Californium Californium is a radioactive chemical element with the symbol Cf and atomic number 98. The element was first synthesized in 1950 at Lawrence Berkeley National Laboratory (then the University of California Radiation Laboratory), by bombarding ...

(₉₈Cf) is an artificial element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no

stable isotope The term stable isotope has a meaning similar to stable nuclide, but is preferably used when speaking of nuclides of a specific element. Hence, the plural form stable isotopes usually refers to isotopes of the same element. The relative abundanc ...

s. The first

isotope Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numbers) ...

to be synthesized was ²⁴⁵Cf in 1950. There are 20 known

radioisotope A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transferr ...

s ranging from ²³⁷Cf to ²⁵⁶Cf and one

nuclear isomer A nuclear isomer is a metastable state of an atomic nucleus, in which one or more nucleons (protons or neutrons) occupy excited state, higher energy levels than in the ground state of the same nucleus. "Metastable" describes nuclei whose excited ...

, ^249mCf. The longest-lived isotope is ²⁵¹Cf with a

half-life Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable ato ...

of 898 years.

List of isotopes

, - , rowspan=3, ²³⁷Cf , rowspan=3 style="text-align:right" , 98 , rowspan=3 style="text-align:right" , 139 , rowspan=3, 237.06207(54)# , rowspan=3, 2.1(3) s , SF , (various) , rowspan=3, 5/2+# , - , β⁺ , ²³⁷Bk , - , α , ²³³Cm , - , rowspan=3, ²³⁸Cf , rowspan=3 style="text-align:right" , 98 , rowspan=3 style="text-align:right" , 140 , rowspan=3, 238.06141(43)# , rowspan=3, 21.1(13) ms , SFLightest nuclide known to undergo

spontaneous fission Spontaneous fission (SF) is a form of radioactive decay that is found only in very heavy chemical elements. The nuclear binding energy of the elements reaches its maximum at an atomic mass number of about 56 (e.g., iron-56); spontaneous breakdo ...

as the main decay mode , (various) , rowspan=3, 0+ , - , β⁺ (rare) , ²³⁸Bk , - , α (rare) , ²³⁴Cm , - , rowspan=2, ²³⁹Cf , rowspan=2 style="text-align:right" , 98 , rowspan=2 style="text-align:right" , 141 , rowspan=2, 239.06242(23)# , rowspan=2, 60(30) s
9(+37−12) s, α , ²³⁵Cm , rowspan=2, 5/2+# , - , β⁺ (rare) , ²³⁹Bk , - , rowspan=3, ²⁴⁰Cf , rowspan=3 style="text-align:right" , 98 , rowspan=3 style="text-align:right" , 142 , rowspan=3, 240.06230(22)# , rowspan=3, 1.06(15) min , α (98%) , ²³⁶Cm , rowspan=3, 0+ , - , SF (2%) , (various) , - , β⁺ (rare) , ²⁴⁰Bk , - , rowspan=2, ²⁴¹Cf , rowspan=2 style="text-align:right" , 98 , rowspan=2 style="text-align:right" , 143 , rowspan=2, 241.06373(27)# , rowspan=2, 3.78(70) min , β⁺ (75%) , ²⁴¹Bk , rowspan=2, 7/2−# , - , α (25%) , ²³⁷Cm , - , rowspan=3, ²⁴²Cf , rowspan=3 style="text-align:right" , 98 , rowspan=3 style="text-align:right" , 144 , rowspan=3, 242.06370(4) , rowspan=3, 3.49(15) min , α (80%) , ²³⁸Cm , rowspan=3, 0+ , - , β⁺ (20%) , ²⁴²Bk , - , SF (.014%) , (various) , - , rowspan=2, ²⁴³Cf , rowspan=2 style="text-align:right" , 98 , rowspan=2 style="text-align:right" , 145 , rowspan=2, 243.06543(15)# , rowspan=2, 10.7(5) min , β⁺ (86%) , ²⁴³Bk , rowspan=2, (1/2+) , - , α (14%) , ²³⁹Cm , - , rowspan=2, ²⁴⁴Cf , rowspan=2 style="text-align:right" , 98 , rowspan=2 style="text-align:right" , 146 , rowspan=2, 244.066001(3) , rowspan=2, 19.4(6) min , α (99%) , ²⁴⁰Cm , rowspan=2, 0+ , - , EC (1%) , ²⁴⁴Bk , - , rowspan=2, ²⁴⁵Cf , rowspan=2 style="text-align:right" , 98 , rowspan=2 style="text-align:right" , 147 , rowspan=2, 245.068049(3) , rowspan=2, 45.0(15) min , β⁺ (64%) , ²⁴⁵Bk , rowspan=2, (5/2+) , - , α (36%) , ²⁴¹Cm , - , rowspan=3, ²⁴⁶Cf , rowspan=3 style="text-align:right" , 98 , rowspan=3 style="text-align:right" , 148 , rowspan=3, 246.0688053(22) , rowspan=3, 35.7(5) h , α , ²⁴²Cm , rowspan=3, 0+ , - , EC (5×10⁻⁴%) , ²⁴⁶Bk , - , SF (2×10⁻⁴%) , (various) , - , rowspan=2, ²⁴⁷Cf , rowspan=2 style="text-align:right" , 98 , rowspan=2 style="text-align:right" , 149 , rowspan=2, 247.071001(9) , rowspan=2, 3.11(3) h , EC (99.96%) , ²⁴⁷Bk , rowspan=2, (7/2+)# , - , α (.04%) , ²⁴³Cm , - , rowspan=2, ²⁴⁸Cf , rowspan=2 style="text-align:right" , 98 , rowspan=2 style="text-align:right" , 150 , rowspan=2, 248.072185(6) , rowspan=2, 333.5(28) d , α (99.99%) , ²⁴⁴Cm , rowspan=2, 0+ , - , SF (.0029%) , (various) , - , rowspan=2, ²⁴⁹Cf , rowspan=2 style="text-align:right" , 98 , rowspan=2 style="text-align:right" , 151 , rowspan=2, 249.0748535(24) , rowspan=2, 351(2) y , α , ²⁴⁵Cm , rowspan=2, 9/2− , - , SF (5×10⁻⁷%) , (various) , - , style="text-indent:1em" , ^249mCf , colspan="3" style="text-indent:2em" , 144.98(5) keV , 45(5) μs , , , 5/2+ , - , rowspan=2, ²⁵⁰Cf , rowspan=2 style="text-align:right" , 98 , rowspan=2 style="text-align:right" , 152 , rowspan=2, 250.0764061(22) , rowspan=2, 13.08(9) y , α (99.92%) , ²⁴⁶Cm , rowspan=2, 0+ , - , SF (.077%) , (various) , - , ²⁵¹CfHigh

