Strontium and Actinide Separations from High Level Nuclear Waste Solutions Using Monosodium Titanate 2. Actual Waste Testing

Abstract

Pretreatment processes at the Savannah River Site will separate 90 Sr, alpha-emitting and radionuclides (i.e., actinides) and 137Cs prior to disposal of the high-level nuclear waste.Separation of 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 ionic 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 2 -700 times larger) and exhibits little affinity for desorption of strontium and plutonium during washing.3

The Role of Liquid Waste Pretreatment Technologies in Solving the Doe Clean-Up Mission

“…The Savannah River Site selected this material for strontium and plutonium removal from high-level waste solutions in the early 1980s as part of the In-Tank Precipitation (ITP) process. SRNL modified the synthesis of the MST to optimize performance and transferred this technology to commercial vendors (Hobbs et al 2005 andPeters et al 2006]. Figure 11 shows a Scanning Electron Microscope (SEM) image of MST particles.…”

Characterization of Modified Monosodium Titanate – An Improved Sorbent for Strontium and Actinide Separations

“…Settling characteristics of the MST and mMST particles are important in assessing nuclear criticality safety upon settling in batch contact reactors within operating and planned pretreatment facilities at the Savannah River Site. [4,5] Resuspension of densely-packed solids can be an engineering concern in large batch reactors. Thus, we performed a limited number of settling tests to compare the settling characteristics of mMST and MST materials.…”

“…This material currently serves as the baseline sorbent for the removal of 90 Sr and alpha-emitting radionuclides from HLW at the Savannah River Site (SRS). [1][2][3][4][5] Efforts to increase efficiency and rapidly remove alphaemitting radionuclides to increase operational throughput led to the identification of a peroxotitanate material with improved strontium and actinide removal characteristics. [6] Compared to the baseline MST material, the new peroxotitanate material, referred to as modified MST, or mMST, exhibits higher batch (short-term) capacities and kinetics for the separation of strontium and actinides from alkaline waste solutions.…”

Sorption Behavior of Monosodium Titanate and Amorphous Peroxotitanate Materials Under Weakly Acidic Conditions

“…[19][20][21][22][23] Sorption of heavy metals and other nonradioactive metals found in industrial waste streams receives less attention, however, a number of examples can be found. Sorption of barium, chromium, mercury and zinc onto MST, [24][25][26] sorption of cadmium onto lithium, sodium, and potassium-titanates, [27,28] and sorption of copper, zinc, and nickel onto lithium-titanate are reported.…”

“…A series of peroxotitanates were recently reported displaying significantly improved sorption characteristics for strontium and actinides compared to MST. [19][20][21] These peroxotitanate materials, which have the…”