A global threat for millennia: experts warn Australia’s nuclear submarine legacy will be weapons-usable uranium cache

Australia’s proposed nuclear submarine fleet will leave behind tonnes of weapons-usable uranium-235: radioactive for hundreds of millions of years, and capable of being processed into scores of warheads, nuclear experts have told a public inquiry into Aukus.

And a former White House national security adviser has told the Guardian that Australia’s Aukus deal – involving the transfer of highly enriched uranium to a non-nuclear weapons nation – sets a dangerous proliferation precedent that other countries such as Iran could try to exploit, weakening global control of the spread of weapons-usable nuclear material.

Associate Prof Tilman Ruff, founding chair of the Nobel prize-winning International Campaign to Abolish Nuclear Weapons, told the Aukus public inquiry that the legacy of Australia’s nuclear submarine fleet – of which each vessel will have a service life of about three decades – will be hundreds of kilograms of high-level radioactive waste. Even as waste, the submarines’ spent reactor fuel will be highly enriched uranium (HEU), usable to build nuclear weapons.

“No nation has resolved the huge problem of how to manage this material and there’s no guarantee – given the timeframes involved and the hazards of the material over geological time – that any arrangement that we come up with could reliably isolate that material for hundreds of thousands, or millions of years.

“The additional complication here is that it needs a really high level of security because, in 10,000 years, somebody could still go and dig that stuff up and build nuclear weapons with it.”

The uranium left behind by Australia’s nuclear submarines at the end of their working lives will likely still be enriched to about 80%: the same level as the atomic bomb dropped on Hiroshima.

The Australian government has repeatedly said the precise amount of high-level nuclear waste that will be left behind by its submarine fleet is classified.

But documents released under freedom of information laws show Australia will be responsible for each submarine’s nuclear reactor compartment, “roughly the size of a four-wheel drive”, and spent nuclear fuel “roughly the size of a small hatchback”.

Leading global experts on non-proliferation have now estimated each nuclear submarine decommissioned by Australia – beginning in the 2050s – will contain about 400kg of HEU, enriched to about 80%, containing about 320kg of uranium-235 (U-235).

The International Atomic Energy Agency states a “significant quantity” of highly enriched uranium – enough to make a weapon – is 25kg of contained U-235.

U-235 has a half-life of 700m years: it will be a weapons proliferation risk for millennia. And the radioactive materials generated by its fission process will be toxic to humanity and the environment for millions of years.

The HEU left behind by each one of Australia’s three second-hand Virginia-class submarines bought from the US would be sufficient for more than a dozen weapons.

Australia’s domestically built Aukus-class submarines – Australia is proposing to build five – will be powered by Rolls-Royce’s in-development PWR3+ reactor. The quantity of HEU required to power that reactor is classified but they are expected to be larger than the Virginia-class reactors, Ruff said.

The Aukus agreement mandates that Australia is responsible for the disposal and storage of all of the nuclear waste left behind by its nuclear-powered submarines in perpetuity.

By the end of the century, when all eight of Australia’s planned nuclear powered submarines have been retired, Australia will be responsible for the management of “at least 3 tonnes” of U-235 in the highly enriched uranium spent fuel waste, Ruff told the Guardian.

“That’s enough for 120 nuclear weapons using the International Atomic Energy Agency standard.”

Australia has spent decades reducing its HEU stocks. There is presently less than 3kg of HEU in the entire country, held for research purposes.

Ruff told the public inquiry into Aukus, established by the Australian Peace and Security Forum, that his primary concern over Aukus was that it exacerbated regional tensions and made Australia “a higher priority target, including for nuclear attack”.

Ruff cited the work of Dr Frank von Hippel, senior research physicist and professor of public and international affairs emeritus at Princeton University, who estimated that the reactor of a Virginia-class submarine – such as those Australia is set to buy from the US – would be decommissioned at the end of its working life still containing about 400kg of HEU, enriched to about 80%.

Von Hippel, who served as an assistant director for national security in the Clinton White House, told the Guardian “by the IAEA’s metric, 0.4 tons of 80% enriched uranium would be sufficient for 13 implosion bombs”.

“That’s a lot of weapons potential there. And that’s just one submarine. That is going to change the situation in Australia with regard to the proliferation potential.”

Von Hippel said successive US administrations had spent decades bringing thousands of kilograms of HEU on to American soil to reduce the risk of nuclear terrorism.

Since the 1990s, about 30 countries have reduced their HEU stocks down to less than 1kg. Countries such as France and China run nuclear-powered submarine fleets on low-enriched uranium, a far lower proliferation risk.

“The worry is not so much Australia as the precedent,” von Hippel said, citing countries such as Iran which has previously justified enriching uranium to 60% by saying that in the future it might want to have naval reactors.

“My concern is the proliferation example that the US and Australia and the UK have established by legitimising the use of weapons-grade uranium for attack submarines by non-weapons states: they have lowered the barriers to acquisition of nuclear weapons by this action.”

Von Hippel said Article IV D in the Aukus agreement, mandating Australia store and manage all spent nuclear fuel and radioactive waste, defied decades of non-proliferation efforts.

“The US has been insisting that spent fuel be sent back to it, because of this concern that the uranium is still weapons usable in the spent fuel. And now, in the case of Aukus, the US … is insisting that Australia keep the uranium … setting a new kind of precedent.”

‘Highest levels of nuclear stewardship’

A spokesperson for the Australian Submarine Agency told the Guardian the government was committed to the “highest levels of nuclear stewardship”, including responsibility for “management, storage, and disposal of spent nuclear fuel and radioactive waste generated from its conventionally-armed, nuclear-powered submarines”.

But Australia won’t need to dispose of high-level nuclear waste until the 2050s, when the country’s first nuclear-powered boats are decommissioned, the spokesperson said.

“That means we have time to get this decision right, including through a thorough process informed by technical advice and extensive consultation.”

The ASA reiterated Australia would not accept intermediate or high-level radioactive waste – including spent nuclear fuel – from any country, including the UK or US.

“Aukus is about keeping Australians safe in the most challenging strategic environment since the Second World War. It … strengthens our ability to deter coercion and contribute to regional stability.”

The defence department commissioned a review of potential nuclear waste sites in 2023. It has had that report for more than two years but has consistently refused to release it.

The defence minister, Richard Marles, said last month Aukus was on track, including consideration of a nuclear waste site.

“We have time to work this through, and we will work it through. And … what we have made clear is that the disposal facility will be on existing or future defence ground.”