Heavy Loads

Most plutonium-based technologies use plutonium that has been purified by aqueous separation. The trouble is, right now, aqueous separation relies on the use of redox agents, chemicals that give electrons to plutonium or that take electrons away from plutonium. In recent years, many redox agents have been reclassified as hazardous. In other cases, these agents are simply incompatible with modern-day nuclear facilities. Signs suggest that the list of approved chemicals will only keep shrinking. “It seems like some of the redox agents used today will be incompatible with future requirements,” says Stosh Kozimor, a scientist at Los Alamos. In response to this rising need in plutonium production, two summers ago, Kozimor and a team of scientists set out to find an alternative way to add electrons to plutonium in aqueous media—one that wouldn’t require the use of chemical redox agents. Light, they found, did the trick, through photochemical processes. Better yet, the light-based photochemistry is compatible with existing separation techniques. Here are the six straightforward steps that Kozimor and his team took for the photochemical separation of plutonium.

1. Start with a hydrochloric acid solution and add a small amount of isopropyl alcohol. The alcohol provides the extra electron needed to change the uranium’s oxidation state.
2. Mix the plutonium and uranium into the colorless solution.
3. Pour the solution onto an anion exchange resin. The plutonium and uranium will both stick to the resin. 
4. Set an ultraviolet light source to 450 nanometers and irradiate the sample for 15 minutes. The combination of alcohol and energy from the light fosters an oxidation state change for plutonium and it is released from the resin. Uranium remains stuck.
5. Pass the mixture through a filter. 
6. Enjoy the use or reuse of chemically pure samples of plutonium!