One microgram — and 170 million neutrons per second. Californium-252 is the most powerful compact neutron source known to humanity. This tiny speck of metal can replace an entire nuclear reactor for certain tasks. And its price matches — about $27 million per gram.
Californium was synthesized in 1950 in Berkeley and named after the state of California. Unlike most transuranic elements, it has real practical applications. Californium's neutrons find gold in ore, treat cancer, and start up nuclear reactors.
Californium is a silvery radioactive metal from the actinide group. Only two reactors in the world produce it — in the USA and Russia. Annual output is less than half a gram. The isotope Cf-252 is valuable due to spontaneous fission: each microgram emits 170 million neutrons every second.
These neutrons are used in medicine for neutron brachytherapy of cancer, in geology for rock analysis, and in industry for metal quality control. Californium is a rare example of a transuranic element with genuine practical value.
Californium is one of the most dangerous radioactive materials. Cf-252 emits millions of neutrons per second, which penetrate most materials. Protection requires thick layers of water or paraffin (for neutrons) plus lead (for gamma rays). If ingested, it accumulates in bones. Work is only possible remotely, inside multilayer hot cells.
One gram of californium-252 costs about $27 million. It is one of the most expensive materials on Earth — pricier than diamonds, gold, and antimatter.
One microgram of Cf-252 emits 170 million neutrons per second. This speck of metal replaces bulky laboratory equipment weighing tons.
Only two reactors in the entire world produce californium: HFIR in the USA (Oak Ridge) and SM-3 in Russia (Dimitrovgrad). Together they yield less than 0.5 g per year.
Californium-252 kills cancer cells. In neutron brachytherapy, a microscopic Cf-252 source is implanted directly into the tumor — neutrons destroy cancer from the inside.
Californium was named after the state of California and the University of California. It is one of two elements bearing this state's name (the other is berkelium, after the city of Berkeley).
| Isotope | Mass (u) | Abundance | Half-life | Decay |
|---|---|---|---|---|
249Cf☢ | 249.074853 | synthetic | 351 years | α |
250Cf☢ | 250.076406 | synthetic | 13.08 years | α |
251Cf☢ | 251.079587 | synthetic | 900 years | α |
252Cf☢ | 252.081626 | synthetic | 2.645 years | α |
Cyclotron bombardment of curium