At the Nuclear Energy Insider SMR Conference in Columbia, S.C., Dr. Jose Reyes, a co-founder and the Chief Technology Officer of NuScale Power, announced that his team had achieved an impressive design breakthrough.
Two years after the Fukushima event, NuScale is introducing a safety system for our nuclear reactor that does not require DC batteries to place the plant in a safe cool-down condition following an extreme event. This is a revolutionary solution to one of the biggest technical challenges for the current fleet of nuclear energy facilities. Because of our unique design, it allows the NuScale plant to achieve a ‘Triple Crown’ for nuclear plant safety—to safely shut down and self-cool, indefinitely, with no operator action, no AC or DC Power and no additional water.
He and his team approached the design problem from a somewhat unconventional direction. They determined the system configuration required to provide long-term passive cooling of the plant and then selected valves designed to mechanically realign to that configuration during a loss of power event. In design-speak, the valves either “failed shut” or “failed open”, depending on their position in the system. This requirements-driven design process success was made possible because the system has been conceived from the ground up to have as few valves and active components as possible.
For example, the 45 MWe NuScale reactor modules do not use any pumps during power operations; the coolant flow required to move heat from the reactor core to the steam generator is driven solely by natural circulation. Here is how Dr. Reyes describes the design that has resulted from his passive safety-focused approach.
This innovation required taking a look at the station blackout problem in reverse. Rather than requiring power to put the plant in a safe configuration following a station blackout, our engineers found it much simpler and safer to design the ECCS and supporting systems for failsafe operation. That is, the safety valves align in their safest configuration on loss of all plant power. This only works because of the few number of components involved and the fact that the safety systems themselves do not require electrical power to work.