Isotopes of californium

Californium (98Cf) is an artificial element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 245Cf in 1950. There are 20 known radioisotopes ranging from 237Cf to 256Cf and several short-lived nuclear isomers. The longest-lived isotope is 251Cf with a half-life of 898 years; followed by 249Cf (available isotopically pure from decay of berkelium) at 351 years.

List of isotopes

Nuclide	Z	N	Isotopic mass (Da)	Discovery year	Half-life	Decay mode	Daughter isotope	Spin and parity
Excitation energy
237Cf	98	139	237.06220(10)		0.8(2) s	α (70%)	233Cm	5/2+#
SF (30%)	(various)
238Cf	98	140	238.06149(32)#		21.1(13) ms	SF (97.5%)	(various)	0+
α (2.5%)	234Cm
239Cf	98	141	239.06248(13)#		28(2) s	α (65%)	235Cm	5/2+#
β+? (35%)	239Bk
240Cf	98	142	240.062253(19)		40.3(9) s	α (98.5%)	236Cm	0+
SF (1.5%)	(various)
241Cf	98	143	241.06369(18)#		2.35(18) min	β+? (85%)	241Bk	7/2−#
α (15%)	237Cm
242Cf	98	144	242.063755(14)		3.49(15) min	α (61%)	238Cm	0+
β+ (39%)	242Bk
SF (<0.014%)	(various)
243Cf	98	145	243.06548(19)#		10.8(3) min	β+ (86%)	243Bk	(1/2+)
α (14%)	239Cm
243mCf	~315 keV		5.1 s	α (?%)	239Cm	(7/2+)
244Cf	98	146	244.0659994(28)		19.5(5) min	α (75%)	240Cm	0+
EC (25%)	244Bk
245Cf	98	147	245.0680468(26)		45.0(15) min	β+ (64.7%)	245Bk	1/2+
α (35.3%)	241Cm
245mCf	57(4) keV	(2004)	>100# ns	IT	245Cf	(7/2+)
246Cf	98	148	246.0688037(16)		35.7(5) h	α	242Cm	0+
SF (2.4×10−4%)	(various)
247Cf	98	149	247.070971(15)		3.11(3) h	EC (99.965%)	247Bk	(7/2+)
α (0.035%)	243Cm
248Cf	98	150	248.072183(5)		333.5(28) d	α	244Cm	0+
SF (0.0029%)	(various)
248mCf	900(300) keV		~139 ns	IT?	248Cf
249Cf	98	151	249.0748504(13)		351(2) y	α	245Cm	9/2−
SF (5×10−7%)	(various)
249mCf	144.98(5) keV		45(5) μs	IT	249Cf	5/2+
250Cf	98	152	250.0764045(17)		13.08(9) y	α (99.923%)	246Cm	0+
SF (0.077%)	(various)
251Cf	98	153	251.079587(4)		898(44) y	α	247Cm	1/2+
251mCf	370.47(3) keV		1.3(1) μs	IT	251Cf	11/2−
252Cf	98	154	252.0816265(25)		2.645(8) y	α (96.8972%)	248Cm	0+
SF (3.1028%)	(various)
253Cf	98	155	253.085134(5)		17.81(8) d	β− (99.69%)	253Es	(7/2+)
α (0.31%)	249Cm
254Cf	98	156	254.087324(12)		60.5(2) d	SF (99.69%)	(various)	0+
α (0.31%)	250Cm
255Cf	98	157	255.09105(22)#		85(18) min	β−	255Es	(7/2+)
256Cf	98	158	256.09344(34)#		12.3(12) min	SF	(various)	0+
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Actinides vs fission products

Actinides and fission products by half-life vte
Actinides by decay chain	Half-life range (a)	Fission products of 235U by yield
4n (Thorium)	4n + 1 (Neptunium)	4n + 2 (Radium)	4n + 3 (Actinium)	4.5–7%	0.04–1.25%	<0.001%
228Ra№				4–6 a		155Euþ
248Bk				> 9 a
244Cmƒ	241Puƒ	250Cf	227Ac№	10–29 a	90Sr	85Kr	113mCdþ
232Uƒ		238Puƒ	243Cmƒ	29–97 a	137Cs	151Smþ	121mSn
	249Cfƒ	242mAmƒ		141–351 a	No fission products have a half-life in the range of 100 a–210 ka ...
	241Amƒ		251Cfƒ	430–900 a
		226Ra№	247Bk	1.3–1.6 ka
240Pu	229Th	246Cmƒ	243Amƒ	4.7–7.4 ka
	245Cmƒ	250Cm		8.3–8.5 ka
			239Puƒ	24.1 ka
		230Th№	231Pa№	32–76 ka
236Npƒ	233Uƒ	234U№		150–250 ka	99Tc₡	126Sn
248Cm		242Pu		327–375 ka		79Se₡
				1.33 Ma	135Cs₡
	237Npƒ			1.61–6.5 Ma	93Zr	107Pd
236U			247Cmƒ	15–24 Ma		129I₡
244Pu				80 Ma	... nor beyond 15.7 Ma
232Th№		238U№	235Uƒ№	0.7–14.1 Ga
₡, has thermal neutron capture cross section in the range of 8–50 barnsƒ, fissile№, primarily a naturally occurring radioactive material (NORM)þ, neutron poison (thermal neutron capture cross section greater than 3k barns)

Californium-252

Californium-252 (Cf-252, 252Cf) undergoes spontaneous fission with a branching ratio of 3.09% and is used in small neutron sources. Fission neutrons have an energy range of 0 to 13 MeV with a mean value of 2.3 MeV and a most probable value of 1 MeV.

This isotope produces high neutron emissions and has a number of uses in industries such as nuclear energy, medicine, and petrochemical exploration.

Nuclear reactors

Californium-252 neutron sources are most notably used in the start-up of nuclear reactors. Once a reactor is filled with nuclear fuel, 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 National Guard, Homeland Security, and Customs and Border Protection, uses 252Cf sources to detect hazardous contents inside artillery projectiles, mortar projectiles, rockets, bombs, land mines, and improvised explosive devices (IED).

Oil and petroleum

In the oil industry, 252Cf is used to find layers of petroleum and water in a well. Instrumentation is lowered into the well, which bombards the formation with high energy neutrons to determine porosity, permeability, and hydrocarbon presence along the length of the borehole.

Medicine

Californium-252 has also been used in the treatment of serious forms of cancer. For certain types of brain and cervical cancer, 252Cf can be used as a more cost-effective substitute for radium in brachytherapy.

Sources

Lide, David R., ed. (2006). Handbook of Chemistry and Physics (87th ed.). CRC Press, Taylor & Francis Group. ISBN 978-0-8493-0487-3.