In the second of a two-part series, Peter Briggs examines the decommissioning, dismantling and waste-disposal risks Australia will inherit from AUKUS reactors.
The political narrative surrounding the AUKUS submarine project has heavily prioritised the immediate advantages of acquiring a “sealed, life-of-type” reactor. By eliminating the mid-life requirement for domestic refuelling infrastructure, the Highly Enriched Uranium (HEU) pathway has been presented as an elegant sovereign solution. The first part of this analysis detailed the early-stage industrial integration hurdles at Osborne and the risk of relying on an unproven, un-prototyped, sealed PWR3+ reactor in the event of manufacturing or design shortcomings.
This article focuses on the most technically demanding and hazardous phase of nuclear stewardship: the final decommissioning, dismantling and disposal of the reactor cores and used fuel. When these submarines eventually reach the end of their operational service lives, Australia faces an unprecedented industrial hurdle to dispose of the reactor and its spent fuel. The technical divergence between Low Enriched Uranium (LEU) and weapons-grade HEU technologies during end-of-life handling reveals starkly contrasted risk profiles, infrastructure requirements and long-term security obligations.
The United Kingdom’s experience offers a blunt reminder that deferring these end-of-life liabilities can quickly paralyse a nuclear enterprise. To date, the Royal Navy has not completely dismantled a single decommissioned nuclear submarine, leaving a legacy backlog of 22 hulls stored afloat at Rosyth and Devonport while awaiting disposal. This systemic failure to address the backend of the lifecycle is detailed comprehensively in a 2019 UK National Audit Office Report.
Because the British experience reflects decades of industrial delays rather than an established, repeatable template, we must turn to United States and French practices to illustrate the true range of engineering paths, infrastructure demands and structural choices Australia will inevitably confront.
While the precise internal design arrangements for the future SSN-AUKUS platform remain under tight security parameters, the baseline industrial footprint of a sealed HEU propulsion system, as demonstrated by US management frameworks, imposes significant, predictable demands at the end of its lifecycle. A completely closed reactor core complicates ultimate decommissioning. If the platform configuration requires an intrusive engineering intervention to access the core, the shipyard burden escalates dramatically, particularly if creating a vertical lift path involves cutting structural openings directly through high-strength submarine pressure hull plating.
To mitigate risk, specialised heavy-duty radiological containment structures must be erected over the hull cuts and the reactor compartment flooded with borated water to act as a fluid shield during remote tool operations, an engineered approach documented in the 2023 US Department of the Navy/Department of Energy Final Environmental Impact Statement on the Disposal of Decommissioned, Defueled Ex-Enterprise (CVN 65) Naval Reactor Plants. This intricate extraction process removes the used fuel but leaves a monolithic waste package containing the activated reactor pressure vessel and internal components, weighing well over a thousand tonnes. Managing, moving and permanently isolating these structures requires a completely dedicated domestic heavy-lift infrastructure with specialised docks and custom engineering.
The unproven, un-prototyped nature of the underlying British reactor design introduces an acute element of sovereign vulnerability that heavily backloads operational risk. As established in the primary coolant circuit failure of HMS Tireless at Gibraltar, even a minor internal technical defect or material fatigue crack in a sealed system constitutes a low-probability, high-consequence event that can completely paralyse the asset.
In a decommissioning context, if an un-prototyped design exhibits unexpected structural distortions or premature internal cladding failures at the end of its life, the lack of an existing land-based test prototype leaves engineers without a safe, radiologically clean testbed to rehearse complex, highly hazardous hull-cutting and core-extraction procedures. Australia would be forced to execute these unprecedented engineering interventions for the first time on a highly radioactive operational hull, dramatically compounding the risk of a catastrophic industrial bottleneck.
