Frontier Technology Corp (FTC) is a leading global supplier of californium-252 (Cf-252) neutron sources and radioactive shipping containers. We offer a full range of Cf-252 sources, rod assemblies, custom shielding and containers. In this guide, we answer some of the most frequently asked questions about Cf-252.

General Questions

What is Cf-252? What does it look like?

Californium is a radioactive element with extensive industrial applications. First identified in 1950 at the University of California Berkeley, Cf-252 is the only isotope of californium that spontaneously emits neutrons. A single microgram can release up to 170 million neutrons per minute. Californium was the sixth transuranium element to be discovered, but it remains one of the only to be broadly used in applications such as nuclear start-up, sand, shale, oil and gas, and more.

Cf-252 is a silver-white metal, and the isotope has a half-life of just 2.65 years. It has a primary energy of 2 MeV. 

View of Californium under a microscope

How is Cf-252 made?

Most of the Cf-252 used in the western world comes from Oak Ridge National Laboratory (ORNL), a facility that also serves as a leading global supplier of Cf-252. Scientists at ORNL use a high flux isotope reactor (HFIR) to produce Cf-252 and other isotopes. Using curium as a fuel source, the HFIR uses the flux trap principle to generate and trap neutrons, which can then be used in isotope production.

How is the activity of Cf-252 measured?

Californium-252 is a radioactive metal that is measured in micrograms and milligrams.

All other isotopes are measured in the form of Curies.

What are the advantages of Cf-252?

Cf-252 offers several key advantages that make it useful in a range of industries. As an extremely powerful neutron emitter, it is an ideal startup source for nuclear reactors, which require a large and stable neutron source. Its powerful neutron emission means a small piece of Cr-252 can be used in applications with size limitations such as boreholes and well logging. 

Cf-252 sources are portable and temperature-stable, so they can be used in extreme high-temperature environments in the field, not only in labs or other facilities.

What is Cf-252 used for?

The primary applications of Cf-252 are: material analysis and neutron emission. Material analysis applications include detecting hazardous materials – including IEDs –  via PINS systems by the military and defense industries, as well as composition analysis in the oil and gas industry to analyze drill sites, and in the coal and cement industries to detect the elemental composition of the material in real-time.

In the nuclear energy industry, Cf-252’s spontaneous neutron emission is used to initiate the nuclear chain reaction needed to start up a nuclear reactor. 

Other industries that rely on Cf-252 include academic and research institutions, governmental research and lab facilities, and medical facilities, which primarily use Cf-252 for research or spectroscopy.

How is Cf-252 contained and protected?

Since Cf-252 is radioactive, it must be thoroughly contained to protect nearby people, structures, and equipment. At Frontier, we offer both single and double encapsulation for Cf-252 neutron sources. An inner capsule can be used on its own as a single encapsulated capsule,  whereas a double encapsulated capsule contains both an inner and an outer capsule. Our capsules are constructed from durable stainless steel or Zircaloy-2.

How is Cf-252 shipped?

With proper shielding, Cf-252 can be safely shipped to virtually any location worldwide (please note that Frontier Technology Corporation does not ship to countries on the embargo list). The key to proper shielding is the use of Type-A radioactive neutron shipping containers. Frontier’s Type-A containers are made with a steel outer shell and filled with proprietary water-extended polyester (WEP) shielding material for safety. They comply with 10CFR50 Appendix B, U.S. Department of Transportation (USDOT), and U.S. Nuclear Regulatory Commission (USNRC) regulations.

All of Frontier’s radioactive shipping containers are tested to ensure their ability to maintain integrity during normal transport conditions. This includes specific testing to withstand jostling, drops and impact as well as exposure to precipitation. 

Why is Cf-252 expensive?

The main driver of the price for Cf-252 is the fact that there is a limited global supply of it.  Californium-252 does not occur in the natural world and must be synthesized with special high-flux isotope reactors. Because there are only two of these reactors worldwide, and the production process for Cf-252 can take up to two years, the isotope supply remains limited and, therefore, costly.

Production and transportation costs also influence cost.   

What are the conversion measurements for 1 microgram (µg) of Cf-252?

  • 1µg = 2.31 x 106 neutrons/second (n/s)
  • 1µg = 0.5mCi
  • 1 µg = 0.02 GBq

What are Yellow III, Yellow II, and White I classifications?

Radioactive Category LabelsMaximum Surface mRem/hrTransport Index
White I0.50
Yellow II501.0
Yellow III20010

What is the proper label for shipping containers containing Cf-252?


What is the proper labeling format for EMPTY shipping containers that previously contained radioactive material?


Questions About Californium-252 at Frontier Technology Corporation

What are the similarities and differences between Frontier's Model 10 and Model 10S capsules?

  • Both are single-encapsulated sources.
  • Both are certified as Special Form by IAEA.
  • Both are inner capsules for double-encapsulated sources. (Model 100)
  • Model 10 = 5.5mm x 24.8mm
  • Model 10S = 5.5mm x 11.9mm

How are Frontier's sources sealed?

All sources are encapsulated in stainless steel or Zircaloy 2 capsules and welded with Tungsten Inert Gas (TIG) welding to meet Special Form requirements.

What does “NIST-traceable” mean, and are Frontier sources NIST-traceable?

NIST stands for the National Institute of Standards and Technology, and is an agency of the U.S. Department of Commerce. NIST measurements are the standard that all industrial measurements are held to.

ALL Frontier sources are NIST-traceable, and certification can be provided upon request.

Does Frontier provide certified neutron emission statements?

Certified neutron emission statements are provided upon request.

Can Frontier ship Cf-252 sources to all countries?

Frontier ships Cf-252 sources, startup rod assemblies, shipping containers, and shielding walls to every country in the world with the exception of those on the embargo list.

Why choose Frontier Technology Corporation for Cf-252?

Frontier Technology Corporation has over 40 years of experience in providing customer-tailored neutron sources, including PINS sources and nuclear start-up rods. We also supply Type-A radioactive neutron shipping containers, custom shielding, and antimony-beryllium pellets. With decades of experience, we have become a leading global provider of Cf-252. Our quality standards are unmatched in the industry. 


Frontier is licensed by the Ohio Department of Health, and our design processes, fabrication, construction, and testing all comply with 10CFR50, Appendix B standards. We also comply with stringent ODH, Nuclear Regulatory Commission, ISO 2919, ASTM, and ANSI standards, and our neutron sources meet the requirements for IAEA Special Form Certification issued by the U.S. Department of Transportation.

For more information, or to learn more about Cf-252, contact us or request a quote today.

For more information, or to learn more about Cf-252, contact us or request a quote today.

Frequently Asked Questions About Californium-252
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