Californium is a synthetic radioactive element found on the bottom row of the periodic table, along with other actinides. 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.
What Is Californium?
Californium is a synthetic, radioactive chemical element with the symbol Cf and atomic number 98. Discovered in 1950 by researchers at the University of California, Berkeley, californium was named after the university where the research took place and the state of California. It is one of the heaviest known elements and belongs to the actinide series on the bottom of the periodic table.
Physical Properties of Californium
| Atomic Symbol: | Cf |
| Atomic Number: | 98 |
| Atomic Mass/Weight: | 251 (most stable isotope) -Second-highest atomic mass of all known elements |
| Appearance: | Californium is a silvery-white metal, though it is rarely seen in its pure form due to its high radioactivity. The californium metal is malleable, can be cut using a razor blade, and can tarnish when exposed to air. |
| Density: | 15.1 g/cm³ |
| Melting Point: | Approximately 900 °C (1173 K, 1652 °F) |
| Boiling Point: | Unknown, but likely to be above 1470 °C (1743 K, 2678 °F) |
| Phase at Room Temperature: | Solid |
| Structure: | Californium has a face-centered cubic crystal structure at room temperature. |
Chemical Properties of Californium
Oxidation States: Californium primarily exhibits the +3 oxidation state, which is the most stable and common. There is also evidence of a +2 state.
Reactivity: Californium is highly radioactive and reacts with air, water, and acids. It does not react with bases. It can form compounds, including oxides and halides, and be used in different chemical processes and studies.
- It will form compounds such as californium oxide (Cf₂O₃), californium trichloride (CfCl₃), and other complex compounds.
Radiation: Californium is highly radioactive and emits alpha particles. Some of its isotopes, such as Cf-252, are strong neutron emitters.
- One microgram of Cf-252 can release 170 million neutrons every minute. This presents significant radioactivity to nearby people, animals, structures, equipment; therefore, proper safety measures must be followed when handling the material.
Where Can Californium Be Found Naturally, Or Is It A Synthetic, Man-Made Element?
Californium is not found naturally on Earth. It is a purely synthetic element, and the production process is complex, with multiple steps of neutron capture and decay.
Isotopes of Californium
Californium has several isotopes, all of which are radioactive. These isotopes vary in their half-lives, modes of decay, properties, and applications. These isotopes play crucial roles in scientific research, medical treatments, industrial processes, and security applications. Notable californium isotopes include:
- Californium-252 (Cf-252): This isotope is highly valuable due to its ability to emit neutrons. It has a half-life of about 2.645 years.
- Californium-249 (Cf-249): With a half-life of 351 years, this isotope is used in research and scientific applications.
- Other Californium Isotopes Include: Cf-237, Cf-238, Cf-239, Cf-240, Cf-241, Cf-242, Cf-243, Cf-244, Cf-245, Cf-246, Cf-247, Cf-248, Cf-250, Cf-251, Cf-253, Cf-254, Cf-255, and Cf-256
Although 20 isotopes of californium have been identified and characterized, most of them have issues that limit their applicability.
How Is Californium Used?
Californium, and particularly Cf-252 with its high neutron emission capabilities, has a wide range of applications across various fields. These are some of the primary uses of californium:
Nuclear Reactors
Californium-252 is an important source of neutrons within the start-up rods that are used to initiate a nuclear fission reaction. Cf-252 has high neutron flux and spontaneous fission that causes the fission reaction in uranium oxide fuel rods. Start-up rods can be used to trigger the initial startup chain reaction in a new reactor or to restart a reactor that has been taken offline.
Small Modular Reactors (SMRs)
Currently in development, these small-scale nuclear reactors offer safe, clean, and cost-conscious nuclear power for locations that are not equipped to accommodate full nuclear plants. With a power capacity of up to 300 MW(e) per unit, approximately a third of the conventional nuclear reactors’ power capacity, SMRs typically have a footprint ¼ the size of traditional nuclear plants.
Medical Treatments
Californium plays a crucial role in cancer treatment through a method known as neutron therapy. In this therapy, californium-252 is used to target and destroy cancerous cells with high precision, minimizing damage to surrounding healthy tissues.
Space Exploration
There are potential applications for californium in space exploration, particularly in powering space probes and satellites. The high energy output from californium’s radioactive decay could be harnessed for long-term energy needs in space missions. NASA is also studying the differences between the effects of radiation in space and on Earth using californium.
Homeland Security
Californium-252 is used in security scanning equipment to detect explosives and other hazardous materials. Neutron emission helps identify the elemental composition of suspicious objects.
- Portable isotopic neutron spectroscopy (PINS) uses a neutron emission process to analyze the contents of explosive devices by measuring and analyzing the gamma-ray signatures of a target. PINS devices are used by the Department of Homeland Security, the National Guard, customs and border protection personnel, and the military.
