FUEL & FUEL CYCLE | TRISO SPENT FUEL
Engineering a future for TRISO waste
With a new generation of reactor technologies on the cusp
of commercial deployment a new regulatory-ready, globally deployable canister solution is essential to keep pace.
By Jesse Sloane, Chris Parker, Matt Waples, and Vaibhav Sharma of Deep Isolation.
A new generation of nuclear reactors is gaining traction, driven not only by energy policy but also by powerful new end-users like tech giants Google, Microsoft, and Amazon. Google’s agreement with Kairos Power in October 2024 kickstarted the trend, soon followed by Amazon, Microsoft, Meta, and others forming similar partnerships. But while reactor innovation is accelerating, one critical piece of the puzzle remains unsolved: how to manage and dispose of the new types of waste these reactors will generate. Enter Project PUCK – a collaboration between Deep Isolation and Kairos Power. Funded by the US Department of Energy’s Small Business Innovation Research (SBIR) programme, Project PUCK (Performance Validation of the Universal Canister System for Kairos Power) has delivered a first-of-its-kind solution for the safe storage, transport, and disposal of the TRISO (tri-structural isotropic) fuel used in high-temperature gas reactors. The timing is critical: in May President Trump signed four Executive Orders launching a national mission to accelerate deployment of advanced nuclear with an explicit focus on waste.
Tackling a new generation of waste Deep Isolation’s Universal Canister System (UCS) is engineered to safely store, transport, and dispose of advanced reactor waste in both traditional mined repositories and novel deep borehole configurations. The UCS was designed, prototyped, and tested with support from the US Department of Energy’s Advanced Research Projects Agency–Energy (ARPA-E) through a multi-year project involving Deep Isolation, NAC International, UC Berkeley, and Lawrence Berkeley National Laboratory. That effort focused on identifying key waste streams from advanced reactors, including TRISO spent fuel, and creating a canister system capable of safely managing them through all stages of the back-end fuel cycle. It also established universal waste acceptance criteria and conducted extensive safety and performance modelling across repository types. Building on that foundation, Deep Isolation launched
Project PUCK to validate the technical and economic viability of the UCS for real-world advanced reactor waste management – specifically, TRISO spent fuel from Kairos Power’s Fluoride Salt-Cooled High-Temperature Reactor (KP-FHR).
The Universal Canister System The UCS is a triple-purpose container that integrates storage, transportation, and geologic disposal into a single robust package. It accommodates a wide range of advanced reactor
18 | July 2025 |
www.neimagazine.com
waste forms, including TRISO fuel in various configurations (pebbles, cylindrical compacts, and prismatic assemblies), lanthanide borosilicate (LaBS) glass with high waste-loading capacity, and intact halide salts from molten salt reactors. Derived from Deep Isolation’s intellectual property
originally developed for the disposal of spent fuel from conventional pressurised water reactors (PWRs), the expanded UCS includes a family of canisters in varying sizes to accommodate a range of waste types and disposal depths – all enabling a unified approach across various reactor technologies, and all keeping costs down by re-using core standardised features. Three main canister classes have been developed, varying in diameter, wall thickness, and volumetric capacity, yet compatible with both deep borehole and mined repository disposal. Standard design features include a corrosion-resistant stainless-steel shell, closure lid system, and lift adapter assemblies compatible with oil and gas handling infrastructure. The UCS is designed to be interoperable with NAC International’s MAGNASTOR® and MAGNATRAN® systems, enabling near-term deployment within established licensing frameworks. Project PUCK included comprehensive assessments of the
UCS’s technical performance and cost implications when paired with TRISO spent fuel. Analyses evaluated structural, thermal, shielding, and criticality performance for a UCS loaded with TRISO fuel. Safety and performance assessment models were used to evaluate repository performance of TRISO in each UCS class across multiple configurations including mined repository in shale, horizontal borehole repository in shale, and vertical borehole repository in crystalline basement rock. The results confirmed that the UCS design meets the requirements for safe handling and long-term isolation of TRISO waste in both mined and borehole repositories. A separate techno-economic analysis applied Deep Isolation’s cost modeling framework to assess lifecycle
disposal costs. Key insights included: ● TRISO waste’s graphite matrix increases disposal volume compared to conventional PWR spent fuel. This increase potentially raises disposal costs by 37-100%.
● Volume reduction strategies – such as removing the graphite coating and consolidating TRISO pebbles into particulate form could reduce disposal costs by 18-23%, albeit with added complexity.
● Co-locating borehole repositories with reactors or waste-generating sites can cut total costs by up to 40% by minimising transport and infrastructure requirements.
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36
