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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 one nuclear isomer, 249mCf. The longest-lived isotope is 251Cf with a half-life of 898 years.
Nuclide [n 1] | Z | N | Isotopic mass (Da) [3] [n 2] [n 3] | Half-life [4] | Decay mode [4] [n 4] | Daughter isotope | Spin and parity [4] [n 5] [n 6] | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Excitation energy | |||||||||||||||||||
237Cf | 98 | 139 | 237.06220(10) | 0.8(2) s | α (70%) | 233Cm | 5/2+# | ||||||||||||
SF (30%) | (various) | ||||||||||||||||||
β+ (rare) | 237Bk | ||||||||||||||||||
238Cf | 98 | 140 | 238.06149(32)# | 21.1(13) ms | SF [n 7] | (various) | 0+ | ||||||||||||
α (<5%) | 234Cm | ||||||||||||||||||
239Cf [5] | 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) | ||||||||||||||||||
β+? | 240Bk | ||||||||||||||||||
241Cf [5] | 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 | ||||||||||||||||||
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 | >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) | ||||||||||||||||||
EC? | 246Bk | ||||||||||||||||||
247Cf | 98 | 149 | 247.070971(15) | 3.11(3) h | EC (99.965%) | 247Bk | (7/2+) | ||||||||||||
α (.035%) | 243Cm | ||||||||||||||||||
248Cf | 98 | 150 | 248.0721829(55) | 333.5(28) d | α (99.997%) | 244Cm | 0+ | ||||||||||||
SF (.0029%) | (various) | ||||||||||||||||||
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 (.077%) | (various) | ||||||||||||||||||
251Cf [n 8] | 98 | 153 | 251.0795872(42) | 898(44) y | α | 247Cm | 1/2+ | ||||||||||||
251mCf | 370.47(3) keV | 1.3(1) μs | IT | 251Cf | 11/2− | ||||||||||||||
252Cf [n 9] | 98 | 154 | 252.0816265(25) | 2.645(8) y | α (96.8972%) | 248Cm | 0+ | ||||||||||||
SF (3.1028%) [n 10] | (various) | ||||||||||||||||||
253Cf | 98 | 155 | 253.0851337(46) | 17.81(8) d | β− (99.69%) | 253Es | (7/2+) | ||||||||||||
α (.31%) | 249Cm | ||||||||||||||||||
254Cf | 98 | 156 | 254.087324(12) | 60.5(2) d | SF (99.69%) | (various) | 0+ | ||||||||||||
α (.31%) | 250Cm | ||||||||||||||||||
β−β−? | 254Fm | ||||||||||||||||||
255Cf | 98 | 157 | 255.09105(22)# | 85(18) min | β− | 255Es | (7/2+) | ||||||||||||
SF? | (various) | ||||||||||||||||||
α? | 251Cm | ||||||||||||||||||
256Cf | 98 | 158 | 256.09344(34)# | 12.3(12) min | SF | (various) | 0+ | ||||||||||||
α? | 252Cm | ||||||||||||||||||
β−β−? | 256Fm | ||||||||||||||||||
This table header & footer: |
EC: | Electron capture |
SF: | Spontaneous fission |
Actinides [6] by decay chain | Half-life range (a) | Fission products of 235U by yield [7] | ||||||
---|---|---|---|---|---|---|---|---|
4n | 4n + 1 | 4n + 2 | 4n + 3 | 4.5–7% | 0.04–1.25% | <0.001% | ||
228 Ra№ | 4–6 a | 155 Euþ | ||||||
248 Bk [8] | > 9 a | |||||||
244 Cmƒ | 241 Puƒ | 250 Cf | 227 Ac№ | 10–29 a | 90 Sr | 85 Kr | 113m Cdþ | |
232 Uƒ | 238 Puƒ | 243 Cmƒ | 29–97 a | 137 Cs | 151 Smþ | 121m Sn | ||
249 Cfƒ | 242m Amƒ | 141–351 a | No fission products have a half-life | |||||
241 Amƒ | 251 Cfƒ [9] | 430–900 a | ||||||
226 Ra№ | 247 Bk | 1.3–1.6 ka | ||||||
240 Pu | 229 Th | 246 Cmƒ | 243 Amƒ | 4.7–7.4 ka | ||||
245 Cmƒ | 250 Cm | 8.3–8.5 ka | ||||||
239 Puƒ | 24.1 ka | |||||||
230 Th№ | 231 Pa№ | 32–76 ka | ||||||
236 Npƒ | 233 Uƒ | 234 U№ | 150–250 ka | 99 Tc₡ | 126 Sn | |||
248 Cm | 242 Pu | 327–375 ka | 79 Se₡ | |||||
1.33 Ma | 135 Cs₡ | |||||||
237 Npƒ | 1.61–6.5 Ma | 93 Zr | 107 Pd | |||||
236 U | 247 Cmƒ | 15–24 Ma | 129 I₡ | |||||
244 Pu | 80 Ma | ... nor beyond 15.7 Ma [10] | ||||||
232 Th№ | 238 U№ | 235 Uƒ№ | 0.7–14.1 Ga | |||||
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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. [11]
This isotope produces high neutron emissions and has a number of uses in industries such as nuclear energy, medicine, and petrochemical exploration.
