Radioactive Incident Monitoring Network at a central computer based in a DEFRA building in central London. For security reasons, a backup computer is also in operation at a secret location in the UK. The network was set up in 1988 as a response to the Chernobyl disaster in 1986. As well as being of use in an emergency, the stations also serve to record historical data on radiation levels. Radioactive Incident Monitoring Network The Radioactive Incident Monitoring Network (RIMNET) is a network of 91 monitoring stations, used by the Government of the United Kingdom, which records and analyses the level of radioactivity across the
Caesium-137 limits, but some areas that are currently less than 5 mSv/year may be decontaminated, allowing 22,000 residents to return. Caesium-137 in the environment is substantially anthropogenic (human-made). Caesium-137 is produced from the nuclear fission of plutonium and uranium, and decays into barium-137. Before the construction of the first artificial nuclear reactor in late 1942 (the Chicago Pile-1), caesium-137 had not occurred on Earth in significant amounts for about 1.7 billion years. By observing the characteristic gamma rays emitted by this isotope, one can determine whether the contents of a given sealed container were made before or after the first atomic