Preliminary Results from Plutonium/Americium Studies Using Simulated Savannah River Site Waste Solutions
To address the accelerated disposition of the supernate and salt portions of Savannah River Site, SRS, high level waste (HLW), solubility experiments were performed to develop a predictive capability for plutonium, Pu and americium , Am, solubility. Preliminary results from the experiments indicate hydroxide, OH-, carbonate, CO32-, nitrate, NO3-, and temperature are the predominant parameters affecting Pu and Am solubilities in alkaline salt solutions representative of those present in SRS waste tanks. This study used a statistically designed experimental matrix to evaluate the effects of six major anionic components OH-, aluminate Al(OH)4-, sulfate, SO42-, CO32-, NO3-, and nitrite, NO2-, and temperature, 25 and 80 degrees C. This work extends previous data on Pu solubility to a wider range of solution compositions and is the first systematic evaluation of Am solubility in SRS waste solutions.Analysis of the solubility data collected in nominal 1 month intervals over a 3-month period showed no time-dependence of the Pu and Am concentrations. However, the data scatter among the three data sets was sufficiently large to introduce considerable variance in model parameters. The data scatter likely indicates that not all solutions have obtained equilibrium after 3 months. We recommend that the testing continue to obtain an additional two sets of data as planned in the experimental design. First-order models of the data indicate that the Pu solubility is a function of OH- and CO32- concentrations and that the Am solubility is a function of temperature and OH-, CO32-, and NO3-concentrations. These factors are statistically significant with at least 90 percent confidence. We also evaluated the Pu solubility data obtained in this study with previous data from the literature to develop a modified response surface model. All of the salt concentrations and temperature terms are statistically significant at the 90 percent confidence level. Upon completion of the solubility testing, we will incorporate the additional data into the response surface model and complete an evaluation of parameter sensitivity and validation of predictive performance.
- Research Organization:
- Savannah River Site (SRS), Aiken, SC (United States)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- AC09-96SR18500
- OSTI ID:
- 833398
- Report Number(s):
- WSRC-TR-2004-00349; TRN: US0406679
- Resource Relation:
- Other Information: PBD: 1 Jul 2004
- Country of Publication:
- United States
- Language:
- English
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