Californium Californium is a synthetic chemical element; it has symbol Cf and atomic number 98. It was first synthesized in 1950 at Lawrence Berkeley National Laboratory (then the University of California Radiation Laboratory) by bombarding curium with al ...

(Cf) is an artificial element, and thus a

standard atomic weight The standard atomic weight of a chemical element (symbol ''A''r°(E) for element "E") is the weighted arithmetic mean of the relative isotopic masses of all isotopes of that element weighted by each isotope's abundance on Earth. For example, ...

cannot be given. Like all artificial elements, it has no

stable isotope Stable nuclides are Isotope, isotopes of a chemical element whose Nucleon, nucleons are in a configuration that does not permit them the surplus energy required to produce a radioactive emission. The Atomic nucleus, nuclei of such isotopes are no ...

s. The first

isotope Isotopes are distinct nuclear species (or ''nuclides'') of the same chemical element. They have the same atomic number (number of protons in their Atomic nucleus, nuclei) and position in the periodic table (and hence belong to the same chemica ...

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

radioisotope A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess numbers of either neutrons or protons, giving it excess nuclear energy, and making it unstable. This excess energy can be used in one of three ...

s ranging from Cf to Cf 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 levels (higher energy levels). "Metastable" describes nuclei whose excited states have Half-life, half-lives of ...

, Cf. The longest-lived isotope is Cf with a

half-life Half-life is a mathematical and scientific description of exponential or gradual decay. Half-life, half life or halflife may also refer to: Film * Half-Life (film), ''Half-Life'' (film), a 2008 independent film by Jennifer Phang * ''Half Life: ...

of 898 years.

List of isotopes

, -id=Californium-237 , rowspan=3, Cf , rowspan=3 style="text-align:right" , 98 , rowspan=3 style="text-align:right" , 139 , rowspan=3, 237.06220(10) , rowspan=3, 0.8(2) s , α (70%) , Cm , rowspan=3, 5/2+# , - , SF (30%) , (various) , - , β , Bk , -id=Californium-238 , rowspan=2, Cf , rowspan=2 style="text-align:right" , 98 , rowspan=2 style="text-align:right" , 140 , rowspan=2, 238.06149(32)# , rowspan=2, 21.1(13) ms , SFLightest nuclide known to undergo

spontaneous fission Spontaneous fission (SF) is a form of radioactive decay in which a heavy atomic nucleus splits into two or more lighter nuclei. In contrast to induced fission, there is no inciting particle to trigger the decay; it is a purely probabilistic proc ...

