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The SALT Research Group

UC Berkeley Nuclear Engineering Department

People

Our group is strongly committed to serving the diversity and inclusion responsibilities that the university has because equal access to education is an important value of democracy and because the university shapes the fabric of the culture and the values of future generations.

Riccardo Chebac

Biography

Riccardo is a visiting Ph.D. candidate in the SALT group coming from the Energy and Nuclear Science and Technology program at Politecnico di Milano. In his research he investigates chemical decontamination and robotic solutions for the dismantling of graphite-moderated reactors. Riccardo worked one year for the OECD-NEA in Paris in the Radioactive Waste Management and Decommissioning Division (RWMD). He obtained a M.S. in Nuclear Engineering and a B.S. in Energy Engineering from Politecnico di Milano.

Projects

Irradiated Graphite Decontmination in Molten Salts

Development of a Universal Canister for Advanced Reactors High-Level Waste

Mechanical Properties Characterization of Metals from Molten Salt Corrosion 

Robotic Manipulator for Graphite Bricks Extraction

Riccardo’s research focuses on the chemical decontamination of graphite in molten salts and on developing robotic manipulators for graphite blocks handling for decommissioning scenarios.  Current projects involve using molten salts as the medium for optimal graphite decontamination with focus on fission products, H3 and C14. Riccardo is also aiding in the development a universal canister for advanced reactors waste acceptance within the ARPA-E project Upwards. He’s also working on studying and characterizing the influence of FLiBe corrosion on the mechanical properties of various metallic alloys. Part of Riccardo’s research is performed in collaboration with the H2020 Inno4Graph Project.

Links

Google Scholar, Linkedin

Recent Awards

2022 2nd Best Poster award – DigiDecom 2022 conference

2022 3rd Best Poster award – Decon 2022 conference

2020 ENEN+ grant for academic exchange

Publications

  1. Chebac, R., Vanoni, F., Porta, A., Campi, F., Cocco, A., Barella, S., & Gruttadauria, A. (2023). A multidisciplinary approach to optimizing the mechanical characterization and dismantling of nuclear-grade graphite. Carbon Trends, 10, 100253.
  2. Codispoti, L., Porta, A., Campi, F., Ricotti, M., Chebac, R., Summa, L., Marotta, R., 2022. Radiological Pre-Characterisation for Decommissioning of L-54M Nuclear Research Reactor and Waste Management Strategy. Presented at the 4th International Conference on Nuclear Power Plants; Structures, Risk, Control & Decommissioning NUPP 2022 Proceedings 19-20 September 2022, pp. 50–58.
  3. Ghazaie, S.H., Sadeghi, K., Chebac, R., Sokolova, E., Fedorovich, E., Cammi, A., Ricotti, M.E., Shirani, A.S., 2022. On the use of advanced nuclear cogeneration plant integrated into latent heat storage for district heating. Sustain. Energy Technol. Assess. 50, 101838.
  4. Mazzi, M., Chebac, R., Campi, F., Ricotti, M., Poskas, G., Derudi, M., Porta, A., 2022. Preliminary Study on Oxidation of Nuclear Grade Graphite. Chem. Eng. Trans. 91, 427–432.
  5. Sadeghi, K., Ghazaie, S.H., Chebac, R., Sokolova, E., Fedorovich, E., Cammi, A., Ricotti, M.E., Shirani, A.S., 2022. Towards net-zero emissions through the hybrid SMR-solar cogeneration plant equipped with modular PCM storage system for seawater desalination. Desalination 524, 115476.
  6. Chebac, R., Cammi, A., Ricotti, M., Sadeghi, K., Ghazaie, S., Sokolova, E., Fedorovich, E., 2021. Dynamic Response of LFR in Cogeneration Mode. Presented at the International Conference Nuclear Energy for New Europe (NENE 2021), SVN, pp. 1–8.
  7. Sadeghi, K., Ghazaie, S.H., Chebac, R., Sokolova, E., Fedorovich, E., Cammi, A., Ricotti, M.E., 2020. Implementing Large-Scale Hybrid Desalination System Driven by Alfred Reactor and Parabolic-Trough Solar Power Plant, Equipped with Phase Change Material Storage System: The Case of Emirate. Presented at the International Scientific Conference on Energy, Environmental and Construction Engineering, Springer, Cham, pp. 85–96.
  8. Chebac, R., 2020. Preliminary power plant simulator for modelling of hybrid systems scenarios.
riccardo.chebac@berkeley.edu

