Type of accident in nuclear power plant

Major accident - Major release of radioactive material with widespread health and environmental effects requiring implementation of planned and extended countermeasures.

 

Serious accident - Significant release of radioactive material likely to require implementation of planned countermeasures.

Accident with wider consequences - Limited release of radioactive material likely to require implementation of some planned countermeasures. It is also caused several deaths from radiation. For radiological barriers & control, severe damage to reactor core, release of large quantities of radioactive material within an installation with a high probability of significant public exposure. This could arise from a major critical accident or fire.

Accident with local consequences - Minor release of radioactive material unlikely to result in implementation of planned countermeasures other than local food controls. At least one death from radiation of this type of accident. Fuel melt or damage to fuel resulting in more than 0.1% release of core inventory. Release of significant quantities of radioactive material within an installation with a high probability of significant public exposure.

Incident - Exposure of a member of the public in excess of 10 mSv, exposure of a worker in excess of the statutory annual limits. Radiation levels in an operating area of more than 50 mSv/h. Significant contamination within the facility into an area not expected by design.

For an example, recently there was an accident happened at the Fukushima, Japan where the Reactor shutdown after the 2011 Sendai earthquake and tsunami; failure of emergency cooling caused an explosion.

Fukushima from air