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Hydrogen Management: Research and Development in Mitigation of Severe Accidents for CANDU Reactors in Canada

Abstract of the technical presentation presented at:
7th International Workshop on CANDU Safety Association for Sustainability (CANSAS‑2018)
October 15–18, 2018

Prepared by:
Samuel Gyepi-Garbrah
Canadian Nuclear Safety Commission


The Canadian Nuclear Safety Commission (CNSC) provides regulatory oversight of safe operation of CANDU nuclear power plants (NPPs) in Canada. One current issue that is drawing significant attention is the management, control and mitigation of hydrogen risk. In this view, the practical guidelines, as well as fundamental basic physical principles governing the phenomenon of hydrogen behaviour, are of particular attention to the CNSC.

An understanding of hydrogen generation and behaviour in CANDU NPPs is important to ensure greater robustness in case of a beyond-design-basis accidents (BDBA). During an accident, utilities use analytical models and tools to assess hydrogen behaviour, including its source term, dispersion, key combustion phenomena, and its impacts on containment integrity. Based on these assessments, and to ensure greater robustness during BDBAs and severe accidents, numerous mitigating strategies have been implemented. These strategies include:

  • mixing using local air coolers
  • removal by igniters
  • recombination by passive autocatalytic recombiners
  • active and passive filtered containment venting provisions 

The review of technologies available for mitigation is also essential in assessing risks posed by hydrogen during a severe accident. The CNSC’s collaborative and ongoing R&D efforts to improve understanding of hydrogen-carbon monoxide combustion challenges following severe accidents will be highlighted.

With a focus on CANDU NPPs, this presentation will address strategies for hydrogen management and reduction in containment. It will also discuss some future research and development of hydrogen safety challenges, based on a risk-informed decision-making approach.

Keywords: Hydrogen challenges, CANDU, research and development

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