Ph.D. projects

Interaction of actinides and lanthanides with selected degradation products of organic LILW

Ph.D. student:
Hannes Brinkmann
Prof. Dr. Thorsten Stumpf, Dr. Henry Moll (HZDR)

This PhD thesis is integrated in the EU project H2020-661880 – MIND (Microbiology In Nuclear waste Disposal) and mainly anchored in the work package 1: Improving the geological safety case knowledge of the behavior of organic containing long lived intermediate level wastes.

Organic polymers (e.g. cellulose, PVC, bitumen) present in low and intermediate level wastes (LILW) are exposed to ionizing radiation, alkaline pH, and organic substances degrading microorganisms. This may lead to the formation of smaller, water soluble organic compounds, affecting amongst others the chemical behavior and mobility of radionuclides (RN). In the worst case complexation of such organic compounds with RNs will lead to an increased mobility and a decreased retention of RN in the barriers of a nuclear waste disposal. Therefore, the characterization formed complexes is necessary for risk assessment and the long-term performance of a nuclear waste repository. A review of anthropogenic organic wastes and their degradation behavior was already published within the MIND-project. [1]

At the beginning the focus of the research activities lies on known degradation products of cellulose (acetate, butyrate, and isosaccharinic acid) and the interaction with U(VI). More degradation products acting as complexing compounds will be identified by partners of the MIND-project (UNIMAN and SCK·CEN). The characterization of the interaction of these compounds with selected actinides to underpin the findings from UNIMAN and SCK·CEN is subject of this doctoral thesis. Therefore, modern spectroscopic techniques like Time-resolved Laser-induced Fluorescence, X-ray absorption, UV-vis, and IR spectroscopy will be applied. The aim is to identify and characterize formed species at different geochemical conditions (speciation, stability, structure). In addition, Microcalorimetry will be used to obtain thermodynamic parameters of complex formation reactions.

This project has received funding from the Euratom research and training programme 2014-2018 under Grant Agreement no. 661880.