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Neptunium(IV) oxide

May 04, 2024

Neptunium(IV) oxide, or neptunium dioxide, is a radioactive, olive green[5] cubic[6] crystalline solid with the formula NpO2. It emits both α- and γ-particles.[4]

Neptunium(IV) oxide
Names
IUPAC name
Neptunium(IV) oxide
Other names
Neptunium oxide, neptunium dioxide
Identifiers
  • 12035-79-9 Y
3D model (JSmol)
  • Interactive image
ChemSpider
  • 34997056
ECHA InfoCard 100.031.651
EC Number
  • 234-830-1
  • 44148103
  • InChI=1S/Np.2O/q+4;2*-2
    Key: QKUTVYUEUPNRBO-UHFFFAOYSA-N
  • [O-2].[O-2].[Np+4]
Properties
NpO2
Molar mass 269 g/mol
Appearance Green cubic crystals
Density 11.1 g/cm3
Melting point 2,800 °C; 5,070 °F; 3,070 K[1]
Structure[2]
Flourite (cubic), cF12
Fm3m, #225
a = 543.4 pm
4
Thermochemistry
19.19 ± 0.1 cal·mol−1·K−1
(80.3 ± 0.4 J·mol−1·K−1)[3]
−256.7 ± 0.6 kcal·mol−1
(−1074 ± 3 kJ·mol−1)[4]
Related compounds
Other anions
 Neptunium(III) chloride
Neptunium(IV) chloride
Other cations
 Protactinium(IV) oxide
Uranium(IV) oxide
Plutonium(IV) oxide
Americium(IV) oxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YN ?)

Production edit

Industrially, neptunium dioxide is formed by precipitation of neptunium(IV) oxalate, followed by calcination to neptunium dioxide.[7]

Production starts with a nitric acid feed solution containing neptunium ions in various oxidation states. First, a hydrazine inhibitor is added to slow any oxidation from standing in air. Then ascorbic acid reduces the feed solution to predominantly neptunium(IV):

2Np5+ + C6H8O6 → 2Np4+ + C6H6O6 + 2H+
Np6+ + C6H8O6 → Np4+ + C6H6O6 + 2H+

Addition of oxalic acid precipitates hydrated neptunium oxalate...

Np4+ + 2H2C2O4 + 6H2O → Np(C2O4)2.6H2O(v) + 4H+

...which pyrolyzes when heated:[7]

Np(C2O4)2.6H2O Δ
→ Np(C2O4)2 Δ
→ NpO2 + 2CO(g)

Neptunium dioxide can also be formed from precipitation of neptunium(IV) peroxide, but the process is much more sensitive.[7]

Purification edit

As a byproduct of nuclear fission reactors, neptunium dioxide can be purified by fluorination, followed by reduction with excess calcium in the presence of iodine.[4] However, the aforementioned synthesis yields a quite pure solid, with less than 0.3% mass fraction of impurities. Generally, further purification is unnecessary.[7]

Other properties edit

Neptunium dioxide contributes to the α-decay of 241Am, reducing its usual half-life an untested but appreciable amount.[8] The compound has a low specific heat capacity (900 K, compared with uranium dioxide's specific heat capacity of 1400 K), an abnormality theorized to stem from its 5f electron count.[9] Another unique trait of neptunium dioxide is its "mysterious low-temperature ordered phase". Mentioned above, it references an abnormal level of order for an actinitde dioxide complex at low temperature.[10] Further discussion of such topics could indicate useful physical trends in the actinoides.

Uses edit

The neptunium dioxide complex is used as a means of stabilizing, and decreasing the "long term environmental burden"[11] of neptunium as a nuclear fission byproduct. Actinoide-containing spent nuclear fuel will commonly be treated so that various AnO2 (where An = U, Np, Pu, Am, etc.) complexes form. In neptunium dioxide, neptunium is of reduced radio toxicity compared with elemental neptunium and is thus more desirable for storage and disposal. Neptunium dioxide has also been shown to contribute to increased decay rates of radioactive elements, an application which is currently being explored.[11]

Neptunium dioxide is also used experimentally for research into nuclear chemistry and physics, and it is speculated that it could be used to make efficient nuclear weapons. In nuclear reactors, neptunium dioxide can also be used as the target for plutonium bombardment.[11]

Furthermore, a patent for a rocket powered by neptunium dioxide is held by Shirakawa Toshihisa,[12] but there is little information available into research and production associated with such a product.

