A WATER SOFTENER FOR RADIOACTIVE WASTE has been designed at Sandia, providing a potential new method for removing highly radioactive cesium-137 and strontium-90 isotopes from nuclear waste sites. Separating these isotopes from lower-level waste would make the cleanup process cheaper and easier. At last week's meeting of the American Crystallographic Association (ACA) in Virginia, Abraham Clearfield of Texas A&M (409-845- 2936) described the fabrication of titanium silicate crystals containing specially tailored, 8-angstrom-wide tunnels into which Cs-137 ions can fit exactly. The researchers had previously filled each tunnel with a smaller, narrower, sodium ion. By passing liquid solutions of nuclear waste through a bead of such crystals, a perfectly fitting cesium ion could enter each tunnel, displacing the more loosely held sodium ions. (After absorbing the isotopes, the beads could then be encased and buried directly.) A similar "ion- exchange process" takes place in water softeners, which employ a carbon-based substance (containing sodium ions) to remove calcium and magnesium ions that ordinarily promote the formation of unwanted soap scum in dishwashing and clothes washing.