Californium is a synthetic radioactive element found on the bottom row of the periodic table, along with other actinides. It was first discovered in 1950 at the University of California Radiation Laboratory in Berkeley by bombarding curium with alpha particles (helium nuclei). Pure californium metal has a silvery-white appearance and is soft enough to be easily cut with a razor blade.

Initial experiments with californium in its concentrated form began in 1958. Since then, 20 isotopes of californium have been characterized, with mass numbers ranging from 237 to 256. One of these isotopes is californium-252, which was first isolated from a neutron-irradiated sample of plutonium-239. As an exclusively synthetically made element (it cannot be found in nature), californium-252 is very rare and is produced via neutron bombardment in high flux isotope reactors or particle accelerators.

On this page, we walk through some of the properties and uses of this unique isotope and provide additional resources for your reference.

Californium Properties & Advantages

Much has been learned about the properties of californium since its initial discovery in 1950. A few basic details of this element include:

  • Atomic symbol: Cf
  • Atomic number: 98
  • Atomic weight: 251
  • Second-highest atomic mass of all known elements
  • Categorized as an actinide element
  • Exists in a solid phase at room temperature
  • Exhibits a melting point of 900 °C (1,652 °F) and an estimated boiling point of 1,470 °C (2,678 °F)

Californium-252 is the most commonly used isotope of californium, particularly when it comes to nuclear and industrial applications (see next section for more details). It is a prolific neutron emitter, meaning it releases a substantial number of neutrons when it breaks apart. Just a single microgram of californium can produce approximately 170 million neutrons per minute. This unusual property makes it highly radioactive and a potential biological hazard. If handled properly, however, this strong radioactivity is a valuable trait for specific applications.

What is Californium Used For?

Although 20 isotopes of californium have been identified and characterized, most of them have issues that limit their applicability.

Californium-252 stands out from other californium isotopes for its greater stability and exceptional neutron emission capabilities. In fact, it is presently the only californium isotope that is considered to have substantial practical value. Its current applications span a wide range of industries and new uses are continually being discovered. Some of the most common use cases include:

  • Nuclear. Californium-252 can be used as a neutron source to initiate the nuclear fission process in reactors.
  • Medical. In the medical field, the neutrons released by californium-252 can be used to target certain cancer tumors when other radiation treatments have failed.
  • Oil and petrochemical. When used in well-logging applications, californium-252’s neutron emissions provide drilling operators with critical data that allows them to better understand the surrounding area.
  • Material scanning. The neutron emissions from californium-252 can be used in various material scanning operations. In prompt-gamma neutron activation analysis (PGNAA), for example, neutron beams can be used to irradiate a sample, and the gamma rays emitted from it can be measured and used to determine the composition of the material. Californium-252 can also serve as a neutron source for portable isotopic neutron spectroscopy (PINS), which enables the identification of contents in chemical warfare materials.

Understanding Californium Price

Although californium-252 is known for coming at a higher cost, it remains an extremely valuable neutron source due to its ability to undergo spontaneous fission, as well as costs of production. Some of the factors that influence the price of californium include:

  • Limited availability. Californium-252 is not a naturally occurring element and can only be produced in a high flux isotope reactor. Worldwide there are only two nuclear reactors capable of producing Cf-252: High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL) and SMR3 at RIAR, Russia.
  • Production costs. The production process of californium-252 takes almost two years to complete from start to finish.
  • Transportation costs. Because this isotope is highly radioactive, it requires the construction of specialized Type A shipping containers to protect the contents from damage during the shipping process.

Safely Transporting Californium: Type A Radioactive Shipping Containers

Californium-252 requires specialized shipping containers in order to be transported safely. Neutron-designated shipping containers must be certified as USDOT Type A, Specification 7A packages. These Type A shipping containers are specifically designed for the transportation of neutron contents between production facilities and end-user sites.

At Frontier Technology Corporation (FTC), our californium shipping containers are designed and constructed in-house. Our designs have been subjected to rigorous testing under a series of adverse conditions to validate their strength. This ensures that the containers are properly constructed to withstand any type of threat that may arise during shipping. In addition to specialized shipping containers, the transportation of californium-252 also requires detailed documentation from the consumer. This includes the relevant destination shipping information as well as an end-user statement that specifies how and where the contents will be used.

Additional Californium Facts & Considerations

Since its discovery in 1950, californium has been extensively characterized and has found many valuable uses in neutron source applications. All of californium’s isotopes are radioactive and have varying half-lives. Californium-252 has a half-life of 2.645 years, and it is also the only isotope that spontaneously emits neutrons.

Because it is such a strong neutron emitter, californium-252 should be handled with extreme caution to avoid health hazards. It can enter the body through inhalation of airborne particles or by ingestion of contaminated foods or beverages. Once it has entered the body, 65% will be deposited on bones, 25% will reach the liver, and the remainder will reach other organs or be excreted. It can cause cancer, as well as external tissue damage via gamma-ray emission. Even though neutron emitters can be very dangerous, californium-252 comes in the form of a solid alloy wire and poses less risk of leaking radioactive contamination.

For more information about californium, please visit FTC’s Californium Facts or FAQ pages.

Californium-252 Neutron Sources at Frontier Technology Corporation (FTC)

Californium-252 is a radioactive isotope of the californium element with the ability to emit neutrons. This makes it an important neutron source for a variety of applications, from nuclear reactors to material scanning devices.

Founded in 1984, FTC has established itself as a leading global supplier and manufacturer of custom californium-252 sources for a variety of industrial and research-related applications. In addition to our neutron source offerings, we also design and construct our own high-quality Type A radioactive containers with water-extended polyester (WEP) shielding options for maximum protection during the shipping process. All of our products comply with strict ODH, Nuclear Regulatory Commission, ASTM, and ANSI standards. Additionally, as part of our commitment to safety and customer satisfaction, we offer a return program that allows any FTC-fabricated californium source to be returned to our facility for free disposal.

If you would like to learn more about californium or about FTC’s services and capabilities, please contact us today.

For additional insights about californium-252 and our company, check out the following resources: