Preparation of Americium Containing Transmutation Targets

Promovendus/a: Ayşe Gamze Çolak

Promotor(en): Prof. dr. ir. Jozef Vleugels, Dr. Rémi Delville, Dr. Gregory Leinders

In the frame of sustainable development of nuclear energy, there is a need for a clear and proven vision on spent fuel management. After uranium and plutonium recycling, the long-term radiotoxicity of spent fuel is dominated by the minor actinides (MAs). In order to reduce the long-term radiotoxicity, the MAs could be separated and recycled via a partitioning and transmutation (P&T) strategy. In this PhD, porous uranium oxide (UOX) host matrix microspheres, allowing efficient infiltration of Am(III) (aq.) dopant solutions, were fabricated by the internal gelation process. As a novel application, starch was used as a low-temperature burnable pore-former. A stock solution of Am(NO3)3 (aq.) was first prepared by careful dissolution of AmO2 in nitric acid. Infiltration by Am3+ solution was performed on porous UOX microspheres which were originally fabricated outside the shielded infrastructure. As a result, no secondary, MA-loaded liquid waste was generated during the process. Furthermore, the use of microspheres avoided the handling of powders, which decreased the risk for local contamination during processing. A comprehensive microstructural characterization was conducted. The results revealed that a single-phase (U,Am)O2 composition with average Am(III) levels up to 30 mol% was obtained, with a homogenous distribution of Am and U. The methods developed in this work were specifically adopted to the limitations imposed by working in shielded infrastructure for the handling of highly-radioactive materials. They were found to be safe and very effective in obtaining the desired end-product at a laboratory scale application.