“Isotopes of neptunium”的意思、由来-开放百科全书

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 ²³⁸U with neutrons to produce ²³⁹U, which then underwent beta decay to ²³⁹Np.

Trace quantities are found in nature from neutron capture reactions by uranium atoms, a fact not discovered until 1951.

Twenty-three neptunium radioisotopes have been characterized, with the most stable being {{SimpleNuclide2|Neptunium|237}} with a half-life of 2.14 million years, {{SimpleNuclide2|Neptunium|236}} with a half-life of 154,000 years, and {{SimpleNuclide2|Neptunium|235}} with a half-life of 396.1 days. All of the remaining radioactive isotopes have half-lives that are less than 4.5 days, and the majority of these have half-lives that are less than 50 minutes. This element also has 4 meta states, with the most stable being {{SimpleNuclide2|Neptunium|236m}} (t_1/2 22.5 hours).

The isotopes of neptunium range from {{SimpleNuclide2|Neptunium|219}} to {{SimpleNuclide2|Neptunium|244}}, though the intermediate isotopes {{SimpleNuclide2|Neptunium|220-222}} have not yet been observed. The primary decay mode before the most stable isotope, {{SimpleNuclide2|Neptunium|237}}, is electron capture (with a good deal of alpha emission), and the primary mode after is beta emission. The primary decay products before {{SimpleNuclide2|Neptunium|237}} are isotopes of uranium and protactinium, and the primary products after are isotopes of plutonium. Uranium-237 and neptunium-239 are regarded as the leading hazardous radioisotopes in the first hour-to-week period following nuclear fallout from a nuclear detonation, with Np-239 dominating "the spectrum for several days".^[1]^[2]

Actinides vs fission products

Notable isotopes

Neptunium-235

Neptunium-235 has 142 neutrons and a half-life of 396.1 days. This isotope decays by:

Neptunium-236

Neptunium-236 has 143 neutrons and a half-life of 154,000 years. It can decay by the following methods:

This particular isotope of neptunium has a mass of 236.04657 u. It is a fissile material with a critical mass of 6.79 kg.^[3]

Neptunium-237

In 2002, {{SimpleNuclide2|Neptunium|237}} was shown to be capable of sustaining a chain reaction with fast neutrons, as in a nuclear weapon, with a critical mass of around 60 kg.^[7] However, it has a low probability of fission on bombardment with thermal neutrons, which makes it unsuitable as a fuel for conventional nuclear power plants (as opposed to accelerator-driven systems, etc.).

Use in plutonium-238 production

When exposed to neutron bombardment {{SimpleNuclide2|Neptunium|237}} can capture a neutron and become {{SimpleNuclide2|Plutonium|238|link=yes}}, this product being useful as an thermal energy source in a radio-isotope thermoelectric generator for the production of electricity and heat in deep space probes (such as the New Horizons and Voyager probes) and, of recent note, the Mars Science Laboratory (Curiosity rover). These applications are economically practical where photovoltaic power sources are weak or inconsistent due to probes being too far from the sun or rovers facing climate events that may obstruct sunlight for long periods. Space probes and rovers also make use of the heat output of the generator to keep their instruments and internals warm.^[8]

List of isotopes

nuclide
symbol

Z(p)

N(n)

isotopic mass (u)^[9]

half-life

decay
mode(s)^[10]^[11]

daughter
isotope(s)

nuclear
spin and
parity

excitation energy

Neptunium|219}}^[12]

126

219.03162(9)

0.15(+0.72-0.07) ms

²¹⁵Pa

(9/2−)

Neptunium|223}}^[13]

130

223.03285(21)#

2.15(+100-52) µs

²¹⁹Pa

9/2−

{{SimpleNuclide2|Neptunium|224}}^[14]

131

224.03422(21)#

38(+26-11) µs

α (83%)

^220m1Pa

1-#

α (17%)

^220m2Pa

Neptunium|225}}

132

225.03391(8)

6(5) ms

²²¹Pa

9/2−#

Neptunium|226}}

133

226.03515(10)#

35(10) ms

²²²Pa

134

227.03496(8)