Jefferson Gunahin

Jefferson is currently in his second semester as an undergrad researcher for the SALT Research Group. He is currently working with Timothy Pickarski to develop and manufacture dot microelectrodes using nanofabrication tools. His work focuses on enabling electrochemical sensing in molten FLiBe, contributing to the group’s efforts to better understand mass transfer behavior of hydrogen and tritium in high-temperature molten salt systems.

jefferson_gunahin@berkeley.edu

Sarah Heagy

Sarah is a first-year graduate student who plans to complete her M.S. in Nuclear Engineering in May of 2024. Before coming to Berkeley, Sarah earned her B.S. in Environmental Engineering from The University of Texas at Austin in Austin, TX.

Sarah’s research revolves around graphite. She will use SEM/EDS, XPS, profilometry, LIBS, and optical microscopy to characterize molten-salt-exposed graphite tribology samples. Additionally, she is working with Dr. Kai Vetter’s group to quantify radioactivity levels of several irradiated graphite samples. It is anticipated that Sarah will conduct additional electrochemical experiments on the irradiated graphite in an attempt to remove some of the activated metals for the purpose of lower-level waste disposal.

When she is not focused on her classes or her research, Sarah enjoys being outdoors. She is currently training to run the Oakland Marathon, and she loves all of the trails the Bay Area has to offer (there aren’t many hills in Texas). Sarah is also having fun spending time across the bridge in San Francisco.

sarah_heagy@berkeley.edu

Nicole Johnson

BIOGRAPHY

Nicole started working on her Nuclear Engineering PhD in 2023. She graduated from UC Irvine with a BS in Chemical Engineering and a license to operate the university’s TRIGA reactor in 2019. She then spent the next 4 years working as a nuclear plant operator at Beaver Valley Power Station, near Pittsburgh.

PROJECTS

At UCB, she is currently working on the ThorCon Natural Circulation Loop, which is will simulate ThorCon’s proposed NaFBe salt coolant in the secondary loop of their reactor. The goal is to determine the degree to which the high temperature difference between the hot and cold legs will cause the stainless steel piping to be dissolved in the hot leg and deposited in the cold leg. This project involves a large volume of 600°C salt to remain molten and flowing for six months, so there is a lot of design, fabrication, and assembly involved!

UNDERGRADUATE MENTORING

  • Sean Tang
  • Sebastian Barnes
  • Valentino Saiz

ORCiD profile: https://orcid.org/0009-0005-3409-4935

nicole_johnson@berkeley.edu

Molly Kharya

Molly is currently in her first year as an undergraduate for the SALT Research Group. Currently, she’s working with Timothy Pickarsi, studying nanofabrication and characterization of printed micro-electrodes for hydrogen diffusivity and concentration measurements in molten FLiBe. She is also learning from Jefferson how to manufacture micro-electrodes using nano-fabrication techniques.

molly.kharya@berkeley.edu

David Park

1st Year PhD Student

dpark6@berkeley.edu

Timothy Pickarski

BIOGRAPHY

Tim is a Ph.D. candidate in the SALT Research Group researching the thermodynamics and mass transport of volatile solutes in molten FLiBe for tritium management and extraction applications relevant to liquid breeding blankets for nuclear fusion and advanced reactor safety. He focuses on the use of electroanalytical techniques to quantify tritium’s source term contribution via activity and transport measurements paired with in-situ and post-situ spectroscopy. Before attending Berkeley, he received his B.S. in Materials Science and Engineering from Penn State University and worked as a corrosion engineer at Bayer CropScience. During his undergraduate study, he studied the reduction of transition metal oxides in molten lithium chloride salt with the Kim Group under Dr. Stephanie Castro Baldivieso.