neutron cross-section In nuclear physics, the concept of a neutron cross section is used to express the likelihood of interaction between an incident neutron and a target nucleus. The neutron cross section σ can be defined as the area in cm2 for which the number of ...

, tends to absorb neutrons , style="text-align:right" , 98 , style="text-align:right" , 153 , 251.079587(5) , 900(40) y , α , ²⁴⁷Cm , 1/2+ , - , rowspan=2, ²⁵²CfMost common isotope , rowspan=2 style="text-align:right" , 98 , rowspan=2 style="text-align:right" , 154 , rowspan=2, 252.081626(5) , rowspan=2, 2.645(8) y , α (96.9%) , ²⁴⁸Cm , rowspan=2, 0+ , - , SF (3.09%)High neutron emitter, average 3.7

neutron The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons beh ...

s per fission , (various) , - , rowspan=2, ²⁵³Cf , rowspan=2 style="text-align:right" , 98 , rowspan=2 style="text-align:right" , 155 , rowspan=2, 253.085133(7) , rowspan=2, 17.81(8) d , β⁻ (99.69%) , ²⁵³Es , rowspan=2, (7/2+) , - , α (.31%) , ²⁴⁹Cm , - , rowspan=3, ²⁵⁴Cf , rowspan=3 style="text-align:right" , 98 , rowspan=3 style="text-align:right" , 156 , rowspan=3, 254.087323(13) , rowspan=3, 60.5(2) d , SF (99.69%) , (various) , rowspan=3, 0+ , - , α (.31%) , ²⁵⁰Cm , - , β⁻β⁻ (rare) , ²⁵⁴Fm , - , rowspan=3, ²⁵⁵Cf , rowspan=3 style="text-align:right" , 98 , rowspan=3 style="text-align:right" , 157 , rowspan=3, 255.09105(22)# , rowspan=3, 85(18) min , β⁻ (99.99%) , ²⁵⁵Es , rowspan=3, (7/2+) , - , SF (.001%) , (various) , - , α (10⁻⁵%) , ²⁵¹Cm , - , rowspan=3, ²⁵⁶Cf , rowspan=3 style="text-align:right" , 98 , rowspan=3 style="text-align:right" , 158 , rowspan=3, 256.09344(32)# , rowspan=3, 12.3(12) min , SF (~100%) , (various) , rowspan=3, 0+ , - , α (10⁻⁶%) , ²⁵²Cm , - , β⁻β⁻ (rare) , ²⁵⁶Fm

Actinides vs fission products

Californium-252

Californium-252 (Cf-252, ²⁵²Cf) undergoes spontaneous fission with a

branching ratio In particle physics and nuclear physics, the branching fraction (or branching ratio) for a decay is the fraction of particles which decay by an individual decay mode or with respect to the total number of particles which decay. It applies to eithe ...

