Isotopes of protactinium

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Isotopes of protactinium (91Pa)
Main isotopes[1] Decay
abun­dance half-life (t1/2) mode pro­duct
229Pa synth 1.5 d ε
229Th
230Pa synth 17.4 d
β+
 		230Th
β−
 		230U
α
226Ac
231Pa 100% 3.265×104 y α
227Ac
232Pa synth 1.32 d β− 232U
233Pa trace 26.975 d β− 233U
234Pa trace 6.70 h β− 234U
234mPa trace 1.159 min β− 234U
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    • Protactinium (91Pa) has no stable isotopes. The four naturally occurring isotopes allow a standard atomic weight to be given.

    Twenty-nine

    meta states
    , 217mPa (t1/2 1.15 milliseconds), 220m1Pa (t1/2 = 308 nanoseconds), 220m2Pa (t1/2 = 69 nanoseconds), 229mPa (t1/2 = 420 nanoseconds), and 234mPa (t1/2 = 1.17 minutes).

    The only naturally occurring isotopes are 231Pa, which occurs as an intermediate decay product of 235U, 234Pa and 234mPa, both of which occur as intermediate decay products of 238U. 231Pa makes up nearly all natural protactinium.

    The primary

    decay mode for isotopes of Pa lighter than (and including) the most stable isotope 231Pa is alpha decay, except for 228Pa to 230Pa, which primarily decay by electron capture to isotopes of thorium. The primary mode for the heavier isotopes is beta minus (β−) decay. The primary decay products of 231Pa and isotopes of protactinium lighter than and including 227Pa are isotopes of actinium and the primary decay products for the heavier isotopes of protactinium are isotopes of uranium
    .