- Neutron scanners with Cf-252 are also used for scanning fuel rods, weapons parts, and aircraft components to detect cracks, bad welds, and other faults that may affect the normal operation or integrity of the parts.
Industrial Applications
Californium is employed in several industrial processes due to its neutron emission properties:
- Metal Fatigue Detection: Neutron radiography, which uses californium-252, helps in detecting structural weaknesses and metal fatigue in critical components.
- Oil Exploration: In the oil industry, californium-252 is used in neutron activation analysis to locate oil deposits, and to determine the composition and properties of geological formations immediately surrounding the bore. The neutrons help identify the presence and concentration of various elements within geological samples. This information gives drilling operations a better understanding of the area, and allows them to adjust operations for local conditions.
- Material Scanning & Neutron Activation Analysis: This technique involves irradiating samples with neutrons from californium-252 to determine the composition and concentration of elements within the samples, including trace amounts that may not be detectable with other methods.
Scientific Research & Education
Researchers use californium in various scientific studies and experiments:
- Element Synthesis: Californium is used in the production of heavier transuranium elements. Its high neutron emission helps in the synthesis of heavier elements beyond californium on the periodic table.
- Effects of Radiation: Californium is used in University research to study the acute and delayed effects of radiation.
- Education & Training: Californium is used in educational and training contexts, especially in advanced nuclear science and engineering programs. Many universities and research centers house research reactors that use Cf-252 in start-up rods.
- Calibrating Equipment: Cf-252 is also used for calibrating equipment used in educational and research facilities.
Why Is CF-252 The Most Used Isotope Of Californium?
Californium-252 (Cf-252) is one of the most valuable and widely used isotopes of californium due to its unique neutron emission properties. Cf-252 provides a highly reliable and efficient source of neutrons compared to other neutron sources. Its consistent neutron output ensures dependable performance in various critical applications, making it an essential tool for industries that require high-energy neutron radiation. Here’s a closer look at Cf-252 and its neutron radiation properties.
Neutron Emission
Cf-252 is one of the few isotopes that undergoes spontaneous fission, a process of radioactive decay in which the nucleus splits into two or more smaller nuclei, releasing a substantial amount of energy and neutrons. Approximately 3% of Cf-252’s decay results in spontaneous fission, producing an average of 3.7 neutrons per fission event. 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.
Cf-252’s Half-Life
Cf-252 has a half-life of about 2.645 years, meaning it takes that long for half of the isotope to decay. While relatively short compared to other isotopes, this half-life is practical for various applications that require a consistent neutron source over a few years. Its high neutron flux also means it needs replenishment for continuous-use applications.
Decay Modes
- Alpha Decay: In addition to spontaneous fission, Cf-252 primarily decays by emitting alpha particles (helium nuclei). This process contributes to its overall radioactivity and the emission of gamma rays.
- Gamma Radiation: Alongside neutrons and alpha particles, Cf-252 decay produces gamma radiation. This high-energy electromagnetic radiation requires careful handling and shielding to protect against exposure.
What Are The Alternatives To Using Californium-252 In Its Various Applications?
- Neutron Sources: Alternatives include isotopes like americium-241 and plutonium-238, though they are generally less efficient neutron sources compared to Cf-252.
- Cancer Treatment: Other isotopes such as iodine-125 and iridium-192 are used in brachytherapy but may not offer the same neutron emission properties as Cf-252.
- Nuclear Reactor Startup: Plutonium-238 and other isotopes can be used to initiate chain reactions, although Cf-252 remains highly effective due to its high neutron emission rate.
Handling and Safety
Due to its high radioactivity, handling Cf-252 requires stringent safety protocols. Here are key safety measures:
- Shielding: To protect against neutron and gamma radiation, Cf-252 must be stored and handled with appropriate radiation and neutron shielding materials.
- Distance and Time: Minimizing exposure time and maximizing distance from the Cf-252 source are crucial to reducing radiation exposure.
- Protective Equipment: Personnel handling Cf-252 must use specialized protective equipment and follow rigorous safety procedures to prevent contamination and exposure.
- Transportation: Type-A shipping containers are commonly used to transport radioactive material between facilities and end-user sites. These neutron-designated shipping containers must be certified as USDOT Type A, Specification 7A packages. Frontier designs and fabricates Type-A shipping containers in various sizes for rental or purchase.
How Is Californium Disposed Of After Its Useful Life?
Californium must be disposed of as high-level radioactive waste, which means containing it in appropriately-shielded containers at approved disposal facilities. Frontier offers a free source return program for its customers, ensuring proper disposal of used sources.
How Is Californium Created?
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.
