g. National Dose Assessment Working Group, Safegrounds, Small Users Liaison Group etc.).
- To co-ordinate the review of new and revised radiological monitoring standards and guidance.
- To promote the adoption of radiological monitoring best practice by instrument manufacturers, regulators and the nuclear sector.
- To co-ordinate research and development of appropriate radiological monitoring techniques.
Minutes of the second meeting held on 12 Jan 08 at Manchester Airport can be found here
The work programme for Radiological Monitoring Standards Working Group can be found here
|
