When neutrons penetrate atomic nuclei, they trigger nuclear transformations that produce radioisotopes impossible to create through conventional chemistry. This process is called neutron activation, manufactures the medical isotopes that diagnose heart disease, the power sources that propel spacecraft beyond Jupiter, and the precisely doped semiconductors that control our electrical grid. A single neutron capture event transforms a stable atom into a radioactive isotope with unique decay properties, creating materials whose applications span from cancer therapy to industrial radiography.

Many sectors of the global radioisotope market rely heavily on neutron activation. In medicine, neutron activation produced radioisotopes underpin a multi-billion-dollar market, yet this critical supply chain still rests on a handful of aging research reactors, many built in the 1960s. When Canada’s National Research Universal (NRU) reactor shut down unexpectedly in 2009, it triggered a global shortfall in key diagnostics. That vulnerability has driven urgent efforts to develop alternative neutron sources and production methods, with fusion-based systems emerging as a promising path to distributed, resilient isotope manufacturing.

Beyond medicine, neutron-activated materials enable technologies that would otherwise be impossible. Plutonium-238 produced through neutron irradiation of neptunium-237 powers radioisotope thermoelectric generators (RTGs) that have kept the Voyager spacecraft operational for over 45 years in the cold darkness beyond our solar system. Neutron transmutation doping creates silicon wafers with extremely uniform phosphorus distribution for high-power electronics. Industrial radiography sources, sterilization isotopes, and oil well logging tracers all depend on neutron activation for their production.

Neutron activation creates essential isotopes across multiple industries. Examples include:

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Expanding Production with Fusion Neutron Sources

Today’s isotope supply is neutron-limited. Demand keeps climbing, but multipurpose research reactors are aging, face maintenance constraints, and are concentrated in a few regions. Non-neutron production via cyclotrons and linacs covers many nuclides, yet many products still need intense, well-controlled neutron fluxes, and available capacity falls short.

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Fusion neutron sources expand the available neutron budget and complement existing production:

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• Distributed manufacturing: Compact systems colocate activation with regional radiopharmacy and industrial hubs, shrinking logistics and improving resilience for short half-life products.
• Reduced Regulatory Burden: No spent fuel or special nuclear material reduces licensing complexity, waste streams, and end-of-life burdens.
• Modular scale-up: Add units incrementally as demand grows, avoiding single-point bottlenecks and enabling redundancy.
• Economic viability: As fusion advances toward grid power via higher energy gain (Q), higher duty cycles, and a growing supplier base both the capital cost per neutron and operating cost per neutron decline and help usher in radioisotope abundance.

It's also worth noting that D–T fusion produces 14 MeV neutrons, significantly higher energy than the predominantly thermal/epithermal spectra in moderated research reactors, which can unlock threshold reactions (e.g., (n,2n), (n,p), (n,α)) that are rarely utilized today. Access to these channels may enable novel isotope pathways, new therapeutic radiopharmaceuticals, and advanced materials processing.

As fusion neutron capability scales, isotope production can move from a reactor-constrained bottleneck to a hybrid, distributed platform with sufficient neutrons to stabilize supply, unlock new therapies, and support advanced industrial and research applications.