510(60) ms

α (99.95%)

²²³Pa

5/2−#

β⁺ (.05%)

²²⁷U

135

228.03618(21)#

61.4(14) s

β⁺ (59%)

²²⁸U

α (41%)

²²⁴Pa

β⁺, SF (.012%)

(various)

136

229.03626(9)

4.0(2) min

α (51%)

²²⁵Pa

5/2+#

β⁺ (49%)

²²⁹U

137

230.03783(6)

4.6(3) min

β⁺ (97%)

²³⁰U

α (3%)

²²⁶Pa

138

231.03825(5)

48.8(2) min

β⁺ (98%)

²³¹U

(5/2)(+#)

α (2%)

²²⁷Pa

139

232.04011(11)#

14.7(3) min

β⁺ (99.99%)

²³²U

(4+)

α (.003%)

²²⁸Pa

140

233.04074(5)

36.2(1) min

β⁺ (99.99%)

²³³U

(5/2+)

α (.001%)

²²⁹Pa

Neptunium|234}}

141

234.042895(9)

4.4(1) d

β⁺

²³⁴U

(0+)

142

235.0440633(21)

396.1(12) d

²³⁵U

5/2+

α (.0026%)

²³¹Pa

{{SimpleNuclide2|Neptunium|236}}^[15]

143

236.04657(5)

1.54(6)×10⁵ y

EC (87.3%)

²³⁶U

(6−)

β⁻ (12.5%)

²³⁶Pu

α (.16%)

²³²Pa

60(50) keV

22.5(4) h

EC (52%)

²³⁶U

β⁻ (48%)

²³⁶Pu

{{SimpleNuclide2|Neptunium|237}}^[15]^[16]

144

237.0481734(20)

2.144(7)×10⁶ y

²³³Pa

5/2+

SF (2×10⁻¹⁰%)

(various)

CD (4×10⁻¹²%)

²⁰⁷Tl
³⁰Mg

Neptunium|238}}

145

238.0509464(20)

2.117(2) d

β⁻

²³⁸Pu

2300(200)# keV

112(39) ns

Neptunium|239}}

146

239.0529390(22)

2.356(3) d

β⁻

²³⁹Pu

5/2+

Neptunium|240}}

147

240.056162(16)

61.9(2) min

β⁻

²⁴⁰Pu

(5+)

20(15) keV

7.22(2) min

β⁻ (99.89%)

²⁴⁰Pu

1(+)

IT (.11%)

²⁴⁰Np

Neptunium|241}}

148

241.05825(8)

13.9(2) min

β⁻

²⁴¹Pu

(5/2+)

Neptunium|242}}

149

242.06164(21)

2.2(2) min

β⁻

²⁴²Pu

(1+)

0(50)# keV

5.5(1) min

6+#

Neptunium|243}}

150

243.06428(3)#

1.85(15) min

β⁻

²⁴³Pu

(5/2−)

Neptunium|244}}

151

244.06785(32)#

2.29(16) min

β⁻

²⁴⁴Pu

(7−)

