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Title: Solubility Enhanced Retardation of Neptunium in the Unsaturated Zone at Yucca Mountain


No abstract prepared.

Publication Date:
Research Org.:
Yucca Mountain Project, Las Vegas, Nevada
Sponsoring Org.:
OSTI Identifier:
Report Number(s):
MOL.20060712.0192, DC# 47664; TRN: US0606183
DOE Contract Number:
Resource Type:
Technical Report
Country of Publication:
United States

Citation Formats

G. Lu, and T. Xu. Solubility Enhanced Retardation of Neptunium in the Unsaturated Zone at Yucca Mountain. United States: N. p., 2006. Web. doi:10.2172/893898.
G. Lu, & T. Xu. Solubility Enhanced Retardation of Neptunium in the Unsaturated Zone at Yucca Mountain. United States. doi:10.2172/893898.
G. Lu, and T. Xu. Mon . "Solubility Enhanced Retardation of Neptunium in the Unsaturated Zone at Yucca Mountain". United States. doi:10.2172/893898.
title = {Solubility Enhanced Retardation of Neptunium in the Unsaturated Zone at Yucca Mountain},
author = {G. Lu and T. Xu},
abstractNote = {No abstract prepared.},
doi = {10.2172/893898},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon May 08 00:00:00 EDT 2006},
month = {Mon May 08 00:00:00 EDT 2006}

Technical Report:

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  • This report is primarily a means of transmitting thermal-conductivity data to the Yucca Mountain Project properties data base. As such, the majority of the report is a compilation of these data for 45 samples of tuffaceous rocks from Yucca Mountain, Nevada; some of the data have been published previously. Brief discussions of the experiment technique (transient-line-source) and experiment uncertainties also are included. The accuracy of the thermal-conductivity data cannot be assessed at present; precision (repeatability) has been determined to be better than {+ -}2%, in most cases. 15 refs., 5 figs., 1 tab.
  • Yucca Mountain, located on and adjacent to the Nevada Test Site in southern Nevada, is being evaluated as a potential site for underground disposal of nuclear wastes. At present, the physical, thermal, and mechanical properties of tuffaceous rocks from Yucca Mountain are being determined as part of the Yucca Mountain Project. This report documents experiment data, which have been obtained by Sandia National Laboratories or its contractors, for the density and porosity of tuffaceous rocks that lie above the water table at Yucca Mountain. 7 refs., 2 figs., 3 tabs.
  • In the absence of experimentally determined heat capacity data, bulk-chemical analyses of 20 samples of tuffs from Yucca Mountain have been used to calculate heat capacities of the solid components of the tuffs as a function of temperature. These calculated values, which should be validated by experiments as soon as practicable, have been combined with data on grain density, matrix porosity, lithophysal-cavity abundance, mineral abundance, in situ saturation, and the properties of water to estimate rock-mass thermal capacitances. In general, thermal capacitance is higher for tuffs with higher porosity for the same pore fluid; saturated tuffs have higher thermal capacitancesmore » than partially saturated or dry tuffs. The heat capacity of the solid components provides a secondary contribution. 34 refs., 14 figs., 9 tabs.« less
  • Experiment results are presented for linear thermal expansion measurements on tuffaceous rocks from the unsaturated
  • We have studied the solubilities of neptunium, plutonium, and americium in J-13 groundwater from Yucca Mountain (Nevada) at three temperatures and hydrogen ion concentrations. They are 25{degree}, 60{degree}C, and 90{degree}C and pH 5.9, 7.0, and 8.5. The results for 25{degree}C are from a study which we did during FY 1984. We included these previous results in the tables to give more information on the solubility temperature dependence; they were, however, done at only one pH (7.0). The solubilities were studied from oversaturation. The nuclides were added at the beginning of each experiment as NpO{sub 2}{sup +}, Pu{sup 4+}, and Am{supmore » 3+}. The neptunium solubility decreased with increasing temperature and with increasing pH. The soluble neptunium did not change oxidation state at steady state. The pentavalent neptunium was increasingly complexed by carbonate with increasing pH. All solids were crystalline and contained carbonate, except the solid formed at 90{degree}C and pH 5.9. We identified this solid as crystalline Np{sub 2}P{sub 5}. The 25{degree}C, pH 7 solid was Na{sub 3}NpO{sub 2}(CO{sub 3}){sub 2} {center_dot} nH{sub 2}O. Plutonium concentrations decreased with increasing temperature and showed no trend with pH. Pu(V) and Pu(VI) were the dominant oxidation states in the supernatant solution; as the amount of Pu(V) increased with pH, Pu(VI) decreed. The steady-state solids were mostly amorphous, although some contained a crystalline component. They contained Pu(IV) polymer and unknown carbonates.« less