PROJECTS

Electrochemical sensing of hydrogen and beryllium hydride in FLiBe.

Printed microelectrode development for hydrogen sensing in FLiBe and COMSOL modeling of their transport equations.

Thermodynamic reference electrode development in FLiBe.

Electrochemical measurements of carbonate anion stability in FLiBe.

Redox chemistry of uranium chloride in sodium chloride-uranium chloride eutectic.

Beryllium safety manager for the SALT lab.

CONFERENCE TALKS

  • Towards Tritium Measurement: Evaluation of Electrochemical Methods to Measure Hydrogen in Molten FLiBe | Tritium 2025 – Oral
  • Evaluating Hydrogen Bonding in Molten Halides: Implications for 2LiF-BeF2 (FLiBe) Tritium Breeding Blankets | 248th ECS Meeting – Oral
  • High-temperature coordination phenomena in molten salts and their impact on electrochemical data in the Tritium-FLiBe system | MyGRC – Chemistry and Physics of Liquids July 2025 – Poster
  • How does understanding Hydrogen in Molten Halides help define a roadmap to Electrochemical Tritium Management in FLiBe Breeding Blankets? | Reactive Metal Workshop (RMW 18) 2025 – Poster
  • Evaluation of an Ag/AgF Reference Electrode for Electrochemical Measurements of Molten 2LiF-BeF2 (FLiBe) | PRiME 2024 – Oral
  • Electrochemical Thermal Desorption Spectrometry development of hydrogen degassing from graphite in molten 2LiF-BeF2 (FLiBe) | INGSM 2024 – 24th International Nuclear Graphite Specialist Meeting – Poster
  • Fluoroberyllate High-Temperature Molten Salt: Beryllium Safety Experience in a University Research Lab | Beryllium Health and Safety Committee Nevada – Oral
  • (Presented in lieu of first author Haley Williams) Speciation and Diffusivity of Hydrogen in Molten 2LiF-BeF2 for Nuclear Fission and Fusion Applications | 245th ECS Meeting – Oral
  • Microelectrode-Based Diffusivity Measurements of Hydrogen in Molten 2LiF-BeF2 | 245th ECS Meeting – Poster

AWARDS

Student Award for Best Oral Presentation at Tritium 2025

GEM Graduate Fellowship 2025

UNDERGRADUATE MENTEES

  • Eric Smith (UCB MechE) CAD and Experimental Development for microelectrodes, molten salt test stands, and vacuum systems.
  • Jefferson Gunahin (UCB ChemE) Printed microelectrode fabrication and qualification (Marvell Nanofabrication Lab).
  • Molly Kharya (UCB EECS) Printed microelectrode fabrication and characterization via SEM/OM (Marvell Nanofabrication Lab).
  • Shane Canet (UCB NucE) Thermodynamic calculations for molten FLiBe half-reactions and salt preparation.
  • Claire T. Chen (UCB Phys & Astrophys) COMSOL modeling of microelectrode construction.

Sander Ratso

Biography

Sander is a postdoctoral researcher in the SALT group coming from the National Institute of Chemical Physics and Biophysics in Tallinn, Estonia. He received his BSc, MSc and PhD from the University of Tartu in Estonia in 2015, 2017 and 2021, respectively, with a focus on electrocatalysis and the development of non-precious metal catalysts for low-temperature fuel cells. Since 2019 he has worked on the molten electrolytic splitting of CO2 in carbonate-containing melts. From 2021 to 2023 he was a postdoctoral researcher in the European Space Agency working on the project “Electrochemical splitting of CO2 for carbon and oxygen production in Mars conditions”.

