Thermodynamics of Uranyl Minerals: Enthalpies of Formation of Uranyl Oxide Hydrates

Technical Report · Wed May 11 04:00:00 EDT 2005

DOI:https://doi.org/10.2172/859066· OSTI ID:859066

Kubatko, K; Helean, K; Navrotsky, A; Burns, P C

The enthalpies of formation of seven uranyl oxide hydrate phases and one uranate have been determined using high-temperature oxide melt solution calorimetry: [(UO{sub 2}){sub 4}O(OH){sub 6}](H{sub 2}O){sub 5}, metaschoepite; {beta}-UO{sub 2}(OH){sub 2}; CaUO{sub 4}; Ca(UO{sub 2}){sub 6}O{sub 4}(OH){sub 6}(H{sub 2}O){sub 8}, becquerelite; Ca(UO{sub 2}){sub 4}O{sub 3}(OH){sub 4}(H{sub 2}O){sub 2}; Na(UO{sub 2})O(OH), clarkeite; Na{sub 2}(UO{sub 2}){sub 6}O{sub 4}(OH){sub 6}(H{sub 2}O){sub 7}, the sodium analogue of compreignacite and Pb{sub 3}(UO{sub 2}){sub 8}O{sub 8}(OH){sub 6}(H{sub 2}O){sub 2}, curite. The enthalpy of formation from the binary oxides, {Delta}H{sub f-ox}, at 298 K was calculated for each compound from the respective drop solution enthalpy, {Delta}H{sub ds}. The standard enthalpies of formation from the elements, {Delta}H{sub f}{sup o}, at 298 K are -1791.0 {+-} 3.2, -1536.2 {+-} 2.8, -2002.0 {+-} 3.2, -11389.2 {+-} 13.5, -6653.1 {+-} 13.8, -1724.7 {+-} 5.1, -10936.4 {+-} 14.5 and -13163.2 {+-} 34.4 kJ mol{sup -1}, respectively. These values are useful in exploring the stability of uranyl oxide hydrates in auxiliary chemical systems, such as those expected in U-contaminated environments.

• Research Organization: YMP (Yucca Mountain Project, Las Vegas, Nevada)
• Sponsoring Organization: USDOE
• OSTI ID: 859066
• Report Number(s): NA; MOL.20050705.0239, DC#44635
• Country of Publication: United States
• Language: English

Related Subjects

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
BECQUERELITE
CALORIMETRY
CLARKEITE
COMPREIGNACITE
ENTHALPY
FORMATION HEAT
HYDRATES
OXIDE MINERALS
OXIDES
SODIUM
STABILITY
THERMODYNAMICS
URANATES
URANIUM MINERALS