FDA Framework for Fusion-Produced Isotopes

Overview

The U.S. Food and Drug Administration (FDA) framework for fusion-produced isotopes is the evolving regulatory structure governing the production, processing, and approval of radiopharmaceuticals manufactured using fusion energy devices. Unlike traditional production methods that rely on nuclear fission reactors or particle accelerators, fusion-based systems generate high-energy neutrons from deuterium-tritium (D-T) or deuterium-deuterium (D-D) reactions. These neutrons can then be used to irradiate target materials, creating medically valuable isotopes through neutron activation.

The primary importance of this framework lies in its potential to establish a new, reliable, and potentially cleaner supply chain for critical medical isotopes. Many essential isotopes, such as Molybdenum-99 (Mo-99), the precursor to the most widely used diagnostic imaging isotope Technetium-99m (Tc-99m), are currently produced in a small number of aging, foreign-based fission reactors. This creates significant supply chain vulnerabilities. Fusion offers a non-fission, non-uranium-based alternative that could be deployed in a more distributed manner, enhancing national health security.

The regulatory challenge is to apply the FDA's existing, well-established principles for drug manufacturing to a novel production technology. The FDA's mandate is to ensure the safety, identity, strength, quality, and purity of the final drug product, regardless of the source. Therefore, the framework focuses on adapting regulations like 21 CFR Part 212, which governs Current Good Manufacturing Practice (cGMP) for Positron Emission Tomography (PET) drugs, to the unique environment of a fusion facility.

Physics / Mechanism

Isotope production in a fusion device is fundamentally a process of neutron activation. The core mechanism does not rely on the fusion reaction itself to create the desired isotope, but rather uses the high-energy neutrons produced as a byproduct of the fusion process.

Neutron Generation: In a D-T fusion device, a deuterium nucleus and a tritium nucleus fuse, producing a helium-4 nucleus (alpha particle) and a high-energy neutron with a characteristic energy of 14.1 MeV. This is significantly more energetic than the thermal neutrons (≈0.025 eV) or fission-spectrum neutrons (average ≈2 MeV) found in typical fission reactors. This high energy opens up different nuclear reaction pathways.
Target Irradiation: A stable, non-radioactive target material is placed in a region of high neutron flux. The target material is chosen based on the desired final isotope. For example, to produce Mo-99, a target of stable Molybdenum-98 (⁹⁸Mo) could be used.
Neutron Capture and Transmutation: Neutrons from the fusion plasma bombard the target. The primary reaction is often neutron capture, such as the (n,γ) reaction where a nucleus absorbs a neutron and emits a gamma ray. For example: ⁹⁸Mo + n → ⁹⁹Mo + γ. The high energy of fusion neutrons also enables threshold reactions like (n,2n), (n,p), or (n,α), which are not possible with lower-energy neutrons. These reactions can produce different, often carrier-free, isotopes.
Target Processing: After irradiation for a sufficient period, the target is removed. It now contains the desired radioisotope along with unreacted target material and potentially other activation products. This irradiated target is then transferred to a radiochemistry processing facility. There, the desired isotope is chemically separated and purified to meet stringent pharmaceutical-grade specifications. This purification step is critical for FDA approval, as it must remove any isotopic or chemical impurities that could affect patient safety or diagnostic/therapeutic efficacy.

This process is distinct from fission-based Mo-99 production, which involves irradiating a highly enriched uranium target, causing it to fission into hundreds of different isotopes, from which the Mo-99 must be meticulously separated. The fusion pathway avoids the use of uranium and the generation of long-lived fission product waste.

Historical development

The concept of using fusion neutrons for various applications, including isotope production, dates back to the early days of fusion research. However, for decades, the neutron fluxes available from experimental fusion devices were too low to be commercially viable for isotope production. The focus was on achieving the core physics goals related to the Lawson criterion and energy generation.

The modern push for fusion-based isotope production began in the 2010s, driven by two parallel developments: recurrent global shortages of Mo-99 and the emergence of private fusion companies making rapid progress toward commercially relevant neutron fluxes. The Mo-99 shortages of 2009-2010, caused by unscheduled shutdowns of major production reactors, highlighted the fragility of the global supply chain and spurred government and private investment in alternative production technologies.

