e-Digest Statistics about: Radioactivity
Artificial Sources of Radiation
Exposures from atmospheric effluents
Air contains naturally radioactive species such as ³H, 7Be and 14C produced by cosmic rays. However, traces of artificial species can also be detected from atmospheric discharges. The major part, in terms of radioactive content, of atmospheric discharges from the major nuclear sites consists of ³H and the chemically inert gases argon-41 (41Ar) and krypton-85 (85Kr).
Trends in atmospheric discharges from nuclear installations are given in table Annual emissions of radioactive atmospheric discharges by site. These often reflect plant throughput and reactor operation and should be interpreted with great care since the amount of radioactivity discharged is not necessarily the best guide to its radiological significance. There are differences in the half-lives and radio-toxicities of individual radionuclides. In particular, the large discharges of ³H and inert gases such as 85Kr make a negligible contribution to the radiation exposure of the local population although slightly increasing global doses. Authorised numerical limits to the levels of radioactivity in atmospheric discharges apply to nuclear establishments (see footnotes to the table). All discharges of radioactive wastes to the atmosphere in 2000 and 2001 were within permitted limits.
The Key Fact 'Discharges for the nuclear industry' shows total discharges since 1983 to air, for the sites listed in the table 'Annual emissions of radioactive atmospheric discharges by site', and also to water, for the sites listed in the table 'Annual emissions of radioactive liquid discharges by site'. As different radionuclides have different toxicities, the discharge data have been weighted, using discharges of 137Cs as the baseline, to take account of the relative toxicities. These totals have been indexed, with 1985 as the base year. This shows that discharges have reduced over this period.
Food consumption is a major pathway leading to radiation exposure from radioactive atmospheric discharges. Diet, location, daily habits and age are some of the factors that affect actual doses to individuals. Amongst the items regularly sampled is milk because of its importance in the diet of children and babies, and also because cows graze large areas of pasture each day. Pasture is an efficient collector of atmospheric contaminants resulting from deposition because of its large surface area relative to its mass. The table 'Annual average concentrations of strontium-90 and caesium-137 in milk' shows annual average concentrations of 90Sr and 137Cs in milk sampled from farms around Sellafield, Dounreay, Harwell and Winfrith by site operators. The deposition of radionuclides from the Chernobyl reactor incident caused a sharp rise in concentrations of 137Cs in 1986 and 1987, but concentrations fell considerably thereafter.
Doses to critical groups (people living in the vicinity of nuclear installations) from atmospheric discharges in the UK, except Scotland, are derived by the Terrestrial Radioactivity Monitoring Programme (TRAMP). Results from this Ministry of Agriculture, Fisheries and Food (MAFF) programme were combined with those from MAFF's Aquatic Environmental Monitoring Programme for the marine environment in an annual report, first produced in 1995, "Radioactivity in Food and the Environment" [18]. Prior to 1995 results from TRAMP and from the Aquatic Environmental Monitoring Programme were published separately. For the 1996 RIFE report and subsequently, the results of all environmental monitoring for radioactivity carried out on behalf of the Scottish Environment Protection Agency, the regulatory authority in Scotland, were added. In April 2000 the Food Standards Agency (FSA) was set up and it has taken over MAFF's (now Defra) responsibilities to report radioactivity levels in foodstuffs and associated doses. The table 'Estimates of public radiation exposure of critical group due to aerial discharges' shows recent trends in critical group doses resulting from atmospheric discharges from particular groups of sites. The critical group doses shown in the table 'Estimates of public radiation exposure of critical group due to aerial discharges' have been derived from radioactivity concentrations in samples of milk and terrestrial foodstuffs collected at or near nuclear installations. The types of foodstuffs sampled are chosen on a site-to-site basis to reflect local availability. Details of the critical groups, the pathways through which they are exposed and the levels of exposure of such groups to aerial discharges of radioactive waste from nuclear sites are given in the table 'Exposure of members of the public from atmospheric discharges of radioactive waste'. Discharges from more than one site may contribute to the exposure of the critical group and thus the levels of exposure given in the tables may, in some cases, include a contribution from more than one site. The analysis of samples in food show that radionuclide concentrations and radiation dose rates as a result of atmospheric discharges in 2001 were generally similar to those in 2000 and 1999.
In Detail:
Exposure to the publicFurther Information:
- Key Facts:
- Sources
- Artificial sources:
- Occupational radiation
- Medical
- Fallout
- Products
- Direct shine
- Discharges
Data Tables:
- References, further reading and links to other resources:
- [18] Food Standards Agency, Scottish Environment Protection Agency (2002). Radioactivity in Food and the Environment, 2001. FSA/SEPA
- Amersham plc: Environment and social report - radioactivity
- Department for Environment Food and Rural Affairs (Defra): UK Strategy for radioactive discharges 2001-2010
- Internet Links:
- British Nuclear Fuels plc (BNFL)
- British Energy Generation
- Centre for Environment, Fisheries and Aquaculture Science (CEFAS)
- Food Standards Agency (FSA): Radioactivity in Food
- National Dose Assessments Working Group (NDAWG)
- OSPAR Commission (The Convention for the Protection of the Marine Environment of the North-East Atlantic)
- United Kingdom Atomic Energy Authority (UKAEA)
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Page last modified: 16 September 2003
Page published: 10 September 2003