Stable
isotope
(none)
Relative
atomic mass
Mole
fraction
Californium does not occur naturally in the Earth’s crust. It was first synthesized in 1950 by
Glenn T. Seaborg and his team at the University of California using the reaction
242
Cm (4He, n) 245Cf. The element was named for the state where it was first synthesized.
Californium isotopes in industry
252
Cf is a very active source of neutrons (2.3 × 106 neutrons per second per microgram) with a
half-life of 2.65 years. The energy spectrum of the neutrons is very similar to that of a fission
reactor, and small amounts of 252Cf provide an ideal portable source for low neutron flux
applications [66] [631, 632]. 252Cf is used for PGNAA (prompt gamma neutron activation
analysis method for detecting many chemical elements in samples simultaneously) [633] of coal,
cement, and minerals, weapon components, and chemical munitions. This method provides quick
and non-destructive elemental analysis of a sample. For example, 252 Cf, as the neutron source for
PGNAA, is used to detect the presence of antitank mines [631, 632].
Neutron activation analysis (NAA) uses 252Cf as a portable neutron source to bombard a
small sample from the area of interest with neutrons and analyze the radioactive emissions from
that bombardment to help identify silver or gold ore [66, 634]. 252Cf can be used in neutron
moisture gauges to locate water [66, 634]. 252Cf can be used in borehole geophysical logging for
subsurface PGNAA investigation of waste (Figure 1) [631, 632, 635].
Formation fluid identification uses 252Cf as a chemical neutron source for elastic/inelastic
neutron backscattering and/or neutron activation methods in well-logging to determine water and
oil-bearing layers and other downhole properties of the well bore [66, 631, 632, 634, 635].
Fig. 1: 252 Cf is a logging tool used in well logging to identify downhole properties of a well bore.
(Photo Source: U.S. Department of Labor- Occupational Safety & Health Administration) [636].
Californium isotopes in medicine
252
Cf is sometimes used as a source of neutrons in boron neutron capture therapy (BNCT) that
can be delivered close to the region of a tumor [66, 631, 632]. Brachytherapy can use 252Cf to
treat many types of cancer [66, 631, 632].
Glossary
atomic number (Z) – The number of protons in the nucleus of an atom.
brachytherapy – the treatment of cancer, especially prostate cancer, by the insertion of
radioactive implants directly into the tissue near the tumor. [return]
electron – elementary particle of matter with a negative electric charge and a rest mass of about
9.109 × 10–31 kg.
element (chemical element) – a species of atoms; all atoms with the same number of protons in
the atomic nucleus. A pure chemical substance composed of atoms with the same number of
protons in the atomic nucleus [703]. [return]
fission – the spontaneous (or induced by particle collision) splitting of a heavy nucleus into a
pair (only rarely more) of nearly equal fission fragments (fission products) generally with some
neutrons. Fission is accompanied by the release of a large quantity of energy. [return]
gamma rays (gamma radiation) – a stream of high-energy electromagnetic radiation given off
by an atomic nucleus undergoing radioactive decay. The energies of gamma rays are higher
than those of X-rays; thus, gamma rays have greater penetrating power.
half-life (radioactive) – the time interval that it takes for the total number of atoms of any
radioactive isotope to decay and leave only one-half of the original number of atoms. [return]
isotope – one of two or more species of atoms of a given element (having the same number of
protons in the nucleus) with different atomic masses (different number of neutrons in the
nucleus). The atom can either be a stable isotope or a radioactive isotope.
neutron – an elementary particle with no net charge and a rest mass of about 1.675 × 10–27 kg,
slightly more than that of the proton. All atoms contain neutrons in their nucleus except for
protium (1H). [return]
proton – an elementary particle having a rest mass of about 1.673 × 10–27 kg, slightly less than
that of a neutron, and a positive electric charge equal and opposite to that of the electron. The
number of protons in the nucleus of an atom is the atomic number.
radioactive decay – the process by which unstable (or radioactive) isotopes lose energy by
emitting alpha particles (helium nuclei), beta particles (positive or negative electrons), gamma
radiation, neutrons or protons to reach a final stable energy state.
radioactive isotope (radioisotope) – an atom for which radioactive decay has been
experimentally measured (also see half-life).
stable isotope – an atom for which no radioactive decay has ever been experimentally measured.
X-rays – electromagnetic radiation with a wavelength ranging from 0.01 to 10 nanometers—
shorter than those of UV rays and typically longer than those of gamma rays.
References
66.
J. Peterson, McDonell, M., Haroun, L., Monette, F., Hildebrand, R.D., and Taboas, A.
Radiological and Chemical Fact Sheets to Support Health Risk Analyses for Contaminated
Areas. Prepared by Argonne National Laboratory Environmental Science Division in
collaboration with U.S. Department of Energy, Richland Operations Office and Chicago
Operations Office. 2014 Feb. 22.
http://www.remm.nlm.gov/ANL_ContaminantFactSheets_All_070418.pdf
631. a. A. C. W. Osborne-Lee I.W. Californium-252 A Remarkably Versatile Radioisotope. O.
R. N. Laboratory. ORNL/TM-12706.
632. R. C. Martin, Knauer, J.B., and Balo, P.A. Production, Distribution, and Applications of
Californium-252 Neutron Sources. O. R. N. Laboratory. DE-AC05960R22464.
633. NIST. Prompt gamma-ray activation analysis. NIST.
http://www.nist.gov/mml/csd/inorganic/pgaa.cfm
634. L. A. N. Laboratory. Periodic Table of Elements: LANL- Californium. Los Alamos
National Laboratory. 2014 Feb. 25. http://periodic.lanl.gov/98.shtml
635. L. J. Bond, Harris, R.V., Denslow, K.M., Moran, T.L., Griffin, J.W., Sheen, D.M., Dale,
G.E., and Schenkel, T. Evaluation of Non-Nuclear Techniques for Well Logging: Technology
Evaluation. P. N. N. Laboratory.
636. U. S. D. o. Labor. Oil and Gas Well Drilling and Servicing eTool-Servicing-Special
Services- Well Logging. Occupational Safety & Health Administration, United States
Department of Labor. 2014 Feb, 25.
http://www.osha.gov/SLTC/etools/oilandgas/servicing/special_services.html#well_logging
703. I. U. o. P. a. A. Chemistry. Compendium of Chemical Terminology, 2nd ed. (the "Gold
Book"). Blackwell Scientific Publications, Oxford (1997).