Californium
On the 9th of February 1950, a team at Lawrence Berkeley National Laboratory achieved a feat that had never been done before. Stanley Gerald Thompson, Kenneth Street Jr., Albert Ghiorso, and Glenn T. Seaborg bombarded curium-242 with alpha particles inside a cyclotron machine. This process created only about 5,000 atoms of a new element. The scientists announced their discovery to the world on the 17th of March 1950. They named this sixth transuranium element californium after both the university and the state where it was found. This naming choice broke from previous conventions that honored elements directly above them in the periodic table. The researchers noted that early explorers had struggled to reach California, making the name fitting for such a difficult achievement.
Californium exists as a silvery-white metal that is soft enough to be cut with a knife. It melts at an unknown temperature but vaporizes when exposed to vacuum conditions above 900 degrees Celsius. The material displays complex magnetic behaviors depending on its temperature. Below 51 Kelvin, the metal acts like a magnet through ferromagnetic or ferrimagnetic properties. Between 48 and 66 Kelvin, it enters an antiferromagnetic state. Above 66 Kelvin, external fields can make it magnetic again. Two crystalline forms exist under normal pressure. The alpha form has a density of 15.10 grams per cubic centimeter below 600 to 800 degrees Celsius. The beta form drops to 8.74 grams per cubic centimeter above that same temperature range. At extreme pressures of 48 gigapascals, the crystal structure shifts into an orthorhombic system due to electron delocalization.
Only two facilities in the world currently produce californium-252 for commercial use. Oak Ridge National Laboratory in Tennessee manufactures approximately 0.25 grams annually. The Research Institute of Atomic Reactors in Dimitrovgrad, Russia produces about 0.025 grams each year. These microgram quantities are generated by irradiating curium isotopes with neutrons in special reactors. The process requires fifteen neutron captures starting from uranium-238 without triggering nuclear fission. Plutonium supplied by the United Kingdom under the 1958 US, UK Mutual Defence Agreement was historically used for production. By 1995, the High Flux Isotope Reactor at Oak Ridge nominally produced one gram of californium annually. The Atomic Energy Commission sold these materials to industrial and academic customers in the early 1970s for ten dollars per microgram.
Californium-252 emits 139 million neutrons per microgram every minute. This intense emission allows it to start up nuclear reactors that would otherwise remain dormant. Medical teams use portable sources to treat certain cervical and brain cancers when other therapies fail. Industrial applications include detecting corrosion in aircraft components or finding water layers in oil wells. Neutron moisture gauges utilize the element to locate petroleum deposits underground. In 1982, reactor startup accounted for nearly half of all usage while fuel rod scanning made up a quarter. By 1994, most californium went toward neutron radiography for inspecting weapons and machinery. Educational institutions received loans of the isotope as early as 1969 from the Savannah River Site. Wireless data transmission systems began using fast neutrons from the element in 2021.
Researchers used californium-249 to create oganesson, the heaviest element ever synthesized. Three atoms of this new element were identified at the Joint Institute for Nuclear Research in Dubna, Russia in October 2006. The target contained about ten milligrams of californium deposited on a titanium foil covering thirty-two square centimeters. Scientists bombarded these atoms with calcium-48 ions to achieve the synthesis. Lawrencium was also first created in 1961 by bombarding californium with boron nuclei. These experiments demonstrate how microgram amounts of one element can serve as building blocks for heavier transuranic elements. The process requires precise conditions and massive infrastructure to succeed.
Californium poses severe health risks when it enters the human body through contaminated food or air. Only 0.05 percent reaches the bloodstream after ingestion. About 65 percent of that amount deposits directly into skeletal tissue while 25 percent goes to the liver. Half of the material in the skeleton disappears over fifty years, but the rest remains embedded in bone surfaces. This bioaccumulation disrupts red blood cell formation and releases ionizing radiation that causes cancer. External exposure from gamma rays can damage tissues containing californium-249 or californium-251. The element plays no natural biological role due to its intense radioactivity and low environmental concentration. Traces found near facilities often adhere to soil particles at concentrations five hundred times higher than surrounding water.
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Common questions
When was californium discovered and by whom?
Stanley Gerald Thompson, Kenneth Street Jr., Albert Ghiorso, and Glenn T. Seaborg discovered californium on the 9th of February 1950 at Lawrence Berkeley National Laboratory. They announced their discovery to the world on the 17th of March 1950 after creating about 5,000 atoms inside a cyclotron machine.
What are the physical properties and magnetic states of californium?
Californium exists as a silvery-white metal that vaporizes when exposed to vacuum conditions above 900 degrees Celsius. Below 51 Kelvin the metal acts like a magnet through ferromagnetic or ferrimagnetic properties while it enters an antiferromagnetic state between 48 and 66 Kelvin.
Where is californium-252 produced today and how much is made annually?
Only two facilities in the world currently produce californium-252 for commercial use including Oak Ridge National Laboratory which manufactures approximately 0.25 grams annually. The Research Institute of Atomic Reactors in Dimitrovgrad, Russia produces about 0.025 grams each year by irradiating curium isotopes with neutrons.
How does californium-252 function in medical and industrial applications?
Californium-252 emits 139 million neutrons per microgram every minute allowing it to start up nuclear reactors that would otherwise remain dormant. Medical teams use portable sources to treat certain cervical and brain cancers while industrial applications include detecting corrosion in aircraft components or finding water layers in oil wells.
What role did californium play in creating oganesson and lawrencium?
Researchers used californium-249 to create oganesson at the Joint Institute for Nuclear Research in Dubna, Russia in October 2006. Lawrencium was also first created in 1961 by bombarding californium with boron nuclei to demonstrate how microgram amounts serve as building blocks for heavier transuranic elements.