Enthalpies of formation of Ce-pyrochlore, Ca0.93Ce1.00Ti2.035O7.00, U-pyrochlore, Ca1.46U0.234+U0.466+Ti1.85O7.00 and Gd-pyrochlore, Gd2Ti2O7:: three materials relevant to the proposed waste form for excess weapons plutonium

被引:83
作者
Helean, KB [1 ]
Navrotsky, A
Vance, ER
Carter, ML
Ebbinghaus, B
Krikorian, O
Lian, J
Wang, LM
Catalano, JG
机构
[1] Univ Calif Davis, Dept Chem Engn & Mat Sci, Thermochem Facil, Davis, CA 95616 USA
[2] Australian Nucl Sci & Technol Org, Menai, NSW 2234, Australia
[3] Lawrence Livermore Natl Lab, Livermore, CA 94551 USA
[4] Univ Michigan, Dept Nucl Engn & Radiol Sci, Ann Arbor, MI 48111 USA
[5] Stanford Univ, Dept Geol & Environm Sci, Stanford, CA 94305 USA
关键词
D O I
10.1016/S0022-3115(02)00795-X
中图分类号
T [工业技术];
学科分类号
08 ;
摘要
High temperature oxide melt solution calorimetry was used to derive standard enthalpies of formation, AHf (kJ/mol), for three pyrochlore phases: Ca0.93Ce1.00Ti2.035O7.00 (-3656.0 +/- 5.6), Ca1.46U0.234+U0.466+Ti1.85O7.00 (-3610 +/- 4.1) and Gd2Ti2O7 (-3822.5 +/- 4.9). Enthalpy of drop solution data, DeltaH(ds), were used to calculate enthalpies of formation with respect to an oxide/perovskite phase assemblage AH(f-ox)(0): CaO + MO2 + 2TiO(2) = CaMTi2O7 or Gd2O3 + 2TiO(2) = Gd2Ti2O7, and an oxide/perovkite phas assemblage AH(f-pv+ox)(0): CaTiO3 + MO2 + TiO2 = CaMTi2O7, where M = Ce or U. All three pyrochlore samples were stable in enthalpy relative to an oxide assemblage with DeltaH(f-ox)(0) (kJ/mol) (Gd2Ti2O7) = -113.4 +/- 2.8; DeltaH(f-ox)(0)(Ca1.46U0.234+U0.466+Ti0.85O7.00) = -123.1 +/- 3.4; DeltaH(f-ox)(0)(Ca0.93Ce1.00Ti2.035O7.00) = -54.1 +/-5.2. U pyrochlore was stable in enthalpy relative to an oxide/perovskite assemblage (DeltaH(f-pv-ox)(0) = -5.1 +/- 4.0 kJ/mol). Ce-pyrochlore was metastable in enthalpy relative to the oxide/perovskite phase assemblage (DeltaH(f-pv-ox)(0) = +21.0 +/- 5.5 kJ/mol). A significant metastability field was defined with respect to an oxide.perovskite phase assemblage. However, the proposed waste form baseline composition lies in the stable regions of the phase diagrams. (C) 2002 Elsevier Science B.V. All rights reserved.
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页码:226 / 239
页数:14
相关论文
共 58 条
  • [1] [Anonymous], 1995, US GEOL SURV B
  • [2] ESTIMATION OF THE HEAT OF FORMATION OF REFRACTORY MIXED OXIDES
    ARONSON, S
    [J]. JOURNAL OF NUCLEAR MATERIALS, 1982, 107 (2-3) : 343 - 346
  • [3] Heavy-ion irradiation effects in Gd2(Ti2-xZrx)O7 pyrochlores
    Begg, BD
    Hess, NJ
    McCready, DE
    Thevuthasan, S
    Weber, WJ
    [J]. JOURNAL OF NUCLEAR MATERIALS, 2001, 289 (1-2) : 188 - 193
  • [4] BEGG BD, 1997, SCI BASIS NUCL WASTE, V20, P325
  • [5] IN-SITU CHEMICAL SPECIATION OF URANIUM IN SOILS AND SEDIMENTS BY MICRO-X-RAY ABSORPTION-SPECTROSCOPY
    BERTSCH, PM
    HUNTER, DB
    SUTTON, SR
    BAJT, S
    RIVERS, ML
    [J]. ENVIRONMENTAL SCIENCE & TECHNOLOGY, 1994, 28 (05) : 980 - 984
  • [6] Bloss FD, 1994, CRYSTALLOGRAPHY CRYS, P545
  • [7] BUCK EC, 1999, SCI BASIS NUCL WASTE, V22, P19
  • [8] ALPHA-DECAY SELF-IRRADIATION DAMAGE IN PU-238-SUBSTITUTED ZIRCONOLITE
    CLINARD, FW
    HOBBS, LW
    LAND, CC
    PETERSON, DE
    ROHR, DL
    ROOF, RB
    [J]. JOURNAL OF NUCLEAR MATERIALS, 1982, 105 (2-3) : 248 - 256
  • [9] SELF-IRRADIATION EFFECTS IN PU-238-SUBSTITUTED ZIRCONOLITE .1. TEMPERATURE-DEPENDENCE OF DAMAGE
    CLINARD, FW
    PETERSON, DE
    ROHR, DL
    HOBBS, LW
    [J]. JOURNAL OF NUCLEAR MATERIALS, 1984, 126 (03) : 245 - 254
  • [10] Deer W.A., 1996, INTRO ROCK FORMING M, V2nd