as its main decay mode , (various) , rowspan=2, 0+ , - , α (<5%) , Cm , -id=Californium-239 , rowspan=2, Cf , rowspan=2 style="text-align:right" , 98 , rowspan=2 style="text-align:right" , 141 , rowspan=2, 239.06248(13)# , rowspan=2, 28(2) s , α (65%) , Cm , rowspan=2, (5/2+) , - , β (35%) , Bk , -id=Californium-240 , rowspan=3, Cf , rowspan=3 style="text-align:right" , 98 , rowspan=3 style="text-align:right" , 142 , rowspan=3, 240.062253(19) , rowspan=3, 40.3(9) s , α (98.5%) , Cm , rowspan=3, 0+ , - , SF (1.5%) , (various) , - , β? , Bk , -id=Californium-241 , rowspan=2, Cf , rowspan=2 style="text-align:right" , 98 , rowspan=2 style="text-align:right" , 143 , rowspan=2, 241.06369(18)# , rowspan=2, 2.35(18) min , β (85%) , Bk , rowspan=2, (7/2−) , - , α (15%) , Cm , -id=Californium-242 , rowspan=3, Cf , rowspan=3 style="text-align:right" , 98 , rowspan=3 style="text-align:right" , 144 , rowspan=3, 242.063755(14) , rowspan=3, 3.49(15) min , α (61%) , Cm , rowspan=3, 0+ , - , β (39%) , Bk , - , SF (<0.014%) , (various) , -id=Californium-243 , rowspan=2, Cf , rowspan=2 style="text-align:right" , 98 , rowspan=2 style="text-align:right" , 145 , rowspan=2, 243.06548(19)# , rowspan=2, 10.8(3) min , β (86%) , Bk , rowspan=2, (1/2+) , - , α (14%) , Cm , -id=Californium-244 , rowspan=2, Cf , rowspan=2 style="text-align:right" , 98 , rowspan=2 style="text-align:right" , 146 , rowspan=2, 244.0659994(28) , rowspan=2, 19.5(5) min , α (75%) , Cm , rowspan=2, 0+ , - , EC (25%) , Bk , -id=Californium-245 , rowspan=2, Cf , rowspan=2 style="text-align:right" , 98 , rowspan=2 style="text-align:right" , 147 , rowspan=2, 245.0680468(26) , rowspan=2, 45.0(15) min , β (64.7%) , Bk , rowspan=2, 1/2+ , - , α (35.3%) , Cm , -id=Californium-245m , style="text-indent:1em" , Cf , colspan="3" style="text-indent:2em" , 57(4) keV , >100# ns , IT , Cf , (7/2+) , -id=Californium-246 , rowspan=3, Cf , rowspan=3 style="text-align:right" , 98 , rowspan=3 style="text-align:right" , 148 , rowspan=3, 246.0688037(16) , rowspan=3, 35.7(5) h , α , Cm , rowspan=3, 0+ , - , SF (2.4×10%) , (various) , - , EC? , Bk , -id=Californium-247 , rowspan=2, Cf , rowspan=2 style="text-align:right" , 98 , rowspan=2 style="text-align:right" , 149 , rowspan=2, 247.070971(15) , rowspan=2, 3.11(3) h , EC (99.965%) , Bk , rowspan=2, (7/2+) , - , α (.035%) , Cm , -id=Californium-248 , rowspan=2, Cf , rowspan=2 style="text-align:right" , 98 , rowspan=2 style="text-align:right" , 150 , rowspan=2, 248.0721829(55) , rowspan=2, 333.5(28) d , α (99.997%) , Cm , rowspan=2, 0+ , - , SF (.0029%) , (various) , -id=Californium-249 , rowspan=2, Cf , rowspan=2 style="text-align:right" , 98 , rowspan=2 style="text-align:right" , 151 , rowspan=2, 249.0748504(13) , rowspan=2, 351(2) y , α , Cm , rowspan=2, 9/2− , - , SF (5×10%) , (various) , -id=Californium-249m , style="text-indent:1em" , Cf , colspan="3" style="text-indent:2em" , 144.98(5) keV , 45(5) μs , IT , Cf , 5/2+ , -id=Californium-250 , rowspan=2, Cf , rowspan=2 style="text-align:right" , 98 , rowspan=2 style="text-align:right" , 152 , rowspan=2, 250.0764045(17) , rowspan=2, 13.08(9) y , α (99.923%) , Cm , rowspan=2, 0+ , - , SF (.077%) , (various) , -id=Californium-251 , CfHigh

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 , 251.0795872(42) , 898(44) y , α , Cm , 1/2+ , -id=Californium-251m , style="text-indent:1em" , Cf , colspan="3" style="text-indent:2em" , 370.47(3) keV , 1.3(1) μs , IT , Cf , 11/2− , - , rowspan=2, CfMost common isotope , rowspan=2 style="text-align:right" , 98 , rowspan=2 style="text-align:right" , 154 , rowspan=2, 252.0816265(25) , rowspan=2, 2.645(8) y , α (96.8972%) , Cm , rowspan=2, 0+ , - , SF (3.1028%)High neutron emitter, average 3.7

neutron The neutron is a subatomic particle, symbol or , that has no electric charge, and a mass slightly greater than that of a proton. The Discovery of the neutron, neutron was discovered by James Chadwick in 1932, leading to the discovery of nucle ...

