Electricity production from nuclear energy has only a short history; the first power station started producing commercially in Russia, when the Obninsk power plant was connected to the grid on June 26th 1954. As of May 2006 there were 443 nuclear power plants worldwide, according to the International Atomic Energy Agency (IAEA, 2006) and possibly one or two more since then. Currently, about 17% of the global energy supply comes from nuclear power.
There have only been three accidents that released sufficient amounts of radiation to be of concern to the public. That we know of. Small releases may not be as well publicized but they are still a danger. This is why.
The radioactive half life
When a lump of radioactive material is left to its own devices it decays and becomes another chemical element. Beryllium turns into boron, uranium turns into lead, eventually. During this decay the material is unstable, releasing energy in the form of radiation. The amount of time for the material to release half the radioactive energy it contains is called the half life. It is generally thought that the more dangerous radioactive materials are safe after 10 half-lives. This means that eventually the radioactive releases will decay and become safe. The trick is in defining the ‘eventually.’ Pure uranium-238 has a half life of 4.5 billion years, iodine-131 just 8 days.
The Chernobyl incident sent plumes of caesium-137 into the atmosphere, drifting across northern Europe to fall or be washed to the ground by rain. Caesium-137 has a half life of 30 years, and the fallout was sufficient to raise concern about livestock exposed to it. Only in 2010 were the last affected sheep farms in Scotland declared safe. The accident happened 24 years ago and 1300 miles away, and since then the farmers in affected areas have been unable to sell or even move their sheep without the animals being tested for elevated levels of radioactivity (Rawlinson and Hovenden, 2010). In regions that were closer and suffered greater exposure the risk will last far longer. The land extending for 19 miles around Chernobyl is still an exclusion zone.
Risk estimates
Estimating the risk from a nuclear accident is difficult and can only be modeled based on our current knowledge. Estimates of cancer cases arising from the Chernobyl accident offer a number of 36,000 extra cases of cancer by 2065, in addition to the 5,000 cases already attributed to the accident and fallout (Cardis et al, 2006). Is this a reliable estimate? We don’t know.
With such a long period of time before substances decay any accident which spreads radioactive material is only adding to current contamination, if it falls in the same area. The Japanese reactor at Fukushima is releasing Caesium-137 and Iodine-131, in amounts equivalent to approximately 70% of the Chernobyl release. Where will it fall and what effect will it have? We don’t know.
Future dangers
Nuclear power plants are certainly a lot safer than they were when the first were built, but this does not remove the risk totally. There is always a danger of catastrophic failure due to human error, or possibly terrorist or military action, but the risk factors associated with seismic events, flood or hurricane are being considered all the time. Every time a plant is reassessed other safety measures are considered and often implemented. What is the probability of future nuclear accidents? We just don’t know.
Sources
- IAEA, (2006) Nuclear Energy and the IAEA: Fostering the efficient and safe use of nuclear power.
- Cardis E, et al, (2006), Estimates of the cancer burden in Europe from radioactive fallout from the Chernobyl accident, International Journal of Cancer. Sep 15 2006.
- Rawlinson, K., and Hovenden. R., (2010), Scottish sheep farms finally free of Chernobyl fallout, The Independent, July 7 2010.
Sally Anne Lewis - Sally has master's degrees in science and journalism, is fascinated to a degree in most things. Always something to learn.
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