Isotopes of californium

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Isotopes of californium  (98Cf)
Main isotopes [1] [2] Decay
abun­dance half-life (t1/2) mode pro­duct
248Cf synth 333.5 d α 100% 244Cm
SF <0.01%
249Cfsynth351 yα100% 245Cm
SF≪0.01%
250Cfsynth13.08 yα99.9% 246Cm
SF0.08%
251Cfsynth898 yα 247Cm
252Cfsynth2.645 yα96.9% 248Cm
SF3.09%
253Cfsynth17.81 d β 99.7% 253Es
α0.31% 249Cm
254Cfsynth60.5 dSF99.7%
α0.31% 250Cm

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.

Contents

List of isotopes

Cf-249 Cf-249.png
Cf-249
Cf-251 Cf-251.png
Cf-251
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
237Cf98139237.06220(10)0.8(2) s α (70%)233Cm5/2+#
SF (30%)(various)
238Cf98140238.06149(32)#21.1(13) msSF (97.5%) [n 7] (various)0+
α (2.5%)234Cm
239Cf98141239.06248(13)#28(2) sα (65%)235Cm5/2+#
β+? (35%)239Bk
240Cf98142240.062253(19)40.3(9) sα (98.5%)236Cm0+
SF (1.5%)(various)
241Cf98143241.06369(18)#2.35(18) minβ+? (85%)241Bk7/2−#
α (15%)237Cm
242Cf98144242.063755(14)3.49(15) minα (61%)238Cm0+
β+ (39%)242Bk
SF (<0.014%)(various)
243Cf98145243.06548(19)#10.8(3) minβ+ (86%)243Bk(1/2+)
α (14%)239Cm
244Cf98146244.0659994(28)19.5(5) minα (75%)240Cm0+
EC (25%)244Bk
245Cf98147245.0680468(26)45.0(15) minβ+ (64.7%)245Bk1/2+
α (35.3%)241Cm
245mCf57(4) keV>100# ns IT 245Cf(7/2+)
246Cf98148246.0688037(16)35.7(5) hα242Cm0+
SF (2.4×10−4%)(various)
247Cf98149247.070971(15)3.11(3) hEC (99.965%)247Bk(7/2+)
α (0.035%)243Cm
248Cf98150248.072183(5)333.5(28) dα244Cm0+
SF (0.0029%)(various)
249Cf98151249.0748504(13)351(2) yα245Cm9/2−
SF (5×10−7%)(various)
249mCf144.98(5) keV45(5) μsIT249Cf5/2+
250Cf98152250.0764045(17)13.08(9) yα (99.923%)246Cm0+
SF (0.077%)(various)
251Cf [n 8] 98153251.079587(4)898(44) yα247Cm1/2+
251mCf370.47(3) keV1.3(1) μsIT251Cf11/2−
252Cf [n 9] 98154252.0816265(25)2.645(8) yα (96.8972%)248Cm0+
SF (3.1028%) [n 10] (various)
253Cf98155253.085134(5)17.81(8) dβ (99.69%)253Es(7/2+)
α (0.31%)249Cm
254Cf [n 11] 98156254.087324(12)60.5(2) dSF (99.69%)(various)0+
α (0.31%)250Cm
255Cf98157255.09105(22)#85(18) minβ255Es(7/2+)
256Cf [n 12] 98158256.09344(34)#12.3(12) minSF(various)0+
This table header & footer:
  1. mCf  Excited nuclear isomer.
  2. ()  Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
  3. #  Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
  4. Modes of decay:
    EC: Electron capture
    SF: Spontaneous fission
  5. () spin value  Indicates spin with weak assignment arguments.
  6. #  Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
  7. Lightest nuclide known to undergo spontaneous fission as its main decay mode
  8. High neutron cross-section, tends to absorb neutrons
  9. Most common isotope
  10. High neutron emitter, average 3.7 neutrons per fission
  11. Theoretically capable of ββ decay to 254Fm
  12. Theoretically capable of ββ decay to 256Fm or perhaps β decay to 256Es

Actinides vs fission products

Actinides [5] by decay chain Half-life
range (a)
Fission products of 235U by yield [6]
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 [7] > 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 Amƒ141–351 a

No fission products have a half-life
in the range of 100 a–210 ka ...