In sharp contrast to the Anglo-American footprint, France’s established operational record provides empirical proof of a highly successful, industrialised alternative. Using a low-enriched uranium (LEU) pathway, the French procurement agency (DGA) and Naval Group at Cherbourg have systematically executed a disciplined three-phase decommissioning program. Because French LEU reactors are designed from inception for periodic refuelling, the submarine platforms incorporate standard, integrated core-access features. This allows shipyards to leverage built-in paths using routine dockside procedures and pre-existing containment housings that completely avoid the need to cut open the primary pressure hull structure.
Following core extraction, the empty reactor compartment is cut out, the non-nuclear hull sections are re-welded for immediate conventional scrapping and the defuelled reactor shell is transferred to a land-based storage facility to allow short-lived isotopes to decay naturally. This streamlined assembly line has already successfully processed France’s first generation of ballistic missile submarines (SSBNs) and is seamlessly absorbing decommissioned Rubis-class attack submarines as they are replaced by the new Suffren-class. Rather than demanding a bespoke, highly specialised heavy-trench burial site, the defuelled LEU reactor shell can be cut up and packaged in standard nuclear waste containers within existing civil intermediate-level storage facilities. This represents a major advantage for domestic infrastructure planning, since no special, dedicated site is required.
The two pathways diverge most critically in the long-term radiological profile and physical handling of their spent fuel elements. Spent HEU fuel is an intensely toxic, high-level liability. Even after decades of operational depletion, the core retains a concentrated weapons-grade isotopic profile dominated by unconsumed Uranium-235 alongside long-lived actinides – the heavy, highly radioactive elements formed during reactor operation that keep waste dangerously toxic and hot for millennia. Because of these elements, the radiotoxic half-life of intact HEU spent fuel extends beyond hundreds of thousands of years.
In contrast, the spent fuel from an LEU core offers a highly practical pathway for chemical reprocessing. Subjecting spent LEU fuel to established commercial reprocessing technologies allows the unused uranium and plutonium to be separated and recycled into fresh civil fuel blends, utilising PUREX-derived reprocessing technologies. This extraction leaves behind a highly concentrated waste stream that undergoes vitrification, a process where the hazardous radioactive waste is permanently locked away by blending it into a durable, solid block of glass.
This method results in a drastic reduction in both the total physical weight and overall volume of the final waste material compared to leaving intact fuel assemblies untouched. Most importantly, by separating out these long-lived radioactive elements for targeted management, the remaining vitrified glass waste features a significantly shortened radiotoxic half-life, drastically compressing the timeframe required for secure geological isolation compared to the hundreds of thousands of years required for HEU.
Beyond the physical dimensions of the waste, the long-term geopolitical obligations diverge dramatically. Spent LEU fuel remains well below the weapons-usable threshold, allowing it to be monitored under standard international civil safeguards. Conversely, the spent fuel from an HEU core represents a permanent high-security liability. Because the material remains inherently weapons-usable, the Australian Naval Nuclear Power Safety Framework must account for ultra-high-security physical barriers, continuous International Atomic Energy Agency (IAEA) telemetry, and armed security constabularies at its final disposal site in perpetuity, fulfilling the maximum protection frameworks set out by the IAEA. We are not merely building a standard waste repository; we are establishing a permanently militarised Category I nuclear exclusion zone on Australian soil.
Choosing an HEU sealed-reactor strategy avoids the short-term requirement for domestic refuelling infrastructure but it aggressively backloads the sovereign risk. It legally and financially binds future generations to managing complex decommissioning logistics, specialised monolithic waste handling and a permanent, high-security safeguards burden.
True nuclear stewardship means looking beyond the horizon of the first operational commissions and fully accounting for the heavy realities of the long goodbye. When it comes to managing the end-of-life realities of these propulsion systems on our shores, there is indeed far more than meets the eye.
Peter Briggs
Peter Briggs retired from the RAN in 2001 after a 40-year career, specialising in submarines. This included two submarine commands, command of the RAN Submarine Squadron, director of Submarine Policy and Warfare and Head of Submarine Capability Team, established to rectify Collins introduction into service issues. He was the president of the Submarine Institute of Australia from 2006-09 and is a frequent contributor to public debate on Australian submarine matters.