Removal of Cesium from Savannah River Site Waste with Spherical Resorcinol Formaldehyde Ion Exchange Resin: Experimental Tests

Abstract

A principal goal at the Savannah River Site (SRS) is to safely dispose of the large volume of liquid nuclear waste held in many storage tanks. In-tank ion exchange (IX) columns are being considered for cesium removal. The spherical form of resorcinol formaldehyde ion exchange resin (sRF) is being evaluated for decontamination of dissolved saltcake waste at SRS, which is generally lower in potassium and organic components than the Hanford waste. The sRF performance with SRS waste was evaluated in two phases: resin batch contacts and IX column testing with both simulated and actual dissolved salt waste. The tests, equipment, and results are discussed.

Keywords:

• batch tests
• in-tank Cs separation
• small column ion exchange

ACKNOWLEDGEMENTS

The U.S. Department of Energy supported this work through contract no. DE-A-AC09-08SR22470.

Notes

¹CST and SL-644 are two cesium specific IX resins. CST is a Crystalline Silicotitanate resin trademarked as IONSIV® IE-911 by UOP LLC, and SL-644 is trademarked as SupLig®-644 by IBC Advanced Technologies Inc.

(1) Values were taken from (11); (Table 4).

(2) Values were calculated with software by OLI Systems, Inc (2).

²The concentration of potassium in seven Hanford wastes of one study (10) indicated an average of 0.2 M while 0.74 M has been reported for Hanford Tank 241-AP-101 (7).

(1) This mass would be 8.77E + 04 dpm/mL Tc-99.

(2) Cs-137 gamma activity implies 699 ug/L.

(3) This mass would be 6.85E + 04 dpm/mL Tc-99.

(4) Cs-137 gamma activity implies 678 ug/L.

NA = not available.

³This height is given for the Na-form of resin, which it has while treating waste. Once the resin is saturated with Cs ions, it undergoes elution in acid to remove those ions, which causes the resin to shrink. After elution, the resin undergoes alkaline regeneration during which it returns close to its original height.

⁴Adsorption isotherms are analytical models from chemisorption theory (14) developed to predict the amount of atoms or molecules (e.g., Cs) adsorbed on a surface. For this study that surface is of the sRF resin. Moreover, the word “isotherm” refers to adsorption being a strong function of temperature; therefore, models predict adsorption efficiencies at constant temperature.

⁵“Isotherm” refers to a chemisorption model of ion adsorption and the improvement was to an existing model to better predict adsorption at low concentrations of cesium (2).

⁶Saturation is a function of many variables; i.e., temperature, flow rate of feed, regenerated state of resin, life of resin, etc. Because this test maintained these parameters constant, a comparison can be made.

⁷As noted in Fig. 14 and explained in the preceding paragraph, not only the color is changing, but the bed volume or bed height is changing, too. As the color interface moves along the resin bed, the bed's initial 6.5-cm height concurrently drops 80% to its final height of 5.2 cm by the time the color is completely changed.