241 Amƒ 251 Cfƒ [8] 430–900 a
226 Ra 247 Bk1.3–1.6 ka
240 Pu 229 Th 246 Cmƒ 243 Amƒ4.7–7.4 ka
245 Cmƒ 250 Cm8.3–8.5 ka
239 Puƒ24.1 ka
230 Th 231 Pa32–76 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 Pu80 Ma

... nor beyond 15.7 Ma [9]

232 Th 238 U 235 Uƒ№0.7–14.1 Ga

Californium-252

Californium-252 production diagram Cf 252 Produktion.png
Californium-252 production diagram

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. [10]

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). [11] [12]

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. [13]

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. [14]

References

  1. CRC 2006, p. 11.196.
  2. Sonzogni, Alejandro A. (Database Manager), ed. (2008). "Chart of Nuclides". National Nuclear Data Center, Brookhaven National Laboratory. Retrieved 1 March 2010.
  3. Wang, Meng; Huang, W.J.; Kondev, F.G.; Audi, G.; Naimi, S. (2021). "The AME 2020 atomic mass evaluation (II). Tables, graphs and references*". Chinese Physics C. 45 (3): 030003. doi:10.1088/1674-1137/abddaf.
  4. 1 2 3 Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
  5. Plus radium (element 88). While actually a sub-actinide, it immediately precedes actinium (89) and follows a three-element gap of instability after polonium (84) where no nuclides have half-lives of at least four years (the longest-lived nuclide in the gap is radon-222 with a half life of less than four days). Radium's longest lived isotope, at 1,600 years, thus merits the element's inclusion here.
  6. Specifically from thermal neutron fission of uranium-235, e.g. in a typical nuclear reactor.
  7. Milsted, J.; Friedman, A. M.; Stevens, C. M. (1965). "The alpha half-life of berkelium-247; a new long-lived isomer of berkelium-248". Nuclear Physics. 71 (2): 299. Bibcode:1965NucPh..71..299M. doi:10.1016/0029-5582(65)90719-4.
    "The isotopic analyses disclosed a species of mass 248 in constant abundance in three samples analysed over a period of about 10 months. This was ascribed to an isomer of Bk248 with a half-life greater than 9 [years]. No growth of Cf248 was detected, and a lower limit for the β half-life can be set at about 104 [years]. No alpha activity attributable to the new isomer has been detected; the alpha half-life is probably greater than 300 [years]."
  8. This is the heaviest nuclide with a half-life of at least four years before the "sea of instability".
  9. Excluding those "classically stable" nuclides with half-lives significantly in excess of 232Th; e.g., while 113mCd has a half-life of only fourteen years, that of 113Cd is eight quadrillion years.
  10. Dicello, J. F.; Gross, W.; Kraljevic, U. (1972). "Radiation Quality of Californium-252". Physics in Medicine and Biology . 17 (3): 345–355. Bibcode:1972PMB....17..345D. doi:10.1088/0031-9155/17/3/301. PMID   5070445. S2CID   250786668.
  11. "Portable Isotopic Neutron Spectroscopy (PINS) for the Military". Frontier Technology Corp. Archived from the original on 2018-06-16. Retrieved 2016-02-24.
  12. Martin, R. C.; Knauer, J. B.; Balo, P. A. (2000-11-01). "Production, distribution and applications of californium-252 neutron sources". Applied Radiation and Isotopes. 53 (4–5): 785–792. doi:10.1016/s0969-8043(00)00214-1. ISSN   0969-8043. PMID   11003521.
  13. "Californium-252 & Antimony-Beryllium Sources". Frontier Technology Corp. Retrieved 2016-02-24.
  14. Maruyama, Y.; van Nagell, J. R.; Yoneda, J.; Donaldson, E.; Hanson, M.; Martin, A.; Wilson, L. C.; Coffey, C. W.; Feola, J. (1984-10-01). "Five-year cure of cervical cancer treated using californium-252 neutron brachytherapy". American Journal of Clinical Oncology. 7 (5): 487–493. doi:10.1097/00000421-198410000-00018. ISSN   0277-3732. PMID   6391143. S2CID   12553815.

Sources