Links

Google Scholar

Recent Awards

• 2015, Sander Ratso, Estonian National Contest for University Students, Estonian Research Council, 1st prize for the work “Electrochemical reduction of oxygen on nitrogen-doped carbon nanomaterials” (highest prize for BSc theses at the national level)
• 2017, Sander Ratso, Estonian National Contest for University Students, Estonian Research Council, 1st prize for the work “Electrochemical reduction of oxygen on Co, Fe-containing nitrogen doped multiwalled carbon nanotubes” (highest prize for MSc theses at the national level)
• 2017 Erasmus+ traineeship programme
• 2018 Dora+ scholarship for PhD student mobility
• 2019 Dora+ scholarship for short study visits
• 2019 Prize for the best poster at the conference “Electrolysis and Fuel Cell Discussions – Towards Catalysts Free of Critical Raw Materials for Fuel Cells and Electrolysers”
• 2019, Sander Ratso, First Prize, The Dr. Bernard S. Baker Student Award for Fuel Cell Research
• 2021, Sander Ratso, Estonian National Contest for University Students, Estonian Research Council, national main prize for the work ” Electrocatalysis of oxygen reduction on non-precious metal catalysts” (highest national award given for PhD theses over all scientific fields)
• 2021, Sander Ratso, Materials 2021 Best Ph.D. Thesis Award
• 2022, MSCA Postdoctoral Fellowships 2022 Seal of Excellence

Publications

[1] E. Najafli, S. Ratso, Y.P. Ivanov, M. Gatalo, L. Pavko, C.R. Yörük, P. Walke, G. Divitini, N. Hodnik, I. Kruusenberg, Sustainable CO2-Derived Nanoscale Carbon Support to a Platinum Catalyst for Oxygen Reduction Reaction, ACS Appl. Nano Mater. 6 (2023) 5772–5780. https://doi.org/10.1021/acsanm.3c00208.

[2] G. Lacarbonara, S. Chini, S. Ratso, I. Kruusenberg, C. Arbizzani, A MnOx-graphitic carbon composite from CO2 for sustainable Li-ion battery anodes, Mater. Adv. 3 (2022) 7087–7097. https://doi.org/10.1039/d2ma00583b.

[3] A.L. Remmel, S. Ratso, G. Divitini, M. Danilson, V. Mikli, M. Uibu, J. Aruväli, I. Kruusenberg, Nickel and Nitrogen-Doped Bifunctional ORR and HER Electrocatalysts Derived from CO2, ACS Sustain. Chem. Eng. 10 (2022) 134–145. https://doi.org/10.1021/acssuschemeng.1c05250.

[4] S. Ratso, A. Zitolo, M. Käärik, M. Merisalu, A. Kikas, V. Kisand, M. Rähn, P. Paiste, J. Leis, V. Sammelselg, S. Holdcroft, F. Jaouen, K. Tammeveski, Non-precious metal cathodes for anion exchange membrane fuel cells from ball-milled iron and nitrogen doped carbide-derived carbons, Renew. Energy 167 (2021) 800–810. https://doi.org/10.1016/j.renene.2020.11.154.

[5] S. Ratso, P.R. Walke, V. Mikli, J. Ločs, K. Šmits, V. Vītola, A. Šutka, I. Kruusenberg, CO2 turned into a nitrogen doped carbon catalyst for fuel cells and metal-air battery applications, Green Chem. 23 (2021) 4435–4445. https://doi.org/10.1039/d1gc00659b.

[6] R. Sibul, E. Kibena‐Põldsepp, S. Ratso, M. Kook, M.T. Sougrati, M. Käärik, M. Merisalu, J. Aruväli, P. Paiste, A. Treshchalov, J. Leis, V. Kisand, V. Sammelselg, S. Holdcroft, F. Jaouen, K. Tammeveski, Iron‐ and Nitrogen‐Doped Graphene‐Based Catalysts for Fuel Cell Applications, ChemElectroChem 7 (2020) 1739–1747. https://doi.org/10.1002/celc.202000011.