1. ^[Film Badge Dosimetry in Atmospheric Nuclear Tests, By Committee on Film Badge Dosimetry in Atmospheric Nuclear Tests, Commission on Engineering and Technical Systems, Division on Engineering and Physical Sciences, National Research Council. pg24-35]
2. ^Bounding Analysis of Effects of Fractionation of Radionuclides in Fallout on Estimation of Doses to Atomic Veterans DTRA-TR-07-5. 2007
3. ^Final Report, Evaluation of nuclear criticality safety data and limits for actinides in transport {{webarchive|url=https://web.archive.org/web/20110519171204/http://ec.europa.eu/energy/nuclear/transport/doc/irsn_sect03_146.pdf |date=2011-05-19 }}, Republic of France, Institut de Radioprotection et de Sûreté Nucléaire, Département de Prévention et d'étude des Accidents.
4. ^Analysis of the Reuse of Uranium Recovered from the Reprocessing of Commercial LWR Spent Fuel, United States Department of Energy, Oak Ridge National Laboratory.
5. ^**{{cite book |author=Jukka Lehto |author2=Xiaolin Hou |year=2011|chapter=15.15: Neptunium |title=Chemistry and Analysis of Radionuclides |page=231 |nopp=yes |edition=1st |publisher=John Wiley & Sons |isbn=3527633022}}
6. ^¹{{cite journal|last=Jerome|first=S.M.|last2=Ivanov|first2=P.|last3=Larijani|first3=C. |last4=Parker|first4=D.J.|last5=Regan|first5=P.H.|title=The production of Neptunium-236g|date=2014|journal=Journal of Environmental Radioactivity|volume=138|pages=315–322|doi=10.1016/j.jenvrad.2014.02.029}}
7. ^{{cite journal |author=P. Weiss |date=26 October 2002 |title=Neptunium Nukes? Little-studied metal goes critical |url=http://www.sciencenews.org/view/generic/id/3246/title/Neptunium_Nukes%3F_Little-studied_metal_goes_critical |archiveurl=https://www.webcitation.org/6Cw9Vnt0Q?url=http://www.sciencenews.org/view/generic/id/3246/title/Neptunium_Nukes?_Little-studied_metal_goes_critical |archivedate=15 December 2012 |journal=Science News |volume=162 |issue=17 |page=259 |accessdate=7 November 2013 |deadurl=yes |df= }}
8. ^{{Cite journal|last=Witze|first=Alexandra|date=2014-11-27|title=Nuclear power: Desperately seeking plutonium|url=http://www.nature.com/news/nuclear-power-desperately-seeking-plutonium-1.16411|journal=Nature|language=en|volume=515|issue=7528|pages=484–486|doi=10.1038/515484a|bibcode=2014Natur.515..484W}}
9. ^{{NUBASE 2016 II}}
10. ^{{cite web |url=http://www.nucleonica.net/unc.aspx |title=Universal Nuclide Chart |publisher=nucleonica |registration=yes}}
11. ^Abbreviations:
CD: Cluster decay
EC: Electron capture
IT: Isomeric transition
SF: Spontaneous fission
12. ^Yang H, Ma L, Zhang Z, Yang C, Gan Z, Zhang M, et al. Alpha decay properties of the semi-magic nucleus 219 Np. Physics Letters B. 2018;777:212–6.
13. ^New short-lived isotope 223 Np and the absence of the Z = 92 subshell closure near N = 126M.d. Sun-Z. Liu-T.h. Huang-W.q. Zhang-J.g. Wang-X.y. Liu-B. Ding-Z.g. Gan-L. Ma-H.b. Yang-Z.y. Zhang-L. Yu-J. Jiang-K.l. Wang-Y.s. Wang-M.l. Liu-Z.h. Li-J. Li-X. Wang-H.y. Lu-C.j. Lin-L.j. Sun-N.r. Ma-C.x. Yuan-W. Zuo-H.s. Xu-X.h. Zhou-G.q. Xiao-C. Qi-F.s. Zhang - Physics Letters B - 2017
14. ^{{cite journal|last=Huang|first=T.H.|display-authors=etal|date=2018|title=Identification of the new isotope ²²⁴Np|url=https://www.researchgate.net/publication/328038265_Identification_of_the_new_isotope_Np_224|format=pdf|journal=Physical Review C|volume=98|issue=4|pages=044302|doi=10.1103/PhysRevC.98.044302}}
15. ^¹Fissile nuclide
16. ^Most common nuclide

References

Isotope masses from:
- {{NUBASE 2003}}
Isotopic compositions and standard atomic masses from:
- {{CAWIA 2003}}
- {{CIAAW 2005}}
Half-life, spin, and isomer data selected from the following sources. See editing notes on this article's talk page.
- {{NUBASE 2003}}
- {{NNDC}}
- {{CRC85|chapter=11}}

3 : Neptunium|Isotopes of neptunium|Lists of isotopes by element

Actinides vs fission products

Notable isotopes

Neptunium-235

Neptunium-236

Neptunium-237

Use in plutonium-238 production

List of isotopes

Notes

References