The US Department of Energy’s (DOE’s) Oak Ridge National Laboratory (ORNL) is planning to increase production of Californium-252 (Cf-252), which is used to start up nuclear reactors and assay fresh reactor fuel, as well as for oil well logging, national security and other applications.
As the Western world’s sole producer of this rare radioactive isotope, the laboratory is implementing a breakthrough chemical process that cuts production time in half. A new single-cycle chemical separation process, which was nearly a decade in development, reduces processing time by roughly 50% without compromising material quality. Program Manager Samantha Schrell noted that a spike in demand is expected as advanced reactor designs move toward commercial deployment.
Cf-252 provides the initial spark of neutrons needed to ignite a self-sustaining nuclear chain reaction. A new nuclear reactor, or one that has been shut down for an extended period, has zero or very low background neutron activity. Without active neutrons colliding with the fuel rods, the reactor is completely dormant. Operators cannot safely start a reactor without a baseline level of neutron flux.
Cf-252 is used because of its unique property of spontaneous fission. Instead of needing to be struck by outside particles to split, it naturally decays and breaks apart on its own. As it splits, a tiny piece of Cf-252 fires out up to 100bn neutrons every second. For reactor start-up, the isotope is permanently sealed inside high-strength industrial capsules known as startup rods. These are physically inserted into the reactor core next to the fresh uranium oxide fuel rods.
Once the startup rods are in place, operators slowly pull out the reactor’s boron or cadmium control rods (which absorb neutrons). The steady stream of neutrons emitted by the Cf-252 begins colliding with the uranium atoms in the fuel. This causes the uranium to split, releasing more neutrons and triggering a controlled domino effect. Once the reactor achieves criticality and operates through its first fuel cycle, the uranium fuel, the fission products created inside the fuel will emit more than enough background neutrons on their own to sustain or restart the reactor. At this stage, the Cf-252 is no longer required to do the heavy lifting.
The surge in demand for Cf-252 is primarily driven by three types of advanced reactors, while the distribution process relies on a tight collaboration between the federal government and private industry. According to Oak Ridge National Laboratory (ORNL) and industry reports, the commercialisation and legislative push for newer fission technologies require substantial amounts of Cf-252 as a reliable startup neutron source to initiate a predictable chain reaction.
Dozens of private companies are developing advanced small modular reactors (SMRs). Every newly deployed SMR core requires its own Cf-252 startup source. At the same time, US federal policy has shifted toward expanding high-capacity, domestic clean energy, aiming to kickstart the construction of 10 new large reactors by 2030. IN addition, the US military is executing directives to deploy compact, micro-fission reactors at domestic Army bases. These mobile or small-scale reactors require rapid, highly predictable startups, depending heavily on Cf-252.
Because Cf-252 is an intensely powerful neutron emitter, it cannot be shipped or used in its raw form. The distribution pipeline involves significant co-ordination. ORNL’s Radiochemical Engineering Development Center (REDC) isolates the isotope into bulk forms such as californium oxide, palladium-californium alloy pellets, or specialised alloy wires. The raw material is transferred to an industrial consortium of commercial reencapsulators. These specialised companies manufacture and permanently seal the radioactive isotope into heavy-duty, shielded industrial capsules.
Once securely sealed, this consortium distributes the finished, safe-to-handle industrial radioactive sources to commercial customers worldwide for reactor startups, oil logging, and coal analysis. For non-commercial use, the REDC Californium Facility directly administers the Californium-252 Industrial Sales/Loan Program, lending out specialised neutron source capsules to academic universities, research organisations, and other US government agencies.
