TY - JOUR
T1 - Hydrothermal stability of β-Cs2U2O7 and SrZrO3 in fluids
AU - Komarneni, Sridhar
N1 - Funding Information:
Acknowledgements--This research was supported by the Department of Energy through Rockwell Hanford Operations (EE-AC06-77RL-01030) subcontracts SA-918 and SA-923 and through Ot~ce of Nuclear Waste Isolation subcontract E512-3400.
PY - 1981
Y1 - 1981
N2 - The stability of β-Cs2U2O7 and SrZrO3, two possible phases of spent fuel elements, in hydrothermal fluids was investigated. β-Cs2U2O7 was unstable under hydrothermal conditions of 100, 200 and 300°C/300 bars releasing substantial amounts of its Cs in deionized water and all of its Cs in a bittern (high-Mg and-Ca) brine. SrZrO3 was found to be quite stable in deionized water but not in a bittern brine. For example, Sr released into solution decreased from 3.9 to 2.8% with an increase in temperature from 100 to 300°C probably because of better crystallization of SrZrO3 at higher temperatures. In bittern brine, 23.3, 94.9 and 100% of Sr was released into solution at 100, 200 and 300°C respectively as a result of acidic conditions generated by the hydrolysis of MgCl2 and formation of brucite. These results suggest that bittern brine which may be encountered in a salt repository is highly corrosive and may release all the Cs and Sr into solution under hydrothermal conditions if the containment were breached. The use of tailor-made overpacks or backfill barriers of highly stable and sorptive materials is essential especially in a salt repository in order to minimize the threat of highly hazardous Cs and Sr radionuclides finding their way into ground waters.
AB - The stability of β-Cs2U2O7 and SrZrO3, two possible phases of spent fuel elements, in hydrothermal fluids was investigated. β-Cs2U2O7 was unstable under hydrothermal conditions of 100, 200 and 300°C/300 bars releasing substantial amounts of its Cs in deionized water and all of its Cs in a bittern (high-Mg and-Ca) brine. SrZrO3 was found to be quite stable in deionized water but not in a bittern brine. For example, Sr released into solution decreased from 3.9 to 2.8% with an increase in temperature from 100 to 300°C probably because of better crystallization of SrZrO3 at higher temperatures. In bittern brine, 23.3, 94.9 and 100% of Sr was released into solution at 100, 200 and 300°C respectively as a result of acidic conditions generated by the hydrolysis of MgCl2 and formation of brucite. These results suggest that bittern brine which may be encountered in a salt repository is highly corrosive and may release all the Cs and Sr into solution under hydrothermal conditions if the containment were breached. The use of tailor-made overpacks or backfill barriers of highly stable and sorptive materials is essential especially in a salt repository in order to minimize the threat of highly hazardous Cs and Sr radionuclides finding their way into ground waters.
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U2 - 10.1016/0022-1902(81)80626-4
DO - 10.1016/0022-1902(81)80626-4
M3 - Article
AN - SCOPUS:49149134247
VL - 43
SP - 2833
EP - 2837
JO - Polyhedron
JF - Polyhedron
SN - 0277-5387
IS - 11
ER -