Californium can be made by bombarding a variety of different elements with neutrons, commonly berkelium-249 or curium-244. The californium isotope forms through a series of beta decays and further neutron captures. Long-term neutron irradiation of plutonium, americium, and curium can also produce californium in milligram amounts.
The History of Californium
Californium was discovered in 1950 by a team of scientists led by Glenn T. Seaborg, Stanley G. Thompson, Albert Ghiorso, and Kenneth Street, Jr. It was synthesized by bombarding curium-242 with alpha particles (helium ions) in a cyclotron. The resulting element, californium-245, marked a significant milestone in the field of nuclear chemistry, contributing to our understanding of the transuranium elements. Weighable quantities of Cf-252 were later produced in 1954.
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.
How Much Californium Is Produced Annually Worldwide?
Production Levels: Californium is not naturally occurring and is not found anywhere on Earth in a natural supply. Only a few grams of Cf-252 are produced annually worldwide, primarily due to the high cost and complexity of production.
Leading Producers: The United States is the leading producer of Cf-252, particularly the Oak Ridge National Laboratory in Oak Ridge, Tennessee (ORNL). ORNL uses its High Flux Isotope Reactor (HFIR) to produce an average of 25mg of the isotope per year. Russia also produces small quantities of californium.
Californium Price
Californium is one of the most expensive elements, with costs reaching up to $27 million per gram for Cf-252. 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. 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.
Final Thoughts about Californium
Californium (and more specifically Cf-252) holds significant value for scientific research, medical treatments, and industrial applications because of its unique, spontaneous neutron emissions. The discovery and synthesis of californium marked a monumental step in nuclear chemistry, allowing for advancements in neutron activation analysis, neutron radiography, and nuclear reactors. Its role in scientific research extends our understanding of nuclear reactions and the behavior of heavy elements, contributing to ongoing advancements in nuclear physics and chemistry.
As a source of spontaneous neutron emissions, it is an important material for the nuclear start-up process for new reactors, including Small Modular Reactors (SMR), research reactors, and for bringing out-of-use reactors back online.
About Frontier
Founded in 1984 in Xenia, Ohio, Frontier Technology Corporation has established itself as the global leader in the supply and shipment of californium-252 (Cf-252). We offer a broad selection of products—including high-integrity neutron sources, Type-A shipping containers, custom neutron shielding walls, nuclear reactor start-up rods, and much more.
Available in over 200 countries, our products are produced and shipped in compliance with rigorous industry standards, including the Nuclear Regulatory Commission, the Ohio State Department of Health, ISO-2919, ASTM, and ANSI. Our team has over three decades of experience and brings extensive knowledge and expertise to all of our customers.
Frontier’s Californium Neutron Sources
Frontier, a leading provider of californium-252, offers a range of high-quality Cf-252 neutron sources and turnkey californium solutions. Our Cf-252 sources comply with all relevant regulatory requirements, which guarantees their safety and efficacy. We adhere to a strict Quality Assurance Program throughout the production process to ensure our clients receive the highest-quality products and services.
Our primary capabilities include:
- Source design
- Source encapsulation
- Neutron shielding walls
- Nuclear start-up rods
- Antimony-beryllium pellets
- Custom fabrication
- Shipping and logistics
Our Cf-252 Products, Services, & Solutions
Neutron Sources
Frontier’s neutron sources provide a consistent and reliable supply of neutrons for applications such as material analysis, reactor startup, and scientific research. These sources are available in various configurations, including encapsulated and double encapsulated sources for enhanced safety and ease of handling. We offer capsules containing Cf-252 in wire form, up to a maximum content level of 5 mg, in standard and custom single- and double-encapsulated neutron sources.
Radiography & Custom Sources
Frontier’s Cf-252 radiography sources are used in nondestructive testing to inspect materials and components for internal defects. These sources produce high-resolution images that reveal hidden flaws, ensuring structural integrity and safety.
Frontier also offers custom Cf-252 sources tailored to specific customer requirements for specialized applications.
Nuclear Start-Up Rods
We manufacture complete startup rod assemblies that include californium-252 (Cf-252) neutron sources, antimony-beryllium pellets, and all parts of the rod assembly. Rods are produced according to our customer’s specifications and meet or exceed the highest level of safety requirements and standards set by the nuclear industry.
Shielding Walls
Neutron shielding walls are essential for maintaining a safe environment and operational integrity when using neutron emitting sources. Our neutron shielding walls are trusted throughout the mining, nuclear, military and other industries.
Antimony-Beryllium Pellets
Frontier designs and fabricates antimony-beryllium (Sb-Be) pellets for nuclear start-up rod assemblies. All pellets are manufactured per user-supplied specifications for diameter, length, and width. Frontier can accommodate prototype-to-production volume.
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.
To learn more about the production of Cf-252 or about our Cf-252 sources and services, contact us or request a quote today.