of 3.09% and is used in small sized

neutron source A neutron source is any device that emits neutrons, irrespective of the mechanism used to produce the neutrons. Neutron sources are used in physics, engineering, medicine, nuclear weapons, petroleum exploration, biology, chemistry, and nuclear p ...

s. Fission neutrons have an energy range of 0 to 13

MeV In physics, an electronvolt (symbol eV, also written electron-volt and electron volt) is the measure of an amount of kinetic energy gained by a single electron accelerating from rest through an electric potential difference of one volt in vacu ...

with a mean value of 2.3 MeV and a most probable value of 1 MeV. This

produces high neutron emissions and can be used for a number of applications in industries such as nuclear energy, medicine, and

petrochemical Petrochemicals (sometimes abbreviated as petchems) are the chemical products obtained from petroleum by refining. Some chemical compounds made from petroleum are also obtained from other fossil fuels, such as coal or natural gas, or renewable sou ...

exploration.

Nuclear reactors

The neutron sources produced from ²⁵²Cf are most notably used in the start-up of

nuclear reactor A nuclear reactor is a device used to initiate and control a fission nuclear chain reaction or nuclear fusion reactions. Nuclear reactors are used at nuclear power plants for electricity generation and in nuclear marine propulsion. Heat from nu ...

s. Once a reactor is filled with nuclear fuel, the stable neutron emissions from the source material initiates the fission chain reaction.

Military and defense

The portable isotopic neutron spectroscopy (PINS) used by

United States Armed Forces The United States Armed Forces are the military forces of the United States. The armed forces consists of six service branches: the Army, Marine Corps, Navy, Air Force, Space Force, and Coast Guard. The president of the United States is the ...

, the

National Guard National Guard is the name used by a wide variety of current and historical uniformed organizations in different countries. The original National Guard was formed during the French Revolution around a cadre of defectors from the French Guards. Nat ...

Homeland Security Homeland security is an American national security term for "the national effort to ensure a homeland that is safe, secure, and resilient against terrorism and other hazards where American interests, aspirations, and ways of life can thrive" t ...

, and

U.S. Customs and Border Protection United States Customs and Border Protection (CBP) is the largest federal law enforcement agency of the United States Department of Homeland Security. It is the country's primary border control organization, charged with regulating and facilit ...

, employs the use of ²⁵²Cf sources to detect hazardous contents found inside artillery projectiles, mortar projectiles,

rocket A rocket (from it, rocchetto, , bobbin/spool) is a vehicle that uses jet propulsion to accelerate without using the surrounding air. A rocket engine produces thrust by reaction to exhaust expelled at high speed. Rocket engines work entirely fr ...

bomb A bomb is an explosive weapon that uses the Exothermic process, exothermic reaction of an explosive material to provide an extremely sudden and violent release of energy. Detonations inflict damage principally through ground- and atmosphere-t ...

land mine A land mine is an explosive device concealed under or on the ground and designed to destroy or disable enemy targets, ranging from combatants to vehicles and tanks, as they pass over or near it. Such a device is typically detonated automati ...

s, and

improvised explosive device An improvised explosive device (IED) is a bomb constructed and deployed in ways other than in conventional military action. It may be constructed of conventional military explosives, such as an artillery shell, attached to a detonating mechan ...

s (IED).

Oil and petroleum

In the

oil industry The petroleum industry, also known as the oil industry or the oil patch, includes the global processes of exploration, extraction, refining, transportation (often by oil tankers and pipelines), and marketing of petroleum products. The larges ...

, ²⁵²Cf neutron sources are used to find layers of

petroleum Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crud ...

and water in a

well A well is an excavation or structure created in the ground by digging, driving, or drilling to access liquid resources, usually water. The oldest and most common kind of well is a water well, to access groundwater in underground aquifers. The ...

. Instrumentation is lowered into the well which bombards the formation with high energy neutrons to determine

porosity Porosity or void fraction is a measure of the void (i.e. "empty") spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%. Strictly speaking, some tests measure ...

, permeability, and

hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ex ...

presence along the length of the

borehole A borehole is a narrow shaft bored in the ground, either vertically or horizontally. A borehole may be constructed for many different purposes, including the extraction of water ( drilled water well and tube well), other liquids (such as petrol ...

Medicine

Californium-252 has also been used in the treatment of serious forms of

cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...

. In patients with certain types of brain and cervical cancer, ²⁵²Cf can be used as a more cost-effective substitute for

radium Radium is a chemical element with the symbol Ra and atomic number 88. It is the sixth element in group 2 of the periodic table, also known as the alkaline earth metals. Pure radium is silvery-white, but it readily reacts with nitrogen (rather t ...

References

* Isotope masses from: ** * Isotopic compositions and standard atomic masses from: ** ** * Half-life, spin, and isomer data selected from the following sources. ** ** ** {{Authority control Californium