Ph.D. projects

Interactions of selected radionuclides with clay and iron oxide under the influence of microbial activity

Ph.D. student:

Vladyslav Sushko


Dr. Andrea Cherkouk (HZDR)





Microcosms incubated for 9 month ©Copyright: Sushko, Vladyslav

Microcosms incubated for 9 month

Foto: Vladyslav Sushko

In most countries with a nuclear waste management program, deep geological disposal is preferred for the long-term storage of high-level radioactive waste (HLRW).
Here, a multi-barrier system is designed and constructed to isolate and contain the waste from the rock biosphere. It consists of a series of engineered barriers and a geological barrier that is the host itself. Clay is considered as host rock, but also as buffer and sealing material, e.g. bentonite, to prevent the water ingress and the migration of radionuclides. Another part of the engineered barrier system is the containment of the HLRW. Potential materials for the containment are steel or copper. Due to the processes of microbially induced corrosion of the container material, secondary phases can be formed (also, occurring in natural minerals) and released into the system. It can significantly affect the retention properties of the sealing material towards radionuclides.
Understanding of the behavior of radionuclides in complex biogeochemical systems and microbially induced corrosion are essential for nuclear waste management and safety of the HLRW long-term storage.

The aim of this work is to study the interactions in complex repository systems, namely at interfaces between different barriers with respect to radionuclide (Eu, Cm and Pu) retention. One focus will be set on microbially transformed bentonite or bentonite and steel/copper coupons.
To monitor these systems different analytical methods will be used, including ICP-MS, IC, HPLC, UV/VIS and others. A combination of different microscopic, spectroscopic and diffraction techniques, such as RAMAN microscopy, FTIR spectroscopy, SEM-EDX, XRD, Mössbauer spectroscopy will be applied to characterize the bentonite and the surface of the metal coupon.

This work is part of the iCross project (Integrity of nuclear waste repository systems – Cross-scale system understanding and analysis), which is funded by the Federal Ministry of Education and Research under contract number 02NUK053B and by the Helmholtz Association of German Research Centers under contract number SO-093.