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Title: MST Filterability Tests

Abstract

The Savannah River Site (SRS) is currently treating radioactive liquid waste with the Actinide Removal Process (ARP) and the Modular Caustic Side Solvent Extraction Unit (MCU). The low filter flux through the ARP has limited the rate at which radioactive liquid waste can be treated. Recent filter flux has averaged approximately 5 gallons per minute (gpm). Salt Batch 6 has had a lower processing rate and required frequent filter cleaning. Savannah River Remediation (SRR) has a desire to understand the causes of the low filter flux and to increase ARP/MCU throughput. In addition, at the time the testing started, SRR was assessing the impact of replacing the 0.1 micron filter with a 0.5 micron filter. This report describes testing of MST filterability to investigate the impact of filter pore size and MST particle size on filter flux and testing of filter enhancers to attempt to increase filter flux. The authors constructed a laboratory-scale crossflow filter apparatus with two crossflow filters operating in parallel. One filter was a 0.1 micron Mott sintered SS filter and the other was a 0.5 micron Mott sintered SS filter. The authors also constructed a dead-end filtration apparatus to conduct screening tests with potential filter aidsmore » and body feeds, referred to as filter enhancers. The original baseline for ARP was 5.6 M sodium salt solution with a free hydroxide concentration of approximately 1.7 M.3 ARP has been operating with a sodium concentration of approximately 6.4 M and a free hydroxide concentration of approximately 2.5 M. SRNL conducted tests varying the concentration of sodium and free hydroxide to determine whether those changes had a significant effect on filter flux. The feed slurries for the MST filterability tests were composed of simple salts (NaOH, NaNO 2, and NaNO 3) and MST (0.2 – 4.8 g/L). The feed slurry for the filter enhancer tests contained simulated salt batch 6 supernate, MST, and filter enhancers.« less

Authors:
 [1];  [1];  [1]
  1. Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)
Publication Date:
Research Org.:
Savannah River Site (SRS), Aiken, SC (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1177887
Report Number(s):
SRNL-STI-2015-00158
DOE Contract Number:
AC09-08SR22470
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English

Citation Formats

Poirier, M. R., Burket, P. R., and Duignan, M. R. MST Filterability Tests. United States: N. p., 2015. Web. doi:10.2172/1177887.
Poirier, M. R., Burket, P. R., & Duignan, M. R. MST Filterability Tests. United States. doi:10.2172/1177887.
Poirier, M. R., Burket, P. R., and Duignan, M. R. Thu . "MST Filterability Tests". United States. doi:10.2172/1177887. https://www.osti.gov/servlets/purl/1177887.
@article{osti_1177887,
title = {MST Filterability Tests},
author = {Poirier, M. R. and Burket, P. R. and Duignan, M. R.},
abstractNote = {The Savannah River Site (SRS) is currently treating radioactive liquid waste with the Actinide Removal Process (ARP) and the Modular Caustic Side Solvent Extraction Unit (MCU). The low filter flux through the ARP has limited the rate at which radioactive liquid waste can be treated. Recent filter flux has averaged approximately 5 gallons per minute (gpm). Salt Batch 6 has had a lower processing rate and required frequent filter cleaning. Savannah River Remediation (SRR) has a desire to understand the causes of the low filter flux and to increase ARP/MCU throughput. In addition, at the time the testing started, SRR was assessing the impact of replacing the 0.1 micron filter with a 0.5 micron filter. This report describes testing of MST filterability to investigate the impact of filter pore size and MST particle size on filter flux and testing of filter enhancers to attempt to increase filter flux. The authors constructed a laboratory-scale crossflow filter apparatus with two crossflow filters operating in parallel. One filter was a 0.1 micron Mott sintered SS filter and the other was a 0.5 micron Mott sintered SS filter. The authors also constructed a dead-end filtration apparatus to conduct screening tests with potential filter aids and body feeds, referred to as filter enhancers. The original baseline for ARP was 5.6 M sodium salt solution with a free hydroxide concentration of approximately 1.7 M.3 ARP has been operating with a sodium concentration of approximately 6.4 M and a free hydroxide concentration of approximately 2.5 M. SRNL conducted tests varying the concentration of sodium and free hydroxide to determine whether those changes had a significant effect on filter flux. The feed slurries for the MST filterability tests were composed of simple salts (NaOH, NaNO2, and NaNO3) and MST (0.2 – 4.8 g/L). The feed slurry for the filter enhancer tests contained simulated salt batch 6 supernate, MST, and filter enhancers.},
doi = {10.2172/1177887},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Mar 12 00:00:00 EDT 2015},
month = {Thu Mar 12 00:00:00 EDT 2015}
}

Technical Report:

