Initial Testing of Alkaline Earth Metal Ion Absorption on Crystalline Silicotitanate - 20440

Conference · Wed Jul 01 04:00:00 EDT 2020

OSTI ID:23028033

McCabe, D. J.; Taylor-Pashow, K. M. L.; Hang, T.; King, W. D.; Nash, C. A. ^[1]

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1. Savannah River National Laboratory, Savannah River Nuclear Solutions, Aiken, SC 29808 (United States)

The Tank Closure Cesium Removal process at the Savannah River Site (SRS) has processed aqueous tank waste using the inorganic ion exchange media IONSIV{sup TM} R9120-Ba (which is also known as Crystalline Silicotitanate (CST)). Salt-cake in Tank 10H at SRS was dissolved and processed through filters and ion exchange columns. The primary purpose of the process is to remove Cs-137 from the aqueous waste so that it can be disposed as low level waste. It is known that this inorganic media also absorbs strontium from solution, and that strontium competes with cesium ions for absorption sites. The strontium ion is actually more strongly absorbed than the cesium ion from typical tank waste. However, strontium is typically present in low concentrations so does not normally cause a significant impact. Strontium is present as both non-radioactive isotopes and the radioactive Sr-90 isotope; with the non-radioactive isotopes being much more abundant. Although the total strontium solubility is usually much lower than cesium, some tank waste compositions can have a high enough soluble strontium concentration to decrease the cesium absorption. Relatedly, some testing at SRS suggested that another alkaline earth metal, calcium, may also absorb onto CST and may decrease cesium absorption. Barium is also an important species in treatment of tank waste, but is also usually present at low concentrations. However, after the Cs-137 is absorbed onto CST, it emits a beta particle and converts to Ba-137m, which then decays to non-radioactive Ba-137 by emission of a gamma ray. If the Ba-137m were to desorb quickly, it could impact the dose rate in down-stream equipment. In order to understand the impact of these alkaline earth metals on CST, SRNL performed testing using simulants of SRS tank waste that contain soluble barium, strontium, and calcium. Testing examined both removal of the alkaline earth metals and their impact on removal of cesium. Testing involved first developing realistic waste simulant formulations and dissolving the alkaline earth metals to high enough concentrations to potentially impact the Cs absorption. Once the formulations were developed and prepared, computer modeling was used to calculate the expected Cs absorption behavior to determine if the alkaline earth metals impact the performance. Measurements of the alkaline earth metals absorption by the media is also important for disposition of spent media because of the added radionuclide inventory from the Sr-90. These initial tests are examining the general impact and will be used to determine if further testing or measurements are needed. (authors)

• Research Organization: WM Symposia, Inc., PO Box 27646, 85285-7646 Tempe, AZ (United States)
• OSTI ID: 23028033
• Report Number(s): INIS-US--21-WM-20440
• Country of Publication: United States
• Language: English

Related Subjects

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
BARIUM 137
BETA PARTICLES
CESIUM 137
CESIUM IONS
COMPUTERIZED SIMULATION
DOSE RATES
ECOLOGICAL CONCENTRATION
GAMMA RADIATION
ION EXCHANGE
LOW-LEVEL RADIOACTIVE WASTES
SALTS
SAVANNAH RIVER PLANT
SOLUBILITY
STRONTIUM 90
TANKS
TESTING