Nuclear power plants are on track to generate more than 140,000 tonnes of spent nuclear fuel (SNF) before 2060. Every year, 2,000 tonnes of radioactive heavy metal join the growing inventory of fuel removed from nuclear power reactors—both operating and decommissioned. In the coming decades, the U.S. Department of Energy (DOE) will need to transport that material to future storage facilities.
The amount of existing spent fuel—90,000 tonnes—is already outgrowing currently available storage options. Storage casks and cooling pools have reached maximum capacity at many of the 75 plants that host SNF on-site. This material was never intended to stay at these sites long-term. But, with permanent storage efforts gridlocked since the early 2000s, a once-temporary fix became the status quo, leaving the DOE paying US $10.6 billion to cover utilities’ storage costs.
However, regulators and lawmakers are finally moving the needle. Congress recently directed the DOE to seek an interim consolidated storage site to hold SNF until a permanent solution becomes available—likely a geologic repository located between 300 and 1,000 meters underground. Still, this future repository is at least a decade away.
In the meantime, the DOE is tackling a secondary challenge: Modernizing existing railcars to accommodate the eventual scale-up of SNF shipments. The result is Atlas, a multi-car system designed to move about 217 tonnes of SNF and high-level radioactive waste to future storage and disposal destinations.
After a decade and $33 million of development, the Association of American Railroads (AAR) recently cleared the 12-axle system to operate on all major freight railroads in the United States. Atlas’s main railcar bears an SNF container held in place by a 7-tonne cradle and two 10-tonne end stops. Two buffer railcars provide safe spacing between the main railcar and the two locomotives powering the train, as well as a rail escort vehicle (REV) caboose that carries armed security staff for surveillance. The U.S. Navy co-developed the escort vehicle, to replace its own aging REV fleet, which is used to escort naval SNF and classified ship components by rail. Atlas employs both cell and satellite communications and a mesh radio link to stay in touch with the cabs.
Engineers finished final testing on Atlas in September 2023 with a 2,700-kilometer trip from Colorado to Idaho. U.S. Department of Energy
Historically, both trucks and trains have transferred thousands of shipments of irradiated nuclear fuel between DOE research sites, utility-owned reactors, and New Mexico’s Waste Isolation Pilot Plant, the nation’s only deep geologic repository for weapons-generated waste. While trucks’ legal weight limit is 36 tonnes, rail can efficiently handle high-capacity SNF casks and contaminated soil from cleanup sites in one shipment. Atlas’s advanced real-time monitoring system builds on these capabilities.
Atlas comes as nuclear remains a key contributor of clean energy in the U.S., surpassing wind and solar to generate 18.6 percent of the nation’s electricity last year—enough for over 70 million homes. Despite their high capacity, nuclear reactors produce a relatively low volume of waste. Annual SNF outputs translate to less than half of an Olympic pool.
After fuel is spent inside a reactor, plant operators immerse fuel assemblies in 40-foot concrete pools lined with steel to isolate radiation. Once it’s cooled for at least five years, SNF moves to steel canisters shielded by an outer layer of concrete, steel, or both. These dry casks can stay on-site for 40 years.
Spent nuclear fuel is stored across the United States, with much of it thousands of kilometers away from existing and future storage sites.U.S. Government Accountability Office
In the 1980s, the Nuclear Waste Policy Act mandated the DOE to start permanently disposing of SNF in an underground repository at Nevada’s Yucca Mountain. However, social and political opposition ultimately quashed the hotly contested project. The regulatory complexity of a permanent storage solution remains a critical barrier in SNF management, particularly amid uncertainty about the safety of long-term dry storage. As the DOE is in the early stages of siting a federal interim facility, SNF will likely remain at plants until the late 2030s.
The DOE says Atlas’s development spanned 10 years due to the complexity of AAR’s S-2043, the strictest standard for freight railcars transporting SNF and high-level radioactive waste in North America. Atlas has a suite of sensors tracking 11 performance parameters required by S-2043, such as bearing conditions, speed, rocking, and braking. The integrated security and safety monitoring system features mechanisms to prevent derailments from equipment failure or degradation.
The DOE initially envisioned Atlas as an eight-axle railcar. During the conceptual design phase, computer modeling indicated the train’s performance might not meet all S-2043 requirements. Around this time, the Nuclear Regulatory Commission (NRC) certified a new 190-tonne cask, which is too heavy for axle loadings on a smaller railcar. These circumstances inspired a 12-axle redesign.
The Atlas railcars are separated from the locomotives and escort railcar by empty buffer cars to maintain a safe distance from the spent nuclear fuel.U.S. Department of Energy
The railcars and locomotives completed a roughly 2,700-kilometer (1,680-mile) demonstration to ensure on-track compatibility and safety. Traveling smoothly from Colorado to Idaho, the test simulated the heaviest NRC-certified cask with steel dummy weights totaling almost 220 tonnes (480,000 pounds), accompanied by a REV, buffer cars, and Union Pacific Railroad locomotives.
Heavier SNF containers demand the dozen axles that Atlas provides, but eight axles can move relatively lighter packages of at least 72 tonnes more efficiently. After Atlas transitioned to a 12-axle railcar, the DOE initiated an eight-axle project for smaller payloads. The AAR approved the design in 2021, and began prototype fabrication this year.
Fortis, comprising the same payload attachment system, monitoring system, REV, and buffer vehicles, is expected to be completed in the late 2020s. “Both railcars will provide the DOE with flexibility to use the right rail equipment for the job,” a DOE spokesperson told IEEE Spectrum.