[7] S. Ratso, M.T. Sougrati, M. Käärik, M. Merisalu, M. Rähn, V. Kisand, A. Kikas, P. Paiste, J. Leis, V. Sammelselg, F. Jaouen, K. Tammeveski, Effect of Ball-Milling on the Oxygen Reduction Reaction Activity of Iron and Nitrogen Co-doped Carbide-Derived Carbon Catalysts in Acid Media, ACS Appl. Energy Mater. 2 (2019) 7952–7962. https://doi.org/10.1021/acsaem.9b01430.

[8] S. Ratso, M. Käärik, M. Kook, P. Paiste, J. Aruväli, S. Vlassov, V. Kisand, J. Leis, A.M.A.M. Kannan, K. Tammeveski, High performance catalysts based on Fe/N co-doped carbide-derived carbon and carbon nanotube composites for oxygen reduction reaction in acid media, Int. J. Hydrog. Energy 44 (2019) 12636–12648. https://doi.org/10.1016/j.ijhydene.2018.11.080.

[9] S. Ratso, N. Ranjbar Sahraie, M.T. Sougrati, M. Käärik, M. Kook, R. Saar, P. Paiste, Q. Jia, J. Leis, S. Mukerjee, F. Jaouen, K. Tammeveski, Synthesis of highly-active Fe-N-C catalysts for PEMFC with carbide-derived carbons, J. Mater. Chem. A 6 (2018) 14663–14674. https://doi.org/10.1039/c8ta02325e.

[10] S. Ratso, M. Käärik, M. Kook, P. Paiste, V. Kisand, S. Vlassov, J. Leis, K. Tammeveski, Iron and Nitrogen Co-doped Carbide-Derived Carbon and Carbon Nanotube Composite Catalysts for Oxygen Reduction Reaction, ChemElectroChem 5 (2018) 1827–1836. https://doi.org/10.1002/celc.201800132.

[11] S. Ratso, I. Kruusenberg, M. Käärik, M. Kook, L. Puust, R. Saar, J. Leis, K. Tammeveski, Highly efficient transition metal and nitrogen co-doped carbide-derived carbon electrocatalysts for anion exchange membrane fuel cells, J. Power Sources 375 (2018) 233–243. https://doi.org/10.1016/j.jpowsour.2017.08.046.

[12] R. Sibul, E. Kibena-Põldsepp, S. Ratso, M. Kook, M. Käärik, M. Merisalu, P. Paiste, J. Leis, V. Sammelselg, K. Tammeveski, Nitrogen-doped carbon-based electrocatalysts synthesised by ball-milling, Electrochem. Commun. 93 (2018) 39–43. https://doi.org/10.1016/j.elecom.2018.05.027.

[13] S. Ratso, I. Kruusenberg, M. Käärik, M. Kook, R. Saar, M. Pärs, J. Leis, K. Tammeveski, Highly efficient nitrogen-doped carbide-derived carbon materials for oxygen reduction reaction in alkaline media, Carbon 113 (2017) 159–169. https://doi.org/10.1016/j.carbon.2016.11.037.

[14] S. Ratso, I. Kruusenberg, M. Käärik, M. Kook, R. Saar, P. Kanninen, T. Kallio, J. Leis, K. Tammeveski, Transition metal-nitrogen co-doped carbide-derived carbon catalysts for oxygen reduction reaction in alkaline direct methanol fuel cell, Appl. Catal. B Environ. 219 (2017) 276–286. https://doi.org/10.1016/j.apcatb.2017.07.036.

[15] S. Ratso, I. Kruusenberg, A. Sarapuu, M. Kook, P. Rauwel, R. Saar, J. Aruväli, K. Tammeveski, Electrocatalysis of oxygen reduction on iron- and cobalt-containing nitrogen-doped carbon nanotubes in acid media, Electrochimica Acta 218 (2016) 303–310. https://doi.org/10.1016/j.electacta.2016.09.119.

