The choice between high- and low-enriched uranium submarines will shape Australia’s nuclear security, waste and non-proliferation obligations for generations.

The trilateral AUKUS agreement commits Australia to acquiring a fleet of nuclear-powered attack submarines. While public discourse focuses heavily on sovereign risk, capability, cost and delivery timelines, a fundamental technological choice about uranium carries profound lifecycle, industrial and non-proliferation consequences.

The choice is between a Low-Enriched Uranium (LEU) planned-intervention design, such as the French K15 reactor (or the South Korean reactor development, as required by the US) and a High-Enriched Uranium (HEU) sealed reactor system, like the US Navy’s S9G installed in the Virginia Class stop-gap submarines and the baseline chosen for SSN AUKUS. The decision dictates not only how a submarine is maintained but how a nation must ultimately dispose of the uranium.

As Australia navigates this commitment, we must prudently evaluate an AUKUS Plan B – acquiring the French Suffren-class, an existing, operationally proven nuclear-powered submarine that is already at sea. In contrast to the yet-to-be-designed SSN AUKUS and its yet-to-be-proven PWR3 reactor, the _Suffre_n offers a compelling alternative. It is approximately half the size, requires a smaller crew, is significantly cheaper to build and own. Beneath these platform differences lies an even deeper reality regarding reactor design and fuel selection. There is far more than meets the eye when comparing LEU and HEU systems, particularly how they shape our long-term responsibilities as a sovereign nuclear steward.

The operational and structural characteristics of a naval nuclear reactor are governed by the enrichment level of its fuel. The French K15 reactor, which powers the Suffren-class, operates on LEU enriched to less than 6 per cent Uranium-235. This lower enrichment level means the core must be opened and refuelled approximately every 10 years. To facilitate........

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