However this does not mean that accidents are impossible. When an accident does happen, there are many processes and guidelines that are followed to ensure that the people and surrounding areas are safe, i.e. that the danger is contained.
AMHYCO will contribute to this objective by improving the understanding of H2/CO combustion and incorporating this knowledge into SAMGs.
Severe Accident Management Guidelines
Some of these guidelines that are in place to help ensure safety in nuclear plants are called the Severe Accident Management Guidelines (SAMGs). These are a set of guidelines which provides recommendations to mitigate the consequences of beyond design basis accidents, including severe accidents. The SAMGs, which guide the reactor operators on how to handle the response of the nuclear power plant against severe accidents, are not set in stone and are in a living document that needs to be regularly updated and filled with knowledge gained from international efforts, including recent and ongoing research projects (you can read more about the EU’s efforts on nuclear safety here).
AMHYCO will help to update the SAMGs, contributing the expertise and data generated during the lifetime of the project.
Combustion in Severe Accidents
During a severe accident, a large amount of hydrogen gas (H2) can be produced from a process called “exothermal oxidation” of metallic components, e.g. fuel cladding or fuel assembly canisters, and released into the containment vessel.
If the core damage is not confined within the pressure vessel, further large releases of combustible gases will occur as a result of molten corium-concrete interaction (MCCI), where the melted core reacts with the concrete of the surrounding structure. The release of a gaseous mixture including carbon monoxide (CO), carbon dioxide (CO2), H2 and steam (H2O) will depend on the materials present, such as metals which can react to form these compounds. If the gases are not diffused and are concentrated heavily in one area this can lead to a combustion or explosion risk.
AMHYCO is the first project to deal with H2/H2O/CO heterogeneous mixtures under realistic containment conditions. AMHYCO will explore that unknown region to improve nuclear safety.