Neptunium(V) and neptunium(VI) solubilities in synthetic brines of interest to the Waste Isolation Pilot Plant (WIPP)
- Sandia National Labs., Albuquerque, NM (United States)
- Lawrence Berkeley National Lab., CA (United States). Earth Sciences Div.
The solubility of Np(V) and Np(VI) has been measured in three synthetic Na-K-Mg-Cl brines in the presence of CO{sub 2}(g). Experiments were prepared from oversaturation by adding an excess of NpO{sub 2}{sup +} or NpO{sub 2}{sup 2+} to the brines and allowing the neptunium solids to precipitate. Vessels were maintained in contact with fixed CO{sub 2}(g) partial pressures at constant pH and 24 {+-} 1 C. Dissolved Np(V) concentrations decreased several orders of magnitude within the first 100 days of the experiment, while dissolved Np(VI) concentrations decreased initially but then remained relatively constant for more than 400 days. The solid phases formed in all experiments were identified by X-ray powder diffraction as KNpO{sub 2}CO{sub 3}{center_dot}xH{sub 2}O(s). Steady state concentrations for Np(V) are similar to those observed for Pu(V) in the same brines under the same conditions, where Pu occurs predominantly as Pu(V). Similarly, steady state concentrations for Np(VI), which was not reduced over a two year period, compare well with measured Pu(VI) concentrations in the same brines before the Pu(VI) was reduced to Pu(V).
- Research Organization:
- Sandia National Labs., Albuquerque, NM (United States); Lawrence Berkeley National Lab., CA (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States); American Cancer Society, New York, NY (United States); National Insts. of Health, Bethesda, MD (United States)
- DOE Contract Number:
- AC04-94AL85000; AC03-76SF00098
- OSTI ID:
- 463592
- Report Number(s):
- SAND--96-2472C; CONF-950903--1; ON: DE97004037; CNN: Grant ACS 29298-B3; Grant NIH GM08192
- Country of Publication:
- United States
- Language:
- English
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