We are the people in the Nuclear waste disposal group.
Juuso Sammaljärvi

I have been the team leader of the Nuclear Waste Disposal research group since March 2024. I have over 10 years of experience in the field of nuclear waste management. I have worked most of my career on investigating the geological and engineered barriers to radionuclide entry into the biosphere. My research interests, in general, are the diffusion and sorption phenomena of radionuclides in hard materials, and the development of applications of polymers in the study of various porous materials.  

I got my MSc degree from the University of Helsinki in 2011, majoring in polymer chemistry. Thereafter I completed PhD studies at the University of Helsinki, in the field of radiochemistry. My PhD work focused on developing further the C-14-PMMA impregnation technique used in the structural characterisation of porous materials, such as crystalline and sedimentary rock. I spent part of my PhD studies as a visiting PhD student at the University of Poitiers, France. I defended my thesis in December 2017, and since then I’ve been working mostly on projects related to the diffusion of radionuclides in cementitious materials.  

During 2018-2019, I worked on a joint project with BRGM and ANDRA from France on the diffusion of radionuclides in reinforced and unreinforced mortar. This work was followed by the study of radionuclide diffusion in cementitious materials and their interfaces with crystalline rock as part of the KYT2022 project during 2019-2022. Since 2023, I have steered a research project in the SAFER2028 research program focusing on the radionuclide behavior in LILW repository concrete and cementitious waste forms. I have also been involved in the characterisation studies together with IRSN (France) on argillite-cement-interfaces and cementitious materials and gouge clay rock from the Tournemire Underground laboratory during the years 2014-2020. I took part in the EURAD consortium’s MAGIC project in 2020-2023, where the focus was on the study of chemo-mechanical changes in cementitious materials in contact with different conditions. I have research co-operation ongoing with the Geological Survey of Finland, Aalto University, SKB (Sweden), Chalmers University (Sweden), University of Poitiers (France), BRGM (France), ANDRA (France), ONDRAF (Belgium), SKC-CEN (Belgium), Nagra (Switzerland) and Amphos21 (Spain). 

I also teach in the radiochemistry laboratory courses and supervise undergraduate and graduate students as well as doctoral students in RIP team. 

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Marja Siitari-Kauppi

I have been a senior researcher and a leader of Radionuclides migration in the porous bedrock team at the Department of Chemistry since the year 2000. As of March 2024, I will continue as a senior expert and mentor in our team. I have 35 years of experience in the research field of spent nuclear fuel disposal. My interests are in the sorption and diffusion of safety-relevant radionuclides in the engineered and natural barriers of the radioactive waste repositories. In addition, I have developed in collaboration with the Finnish Radiation and Nuclear Safety Authority STUK a method for analyzing the porosity and pore structure of low porous materials with the C-14 PMMA autoradiography technique. This porosity investigation method has  

As I completed my Ph.D. thesis within the framework of the Cotutelle agreement that granted me the Ph.D. both in Finland and in France, I have strong research connections in France.  These include the Institut de Chimie des Milieux et Matériaux at Poitiers University, French Institute for Radiological Protection and Nuclear Safety and the French Geological Survey.  I have been a member of the International Steering Committee for Grimsel Test Site (GTS) Phase VI since 2004 and our group has worked on the in situ projects in GTS together with an international research group managed by Nagra, Switzerland. During the years 2009-2013, we had an EU project together with Poitiers University and ERM company to transfer knowledge and build a shared laboratory for the use of the C-14 PMMA method.  I have research collaborations also with Posiva, Finland, University of Jyväskylä, Finland, Geological Survey of Finland, University of Bern, Switzerland, JAEA, Japan, VTT Technical Research Centre of Finland, NRI-Rez, Czech Republic, Royal Institute of Technology, Sweden, and Technical University of Gothenburg and Geosigma, Sweden. I am also an expert member of the national CCE fission group in the Ministry of Economic Affairs and Employment in Finland. During 2019-2024 I was a mandated actor in the EURATOM EURAD consortium, leading the Finnish Research Entity team including Aalto University, the University of Jyväskylä, the University of Tampere and the Geological Survey of Finland. I continue the scientific work in our team from March 2024. 

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Xiaodong Li

I am a researcher in the field of radiochemistry, currently working as a postdoctoral in the Radiochemistry Unit within the Department of Chemistry. With a Ph.D. obtained from the University of Helsinki (2021), I have been delving into the field of radionuclide transport and geochemistry.

