Accident analysis and management focusses on understanding the causes and consequences of an accident at a nuclear facility, and on how to manage an accident through prevention and mitigation.
Since the inception of the use of nuclear technology for producing power, there has been a strong interest in ensuring a high level of nuclear safety. This interest is partly met through international co-operation on analysis and management of accidents. Co-operation at the NEA on accidents started in the 1960s under the Committee on Reactor Safety Technology (CREST) which later became the current Committee on the Safety of Nuclear Installations (CSNI). Today, co-operation on accidents is still a major focus for the CSNI and is led by the committee’s Working Group on Analysis and Management of Accidents (WGAMA).
There are two main areas of research pursued by WGAMA. The first is thermal hydraulics – the behaviour of a reactor’s cooling system. The reactor cooling system is fundamental to nuclear safety. Loss of cooling is one of the main causes of an accident, and maintaining cooling for nuclear fuel is a primary method for preventing or mitigating an accident. The second area of research is severe accidents – the study of the various phenomena that can occur when there is an accident that leads to damage to the nuclear fuel and release of radioactive material. Since the accident at the Three Mile Island reactor in 1979, there has been extensive research into severe accidents and how to mitigate their consequences. The more recent accident at the Fukushima Daiichi nuclear power station in 2011 has again raised the interest in severe accident behaviour, particularly for highly damaged reactor cores and containment systems.
The more recent accident at the Fukushima Daiichi nuclear power station in 2011 has again raised the interest in severe accident behaviour, particularly for highly damaged reactor cores and containment systems.
The Working Group on the Analysis and Management of Accidents (WGAMA) is responsible for activities related to potential accidental situations in nuclear power plants, including the following technical areas: reactor coolant system thermal-hydraulics; design-basis accidents; pre-core melt conditions and progression of accidents and in-vessel phenomena; coolability of over-heated cores; ex-vessel corium interaction with coolant and structures; in-containment combustible gas generation, distribution and potential combustion; physical-chemical behaviour of radioactive species in the primary circuit and the containment; and source term. The activities mainly focus on existing reactors, but also have application for some advanced reactor designs. Priority setting is based on established CSNI criteria and in particular on safety significance and risk and uncertainty considerations.