The U.S. Department of Energy is betting $40 million that particle accelerators can crack one of nuclear power’s oldest problems: what to do with spent fuel that stays dangerously radioactive for hundreds of thousands of years. The federal investment, channeled through a program called NEWTON, funds research into accelerator-driven transmutation, a process that bombards nuclear waste with high-energy neutrons to convert long-lived isotopes into shorter-lived or stable elements. If the science works at scale, it could slash the radioactive lifespan of waste by orders of magnitude and generate usable electricity in the process.
Federal Dollars Target a Decades-Old Idea
The concept of using accelerators to neutralize nuclear waste is not new. A 1991 Los Alamos National Laboratory conference paper outlined accelerator-driven transmutation as a dual-purpose technology for both waste cleanup and electric power production, describing an “accelerator-multiplying blanket” that could sustain neutron reactions in a subcritical assembly. That early work, cataloged under report number LA-UR-91-2794, drew on earlier fusion technology studies to argue that high-energy proton beams could generate enough spallation neutrons to break apart problematic isotopes. For more than three decades, though, the idea stayed largely theoretical, limited by accelerator reliability and the sheer engineering complexity of coupling a particle beam to a nuclear fuel target.
What changed is money and urgency. ARPA-E, the Department of Energy’s advanced research arm, committed $40 million for the NEWTON program to make transmutation practical and economically viable. The program’s name stands for Nuclear Energy Waste Transmutation Options with Neutrons, and its stated goal is to reduce the long-term impact of used nuclear fuel by pushing accelerator-driven systems beyond the lab. This is not a basic-science grant; the funding explicitly targets engineering barriers that have kept accelerator-driven systems off the grid. Among the first recipients, Argonne National Laboratory and Fermi National Accelerator Laboratory received $3.2 million to develop superconducting linear accelerator cavities designed for the extreme uptime that a transmutation facility would demand.
How Proton Beams Break Down Dangerous Isotopes
The basic physics works like this: a powerful proton accelerator fires a beam into a heavy-metal target, typically lead or bismuth. Each proton collision triggers spallation, a process that ejects dozens of neutrons from the target nuclei. Those neutrons then slam into surrounding nuclear waste, transmuting long-lived fission products into isotopes with far shorter half-lives or into stable, non-radioactive elements. The key targets include technetium-99, iodine-129, selenium-79, zirconium-93, cesium-135, and tin-126, all of which linger in spent fuel for tens of thousands to millions of years. A peer-reviewed simulation published in Scientific Reports modeled spallation-driven transmutation rates for these specific isotopes using proton accelerators, quantifying the feasibility and limits of each reaction pathway and highlighting how beam energy and target composition shape overall performance.
Separate research in fast-spectrum neutron environments, which accelerator-driven systems can replicate, has shown that irradiation can significantly reduce inventories of long-lived fission products. A study in Scientific Reports by Springer Nature quantified reductions in several of these isotope inventories under various irradiation scenarios, demonstrating that fast-spectrum neutrons can shrink effective half-lives for some of the most persistent waste components. The distinction matters because accelerator-driven subcritical systems offer a safety advantage over conventional fast reactors: they cannot sustain a chain reaction on their own, so shutting off the beam immediately stops the nuclear process. That combination of controllability and targeted neutron spectra is what makes the NEWTON program’s focus on accelerators more than a rehash of earlier fast-reactor concepts.
From Lab Simulations to Kilogram-Scale Throughput
Turning theoretical transmutation rates into real waste processing requires systems that can handle meaningful quantities of material. Design studies by the Japan Atomic Energy Research Institute have produced specific throughput figures for accelerator-driven system concepts, measured in kilograms per year, covering minor actinides and selected fission products such as iodine-129 and technetium-99. Those numbers suggest that a single facility could process a measurable fraction of a reactor’s annual waste output, though scaling to the full inventory of a national fleet would require multiple units, significantly higher beam power, or both. The NEWTON program is effectively testing whether incremental advances in accelerator and target technology can close that gap without driving costs beyond what utilities or governments are willing to pay.
The engineering challenge centers on accelerator uptime. A transmutation plant would need its particle beam running nearly continuously to maintain the neutron flux required for efficient isotope conversion, with only brief, scheduled outages for maintenance. The Argonne and Fermilab project is specifically tackling this problem by developing superconducting linac cavities that can sustain high beam power with minimal downtime and stable operation over years. Spallation target design is another open question: the target must withstand intense radiation damage and heat while efficiently converting proton impacts into usable neutrons, all while allowing for remote replacement in a highly radioactive environment. These are not abstract concerns, if uptime falls below the thresholds needed for economic viability, the technology becomes an expensive science experiment rather than a practical waste solution.
Alternative Accelerator Pathways Add Flexibility
Proton beams are not the only accelerator approach under investigation. Researchers are also studying electron accelerators that generate high-energy photons through bremsstrahlung, which then produce neutrons when they strike heavy-metal converters. A peer-reviewed study in Annals of Nuclear Energy examined how electron-driven photon sources coupled to compact subcritical assemblies could provide flexible neutron fields for waste transmutation and materials testing. While electron accelerators generally deliver lower neutron yields than dedicated proton spallation sources, they can be simpler to build and maintain, potentially opening a path for smaller regional facilities that complement larger, high-power proton-based plants.
Other concepts look at hybrid configurations, where accelerators supplement existing reactors or critical test loops rather than serve as stand-alone waste burners. In these scenarios, an accelerator might be used intermittently to boost neutron flux for specific isotopes or to validate transmutation cross sections under tightly controlled conditions. Such hybrid approaches could lower the barrier to entry by leveraging existing nuclear infrastructure, but they also complicate licensing and safety analysis because regulators must evaluate coupled systems with multiple modes of operation. As NEWTON-funded teams refine their designs, part of their task will be to identify which configurations can pass regulatory muster while still delivering enough throughput to matter for national waste inventories.
Risk, Oversight, and What Comes Next
Even if the physics and engineering line up, accelerator-driven transmutation will not move forward without public confidence in safety and oversight. The Department of Energy has signaled that complex, software-heavy systems like high-duty-factor accelerators and their control networks must be designed with cybersecurity in mind, consistent with broader policies such as its published vulnerability disclosure framework. For waste transmutation, that means hardening both physical and digital systems against tampering, ensuring that beam controls, target handling, and remote maintenance tools cannot be easily compromised. It also implies early engagement with regulators to define how subcritical accelerator facilities fit into existing nuclear licensing categories or whether new rules are needed.
Institutional capacity will matter as much as hardware. Organizations like Fermilab, which already operate some of the world’s most advanced high-intensity accelerators, bring decades of experience in beam reliability, cryogenic systems, and radiation shielding that can be repurposed for nuclear applications. National laboratories, universities, and private firms funded under NEWTON will have to translate that expertise into designs that utilities can realistically build and operate, with clear cost and performance targets. The $40 million now on the table is unlikely to deliver a commercial plant on its own, but it can answer the pivotal question that has hovered over accelerator-driven transmutation since the early 1990s: is this a niche research tool, or a scalable technology that can fundamentally reshape how the nuclear industry thinks about waste?
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*This article was researched with the help of AI, with human editors creating the final content.