s per fission , (various) , -id=Californium-253 , rowspan=2, Cf , rowspan=2 style="text-align:right" , 98 , rowspan=2 style="text-align:right" , 155 , rowspan=2, 253.0851337(46) , rowspan=2, 17.81(8) d , β (99.69%) , Es , rowspan=2, (7/2+) , - , α (.31%) , Cm , -id=Californium-254 , rowspan=2, CfTheoretically capable of ββ decay to ²⁵⁴Fm , rowspan=2 style="text-align:right" , 98 , rowspan=2 style="text-align:right" , 156 , rowspan=2, 254.087324(12) , rowspan=2, 60.5(2) d , SF (99.69%) , (various) , rowspan=2, 0+ , - , α (.31%) , Cm , -id=Californium-255 , rowspan=3, Cf , 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 , Es , rowspan=3, (7/2+) , - , SF? , (various) , - , α? , Cm , -id=Californium-256 , rowspan=2, CfTheoretically capable of ββ decay to ²⁵⁶Fm or perhaps β decay to ²⁵⁶Es , rowspan=2 style="text-align:right" , 98 , rowspan=2 style="text-align:right" , 158 , rowspan=2, 256.09344(34)# , rowspan=2, 12.3(12) min , SF , (various) , rowspan=2, 0+ , - , α? , Cm , -

Actinides vs fission products

Californium-252

Californium-252 (Cf-252, Cf) undergoes spontaneous fission with a branching ratio of 3.09% and is used in small

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 through an electric potential difference of one volt in vacuum. When us ...

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

produces high neutron emissions and has a number of uses 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 s ...

exploration.

Nuclear reactors

Californium-252 neutron sources are most notably used in the start-up of

nuclear reactor A nuclear reactor is a device used to initiate and control a Nuclear fission, fission nuclear chain reaction. They are used for Nuclear power, commercial electricity, nuclear marine propulsion, marine propulsion, Weapons-grade plutonium, weapons ...

s. Once a reactor is filled with

nuclear fuel Nuclear fuel refers to any substance, typically fissile material, which is used by nuclear power stations or other atomic nucleus, nuclear devices to generate energy. Oxide fuel For fission reactors, the fuel (typically based on uranium) is ...

, the stable neutron emission from said source starts the 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, military forces of the United States. U.S. United States Code, federal law names six armed forces: the United States Army, Army, United States Marine Corps, Marine Corps, United States Navy, Na ...

, 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. ...

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" to ...

, and Customs and Border Protection, uses Cf sources to detect hazardous contents inside artillery projectiles, mortar projectiles,

rocket A rocket (from , and so named for its shape) is a vehicle that uses jet propulsion to accelerate without using any surrounding air. A rocket engine produces thrust by reaction to exhaust expelled at high speed. Rocket engines work entirely ...

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

land mine A land mine, or landmine, is an explosive weapon often concealed under or camouflaged on the ground, and designed to destroy or disable enemy targets as they pass over or near it. Land mines are divided into two types: anti-tank mines, wh ...

s, and

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

s (IED).

Oil and petroleum

In the

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

, Cf is used to find layers of

petroleum Petroleum, also known as crude oil or simply oil, is a naturally occurring, yellowish-black liquid chemical mixture found in geological formations, consisting mainly of hydrocarbons. The term ''petroleum'' refers both to naturally occurring un ...

and water in a

well A well is an excavation or structure created on the earth 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 Hydrophobe, hydrophobic; their odor is usually fain ...

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 petr ...

Medicine

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

cancer Cancer is a group of diseases involving Cell growth#Disorders, abnormal cell growth with the potential to Invasion (cancer), invade or Metastasis, spread to other parts of the body. These contrast with benign tumors, which do not spread. Po ...

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

radium Radium is a chemical element; it has chemical symbol, symbol Ra and atomic number 88. It is the sixth element in alkaline earth metal, group 2 of the periodic table, also known as the alkaline earth metals. Pure radium is silvery-white, ...

References

Sources

* {{Authority control Californium