Hydrological Methods Can Separate Cesium from Nuclear Waste Salt Cake

Interstitial Fluid Displacement (IFD) is a new and novel method for separating cesium from saltcake waste. It was identified by reevaluating fundamental factors of the saltcake recovery system, such as physical and chemical properties of saltcake, experience from other technical disciplines and industries, processing rate requirements, process safety requirements, and use of proven-successful processes and equipment. Chemical theory and limited data indicate that none, or very little, of the cesium is contained in the saltcake crystal structure. Similar logic also applies to potassium and sodium hydroxide, other chemicals important to waste processing. Laboratory and field data demonstrate that saltcake is usually porous, permeable, and dissolves rapidly. Hydrologic modeling of liquid flow through porous saltcake suggests that the cesium, potassium and sodium hydroxide can be separated at high recovery and low volume using IFD. IFD requires amazingly little equipment—a transfer pump and a few water injection pipes. The benefits include reductions in safety risk and total costs, fewer and simpler unit operations, and improved operability. Cost savings could be significant compared to the baseline process. A holistic or systems approach, where water output from one cleanup operation becomes the water input for another of the waste processing operations, could further reduce the cost of waste tank clean-out.