Severe accident management

Nuclear power plant safety systems are designed to mitigate a range of abnormal operating conditions. In the unlikely case of a severe accident, plant operators use guidelines developed specifically for the purpose. The IAEA has a toolkit to help operators develop these guidelines and offers training to its Member States.

Nuclear power plants are equipped with multiple safety systems able to deal with a wide range of abnormal operating conditions. They also have well-proven emergency operating procedures that help operators achieve a stable and safe end state. However, the most severe circumstances can result in damage to the nuclear fuel and the containment structures, possibly leading to a release of radioactivity to the environment. Yet even in these events the consequences can still be mitigated using available and, in some cases, dedicated plant equipment.

To protect the public and the environment from the consequences of a nuclear power plant accident, each plant operator establishes a severe accident management programme, which is kept under constant review and development. The main objective of the guidelines used to design such programmes is to utilize any available equipment at the nuclear power plant to terminate core damage, maintain containment integrity and minimize the release of radioactivity from the site.

The severe accident management guidelines naturally vary according to plant design, local regulations and the site’s characteristics. The IAEA has developed a toolkit to help operators develop their own guidelines and offers its Member States modular training programmes in this area.

Although they are unlikely to be needed, severe accident management programmes are a critical part of the Defence in Depth concept, which is a hierarchical deployment of different levels of equipment and procedures in a graded approach to protect against a wide variety of incidents, accidents, equipment failures, human errors and events initiated outside the plant. In general, severe accident management programmes are designed to:

  • evaluate generically the capability of existing plants to tolerate a severe accident;
  • identify events that can lead to severe accidents and formulate preventive and mitigation strategies; and
  • identify short-term and long-term measures for handling severe accidents.

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