Part 2 of 2 Parts (Please read Part 1 first)
Processes have been developed which can separate uranium, plutonium and neptunium. The problem is that these processes are very complex. The separation of americium has proven to be especially difficult. Burns said that the United States Department of Energy requires any spent nuclear fuel recycling to be proliferation resistant. This means that plutonium which can be use to create nuclear weapons must never be separated for the other elements in spent nuclear fuel during the recycling process.
The researchers at Texas A&M investigated nuclear chemistry to find out if there was a simple nuclear reaction that could separate all the desirable elements in spent nuclear fuel at one time. It is well known that at room temperature, uranium will spontaneously form crystals in strong nitric acid. Inside these crystals, a central uranium atom is incorporated between two oxygen atoms. The uranium atom shares six electrons with each oxygen atom. Burns said, “We immediately realized that this crystal structure could be a way to separate out plutonium, neptunium and americium since all of these heavy elements belong to the same family as uranium.”
The researchers hypothesized that if plutonium, neptunium and americium formed a similar bonding structure with oxygen that was the same as uranium bonding, then in a strong solution of nitric acid at room temperature, these elements should integrate themselves into the crystal as it formed.
In order to test their hypothesis, the researchers created a surrogate solution of uranium, plutonium, neptunium and americium in highly concentrated nitric acid at sixty to ninety degree Celsius to imitate dissolving a real spent nuclear fuel rod in strong acid. They discovered that when the solution reached room temperature, the uranium, plutonium, neptunium and americium did separate from the solution together and uniformly distributed themselves in the crystal as had been predicted confirming their hypothesis.
Burns pointed out that this simple one-step process met the requirement that any recycling process be proliferation resistant. The plutonium was not isolated but incorporated into the uranium crystals along with the other radioactive isotopes. He said, “The idea is that the reprocessed fuel generated from our prescribed chemical reaction can be used in future generations of reactors, which would not only burn uranium like most present-day reactors but also other heavy elements such as neptunium, plutonium and americium. In addition to addressing the fuel recycling problem and reducing proliferation risk, our strategy will drastically reduce nuclear waste to just the fission products whose radioactivity is hundreds rather than hundreds of thousands of years.”
The results of the research at Texas A&M are very important for the nuclear industry. One of the major problems with the use of nuclear fission to generate electricity is the creation of tons and tons of spent nuclear fuel that must be dealt with in a safe and secure manner. This simple crystallization process will take the industry much closer to a realistic, inexpensive, safe way to deal with spent nuclear fuel. Next, the crystals containing the radioactive elements must be either converted into some kind of nuclear fuel or disposed of permanently in geological repositories.