In the United States, the American Medical Isotopes Production Act of 2012 directed the Department of Energy (DOE) to support the establishment of domestic, non-HEU-based Mo-99 production. While this primarily funded accelerator and solution-reactor projects, it created a commercial and regulatory environment receptive to novel technologies.

Key milestones in the development of the FDA framework include:

Mid-2010s: Private fusion companies, such as SHINE Technologies (then SHINE Medical Technologies) and Phoenix LLC, began engaging with the FDA. Their initial focus was on using accelerator-driven fusion (D-T reactions in a particle accelerator) to generate neutrons, which provided a regulatory stepping stone. This work established that the FDA would regulate the final isotope product as a drug, irrespective of the neutron source.
2018: The FDA issued guidance clarifying the regulatory pathway for non-fission radioisotopes, signaling a clear process for new production methods. This guidance emphasized that existing cGMP regulations (21 CFR Part 212) would be the primary standard.
2021: SHINE submitted a New Drug Application (NDA) to the FDA for Lutetium-177 (Lu-177) produced via its accelerator-based fusion technology. This was a landmark event, representing the first time a drug produced using fusion-based neutrons was submitted for FDA approval.
2023: The FDA approved SHINE's NDA for Lu-177, marking the first-ever approval of a medical isotope produced with fusion technology. While not from a net-energy-gain fusion device, this approval set a critical precedent, demonstrating that the FDA's existing framework is adaptable to fusion-derived products. It validated the approach of separating the neutron source from the cGMP-compliant drug processing facility.

These developments have paved the way for companies developing magnetic confinement and other fusion energy systems to plan for medical isotope production as an early market application.

Current status

As of 2026, the regulatory framework is established but continues to be refined as more complex fusion devices approach commercialization. The FDA's position is technology-agnostic; its focus remains on the final drug product's quality and the manufacturing process's control and validation, as outlined in cGMP.

The precedent set by the approval of accelerator-fusion-produced Lu-177 is the cornerstone of the current status. It confirms that the pathway for new fusion-derived isotopes involves:

Pre-Submission Meetings: Proactive engagement with the FDA's Center for Drug Evaluation and Research (CDER) is standard practice. Companies present their production and processing plans to get early feedback on potential regulatory hurdles.
Drug Master File (DMF): A DMF can be submitted to the FDA containing confidential, detailed information about the facilities, processes, or materials used in manufacturing. This allows the FDA to review the technical details of the isotope production without the company disclosing proprietary information to its customers.
New Drug Application (NDA): The final application for approval, which must demonstrate the drug's safety and efficacy. For a well-established isotope like Mo-99, the focus is on demonstrating bioequivalence to the existing product and proving that the manufacturing process is robust and compliant with cGMP.

The primary regulation applied is 21 CFR Part 212, "Current Good Manufacturing Practice for Positron Emission Tomography (PET) Drugs." Although originally designed for PET isotopes, its principles of process control, quality assurance, and facility validation are broadly applicable to other short-lived radiopharmaceuticals.

The Nuclear Regulatory Commission (NRC) and state-level bodies regulate the safety and operation of the fusion device itself, creating a dual-regulatory environment. The FDA's jurisdiction begins once the irradiated target is removed from the device and enters the pharmaceutical processing stream.

Notable implementations

Several commercial entities and programs are actively navigating or planning to navigate this FDA framework.

SHINE Technologies: The clear leader in this space. Based in Janesville, Wisconsin, SHINE operates large accelerator-based D-T fusion systems to produce medical isotopes. Their successful FDA approval for Lu-177 in 2023 was a pivotal moment. The company is also in the late stages of commissioning a facility, 'The Chrysalis,' for large-scale Mo-99 production, for which it will also seek FDA approval.
Phoenix LLC: A collaborator with SHINE, Phoenix manufactures the high-yield neutron generators used in their facilities. Phoenix's technology underpins the first generation of commercially and regulatorily successful fusion-based isotope production.
Helion: This company, focused on pulsed non-ignition fusion, has publicly stated that producing medical isotopes is a potential early application for its devices. Their approach could offer a different neutron spectrum and operational profile, which would require its own validation under the FDA framework.
TAE Technologies: While primarily focused on an aneutronic fuel cycle (p-¹¹B), TAE's current D-D devices produce neutrons. The company has explored using these neutrons for applications like neutron-capture cancer therapy, which would involve FDA regulation of both the drug and the procedure.
ITER and other large research tokamaks: While their primary mission is energy research, large-scale devices like ITER will produce unprecedented neutron fluxes. Programs are in place to study the use of 'port plugs' for test blanket modules, a concept that could be adapted for isotope production targets. Any medical isotopes produced would fall under the relevant regulatory body, such as the European Medicines Agency (EMA) or the FDA if intended for the U.S. market.

