e-Digest Statistics about: Radioactivity
Radioactive Incident Monitoring Network (RIMNET)
Following the Chernobyl reactor accident in 1986, RIMNET, the nuclear radiation monitoring and nuclear emergency response system, was installed in 1988 to monitor the consequences for the UK of nuclear incidents abroad [20]. Radiation dose rate readings (gamma plus cosmic) from the 91 sites are collected every hour and checked by a Defra computer in London for any indication of abnormal increase. Any evidence of a nuclear incident of radiological significance for the UK would result in a national alert being raised.
The main factor influencing the observed radiation dose rate is the geology of the site. Higher levels are found in areas of igneous rocks, which have relatively high uranium and thorium contents, whilst lower levels are typical of clay and chalk areas. The pattern can be influenced by height above sea level for the cosmic component and climatic effects, for example heavy rain, can cause increased levels of gamma dose rate owing to the wash-out of radioactive daughter products from the decay of naturally occurring radon. the tables 'Average gamma radiation dose rate for Phase 2 RIMNET monitoring sites' show average radiation dose rates for 1997 to 2003 for the sites. Quarterly summaries are published on the Defra website [21]. Background radiation continues to be the main component of observed levels of gamma radiation recorded at RIMNET sites. The observed UK annual radiation dose rate ranges from around 0.5 mSv to 1.0 mSv with an average of less than 0.7 mSv. A different basis for the figures since 1997 compared to those published in previous years has been used; this more accurately reflects the dose an individual would obtain from 100 per cent occupancy of a RIMNET site.
Further Information:
- Key Facts:
- Sources
- Artificial sources: Fallout
- Natural sources: Radon, Gamma
Data Tables:
- References, further reading and links to other resources:
- [20] Department of the Environment (1989). The National Response Plan and Radioactive Incident and Monitoring Network (RIMNET): Phase 1. TSO.
- [21] Quarterly Average Gamma Radiation Dose Rates - Defra website
- Department for Environment Food and Rural Affairs (Defra): Response to radiological emergencies
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Page last modified: 15 June 2005
Page published: 10 September 2003