Radiation Chemistry at the Back End of the Nuclear Fuel Cycle

ChEMS Seminar

Featuring Bruce J. Mincher, Ph.D.
Aqueous Separations and Radiochemistry Department
Idaho National Laboratory, Idaho Falls, ID                                                                                        

Location:  DBH 1500
Free and open to the public
A renewed global interest in nuclear power is underway due to concerns about the contribution of fossil fuels to climate change and the unreliable sources of those fossil fuels. As both developed and developing countries continue to expand their populations and economies, energy demand continues to rise and it is recognized that nuclear energy will be required to meet this demand in an environmentally sustainable manner. However, about 10,500 t of spent fuel are already discharged yearly from more than 400 nuclear reactors. This spent fuel contains appreciable quantities of actinides and fission products, some with very long half-lives. To address this, research programs in several countries are investigating the aqueous reprocessing of these radionuclides and their transmutation to short-lived isotopes. Aqueous reprocessing begins with the chopping and dissolution of the used light water reactor fuel in nitric acid. Uranium, neptunium, and/or plutonium are recovered by extraction of the acidic phase with tributyl phosphate or diamides. Additional solvent extraction steps may employ crown ethers and/or calixarenes to recover short-lived, heat-emitting fission products for short-term near surface disposal.  In addition, the minor actinide elements will be recovered using soft-donor ligands to separate them from the lanthanide fission products. Since these solvent systems will be in contact with highly radioactive solutions, they must be robust toward radiolytic degradation in an irradiated mixed organic, acidic, aqueous environment. The main degradation pathways for ligands irradiated in acidic solution are discussed, including examples from work at Idaho National Lab (INL).

About the Speaker:
Bruce J. Mincher, Ph.D., is a chemist at the Idaho National Laboratory with research interests in actinide separations, including aqueous solvent extraction and the effects of radiation chemistry on radiochemical separations. His radiation chemistry research has included projects investigating the mechanism and kinetics of PCB radiolysis in organic solutions, aromatic nitration reactions in irradiated aqueous nitric acid, and the radiolysis reactions of ligands used in actinide and fission product separations. This work is conducted using both steady state and pulsed radiolysis techniques. He is currently co-authoring an invited series of review articles on the effects of radiation on solvent extraction for the journal Solvent Extraction and Ion Exchange. Additionally he is currently leading a project to exploit novel oxidation states of americium for separations for the U.S. Department of Energy at INL. He received his Ph.D. from the University of Idaho in 1997.