References edit

  1. ^ Böhler, R.; M. J. Welland; F. De Bruycker; K. Boboridis; A. Janssen; R. Eloirdi; R. J. M. Konings; D. Manara (2012). "Revisiting the melting temperature of NpO2 and the challenges associated with high temperature actinide compound measurements". Journal of Applied Physics. 111 (11). American Institute of Physics: 113501–113501–8. Bibcode:2012JAP...111k3501B. doi:10.1063/1.4721655.
  2. ^ Christine Guéneau; Alain Chartier; Paul Fossati; Laurent Van Brutzel; Philippe Martin (2020). "Thermodynamic and Thermophysical Properties of the Actinide Oxides". Comprehensive Nuclear Materials 2nd Ed. 7: 111–154. doi:10.1016/B978-0-12-803581-8.11786-2. ISBN 9780081028667. S2CID 261051636.
  3. ^ Westrum, Jr., Edgar F.; J. B. Hatcher; Darrell W. Osborne (March 1953). "The Entropy and Low Temperature Heat Capacity of Neptunium Dioxide". Journal of Chemical Physics. 21 (3): 419. Bibcode:1953JChPh..21..419W. doi:10.1063/1.1698923.
  4. ^ a b c Huber Jr, Elmer J.; Charles E. Holley Jr (October 1968). "Enthalpy of formation of neptunium dioxide". Journal of Chemical & Engineering Data. 13 (4): 545–546. doi:10.1021/je60039a029.
  5. ^ Patnaik, Pradyot (2003). Handbook of Inorganic Chemical Compounds. McGraw-Hill Professional. p. 271. ISBN 0-07-049439-8.
  6. ^ Lide, D. R. (1998). Handbook of Chemistry and Physics 87 ed. CRC Press. p. 471. ISBN 0-8493-0594-2.
  7. ^ a b c d Porter, J. A. (1964). "Production of Neptunium Dioxide". Industrial & Engineering Chemistry Process Design and Development. 4 (3): 289–292. doi:10.1021/i260012a001. Equations extrapolated from verbal description.
  8. ^ Colle, J.-Y. (2011). "(Solid + gas) equilibrium studies for neptunium dioxide". Journal of Chemical Thermodynamics. 43 (3): 492–498. doi:10.1016/j.jct.2010.10.027.
  9. ^ Serizawa, H.; Arai, Y.; Nakajima, K. (2001). "The estimation of the heat capacity of NpO2". The Journal of Chemical Thermodynamics. 33 (6): 615–628. doi:10.1006/jcht.2000.0775.
  10. ^ Hotta, T. (2009). "Microscopic analysis of multipole susceptibility of actinide dioxides: A scenario of multipole ordering in AmO2". Physical Review B. 80 (2): 024408–1–024408–7. arXiv:0906.3607. Bibcode:2009PhRvB..80b4408H. doi:10.1103/PhysRevB.80.024408. S2CID 119295656.
  11. ^ a b c Colle, J.-Y. (2011). "(Solid + gas) equilibrium studies for neptunium dioxide". Journal of Chemical Thermodynamics. 43 (3): 492–498. doi:10.1016/j.jct.2012.10.027.
  12. ^ Toshihisa, Shirakawa. "Bibliographic data: JP2007040768 (A) - 2007-02-15". Espacenet, patent search. Retrieved 11 April 2012.

