DEVELOPMENT OF A HYDROGEN MANAGEMENT CONCEPT FOR THE CANADIAN SUPERCRITICAL WATER-COOLED REACTOR

Accidental hydrogen production in nuclear reactors has been a significant focus of nuclear reactor safety for decades. However, since the accident at Fukushima Daiichi nuclear generating station, hydrogen safety in nuclear reactors is a more relevant topic. As new reactor concepts, such as the supercritical water-cooled reactor (SCWR), are designed and developed the risk of unintentional hydrogen generation is not eliminated; however, it can be mitigated in the design. A systematic assessment of the hydrogen risk from both normal and accident conditions in the Canadian SCWR design was performed, in which various techniques to mitigate the hydrogen combustion potential were considered. While the rate of hydrogen generation under normal operating conditions was found to be low when held at supercritical water conditions, conservative estimates suggest that a significant quantity of hydrogen may be produced and released to the containment building in a severe accident. As a result, a hydrogen-oxygen management concept has been proposed to mitigate the hydrogen produced in a severe accident that includes a nitrogen-inerted containment building to reduce the combustion potential of hydrogen and the installation of passive autocatalytic recombiners for oxygen management. This hydrogen-oxygen management concept results in significant design changes and likely significant economic and operational impacts on the Canadian SCWR design.