Preparedness for a nuclear emergency, though it is generally rare, needs a proper framework for emergency response as well as proper implementation which for a nuclear power plant may be undertaken at the plant site and its nearby areas for public protection.

The on-site emergency plan focuses on the situation at the nuclear power reactor and its safety protection systems, including any necessary accident mitigation and recovery measures. Its implementation puts into consideration single initiating events both inside the plant such as the failure of plant equipment necessary for reactor safety, as well as outside the plant such as severe storms and floods. However, it often switches to a more holistic approach to consider the physical state of the reactor in implementing protective measures on increasing severity and complexity of the emergency. Plant management will declare the level of emergency according to the severity of a nuclear event, and the level selected will be updated according to the status of the event and communicated to various emergency organisations. Emergency readiness is maintained by regular training, possibly including the set-up of a severe nuclear accident on a simulator for operator training, and emergency exercises that may involve various organisations or departments of the owner utility to test plant operations, engineering support and logistics.

In parallel, the off-site emergency plan focuses on handling the events outside the nuclear power plant, particularly if and when radioactive substances are released from the plant to its exterior in substantial quantity. Particular attention is paid to the monitoring and forecasting of the change of radiation levels in the environment, and any necessary actions to protect the public from an increase in environmental radiation by close monitoring and control of food and water supply, intake of iodine to block the absorption of radioactive iodine by the public, evacuation of people adjacent to the nuclear power plant to avoid their excessive intake of radioactivity, and timely communication to the public for their information and necessary actions. The International Atomic Energy Agency and neighbouring states will also be informed of a nuclear accident in accordance with an established protocol. Emergency exercises are generally conducted at regional and national levels involving various government functions on a regular basis, typically once every several years. On a last note, the nature of the postulated nuclear event in the exercise should be sufficiently severe, so as to properly test key elements in the emergency plan.

This article is contributed by Ir Richard Fung with the coordination of the Nuclear Division