An important objective of the NIRMG Scheme is to provide background information for Northern Ireland over a period of time so that any fluctuations in the radioactive content of environmental materials derived from man-made sources can quickly be identified. The proximity to the Sellafield nuclear reactors and nuclear reprocessing plant highlights the need for continuing monitoring as this is the greatest source of radioactivity concerning Northern Ireland.

Radioactivity measurements involve a detailed radiochemical analysis of environmental samples collected by the participating local authorities for a wide range of alpha, beta and gamma emitting isotopes. Many sample types are examined and this approach provides information on most man-made radioactive elements that exist in any given sample and gives a good indication of the nature and magnitude of environmentally significant radioactivity.