Prof. Dr. Thorsten Stumpf

Director Institute of Resource Ecology
Phone: +49 351 260 3210

Institute for Resource Ecology

Research topics

Foto: Research at IRE ©Copyright: Dr. Katharina Müller

Research to protect people and the environment from the effects of radioactive radiation


Reactor safety

With the end of the use of nuclear energy for power generation in Germany in 2022, work in the field of reactor safety (as also called for in the current energy research program of the German government) will focus entirely on international safety aspects. The overall objective of the topic is to create a validated knowledge base that enables the safety assessment of internationally operated light water reactors of generations II and III as well as innovative reactor concepts under development (e.g. SFR - sodium cooled fast reactor, SMR - small modular reactors). The work concentrates on the development of modern program systems for reactor physics (3D neutron kinetics coupled with thermo-hydraulics and reactor dosimetry) and research into the behavior of construction materials under typical reactor conditions.

In the area of reactor physics/reactor dynamics, new methods of safety ana-lysis are being developed that are capable of bringing computational accuracy and spatial/temporal resolution to a qualitatively new level. The goal is to provide a validated tool for safety analysis of conventional and innovative reactors using multi-physics approaches that couple high-resolution neutron kinetics with state-of-the-art computational fluid dynamics (CFD) methods and fuel rod behavior calculations. In this work, we closely cooperate with the Institute of Fluid Dynamics and specifically take advantage of their large expertise in the development of CFD methods. In addition, our work is closely linked to the ZA Information Services and Computing both through the use of the HZDR computing cluster and through joint methodological developments (e.g. in the exchange of doctoral students).

In the area of materials research, the focus is on the irradiation behavior of reactor pressure vessel steels and innovative materials under development. The infrastructures available at the site, in particular the hot cells and the ion beam center (IBC), provide the basis for current and future work. Complementary methods for the characterization of nano- and microstructure and mechanical properties are used to investigate the relationship between nanometer-scale beam defects and macroscopic property changes. The main focus of future development (beyond POF-IV) is the extension of the method spectrum (APT - atom probe tomography as a complementary method to the existing portfolio) as well as the concentration on new material classes (HEA - high entropy alloys). HEAs have recently become the focus of international material science investigations and are promising candidates for application in innovative reactor systems.

Foto: Reactor safety - Reactor fatety departement (FWOR) ©Copyright: Dr. Sören Kliem

Nuclear Waste Disposal

The safe disposal of heat-generating radioactive waste and the associated demonstration of the long-term safety of a geological repository for up to one million years is one of the great scientific-technical and social challenges of our time. The Site Selection Act in Germany stipulates that repository concepts in different host rock formations (rock salt, crystalline rock and clay rock) are investigated comparatively with the aim of achieving the best possible safety - an approach that is unique in the world.

The main goal of our research is a comprehensive understanding of relevant physical, chemical, and biological processes (including their couplings). This enables the development and parameterization of realistic models, even for complex systems, and the quantification of uncertainties. This, in turn, is the basis for the long-term safety analysis of repository systems and goes far beyond the conservative and simplified perspectives applied so far. Together with our partners in the Helmholtz Association, processes with temporal and spatial variation (the latter from the nanometer scale to the regional scale) are considered. For the validation of process models and parameterizations under realistic boundary conditions, active participation in inter-national experimental programs in the underground laboratory Mt. Terri (Switzerland, Opalinus Clay) and partly in the rock laboratory Grimsel (Switzerland, Crystalline) serve as well as in the future the possibilities in the new radiotechnical center (HOVER).

Research is needed on the speciation chemistry of actinides and fission products in homogeneous solutions and in solids as well as at water-mineral and water-biota interfaces. Challenging, also in the future, are tracer concentrations, high pH, salinities and temperatures. For the characterization of retardation processes, partition coefficients on different rocks and minerals are experimentally determined, evaluated, and incorporated into contaminant migration modeling. In the investigation of the interaction of complex porous solids with fluids, among other things, the influence of material heterogeneities from the nano- to centimeter-scale is considered; the planned radio-technical center will allow the extension up to the meter-scale. The unique control areas at IRE and the close integration of theoretical and experimental work, in particular non-invasive, high-resolution spectroscopic (X-ray absorption, laser-induced fluorescence, infrared, Raman and nuclear magnetic resonance), diffraction and microscopic methods (light and electron microscopy) are essential for this, as are various radioanalytical methods. For more realistic predictions of contaminant migration, reactive transport models are being further developed, with a focus on the variability of surface reactivity. In addition to spatially resolved data sets with the challenge of systematic analysis of large data volumes, improvements in numerics and codes are required. All these results are incorporated into the modeling of thermodynamic equilibria for reactive transport and are made available internationally in databases (THEREDA, RES³T).

