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Australia will get nuclear-powered submarines. Some see a proliferation threat.

The U.S. has shared this type of technology before — with France, in fact.

French President Emmanuel Macron and Australian Prime Minister Malcolm Turnbull stand on the deck of HMAS Waller, a Collins-class submarine operated by the Royal Australian Navy, in Sydney in 2018. (Brendan Esposito/AFP)

The new AUKUS security partnership led to an immediate diplomatic fallout between France and the United States. But beyond the concerns about NATO and the Western alliance, or questions about great-power competition in the Pacific, some analysts see another worry: Will sharing nuclear submarine propulsion technology with Australia set back the nuclear nonproliferation regime?

What does this deal mean for nonproliferation? Have such transfers of nuclear submarine technology occurred in the past? Here are four things to know.

1. What does the deal involve?

The first major AUKUS initiative will help Australia acquire a conventionally armed submarine fleet that’s powered by nuclear reactors. The fleet will consist of at least eight such submarines and the final deal will be negotiated in the next 18 months. The submarines will be built in South Australia.

Australian Prime Minister Scott Morrison emphasized that “Australia is not seeking to acquire nuclear weapons or establish a civil nuclear capability.” Along with the submarines, Australia will buy a number of conventional long-range strike weapons like the Tomahawk missile, and other precision strike guided weapons systems through AUKUS.

2. What are the nuclear proliferation concerns?

According to President Biden, the nuclear technology transfer will occur in accordance to the verification standards and “in partnership and consultation” with the International Atomic Energy Agency. However, the specifics of this deal aren’t clear, leaving a number of big questions. Which parts of the submarine will be built in Australia? Will the U.K. and U.S. build the nuclear reactors for the submarines and then hand them over to Australia — or will Australia build the reactors from scratch? Most importantly, given that the U.S. and the U.K. submarine reactors use highly enriched weapons-grade uranium fuel, will this uranium enrichment take place in Australia?

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Some studies suggest that even with International Atomic Energy Agency stipulations, the system has a well-known loophole: Nonnuclear weapon countries can remove fissile material from the safeguards regime and use it in non-weapon-related military applications like fueling nuclear submarine reactors.

The presence of highly enriched uranium outside of the international safeguards regime could be a proliferation threat, as this material will have to be kept secure. However, the other side of the argument is that submarines with highly enriched uranium cores pose less of a proliferation risk. This is because the cores can last the lifetime of the submarine, and do not require any refueling. Furthermore, they can be sealed and delivered by the supplier nation and then taken back at the end of the submarine’s deployment for safe disposal.

The larger worry, perhaps, is that the AUKUS transaction will set a bad precedent for other transfers of nuclear submarines and nuclear reactors for naval propulsion. This possibility prompts fears of a proliferation cascade leading to similar deals for naval reactors between Russia and China, India and France, and Pakistan and China. Iran, too, is considering the use of highly enriched uranium for submarine propulsion.

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3. French Nuclear Forces enjoyed a similar arrangement

The transfer of sensitive naval propulsion technology from the United States to its allies has many precedents. Despite France’s outrage at the AUKUS submarine arrangement, the French nuclear submarine program was a prominent beneficiary of a similar arrangement with the United States.

Recently declassified documents reveal that in 1958, France approached the United States for help building its nuclear submarine. The U.S. supplied France with 440 kilograms of highly enriched uranium under a bilateral agreement between the two countries on the use of atomic energy for mutual defense. The transfer was under the condition that the uranium could only be used by France in a land-based installation. So the first French naval propulsion reactor (the Prototype à Terre, or PAT reactor) was a land-based one.

This reactor was key to France’s ability to build its first nuclear submarines, which were equipped with first-generation naval nuclear reactors identical to the PAT. Shortly after, France moved to a second generation of naval propulsion reactors that relied on low enriched uranium. In fact, the considerable U.S. assistance to the French nuclear program was key to France’s ability to build up its nuclear forces.

Similarly, the first British nuclear-powered submarine, the HMS Dreadnought — commissioned in 1963 — used a U.S. Westinghouse-designed submarine reactor.

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4. Is there reason to worry?

The main nonproliferation concern with the AUKUS deal is that it might spark off a proliferation cascade in which other countries transfer similar nuclear technology. For example, if Pakistan and Iran acquire naval reactors from other countries because of the precedent set by AUKUS, or if the deal leads to greater cooperation between Russia and China on naval nuclear propulsion, the goal of a safer, more secure, and stable Indo-Pacific may fail. From a nuclear security perspective, such a cascade also would be worrisome because the recipient nations could divert their nuclear materials toward the development of nuclear explosive devices.

Are the nonproliferation concerns from the AUKUS agreement being blown out of proportion, given the precedents? The United States provided both France and the U.K. with nuclear propulsion technology and nuclear materials throughout the Cold War without any loss of nuclear material — at least to public knowledge — or proliferation cascades of naval propulsion technology. Indeed, the United States’ constant creation of “exceptions” to the norms of nonproliferation, as these examples show, demonstrate that the nonproliferation regime has space to accommodate such potentially destabilizing arrangements.

Additionally, the International Atomic Energy Administration and the three AUKUS countries have almost two decades to come to an agreement about the safety of any future transfer of nuclear material. Australia is likely to deploy the first submarines produced via this deal in 2040. In the meanwhile, it’s likely that Australia will lease nuclear submarines from the U.K. or the United States while it waits to build a new submarine fleet. This type of lease deal also has a precedent in the Indo-Pacific, where India has been operating nuclear-powered attack submarines leased from Russia, aimed toward keeping a close eye on China’s naval presence.

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Debak Das (@debakd) is a Stanton Nuclear Security Postdoctoral Fellow at the Center for International Security and Cooperation (CISAC) at Stanford University.