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Properties and data of the isotope 252Cf.


Californium-252 is a radioisotope of the element Californium. In addition to the 98 element-specific protons, the atomic nucleus of the nuclide has 154 neutrons, which results in the mass number of 252.

The high neutron emissions of this isotope and the associated potential applications in nuclear energy, medicine and geochemistry are of interest for research.

252Cf emits 2.314 × 106 s-1 μg-1 neutrons with a specific activity of 0.536 mCi μg-1 > [1]. The isotope is therefore a plentiful, transportable and portable source of neutrons that is independent of a reactor system.

Previous applications include Prompt Gamma Neutron Activation Analysis (PGNAA) of coal, cement and minerals; Cf-252 was also used to identify explosives, landmines and duds. Other areas of application: neutron radiography, investigation of nuclear waste, calibration standard, cancer therapy [1, 2].

Neutron sources made from californium-252 are mainly used when starting up nuclear reactors; the stable neutron emissions from the starting material trigger the actual fission chain reaction.

See also: list of Californium isotopes.


General data

Name of the isotope:Californium-252; Cf-252Symbol:252Cf or 25298CfMass number A:252 (= number of nucleons)Atomic number Z:98 (= number of protons)Neutrons N:154Isotopic mass:252.0816265(25) u (atomic weight of Californium-252)Nuclide mass:252.0278734 u (calculated nuclear mass without electrons)Mass excess:76.03459 MeVMass defect:2.0196237 u (per nucleus)Nuclear binding energy:1881.26735881 MeV (per nucleus)
7.46534666 MeV (average binding energy per nucleon)
Separation energy:SN = 6.172(4) MeV (first neutron)
SP = 6.482(11) MeV (first proton)
Half-life:2.645(8) aDecay constant λ:8.309849871337 × 10-9 s-1Specific activity α:19858367638938 Bq g-1
536.71263889022 Ci g-1
Spin and parity:
(nuclear angular momentum)
0+Year of discovery:1954


Radioactive Decay

Half-life T½ = 2.645(8) a respectively 8.341272 × 107 seconds s.

Decay modeDaughterProbabilityDecay energyγ energy
α248Cm96.908(8) %6.21695(4) MeV
SZdiv3.092(8) %


Californium-252 decay scheme


Parent Nuclides

Direct parent isotopes are: 256Fm, 252Es.


Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 154) and isobaric (same nucleon number A = 252) with Californium-252. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.


OZIsotone N = 154Isobar A = 252


External data and identifiers

CAS:13981-17-4InChI Key:HGLDOAKPQXAFKI-OUBTZVSYSA-NSMILES:[252Cf]PubChem:ID 104846Adopted Levels, Gammas:NuDat 252Cf


Literature and References

[1] - R.C. Martin, J.B. Knauer. P.A. Balo:
Production, distribution and applications of californium-252 neutron sources.
In: Applied Radiation and Isotopes, (2000), DOI 10.1016/S0969-8043(00)00214-1.

[2] - Wen-an Wu et al.:
External beam radiotherapy with or without californium-252 neutron brachytherapy for treatment of recurrence after definitive chemoradiotherapy.
In: Nature Scientific Reports, (2020), DOI 10.1038/s41598-020-78074-y.

[3] - Jingen Chen et al.:
Study on Cf-252 Production in a Molten Salt Reactor.
In: SSRN, (2022), DOI 10.2139/ssrn.4259964.


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Last update: 2023-04-15

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