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.
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). [12] [13]
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. [14]
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. [15]
Berkelium is a synthetic chemical element; it has symbol Bk and atomic number 97. It is a member of the actinide and transuranium element series. It is named after the city of Berkeley, California, the location of the Lawrence Berkeley National Laboratory where it was discovered in December 1949. Berkelium was the fifth transuranium element discovered after neptunium, plutonium, curium and americium.
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 by bombarding curium with alpha particles. It is an actinide element, the sixth transuranium element to be synthesized, and has the second-highest atomic mass of all elements that have been produced in amounts large enough to see with the naked eye. It was named after the university and the U.S. state of California.
In nuclear engineering, fissile material is material that can undergo nuclear fission when struck by a neutron of low energy. A self-sustaining thermal chain reaction can only be achieved with fissile material. The predominant neutron energy in a system may be typified by either slow neutrons or fast neutrons. Fissile material can be used to fuel thermal-neutron reactors, fast-neutron reactors and nuclear explosives.
In nuclear science a decay chain refers to the predictable series of radioactive disintegrations undergone by the nuclei of certain unstable chemical elements.
Thorium-232 is the main naturally occurring isotope of thorium, with a relative abundance of 99.98%. It has a half life of 14 billion years, which makes it the longest-lived isotope of thorium. It decays by alpha decay to radium-228; its decay chain terminates at stable lead-208.
Uranium (92U) is a naturally occurring radioactive element (radioelement) with no stable isotopes. It has two primordial isotopes, uranium-238 and uranium-235, that have long half-lives and are found in appreciable quantity in Earth's crust. The decay product uranium-234 is also found. Other isotopes such as uranium-233 have been produced in breeder reactors. In addition to isotopes found in nature or nuclear reactors, many isotopes with far shorter half-lives have been produced, ranging from 214U to 242U. The standard atomic weight of natural uranium is 238.02891(3).
Protactinium (91Pa) has no stable isotopes. The four naturally occurring isotopes allow a standard atomic weight to be given.
Actinium (89Ac) has no stable isotopes and no characteristic terrestrial isotopic composition, thus a standard atomic weight cannot be given. There are 34 known isotopes, from 203Ac to 236Ac, and 7 isomers. Three isotopes are found in nature, 225Ac, 227Ac and 228Ac, as intermediate decay products of, respectively, 237Np, 235U, and 232Th. 228Ac and 225Ac are extremely rare, so almost all natural actinium is 227Ac.
Radium (88Ra) has no stable or nearly stable isotopes, and thus a standard atomic weight cannot be given. The longest lived, and most common, isotope of radium is 226Ra with a half-life of 1600 years. 226Ra occurs in the decay chain of 238U. Radium has 34 known isotopes from 201Ra to 234Ra.
Lead (82Pb) has four observationally stable isotopes: 204Pb, 206Pb, 207Pb, 208Pb. Lead-204 is entirely a primordial nuclide and is not a radiogenic nuclide. The three isotopes lead-206, lead-207, and lead-208 represent the ends of three decay chains: the uranium series, the actinium series, and the thorium series, respectively; a fourth decay chain, the neptunium series, terminates with the thallium isotope 205Tl. The three series terminating in lead represent the decay chain products of long-lived primordial 238U, 235U, and 232Th. Each isotope also occurs, to some extent, as primordial isotopes that were made in supernovae, rather than radiogenically as daughter products. The fixed ratio of lead-204 to the primordial amounts of the other lead isotopes may be used as the baseline to estimate the extra amounts of radiogenic lead present in rocks as a result of decay from uranium and thorium.