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  • The primary treatment of the tank waste at the DOE Hanford site will be done in the Waste Treatment and Immobilization Plant (WTP) that is currently under construction. The baseline plan for the WTP Pretreatment facility is to treat the waste, splitting it into High Level Waste (HLW) feed and Low Activity Waste (LAW) feed. Both waste streams are then separately vitrified as glass and sealed in canisters. The LAW glass will be disposed onsite in the Integrated Disposal Facility (IDF). There are currently no plans to treat the waste to remove technetium in the WTP Pretreatment facility, so itsmore » disposition path is the LAW glass. Options are being explored to immobilize the LAW portion of the tank waste, i.e., the LAW feed from the WTP Pretreatment facility. Removal of {sup 99}Tc from the LAW Feed, followed by off-site disposal of the {sup 99}Tc, would eliminate a key risk contributor for the IDF Performance Assessment (PA) for supplemental waste forms, and has potential to reduce treatment and disposal costs. Washington River Protection Solutions (WRPS) is developing some conceptual flow sheets for LAW treatment and disposal that could benefit from technetium removal. One of these flowsheets will specifically examine removing {sup 99}Tc from the LAW feed stream to supplemental immobilization. The conceptual flow sheet of the {sup 99}Tc removal process includes a filter to remove insoluble solids prior to processing the stream in an ion exchange column, but the characteristics and behavior of the liquid and solid phases has not previously been investigated. This report contains results of testing of a simulant that represents the projected composition of the feed to the Supplemental LAW process. This feed composition is not identical to the aqueous tank waste fed to the Waste Treatment Plant because it has been processed through WTP Pretreatment facility and therefore contains internal changes and recycle streams that will be generated within the WTP process. Although a Supplemental LAW feed simulant has previously been prepared, this feed composition differs from that simulant because those tests examined only the fully soluble aqueous solution at room temperature, not the composition formed after evaporation, including the insoluble solids that precipitate after it cools. The conceptual flow sheet for Supplemental LAW immobilization has an option for removal of {sup 99}Tc from the feed stream, if needed. Elutable ion exchange has been selected for that process. If implemented, the stream would need filtration to remove the insoluble solids prior to processing in an ion exchange column. The characteristics, chemical speciation, physical properties, and filterability of the solids are important to judge the feasibility of the concept, and to estimate the size and cost of a facility. The insoluble solids formed during these tests were primarily natrophosphate, natroxalate, and a sodium aluminosilicate compound. At the elevated temperature and 8 M [Na+], appreciable insoluble solids (1.39 wt%) were present. Cooling to room temperature and dilution of the slurry from 8 M to 5 M [Na+] resulted in a slurry containing 0.8 wt% insoluble solids. The solids (natrophosphate, natroxalate, sodium aluminum silicate, and a hydrated sodium phosphate) were relatively stable and settled quickly. Filtration rates were in the range of those observed with iron-based simulated Hanford tank sludge simulants, e.g., 6 M [Na+] Hanford tank 241-AN-102, even though their chemical speciation is considerably different. Chemical cleaning of the crossflow filter was readily accomplished with acid. As this simulant formulation was based on an average composition of a wide range of feeds using an integrated computer model, this exact composition may never be observed. But the test conditions were selected to enable comparison to the model to enable improving its chemical prediction capability.« less
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  • A series of tests were planned to examine the removal of Ra and Th by monosodium titanate (MST) and modified monosodium titanate (mMST). Simulated waste solutions were prepared containing Ra and Th, along with Sr, Np, Pu, and U. Following simulant preparation the simulants were filtered through 0.45-m filters. Analysis of the simulants indicated no Th in the filtered solution. This is due to the very low solubility of Th in alkaline solutions. Based on the reported detection limits for {sup 228}Th by gamma analyses, the solubility of Th in the simulant solutions is < 3.0E-10 g/L or < 1.3E-12more » M. Therefore, data could not be obtained regarding the removal of Th by MST and mMST; however, testing proceeded to examine the removal of Ra. Sorption testing indicated that Ra, like Sr, is very rapidly removed from solution by both MST and mMST. The Ra concentration in solution fell below the method detection limit (MDL) within 30 minutes of contact with MST, and within 2 hours of contact with mMST, when tested at 25 C using a 5.6 M Na simulant. Additional testing examined the effects of ionic strength and temperature on the MST and mMST performance. Results from these tests showed that the majority of samples still reached a Ra concentration below the MDL, indicating excellent removal. For the highest ionic strength solution (6.6 M Na), there did appear to be a slight decrease in the Ra removal by mMST, as indicated by a larger number of samples just above the MDL. The effect of temperature on {sup 226}Ra removal is indeterminate for either MST or mMST in the temperature range (25-60 C) and concentrations studied since the final soluble concentration of Ra remained at or below the detection limits for all tests. Desorption testing was also performed using decontaminated salt solution (DSS) diluted to sodium concentrations of 2 M and 0.5 M, to represent the intermediate and final stages of washing. Results from these tests indicated no desorption of any sorbents, with the exception of Pu from mMST, which desorbed slightly (0.02%). Rather, the testing showed additional sorption of sorbates, likely due to the higher sorbent concentrations in these tests compared to the concentrations used for loading (i.e. 13 g/L vs. 0.4 g/L). SRNL recommends additional testing to confirm the low solubility of Th in a range of simulants representing SRS HLW. We also recommend additional sorption testing with simulants containing a higher concentration of {sup 226}Ra, to allow for the determination of actual DF values, rather than the minimum DF values reported here.« less
  • The Savannah River National Laboratory performed measurements of the rheology of suspensions and settled layers of treated material applicable to the Savannah River Site Salt Waste Processing Facility. Suspended solids mixtures included monosodium titanate (MST) or modified MST (mMST) at various solid concentrations and soluble ion concentrations with and without the inclusion of kaolin clay or simulated sludge. Layers of settled solids were MST/sludge or mMST/sludge mixtures, either with or without sorbed strontium, over a range of initial solids concentrations, soluble ion concentrations, and settling times.
  • The microcomputer revolution in electronics is spreading so rapidly that it is difficult to educate enough people quickly and thoroughly in the new technology. Lawrence Livermore Laboratory's MST-80B was developed as a way to speed learning in in-house training courses, and it is now being widely used outside LLL. The MST-80B trainer is a complete, self-contained microcomputer system housed in a briefcase. The trainer uses the Intel 8080A 8-bit microprocessor (CPU), and it has its own solid-state memory, a built-in keyboard, and a display for input/output. The trainer is furnished with a permanent Monitor program (in read-only memory) that allowsmore » users to enter, debug, modify, and run programs of their own easily. 8 figures.« less