Natalia Mayordomo Herranz (HZDR)

Natalia Mayordomo Herranz earned her doctorate at CIEMAT in Madrid and joined the Helmholtz-Zentrum Dresden Rossendorf (HZDR) as a postdoc in 2017. Since 2022, she has headed the TecRad junior research group there, which is funded by the German Federal Ministry of Education and Research. With her team, she is investigating the interactions of the long-lived fission product technetium-99 (99Tc) with materials that could be present in a possible repository for radioactive waste. These could be for example, various iron phases after corrosion of the steel containers or widespread minerals, metabolites and microorganisms from the various geotechnical and geological barriers of the repository. The goal of the research is to fundamentally understand the behavior of this radionuclide in the repository. We talked to Natalia Mayordomo Herranz in an interview about her work and her motivation.

Interview:

What are you currently working on?

Natalia Mayordomo Herranz: Technetium-99 (99Tc) is a long-lived radioactive isotope with a half-life of 210,000 years. 99Tc is one of the products formed during neutron irradiation of the isotopes uranium-235 and plutonium-239, both of which are components of nuclear fuel. Thus, 99Tc contributes massively to the radioactive waste produced during power generation. In addition, 99Tc is the decay product of the metastable technetium-99 isotope (99mTc), a short-lived isotope (half-life about 6 hours) used in radiopharmaceutical cancer diagnostics and therapy. In fact, 99mTc is the most commonly used isotope for positron emission tomography, with approximately 40 million applications per year worldwide.

The chemistry of Tc is particularly challenging due to its diverse redox properties. Tc has nine oxidation states, which can be stable depending on the prevailing environmental conditions. Whether Tc can spread in the environment depends, for example, on the pH, the ability to bind to organic and inorganic ligands, or the electrical potential. These questions are relevant because 99Tc is highly mobile, especially in groundwater, and thus could enter the food chain of living organisms. Therefore, we are developing strategies to prevent Tc from spreading out and further into the environment.

Of course, this plays a decisive role especially in the planned final repository for highly radioactive materials. Together with my team, I am contributing to the evaluation of possible sites. Such repositories are complex structures in which many factors - from thermal and hydraulic to mechanical, chemical and biological - influence safety. Our focus is on biogeochemistry. Specifically, we are investigating how microorganisms, metabolic products, or minerals that may be present in the repository interact with Tc.

To do this, we combine contaminant-sorbent contact experiments, electrochemical methods, partially X-ray-based diffraction, microscopic and spectroscopic techniques, and geochemical modeling. Our research provides important robust thermodynamic data for chemical complexes that we verify at the molecular level. This is not only important for the safety assessment of a repository, but can also be applied to the study of other contaminants in the environment, for example, selenium, arsenic, and lead. Our data can also be used to develop strategies for decontaminating Tc-contaminated sites.

What is your personal motivation?

Natalia Mayordomo Herranz: Since I started my scientific career, I have always been motivated to bring new methods and disciplines into my research in order to gain a broader perspective on chemical processes and a sound understanding of the systems I study. In my research area, this is of utmost importance, as only a multidisciplinary approach will help to find a safe site for the disposal of our radioactive waste. This also applies to the assessment and sustainable treatment of contamination in the environment.

In addition, I am very passionate about passing on my knowledge to the next generation of researchers and engineers. I would like to awaken their interest in the fascinating field of chemistry and make them strong for the new challenges of our time, especially with regard to environmental protection and the energy transition.

Welche Herausforderungen siehst du für dich in der nächsten Zeit?

Natalia Mayordomo Herranz: Eine sehr konkrete Herausforderung in meiner Nachwuchsforschungsgruppe TecRad ist die Kopplung von spektroskopischen und elektrochemischen Techniken. Dies wird große wissenschaftliche und technologische Anstrengungen von meinem Team, meinen Kollegen und Kolleginnen und den beteiligten Herstellerfirmen erfordern. Wenn uns dies jedoch gelingt, werden wir ein besseres und realistischeres Verständnis des Redoxverhaltens von Tc und anderen redoxaktiven Schadstoffen in Lösung und an der Grenzfläche zwischen Wasser und Mineralien bzw. Wasser und Mikroorganismen erhalten, was bisher technisch kaum zugänglich ist.

If yu could make a wish for something for your research, what would you wish for?

Natalia Mayordomo Herranz: I would like to see more experiments conducted under complex and realistic conditions. It would be excellent if we could follow the behavior of redox-active pollutants in-situ with spectroscopic and electrochemical methods and describe the immobilization of redox-active pollutants, such as technetium, with geochemical models.

From a personal point of view, I hope that the next generation of scientists will continue to be interested in qualifying themselves in this research area, and that together with politics and society we will move closer to the sustainability goals for a clean environment and clean energies.

Where do you see your discipline in 5-10 years?

Natalia Mayordomo Herranz: Thanks to technological advances, computer-aided (including AI) and experimental methods have developed considerably in recent years. This trend will continue. For our future work, this means a stronger integration of theoretical and experimental approaches.

Furthermore, methods for quantifying and monitoring the behavior of radionuclides in the ultratrace range under more realistic environmental conditions (pH, coexistence of multiple components, electrical potential, temperatures) will evolve. This will be of great importance for the disposal of high-level radioactive waste in Germany.

ORCID: 0000-0003-4433-9500