Naturally occurring xenon (54Xe) consists of seven stable isotopes and two very long-lived isotopes. Double electron capture has been observed in 124Xe and double beta decay in 136Xe, which are among the longest measured half-lives of all nuclides. The isotopes 126Xe and 134Xe are also predicted to undergo double beta decay, but this process has never been observed in these isotopes, so they are considered to be stable. Beyond these stable forms, 32 artificial unstable isotopes and various isomers have been studied, the longest-lived of which is 127Xe with a half-life of 36.345 days. All other isotopes have half-lives less than 12 days, most less than 20 hours. The shortest-lived isotope, 108Xe, has a half-life of 58 μs, and is the heaviest known nuclide with equal numbers of protons and neutrons. Of known isomers, the longest-lived is 131mXe with a half-life of 11.934 days. 129Xe is produced by beta decay of 129I ; 131mXe, 133Xe, 133mXe, and 135Xe are some of the fission products of both 235U and 239Pu, so are used as indicators of nuclear explosions.
Caesium (55Cs) has 41 known isotopes, the atomic masses of these isotopes range from 112 to 152. Only one isotope, 133Cs, is stable. The longest-lived radioisotopes are 135Cs with a half-life of 1.33 million years, 137
Cs
with a half-life of 30.1671 years and 134Cs with a half-life of 2.0652 years. All other isotopes have half-lives less than 2 weeks, most under an hour.
Tin (50Sn) is the element with the greatest number of stable isotopes. This is probably related to the fact that 50 is a "magic number" of protons. In addition, twenty-nine unstable tin isotopes are known, including tin-100 (100Sn) and tin-132 (132Sn), which are both "doubly magic". The longest-lived tin radioisotope is tin-126 (126Sn), with a half-life of 230,000 years. The other 28 radioisotopes have half-lives of less than a year.
Neptunium (93Np) is usually considered an artificial element, although trace quantities are found in nature, so a standard atomic weight cannot be given. Like all trace or artificial elements, it has no stable isotopes. The first isotope to be synthesized and identified was 239Np in 1940, produced by bombarding 238
U
with neutrons to produce 239
U
, which then underwent beta decay to 239
Np
.
Plutonium (94Pu) is an artificial element, except for trace quantities resulting from neutron capture by uranium, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. It was synthesized long before being found in nature, the first isotope synthesized being plutonium-238 in 1940. Twenty-one plutonium radioisotopes have been characterized. The most stable are plutonium-244 with a half-life of 80.8 million years; plutonium-242 with a half-life of 373,300 years; and plutonium-239 with a half-life of 24,110 years; and plutonium-240 with a half-life of 6,560 years. This element also has eight meta states; all have half-lives of less than one second.
Americium (95Am) is an artificial element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no known stable isotopes. The first isotope to be synthesized was 241Am in 1944. The artificial element decays by ejecting alpha particles. Americium has an atomic number of 95. Despite 243
Am being an order of magnitude longer lived than 241
Am, the former is harder to obtain than the latter as more of it is present in spent nuclear fuel.
Curium (96Cm) is an artificial element with an atomic number of 96. Because it is an artificial element, a standard atomic weight cannot be given, and it has no stable isotopes. The first isotope synthesized was 242Cm in 1944, which has 146 neutrons.
Berkelium (97Bk) 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 243Bk in 1949. There are twenty known radioisotopes, from 233Bk and 233Bk to 253Bk, and six nuclear isomers. The longest-lived isotope is 247Bk with a half-life of 1,380 years.
Plutonium-241 is an isotope of plutonium formed when plutonium-240 captures a neutron. Like some other plutonium isotopes, 241Pu is fissile, with a neutron absorption cross section about one-third greater than that of 239Pu, and a similar probability of fissioning on neutron absorption, around 73%. In the non-fission case, neutron capture produces plutonium-242. In general, isotopes with an odd number of neutrons are both more likely to absorb a neutron and more likely to undergo fission on neutron absorption than isotopes with an even number of neutrons.
Plutonium-242 is one of the isotopes of plutonium, the second longest-lived, with a half-life of 375,000 years. The half-life of 242Pu is about 15 times that of 239Pu; so it is one-fifteenth as radioactive, and not one of the larger contributors to nuclear waste radioactivity. 242Pu's gamma ray emissions are also weaker than those of the other isotopes.