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Title: Modeling of Boehmite Leaching from Actual Hanford High-Level Waste Samples

Abstract

The Department of Energy plans to vitrify approximately 60,000 metric tons of high level waste sludge from underground storage tanks at the Hanford Nuclear Reservation. To reduce the volume of high level waste requiring treatment, a goal has been set to remove about 90 percent of the aluminum, which comprises nearly 70 percent of the sludge. Aluminum in the form of gibbsite and sodium aluminate can be easily dissolved by washing the waste stream with caustic, but boehmite, which comprises nearly half of the total aluminum, is more resistant to caustic dissolution and requires higher treatment temperatures and hydroxide concentrations. In this work, the dissolution kinetics of aluminum species during caustic leaching of actual Hanford high level waste samples is examined. The experimental results are used to develop a shrinking core model that provides a basis for prediction of dissolution dynamics from known process temperature and hydroxide concentration. This model is further developed to include the effects of particle size polydispersity, which is found to strongly influence the rate of dissolution.

Authors:
; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
910261
Report Number(s):
PNNL-SA-51903
Journal ID: ISSN 0149-6395; SSTEDS; TRN: US0704045
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Separation Science and Technology, 42(8):1719-1730; Journal Volume: 42; Journal Issue: 8
Country of Publication:
United States
Language:
English
Subject:
12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; HIGH-LEVEL RADIOACTIVE WASTES; LEACHING; HANFORD RESERVATION; SLUDGES; ALUMINIUM OXIDES; ALUMINIUM HYDROXIDES; DISSOLUTION; CHEMICAL REACTION KINETICS; MATHEMATICAL MODELS; RADIOACTIVE WASTE PROCESSING; Boehmite, Dissolution, High Level Waste

Citation Formats

Peterson, Reid A., Lumetta, Gregg J., Rapko, Brian M., and Poloski, Adam P. Modeling of Boehmite Leaching from Actual Hanford High-Level Waste Samples. United States: N. p., 2007. Web. doi:10.1080/01496390701242111.
Peterson, Reid A., Lumetta, Gregg J., Rapko, Brian M., & Poloski, Adam P. Modeling of Boehmite Leaching from Actual Hanford High-Level Waste Samples. United States. doi:10.1080/01496390701242111.
Peterson, Reid A., Lumetta, Gregg J., Rapko, Brian M., and Poloski, Adam P. 2007. "Modeling of Boehmite Leaching from Actual Hanford High-Level Waste Samples". United States. doi:10.1080/01496390701242111.
@article{osti_910261,
title = {Modeling of Boehmite Leaching from Actual Hanford High-Level Waste Samples},
author = {Peterson, Reid A. and Lumetta, Gregg J. and Rapko, Brian M. and Poloski, Adam P.},
abstractNote = {The Department of Energy plans to vitrify approximately 60,000 metric tons of high level waste sludge from underground storage tanks at the Hanford Nuclear Reservation. To reduce the volume of high level waste requiring treatment, a goal has been set to remove about 90 percent of the aluminum, which comprises nearly 70 percent of the sludge. Aluminum in the form of gibbsite and sodium aluminate can be easily dissolved by washing the waste stream with caustic, but boehmite, which comprises nearly half of the total aluminum, is more resistant to caustic dissolution and requires higher treatment temperatures and hydroxide concentrations. In this work, the dissolution kinetics of aluminum species during caustic leaching of actual Hanford high level waste samples is examined. The experimental results are used to develop a shrinking core model that provides a basis for prediction of dissolution dynamics from known process temperature and hydroxide concentration. This model is further developed to include the effects of particle size polydispersity, which is found to strongly influence the rate of dissolution.},
doi = {10.1080/01496390701242111},
journal = {Separation Science and Technology, 42(8):1719-1730},
number = 8,
volume = 42,
place = {United States},
year = 2007,
month = 6
}
  • The U.S. Department of Energy plans to vitrify approximately 60,000 metric tons of high-level waste (HLW) sludge from underground storage tanks at the Hanford Site in Southwest Washington State. To reduce the volume of HLW requiring treatment, a goal has been set to remove a significant quantity of the aluminum, which comprises nearly 70 percent of the sludge. Aluminum is found in the form of gibbsite and sodium aluminate, which can be easily dissolved by washing the waste stream with caustic, and boehmite, which comprises nearly half of the total aluminum, but is more resistant to caustic dissolution and requiresmore » higher treatment temperatures and hydroxide concentrations. Chromium, which makes up a much smaller amount ({approx}3%) of the sludge, must also be removed because there is a low tolerance for chromium in the HLW immobilization process. In this work, the coupled dissolution kinetics of aluminum and chromium species during caustic leaching of actual Hanford HLW samples is examined. The experimental results are used to develop a model that provides a basis for predicting dissolution dynamics from known process temperature and hydroxide concentration. (authors)« less
  • The purpose of this work was to confirm the adequate performance of a cesium ion exchange resin using actual waste samples from the Hanford High Level Waste tank farm. In particular, the objective was to confirm selected design criteria for the proposed Waste Treatment Plant currently under construction on the Hanford Nuclear Reservation.
  • Pretreatment processes at the Savannah River Site will separate {sup 90}Sr, alpha-emitting and radionuclides (i.e., actinides) and {sup 137}Cs prior to disposal of the high-level nuclear waste. Separation of {sup 90}Sr and alpha-emitting radionuclides occurs by ion exchange/adsorption using an inorganic material, monosodium titanate (MST). Previously reported testing with simulants indicates that the MST exhibits high selectivity for strontium and actinides in high ionic strength and strongly alkaline salt solutions. This paper provides a summary of data acquired to measure the performance of MST to remove strontium and actinides from actual waste solutions. These tests evaluated the effects of ionicmore » strength, mixing, elevated alpha activities, and multiple contacts of the waste with MST. Tests also provided confirmation that MST performs well at much larger laboratory scales (300-700 times larger) and exhibits little affinity for desorption of strontium and plutonium during washing.« less
  • The authors discuss the volatility of /sup 137/Cs and /sup 106/Ru from borosilicate glass containing actual high-level waste measured in an almost closed stainless-steel canister. The temperature dependence of the volatility of /sup 137/Cs was close to that obtained in a previous study using /sup 134/Cs. The volatility of /sup 106/Ru was about one-fifth that of /sup 137/Cs at 600{sup 0} and 800{sup 0}C. The air contamination by /sup 137/Cs and /sup 106/Ru in the canister at 400{sup 0}C was estimated at 1.8 x 10/sup 2/ and 2 x 10 Bq/cm/sup 3/, respectively, when it was assumed that the glassmore » contained a realistic amount of /sup 137/Cs and /sup 106/Ru expected in commercial waste glass. These results are useful for predicting safety in a storage facility under operation.« less