Four US reactors achieved criticality this year, marking significant progress for emerging nuclear technologies amid climate concerns. However, the journey to supplying the grid is far from over.

The achievement is a positive sign, especially given the rapid speed at which these companies hit their milestones. Yet, running a reactor that can produce electricity is distinct from achieving criticality, involving substantial technical challenges such as adding cooling systems. Companies are projecting aggressive timelines but face potential regulatory hurdles.

While some nuclear supporters see this as an unhelpful diversion from increasing capacity, the success of these microreactors could set a precedent for more efficient and rapid deployment of new technologies in the US energy market. The challenge now lies in translating these milestones into practical, scalable solutions that address climate change while maintaining safety standards.

The Nuclear Regulatory Commission will play a crucial role in approving these reactors, with their approval process historically being slow. However, they have proposed a framework to streamline microreactor approvals, though its effectiveness remains to be seen.