President Joe Biden appears with Australian Prime Minister Scott Morrison (L) and United Kingdom Prime Minister Boris Johnson (R) to announce the new AUKUS deal. (Win McNamee/Getty Images)

WASHINGTON: In a new letter, a group of former US officials and non-proliferation experts are urging President Joe Biden to commit the United States to designing future submarines using low enriched uranium, a material capable of powering naval propulsion without the risks of being used to create a nuclear weapon.

It’s the latest salvo in a newly-energized debate about what kind of uranium should be used to power military subs, one that has gained new life since since Biden announced Australia would receive nuclear powered submarines under a new defense pact in September, dubbed AUKUS. The heart of that debate questions whether the world’s superpowers should transition from using highly enriched uranium to LEU to reduce the odds a hostile actor might acquire a nuclear weapon.

The AUKUS agreement, which also includes the United Kingdom, has stirred concerns from both longtime experts on the subject and world leaders, such as the former Australian Prime Minister Malcolm Turnbull, who told Breaking Defense this week that he would encourage the use of LEU only for Australia’s new submarine.

“Australia is a non-nuclear weapon state and has a commitment to, and a massive vested interest in, the upholding of the Non-Proliferation Treaty,” said Turnbull, who is not a party to the new letter and had not seen it. “When you look at it from a non-proliferation point of view, or a management point of view or an environmental point of view, LEU is a much better proposition.”

A copy of the letter can be seen at the bottom of this story. The seven signatories of the new letter are:

  • Robert L. Gallucci, Distinguished Professor, Georgetown Univ.; Former Ambassador at Large and Assistant Secretary of State for Political-Military Affairs
  • Daryl G. Kimball, Executive Director, Arms Control Association
  • Alan J. Kuperman, Assoc. Professor, LBJ School of Public Affairs; Coordinator, Nuclear Proliferation Prevention Project, Univ. of Texas at Austin; former Congressional staff
  • George M. Moore, Scientist-in-Residence, Middlebury Inst. of International Studies at Monterey
  • Thomas Shea, former senior researcher, IAEA Safeguards Division and Head, Defense Nuclear Non-Proliferation Programs, Pacific Northwest National Laboratory
  • Sharon Squassoni, Research Professor, Elliott School of International Affairs, George Washington University; former nonproliferation specialist with US State Department
  • Frank von Hippel, Professor of Public and International Affairs emeritus, Princeton University; former Assistant Director for National Security, White House Office of Science and Technology Policy

“[T]he AUKUS deal to supply Australia with nuclear-powered attack submarines fueled with weapon-grade uranium could have serious negative impacts on the global nuclear nonproliferation regime and thereby on US national security,” the group wrote in their letter addressed to Biden, as well as National Security Advisor Jake Sullivan, State Secretary Anthony Blinken, Defense Secretary Lloyd Austin, Navy Secretary Carlos Del Toro and National Nuclear Security Administrator Jill Hruby.

RELATED: The US Navy’s Nuclear Proliferation Problem

Under AUKUS, the US and UK plan to share the information and support necessary for Australia to initiate a nuclear-powered submarine program. Relatedly, Australia also canceled its pre-existing submarine construction contract with France, triggering international headlines over a diplomatic row between French President Emmanuel Macron and the three AUKUS nations.

The specifics of the submarine deal are still unknown, because the agreement includes an 18-month period in which all three countries will work together to determine the best path forward. But most observers speculate it is inevitable Australia will acquire an HEU-based design, because both the US and UK rely on HEU.

The experts behind the letter write that they are not worried that Australia will produce a nuclear weapon but that the country acquiring HEU could set a dangerous precedent.

The laws developed by the IAEA dictate that non-nuclear weapon states, such as Australia, must allow international inspectors into their nuclear facilities. (The country currently lacks significant nuclear infrastructure, except one reactor used for medicinal purposes.) However, the law contains a significant, but never-before-used loophole: materials designated for naval propulsion may be exempt from inspection.

RELATED: New Australia Nuclear Sub Deal Brings Big Questions, Hard Road Ahead

The fact no country has invoked this loophole is partly due to international pressure the United States, China and other countries place on their allies not to rock the boat. But some experts worry that if the United States and United Kingdom allow an ally to claim the exemption, it is inevitable that an adversary will try to do the same.

“If Iran announced it was removing highly enriched uranium from safeguards for the purpose of naval propulsion, we would go apeshit over that,” James Acton, a prominent expert on non-proliferation who is not a party to the letter, told Breaking Defense in September. “And we should. It would be outrageous for Iran to go ahead and do that.”

That is precisely the scenario the letter lays out to the White House, citing comments from Iranian officials who just last month during a UN meeting used AUKUS as grounds for claiming Iran may wish to pursue weapons-grade uranium.

Concerns About Alliances

During an interview, Turnbull, the former Australian prime minister, criticized the deal both for the precedent it will set and how the current prime minister, Scott Morrison, went about informing the French, characterizing Morrison’s actions as “deceitful.”

Turnbull said the Australian government should have been upfront with France about its concerns and requested the contract be modified, rather than creating a deal with the US and UK in private. Turnbull predicted that had Australia been clear about its desire for nuclear-powered submarines, the French may have been “disappointed” but not felt disrespected or humiliated.

He did concede that AUKUS was initially received positively in Australia, but said public perception began to sway after seeing the French government’s reaction. He predicted whoever succeeds the current prime minister will have to mend fences internationally.

“He’s [Morrison’s successor] going to somehow have to say: ‘Look, that was him. That wasn’t us. We’re not like that. It was just him.’ In a bit the same way the American government will be doing every day vis-à-vis Trump,” said Turnbull.

RELATED: What AUKUS Means For Australia: More Than Nuclear Subs

The letter also notes that AUKUS may trigger problematic discussions with allies. South Korea sought the Trump administration’s assistance in acquiring nuclear attack submarines but were rejected.

“Russia has offered to share LEU-fueled reactor technology with South Korea for civilian maritime use but could be emboldened by the US example to offer HEU-fueled designs,” according to the letter.

Currently, the United States, United Kingdom, Russia and India all rely on HEU, while France and China use LEU. The UK is dependent upon the United States, while India is dependent upon Russia.

The debate over HEU or LEU has also been ongoing domestically within the US Navy for several years.

Rep. Bill Foster, D-Ill., recently proposed an amendment to the upcoming defense policy bill that would force the National Nuclear Security Administration to assess the viability of using LEU in naval nuclear propulsion reactors and what impact it would have on SSN(X), the Navy’s next generation attack submarine. (The amendment was submitted to the House Committee on Rules but not made in order, and therefore will not be included in this year’s National Defense Authorization Act.)

“We urge the Biden administration to — at the very — least initiate an effort along those lines,” the non-proliferation experts wrote.