May 04, 2024
neptunium, oxide, neptunium, dioxide, radioactive, olive, green, cubic, crystalline, solid, with, formula, npo2, emits, both, particles, names, iupac, name, other, names, neptunium, oxide, neptunium, dioxide, identifiers, number, 12035, model, jsmol, interacti. Neptunium IV oxide or neptunium dioxide is a radioactive olive green 5 cubic 6 crystalline solid with the formula NpO2 It emits both a and g particles 4 Neptunium IV oxide Names IUPAC name Neptunium IV oxide Other names Neptunium oxide neptunium dioxide Identifiers CAS Number 12035 79 9 Y 3D model JSmol Interactive image ChemSpider 34997056 ECHA InfoCard 100 031 651 EC Number 234 830 1 PubChem CID 44148103 InChI InChI 1S Np 2O q 4 2 2Key QKUTVYUEUPNRBO UHFFFAOYSA N SMILES O 2 O 2 Np 4 Properties Chemical formula NpO2 Molar mass 269 g mol Appearance Green cubic crystals Density 11 1 g cm3 Melting point 2 800 C 5 070 F 3 070 K 1 Structure 2 Crystal structure Flourite cubic cF12 Space group Fm3m 225 Lattice constant a 543 4 pm Formula units Z 4 Thermochemistry Std molarentropy S 298 19 19 0 1 cal mol 1 K 1 80 3 0 4 J mol 1 K 1 3 Std enthalpy offormation DfH 298 256 7 0 6 kcal mol 1 1074 3 kJ mol 1 4 Related compounds Other anions Neptunium III chlorideNeptunium IV chloride Other cations Protactinium IV oxideUranium IV oxide Plutonium IV oxideAmericium IV oxide Except where otherwise noted data are given for materials in their standard state at 25 C 77 F 100 kPa N verify what is Y N Infobox references Contents 1 Production 2 Purification 3 Other properties 4 Uses 5 ReferencesProduction editIndustrially neptunium dioxide is formed by precipitation of neptunium IV oxalate followed by calcination to neptunium dioxide 7 Production starts with a nitric acid feed solution containing neptunium ions in various oxidation states First a hydrazine inhibitor is added to slow any oxidation from standing in air Then ascorbic acid reduces the feed solution to predominantly neptunium IV 2Np5 C6H8O6 2Np4 C6H6O6 2H Np6 C6H8O6 Np4 C6H6O6 2H Addition of oxalic acid precipitates hydrated neptunium oxalate Np4 2H2C2O4 6H2O Np C2O4 2 6H2O v 4H which pyrolyzes when heated 7 Np C2O4 2 6H2O D Np C2O4 2 D NpO2 2CO g Neptunium dioxide can also be formed from precipitation of neptunium IV peroxide but the process is much more sensitive 7 Purification editAs a byproduct of nuclear fission reactors neptunium dioxide can be purified by fluorination followed by reduction with excess calcium in the presence of iodine 4 However the aforementioned synthesis yields a quite pure solid with less than 0 3 mass fraction of impurities Generally further purification is unnecessary 7 Other properties editNeptunium dioxide contributes to the a decay of 241Am reducing its usual half life an untested but appreciable amount 8 The compound has a low specific heat capacity 900 K compared with uranium dioxide s specific heat capacity of 1400 K an abnormality theorized to stem from its 5f electron count 9 Another unique trait of neptunium dioxide is its mysterious low temperature ordered phase Mentioned above it references an abnormal level of order for an actinitde dioxide complex at low temperature 10 Further discussion of such topics could indicate useful physical trends in the actinoides Uses editThe neptunium dioxide complex is used as a means of stabilizing and decreasing the long term environmental burden 11 of neptunium as a nuclear fission byproduct Actinoide containing spent nuclear fuel will commonly be treated so that various AnO2 where An U Np Pu Am etc complexes form In neptunium dioxide neptunium is of reduced radio toxicity compared with elemental neptunium and is thus more desirable for storage and disposal Neptunium dioxide has also been shown to contribute to increased decay rates of radioactive elements an application which is currently being explored 11 Neptunium dioxide is also used experimentally for research into nuclear chemistry and physics and it is speculated that it could be used to make efficient nuclear weapons In nuclear reactors neptunium dioxide can also be used as the target for plutonium bombardment 11 Furthermore a patent for a rocket powered by neptunium dioxide is held by Shirakawa Toshihisa 12 but there is little information available into research and production associated with such a product References edit Bohler R M J Welland F De Bruycker K Boboridis A Janssen R Eloirdi R J M Konings D Manara 2012 Revisiting the melting temperature of NpO2 and the challenges associated with high temperature actinide compound measurements Journal of Applied Physics 111 11 American Institute of Physics 113501 113501 8 Bibcode 2012JAP 111k3501B doi 10 1063 1 4721655 Christine Gueneau Alain Chartier Paul Fossati Laurent Van Brutzel Philippe Martin 2020 Thermodynamic and Thermophysical Properties of the Actinide Oxides Comprehensive Nuclear Materials 2nd Ed 7 111 154 doi 10 1016 B978 0 12 803581 8 11786 2 ISBN 9780081028667 S2CID 261051636 Westrum Jr Edgar F J B Hatcher Darrell W Osborne March 1953 The Entropy and Low Temperature Heat Capacity of Neptunium Dioxide Journal of Chemical Physics 21 3 419 Bibcode 1953JChPh 21 419W doi 10 1063 1 1698923 a b c Huber Jr Elmer J Charles E Holley Jr October 1968 Enthalpy of formation of neptunium dioxide Journal of Chemical amp Engineering Data 13 4 545 546 doi 10 1021 je60039a029 Patnaik Pradyot 2003 Handbook of Inorganic Chemical Compounds McGraw Hill Professional p 271 ISBN 0 07 049439 8 Lide D R 1998 Handbook of Chemistry and Physics 87 ed CRC Press p 471 ISBN 0 8493 0594 2 a b c d Porter J A 1964 Production of Neptunium Dioxide Industrial amp Engineering Chemistry Process Design and Development 4 3 289 292 doi 10 1021 i260012a001 Equations extrapolated from verbal description Colle J Y 2011 Solid gas equilibrium studies for neptunium dioxide Journal of Chemical Thermodynamics 43 3 492 498 doi 10 1016 j jct 2010 10 027 Serizawa H Arai Y Nakajima K 2001 The estimation of the heat capacity of NpO2 The Journal of Chemical Thermodynamics 33 6 615 628 doi 10 1006 jcht 2000 0775 Hotta T 2009 Microscopic analysis of multipole susceptibility of actinide dioxides A scenario of multipole ordering in AmO2 Physical Review B 80 2 024408 1 024408 7 arXiv 0906 3607 Bibcode 2009PhRvB 80b4408H doi 10 1103 PhysRevB 80 024408 S2CID 119295656 a b c Colle J Y 2011 Solid gas equilibrium studies for neptunium dioxide Journal of Chemical Thermodynamics 43 3 492 498 doi 10 1016 j jct 2012 10 027 Toshihisa Shirakawa Bibliographic data JP2007040768 A 2007 02 15 Espacenet patent search Retrieved 11 April 2012 Retrieved from https en wikipedia org w index php title Neptunium IV oxide amp oldid 1213459382, wikipedia, wiki, book, books, library,

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