Can a nuclear reactor cool itself without a single drop of electricity?

Technology · Published 18 October 2026 Swipe more like this →

In short: Most nuclear plants rely on massive electrical pumps to prevent overheating. But the BWRX-300 is designed to do the opposite. By leveraging the physics of natural circulation, it aims to maintain safety even if all external power fails, potentially redefining the economics of carbon-free energy.

The BWRX-300 is a small modular reactor (SMR) designed by GE Vernova Hitachi Nuclear Energy to produce up to 300 MW of electricity. Unlike traditional large-scale reactors, its primary innovation lies in its 'passive safety' architecture. This means that in extreme circumstances, the system does not require human intervention or external power sources to remain in a safe state. A key mechanism for this is the use of natural circulation to move water through the core, a departure from the active cooling systems—which rely on powered pumps—used in most conventional plants.

Drawing on parts from the active Advanced Boiling Water Reactor (ABWR), this layout represents a development of the Economic Simplified Boiling Water Reactor (ESBWR). The engineering logic is driven by the physics of decay heat: immediately after a reactor shuts down, about 7% of its previous operating power is still generated by the decay of short-half-life fission products. Because the BWRX-300 uses a medium pressure steam-water cycle where water circulates naturally, it can manage this heat more simply and economically than reactors not built for such a mechanism.

The technology is currently seeing global interest with a design lifetime of 60 years. Major projects are underway, including a selection by Ontario Power Generation for the Darlington Nuclear Generating Station and a potential deployment in Saskatchewan by the mid-2030s. In Europe, plans range from a 2029 delivery date in Poland to potential deployments in Sweden, Hungary, and Estonia. While the first unit is expected to cost less than $1 billion, specific project forecasts vary, such as a Canadian investment of $7.7 billion for a single unit at the Darlington site.

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