Open challenges

Despite recent successes, several scientific and engineering challenges remain in applying the FDA framework to next-generation fusion energy systems.

Demonstrating cGMP in a Fusion Environment: A full-scale fusion power plant will be a complex industrial environment with high magnetic fields, radiation, and vacuum systems. Integrating a cGMP-compliant target handling and processing system into this environment is a significant engineering challenge. Proving to the FDA that processes are controlled, validated, and free from contamination risks will be more difficult than in a dedicated accelerator facility.
Impurity Profile Characterization: The unique, high-energy (14.1 MeV) neutron spectrum from D-T fusion can create a different set of activation byproduct impurities compared to fission or accelerator sources. Each new fusion device and target system will require exhaustive characterization of its specific impurity profile. The developer must prove to the FDA that these impurities are consistently removed to levels that are safe for patients.
Material Degradation and Target Integrity: The intense neutron flux in a commercial fusion device can cause target materials and their cladding to degrade, swell, or transmute over time. This could affect the purity of the final product or the reliability of the target handling system. Long-term material performance data will be needed to satisfy regulatory requirements for process consistency.
Tritium Management: For D-T fusion devices, managing the tritium fuel cycle is a major challenge. The FDA will require absolute assurance that no tritium contaminates the final radiopharmaceutical product. This necessitates robust separation and purification processes and highly sensitive detection methods, with validation data to prove their effectiveness.
Scaling and Automation: Moving from pilot-scale to full commercial production requires highly reliable, automated systems for inserting, irradiating, and retrieving targets without disrupting fusion plant operations. The reliability and validation of this automation will be a key part of the regulatory submission.

Outlook

The 5-15 year trajectory for the FDA framework concerning fusion-produced isotopes is one of incremental expansion and adaptation. The foundational regulatory pathway is now proven, but its application will evolve with the technology.

In the near term (5 years), the industry will likely see additional FDA approvals for isotopes produced by the current generation of accelerator-based fusion systems. This may include SHINE's Mo-99 and potentially other therapeutic isotopes like Actinium-225 (Ac-225) from various producers. This period will solidify the FDA's expectations for process control, impurity analysis, and cGMP compliance for fusion-based systems.

In the medium term (5-10 years), the first fusion companies aiming for net energy gain will likely begin building dedicated pilot facilities for isotope production as an early revenue source. These companies will engage in extensive pre-submission discussions with the FDA to address the challenges of integrating cGMP production into more complex fusion machine environments. The first Drug Master Files for isotopes produced in a magnetic or inertial confinement fusion device could be submitted within this timeframe.

In the long term (10-15 years), assuming the successful demonstration of pilot fusion plants, the first NDAs for isotopes from these next-generation devices could be submitted and potentially approved. The FDA framework will have adapted to include specific guidance for these systems, particularly concerning tritium management and material qualification. Successful approvals would establish fusion as a mainstream, reliable source of medical isotopes, potentially transforming the global supply chain and enabling new radiopharmaceutical therapies that are currently limited by isotope availability.

References

Current Good Manufacturing Practice for Positron Emission Tomography Drugs — U.S. Food and Drug Administration
SHINE Announces U.S. FDA Approval of Investigational New Drug Application for Lutetium-177 (Lu-177) — SHINE Technologies (2021)
Regulatory Considerations for Non-Fission Radioisotopes: An Industry Perspective — Journal of Nuclear Medicine (2018)
American Medical Isotopes Production Act of 2012 — U.S. Congress (2012)
Fusion-based production of medical isotopes — Physics of Plasmas (2017)
The Supply of Medical Radioisotopes: An Economic Study of the Molybdenum-99 Supply Chain — Nuclear Energy Agency (NEA) (2019)
SHINE Announces FDA Approval of Its Lutetium-177, Ilumira™ — SHINE Technologies (2023)
Drug Master Files (DMFs) — U.S. Food and Drug Administration

FDA framework for fusion-produced isotopes