Another research aspect is the identification and quantification of the influence of biological processes on repository safety. The focus here is on determining the biological communities living there and their metabolic networks, as well as their effects on the integrity of the container and barrier material and the host rock. Important sub-processes here are the direct interaction of radionuclides with microorganisms, corrosion and gas formation processes, and again surface reactivity. These investigations, which are to be carried out in the future for all potential host rocks and backfill materials, are also of great relevance for microbial material degradation.
Much of the work on repository safety benefits directly from basic research and in turn radiates into radioecology topics. One example is the envisioned application of the smart-KD approach to contaminant transfer in soils and plants.


Foto: Research at IRE from micro- to macro-scale  ©Copyright: Dr. Katharina Müller


In addition to questions of safe final storage and safe technical use of nuclear fuels, the elucidation of the behavior of naturally occurring and anthropogenically released radionuclides in the environment is an important task for society. A central goal of research at IRE is therefore to comprehensively elucidate the fundamental molecular processes of the interaction of radionuclides with the geosphere and biosphere and thus to contribute to the protection of humans and the environment from the effects of radioactive radiation. From the (bio)molecular level to complete organisms and their communities, all scales of size and complexity are considered. This will provide the scientific basis to minimize radiation exposure and develop effective measures to prevent radionuclide transfer into the food chain and thus human uptake. With a molecular process understanding generated in this way, there are many opportunities for cooperation within the HZDR and especially with the Institute for Radiopharmaceutical Cancer Research (radiation research, radioecology) and the Institute for Resource Technology (biotechnology).

Another important step is the implementation of biological processes in existing reactive transport models. For this purpose, complex metabolic processes of entire communities are to be comprehensively elucidated, key processes identified and parameterized. Based on this, the aim is to develop numerical prediction methods for radionuclide transport from a repository and in various environmental compartments, taking into account biological processes, such as modifications of mineral interfaces.

To achieve these ambitious radioecological goals, a unique control area infrastructure is used, in which handling of both radioactive material and genetically modified organisms is possible. Radioecological research topics are currently addressed by combining state-of-the-art molecular biological, microscopic, spectroscopic as well as biophysical methods. The expertise in the generation of intense THz radiation, which has also been established at the HZDR, enables research into hydrate layers and hydrate envelopes, which decisively determine the behavior of radionuclides and biomolecules at interfaces. Here, the IRE is a leader in the inter-institutional establishment of interdisciplinary research with THz radiation in the field of f-element chemistry and biophysics.

Fundamental actinide chemistry

The actinides and, in particular, the transuranium elements Np, Pu and Am determine the radiotoxicity of spent nuclear fuel over several hundred thousand years. A fundamental understanding of their chemical behavior is thus essential for the safety demonstration of a potential repository. At the same time, the behavior of these very elements is poorly studied, and even basic chemical and physical properties are often poorly understood.

The actinides and, in particular, the transuranium elements Np, Pu and Am determine the radiotoxicity of spent nuclear fuel over several hundred thousand years. A fundamental understanding of their chemical behavior is thus essential for the safety demonstration of a potential repository. At the same time, the behavior of these very elements is poorly studied, and even basic chemical and physical properties are often poorly understood.
The research of the IRE, as one of the very few facilities in Germany with the possibility to work with weighable amounts of transuranics in different control areas, therefore aims at understanding the binding properties of these elements with different ligands on the electronic level. In addition, fundamental reactions in solution such as solvation and hydrolysis, but also redox chemistry - especially of plutonium - in solution as well as at interfaces are the focus of our work in order to achieve mechanistic understanding as well as thermodynamic quantification.

Also particularly relevant for Pu is the formation of nanoparticles, so-called intrinsic colloids, which have a significant influence on its chemistry in all aqueous systems. A prerequisite for such fundamental investigations is the application of modern methods for structure elucidation in the solid state [SC-/P-XRD, (HR-)XAS, IR] as well as in solution [NMR, EPR, (HR-)XAS, IR, UV/vis, TRLFS] in the control areas of the IRE. This fundamental research will be extended in the future to fill relevant knowledge gaps in actinide behavior.

The aforementioned experimental approaches will be complemented by theoretical chemistry methods, which often need to be developed in the field of actinide chemistry. In this context, the integration of the professorship for theoretical chemistry at the TU Dresden into the institute will be extended. These fundamental investigations are a prerequisite for the meaningful interpretation of the applied research of the IRE.