The 2011 Fukushima nuclear disaster was the most costly nuclear related incident since Chernobyl 25 years earlier. It was caused by a tsunami following the Tohoku earthquake, which disabled the emergency generators that were employed to cool the reactors. This insufficient cooling led to three nuclear meltdowns, hydrogen-air explosions and the release of radioactive materials.
Though there have been no fatalities linked to radiation due to the accident, the eventual number of cancer deaths, according to the linear no-threshold theory of radiation safety, that will be caused by the accident is expected to be around 130–640 people in the years and decades ahead.
It is estimated that around 600 tonnes of toxic fuel may have leaked out of the reactor during the incident. The cleaning up and decontamination operation at the site is still ongoing and due to the extremely hazardous nature of the site, robots are playing a key role - going into areas where humans cannot to clean up radioactive debris.
Any melted radioactive fuel on the site needs to be found and removed – a tough undertaking when it’s too dangerous for humans to go near the affected areas. The Tokyo Electric Power Company employed a Scorpion robot (so-called because it can lift up its camera mounted tail to achieve better viewing angles), to film the wreckage in Unit 2 at the plant before its cameras were damaged by record levels of radiation.
The 60cm long robot is made by Toshiba and equipped with two cameras and sensors to gauge radiation levels and temperatures.
Unit 3 is flooded with coolant to a depth of about six metres. As such a submersible Mini Sunfish robot was used, developed by Japan-based International Research Institute for Nuclear Decommissioning (IRID), which managing to identify radioactive fuel at the unit in July. The device is equipped with two cameras and can be remotely controlled via a wire, while operators can record its progress via a video feed.
It may take 40 years and over £53bn for the area to be made safe.