Calculated uranium solubility in groundwater: implications for nuclear fuel waste disposal

Abstract

BRUCE GOODWIN. Can. J. Chem. 60, 1759Chem. 60, (1982.Uranium solubilities of the order of M have been calculated for a range of conditions which are considered to be representative of those expected in a Canadian nuclear fuel waste disposal vault. Factors taken into consideration include the pH and Eh range expected for deep groundwaters, the projected temperature range near a nuclear fuel waste disposal vault, the effect of the composition of two representative groundwaters, the effect of non-ideality, and the effect of the stability of several uranium solids.The model used in these calculations is based on the assumption of chemical equilibrium. Calculations show that the most important factors influencing uranium solubility under the postulated conditions are pH and Eh.These results applied to an assessment of the nuclear fuel waste disposal program suggest that uranium concentrations will be very low in the disposal vault, and that the irradiated UO, fuel matrix will remain relatively intact for long periods of time.BRUCE GOODWIN. Can. J . Chem. 60, 1759Chem. 60, (1982.On a calcule des solubilitCs de I'uranium de I'ordre de M dans un intervalle de conditions que I'on considkre representatif de celles attendues dans une voute d'entreposage de dechets de combustibles nuclkaires canadiens. Les facteurs considCrCs comprennent les domaines de pH et de Eh auxquels on peut s'attendre pour les eaux souterraines profondes, le domaine de temperature prevue prks d'une voute de dCchets de combustibles nuclkaires, I'effet de la composition de deux eaux souterraines representatives, I'effet de non-idialitC et I'effet de stabilitk de plusieurs solides contenant de I'uranium.Le modkle utilisC dans ces calculs repose sur I'hypothkse d'un iquilibre chimique. Les calculs rCvklent que la plupart des facteurs importants qui influencent la solubilitk de I'uranium dans les conditions choisies sont le pH et le Eh.Ces calculs, appliques a une evaluation du programme d'entreposage des dCchets de combustible nucleaire, suggkrent que les concentrations en uranium seront trks faibles dans les voutes d'entreposage et que la matrice de combustible UO, irradii restera relativement intacte pendant un temps assez long.[Traduit par le journal] Introduction container, and eventually leaches the contained The solubility of uranium in natural groundwater radioactive waste for transport to the Surface. is of interest from two viewpoints. For some time, One of the parameters critical to these studies is this subject has been studied in relation .to the the degree to which radioactive waste dissolves in formation and dissolution of uranium ores (I), often natural groundwater. In particular, the solubility of in oxidizing environments, More recently the sub-uranium oxide is very important since the irradiatject has become of interest in relation to the nuclear ed a CANDU2 a~~r O xfuel waste disposal program. This report is oriented i m a t e l~ 98% weight U027 and less than 2% by towards the latter aspect.weight of the more hazardous fission pro...

MNDO studies of proton affinity as a probe of electronic structure. 2. Boranes and carboranes

“…B5H9/B5H10+. The MNDO protonation of B5H9 has been reported to result in the formation of a three-center B-H2 bond, at the apical and most negative boron (3).13 Our study also finds this structure, but MNDO prefers by 16.8 kcal/mol a more classical structure (4) in which a B-H-B bond has broken in favor of two classical two-center B-H bonds. Although this energy difference is significant, structure 3, where the B5 cluster is relatively undisturbed, is probably more realistic.18…”

“…Studies in the past decade have shown that it is useful to relate the structure and bonding of transition-metal organometallic cluster molecules to those of the main-group boranes and carboranes through the isolobal principle. 3 In this work we set out to use the proton as a probe of the electronic structure of the boranes and carboranes. Our approach is to use the MNDO molecular orbital method,4 building on our earlier work of MNDO proton affinity studies.…”

“…The temperature dependence of formation constants for metal-bicarbonate systems are important to seawater chemistry,1 geothermal energy studies,2 and nuclear waste disposal. 3 Usually the temperature dependence is described by fitting to nonlinear equations such as log K{ = A + B/T + C In T + DT2 in which either C or D may be zero.1•2 An example is that of Lesht and Bauman,1 who were unable to find a two-parameter equation consistent with their experimental log K¡ values. We report here an approach whereby selected formation constants are fit to a two-term linear equation that permits estimating values at high temperatures by extrapolation.…”

Uranium in Waters of The Southern Colorado Plateau: Implications for the Navajo Nation

“…U occurs naturally in rocks on Earth and tends to have concentrations of 2.8 ppm on average in upper crustal rocks (McLennan, 2001). U tends to dissolve when waters have high Eh and low pH, and is less soluble in waters with low Eh and intermediate pH (Goodwin, 1982). The tailings and materials from U mines are known to contribute to elevated U concentrations in waters through the oxidation of sulfides which decreases the pH (Hoover et al, 2017;Ingram et al, 2020).…”