My research combines both experimental design and model development, primarily concentrating on sorption and diffusion studies of radionuclides across various rock samples and cement materials. A significant milestone in my career has been the creation of a Multi-site Surface Complexation Model. This model addressed the heterogeneity of porewater properties, considered the temporal and spatial evolution, and its impact on radionuclide transport within diverse host rock systems. The model contributes significantly to the long-term safety analysis of nuclear waste repositories. Additionally, I've developed an electromigration device for transport studies, accompanied by advanced models to interpret electromigration data, elevating the realism of Kd data.

Beyond experimental designs, I've developed various modeling tools such as PHREEQC coupled with Python and COMSOL coupled with MATLAB through Livelink, for simulations and calculations related to surface characterization, ion exchange and sorption, diffusion and electromigration, elemental speciation, and (co-)precipitation.

Overall, my research has been focused on improving our understanding of radionuclide geochemistry (speciation, binding modes, sorption affinity etc.) and mechanism descriptions in different host rock systems, using a combination of 3D characterizations of rock samples, aqueous/solid interface studies, experimental sorption and diffusion studies, spectroscopy measurements, and molecular modeling and sorption and diffusion modeling.

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Otto Tikkanen

I have worked with radiochemistry in the RIP research team of Dr. Marja Siitari-Kauppi since 2017, when I investigated concrete samples with the C14-PMMA porosity analysis as my Bachelor's thesis as a part of an industrial project. After this, I was hired as a laboratory and research assistant for the team. Since then I have completed my Master's thesis with the topic of radium sorption in biotite in the spring of 2020. Starting from autumn of the same year, I have been continuing my research with radium behaviour in geologic media as a Posiva Oy funded Ph.D. student in the Doctoral Programme for Chemistry and Molecular Sciences (CHEMS). As a part of my Ph.D. project, I will be conducting sorption and migration analyses for radium to examine its transport and surface behaviour in geologic media and to provide valuable data for the safety case analysis of Olkiluoto deep geological repository ONKALO. In addition to this, the research data will be used to further improve the accuracy of the geochemical modelling software PHREEQC. As a part of my research initiative, I will also be contributing to the EURAD/Future project with radium migration studies by column and structural analyses of fractured rock.

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Noora Pakkanen

I started working in the RIP research team back in the summer of 2018, when I began my Bachelor work under Pirkko Hölttä´s supervision. After finishing my Bachelor´s Thesis, I continued to work in the team as a part-time research assistant. In 2020 I finished my Master´s Thesis while still working part time within the group and in January 2021, I began working full-time with RIP-team´s industrial projects. Later that year, I finalized my Master studies and received a grant for postgraduate studies from Fortum & Neste Foundation. Topic of my PhD research is “Radionuclide transport with colloids in fractured rock”, where I will be studying the effect of detached bentonite colloids on sorption and migration behaviour of an actinide analogue with granitic rock samples. Besides industrial projects and PhD research, I have also taken part in EURAD Hitec –project. In 2024, I am continuing my PhD as a grant researcher to finalize my thesis.  

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Markus Nyman

I did my M.Sc. degree in the University of Jyväskylä, getting involved in gamma-ray and charged-particle spectroscopy and their application in nuclear structure physics. I continued as a Ph.D. student in the Gamma Spectroscopy group at the Accelerator Laboratory, finally completing my thesis in experimental nuclear physics - spectroscopic studies of very neutron-deficient bismuth and astatine isotopes to be more exact. Immediately after that I spent a nice year here in the Laboratory of Radiochemistry, University of Helsinki, as a substitute for the senior laboratory engineer who was on maternity leave. After that I spent one semester as a secondary school teacher in Vantaa. That was a rather colorful experience, but both myself and all the children eventually escaped unscathed. I saw it wise to return to science however, and subsequently joined European Commission's Joint Research Centre (Geel, Belgium) performing neutron scattering experiments. At JRC Geel we collaborated widely with other European research institutes, such as IFIN-HH (Bucharest, Romania), IPHC (Strasbourg, France), HZDR (Dresden, Germany), ENEA (Frascati, Italy), and ILL (Grenoble, France). In February 2021 I joined again the University of Helsinki as a senior laboratory engineer. My work here includes technical support and development of the nuclear spectrometers and the cyclotron, as well as teaching nuclear spectrometry and related topics. I am also the radiation safety officer and the nuclear materials responsible. And finally I am extremely happy to be a member of the RIP team, being able to take part in scientific research projects.