    List of isotopes

    Nuclide
    [n 1]     		Historic
    name     		Z N Isotopic mass (Da)
    [n 2][n 3]     		Half-life
    [n 4]
    Decay
    mode
    [n 5]
    		 Daughter
    isotope
    [n 6]
    Spin and
    parity
    [n 7][n 4]
    		 Natural abundance (mole fraction)
    Excitation energy Normal proportion Range of variation
    211Pa[4] 91 120 3.8(+4.6−1.4) ms α 207Ac 9/2−#
    212Pa 91 121 212.02320(8) 8(5) ms
    [5.1(+61−19) ms]     		α 208Ac 7+#
    213Pa 91 122 213.02111(8) 7(3) ms
    [5.3(+40−16) ms]     		α 209Ac 9/2−#
    214Pa 91 123 214.02092(8) 17(3) ms α 210Ac
    215Pa 91 124 215.01919(9) 14(2) ms α 211Ac 9/2−#
    216Pa 91 125 216.01911(8) 105(12) ms α (80%) 212Ac
    β+ (20%) 216Th
    217Pa 91 126 217.01832(6) 3.48(9) ms α 213Ac 9/2−#
    217mPa 1860(7) keV 1.08(3) ms α 213Ac 29/2+#
    IT
    (rare)     		217Pa
    218Pa 91 127 218.020042(26) 0.113(1) ms α 214Ac
    219Pa 91 128 219.01988(6) 53(10) ns α 215Ac 9/2−
    β+ (5×10−9%) 219Th
    220Pa 91 129 220.02188(6) 780(160) ns α 216Ac 1−#
    220m1Pa[5] 34(26) keV 308(+250-99) ns α 216Ac
    220m2Pa[5] 297(65) keV 69(+330-30) ns α 216Ac
    221Pa 91 130 221.02188(6) 4.9(8) μs α 217Ac 9/2−
    222Pa 91 131 222.02374(8)# 3.2(3) ms α 218Ac
    223Pa 91 132 223.02396(8) 5.1(6) ms α 219Ac
    β+ (.001%) 223Th
    224Pa 91 133 224.025626(17) 844(19) ms α (99.9%) 220Ac 5−#
    β+ (.1%) 224Th
    225Pa 91 134 225.02613(8) 1.7(2) s α 221Ac 5/2−#
    226Pa 91 135 226.027948(12) 1.8(2) min α (74%) 222Ac
    β+ (26%) 226Th
    227Pa 91 136 227.028805(8) 38.3(3) min α (85%) 223Ac (5/2−)
    EC (15%) 227Th
    228Pa 91 137 228.031051(5) 22(1) h β+ (98.15%) 228Th 3+
    α (1.85%) 224Ac
    229Pa 91 138 229.0320968(30) 1.50(5) d EC (99.52%) 229Th (5/2+)
    α (.48%) 225Ac
    229mPa 11.6(3) keV 420(30) ns 3/2−
    230Pa 91 139 230.034541(4) 17.4(5) d β+ (91.6%) 230Th (2−)
    β− (8.4%) 230U
    α (.00319%) 226Ac
    231Pa Protoactinium 91 140 231.0358840(24) 3.276(11)×104 y α 227Ac 3/2− 1.0000[n 8]
    CD (1.34×10−9%) 207Tl
    24Ne
    SF (3×10−10%) (various)
    CD (10−12%) 208Pb
    23F
    232Pa 91 141 232.038592(8) 1.31(2) d β− 232U (2−)
    EC (.003%) 232Th
    233Pa 91 142 233.0402473(23) 26.975(13) d β− 233U 3/2− Trace[n 9]
    234Pa Uranium Z 91 143 234.043308(5) 6.70(5) h β− 234U 4+ Trace[n 10]
    SF (3×10−10%) (various)
    234mPa Uranium X2
    Brevium     		78(3) keV 1.17(3) min β− (99.83%) 234U (0−) Trace[n 10]
    IT (.16%) 234Pa
    SF (10−10%) (various)
    235Pa 91 144 235.04544(5) 24.44(11) min β− 235U (3/2−)
    236Pa 91 145 236.04868(21) 9.1(1) min β− 236U 1(−)
    β−, SF (6×10−8%) (various)
    237Pa 91 146 237.05115(11) 8.7(2) min β− 237U (1/2+)
    238Pa 91 147 238.05450(6) 2.27(9) min β− 238U (3−)#
    β−, SF (2.6×10−6%) (various)
    239Pa 91 148 239.05726(21)# 1.8(5) h β− 239U (3/2)(−#)
    This table header & footer:
    1. ^ mPa – 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. ^ a b # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
    5. ^ Modes of decay:
      CD: Cluster decay
      EC: Electron capture
      IT:
      Isomeric transition
      SF: Spontaneous fission
    6. ^ Bold italics symbol as daughter – Daughter product is nearly stable.
    7. ^ ( ) spin value – Indicates spin with weak assignment arguments.
    8. ^ Intermediate decay product of 235U
    9. 237Np
    10. ^ a b Intermediate decay product of 238U

    Actinides and fission products

    Actinides and fission products by half-life
    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
    244
    Cmƒ     		241Puƒ
    250
    Cf
    227
    Ac№
    10–29 a
    		 90Sr 85Kr
    113m
    Cdþ
    232Uƒ 238Puƒ
    243
    Cmƒ
    29–97 a
    137
    Cs
    151
    Smþ
    121m
    Sn
    248Bk[8]
    249
    Cfƒ
    242m
    Amƒ     		141–351 a

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

    241Amƒ
    251Cfƒ[9]
    		 430–900 a
    226Ra№
    247
    Bk     		1.3–1.6 ka
    240Pu
    229
    Th
    246
    Cmƒ
    243
    Amƒ     		4.7–7.4 ka
    245
    Cmƒ
    250
    Cm     		8.3–8.5 ka
    239Puƒ 24.1 ka
    230
    Th№
    231
    Pa№     		32–76 ka
    236
    Npƒ     		233Uƒ 234U№ 150–250 ka 99Tc₡
    126
    Sn
    248
    Cm     		242Pu 327–375 ka 79Se₡
    1.53 Ma
    93
    Zr
    237
    Npƒ     		2.1–6.5 Ma
    135
    Cs₡
    107
    Pd
    236U
    247
    Cmƒ     		15–24 Ma 129I₡
    244Pu 80 Ma

    ... nor beyond 15.7 Ma[10]

    232Th№ 238U№ 235Uƒ№ 0.7–14.1 Ga
    (thermal neutron capture cross section greater than 3k barns)

    Protactinium-230

    Protactinium-230 has 139

    226Ac.[11] It is not found in nature because its half-life is short and it is not found in the decay chains
    of 235U, 238U, or 232Th. It has a mass of 230.034541 u.

    Protactinium-230 is of interest as a progenitor of uranium-230, an isotope that has been considered for use in

    deuteron irradiation of nautral thorium.[12]

    Protactinium-231

    Transmutations in the thorium fuel cycle
    237Np
    ↑
    231U ← 232U ↔ 233U ↔ 234U ↔ 235U ↔ 236U → 237U
    ↓ ↑ ↑ ↑
    231Pa → 232Pa ← 233Pa → 234Pa
    ↑ ↑
    230Th → 231Th ← 232Th → 233Th
    • Nuclides with a yellow background in italic have half-lives under 30 days
    • Nuclides in bold have half-lives over 1,000,000 years
    • Nuclides in red frames are
      fissile

    Protactinium-231 is the longest-lived isotope of protactinium, with a half-life of 32,760 years. In nature, it is found in trace amounts as part of the

    fast neutron removes a neutron from 232Th or 232U, and can also be destroyed by neutron capture, though the cross section
    for this reaction is also low.

    A solution of Protactinium-231

    binding energy: 1759860 keV
    beta decay energy: −382 keV

    spin: 3/2−
    mode of decay: alpha to 227Ac, also others

    possible parent nuclides: beta from 231Th, EC from 231U, alpha from 235Np.

    Protactinium-233

    Protactinium-233 is also part of the thorium fuel cycle. It is an intermediate beta decay product between

    thorium-233 (produced from natural thorium-232 by neutron capture) and uranium-233
    (the fissile fuel of the thorium cycle). Some thorium-cycle reactor designs try to protect Pa-233 from further neutron capture producing Pa-234 and U-234, which are not useful as fuel.

    Protactinium-234

    Protactinium-234 is a member of the

    uranium series with a half-life of 6.70 hours. It was discovered by Otto Hahn in 1921.[13]

    Protactinium-234m

    Protactinium-234m is a member of the uranium series with a half-life of 1.17 minutes. It was discovered in 1913 by

    234Th produce this isomer instead of the ground state (t1/2 = 6.70 hours).[14]

    References

    1. doi:10.1088/1674-1137/abddae
      .
    2. ^ "Standard Atomic Weights: Protactinium". CIAAW. 2017.
    3. ISSN 1365-3075
      .
    4. S2CID 225343089
      . Retrieved 17 September 2020.
    5. ^
      S2CID 125251822
      .
    6. ^ 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.
    7. thermal neutron fission of uranium-235, e.g. in a typical nuclear reactor
      .
    8. 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]."
    9. sea of instability
      ".
    10. ^ 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.
    11. doi:10.1088/1674-1137/41/3/030001
      .
    12. PMID 29757620
      .
    13. ^ Fry, C., and M. Thoennessen. "Discovery of the Actinium, Thorium, Protactinium, and Uranium Isotopes." January 14, 2012. Accessed May 20, 2018. https://people.nscl.msu.edu/~thoennes/2009/ac-th-pa-u-adndt.pdf.
    14. ^ a b "Human Health Fact Sheet - Protactinium" (PDF). Argonne National Laboratory (ANL). November 2001. Retrieved 17 October 2023.
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