[16] S. Ratso, I. Kruusenberg, A. Sarapuu, P. Rauwel, R. Saar, U. Joost, J. Aruväli, P. Kanninen, T. Kallio, K. Tammeveski, Enhanced oxygen reduction reaction activity of iron-containing nitrogen-doped carbon nanotubes for alkaline direct methanol fuel cell application, J. Power Sources 332 (2016) 129–138. https://doi.org/10.1016/j.jpowsour.2016.09.069.

[17] S. Ratso, I. Kruusenberg, U. Joost, R. Saar, K. Tammeveski, Enhanced oxygen reduction reaction activity of nitrogen-doped graphene/multi-walled carbon nanotube catalysts in alkaline media, Int. J. Hydrog. Energy 41 (2016) 22510–22519. https://doi.org/10.1016/j.ijhydene.2016.02.021.

[18] I. Kruusenberg, D. Ramani, S. Ratso, U. Joost, R. Saar, P. Rauwel, A.M. Kannan, K. Tammeveski, Cobalt–Nitrogen Co-doped Carbon Nanotube Cathode Catalyst for Alkaline Membrane Fuel Cells, ChemElectroChem 3 (2016) 1455–1465. https://doi.org/10.1002/celc.201600241.

[19] I. Kruusenberg, S. Ratso, M. Vikkisk, P. Kanninen, T. Kallio, A.M. Kannan, K. Tammeveski, Highly active nitrogen-doped nanocarbon electrocatalysts for alkaline direct methanol fuel cell, J. Power Sources 281 (2015) 94–102. https://doi.org/10.1016/j.jpowsour.2015.01.167.

[20] M. Vikkisk, I. Kruusenberg, S. Ratso, U. Joost, E. Shulga, I. Kink, P. Rauwel, K. Tammeveski, E. Shulg, I. Kink, P. Rauwel, K. Tammeveski, Enhanced electrocatalytic activity of nitrogen-doped multi-walled carbon nanotubes towards the oxygen reduction reaction in alkaline media, RSC Adv 5 (2015) 59495–59505. https://doi.org/10.1039/C5RA08818F.

[21] S. Ratso, I. Kruusenberg, M. Vikkisk, U. Joost, E. Shulga, I. Kink, T. Kallio, K. Tammeveski, Highly active nitrogen-doped few-layer graphene/carbon nanotube composite electrocatalyst for oxygen reduction reaction in alkaline media, Carbon 73 (2014) 361–370. https://doi.org/10.1016/j.carbon.2014.02.076.

Conference Presentations

  • Ratso et al. (2014), Oxygen electroreduction on Fe, Co-containing and nitrogen-doped carbon nanomaterials, Electrocatalysis and Fuel Cell Discussions, La Grande-Motte, France
  • Ratso et al. (2018), Transition Metal and Nitrogen Co-Doped Carbide-Derived Carbon Catalysts for Oxygen Reduction Reaction in Alkaline Direct Methanol Fuel Cell, 233rd ECS Meeting, Seattle, WA, USA
  • Ratso et al. (2018), Highly active Fe-N-C catalysts for PEMFC from carbide-derived carbons, 69th ISE annual meeting, Bologna, Italy
  • Ratso et al. (2019), Iron and Nitrogen Doped Carbide Derived Carbon and Composite Catalysts for Fuel Cell Cathodes, 236th ECS Meeting, Atlanta, GA, USA
  • Ratso et al. (2019), Fe-N-C catalysts prepared from carbide derived carbons for PEMFC cathodes (Best poster award winner), Electrocatalysis and Fuel Cell Discussions, La Grande-Motte, France
  • Ratso et al. (2019), Highly active Fe-N-C catalysts for PEMFC from carbide-derived carbons (Invited, Baker award first place winner), Hydrogen & Fuel Cell Seminar, Long Beach, CA, USA
  • Ratso et al. (2022), CO2 turned into a nitrogen doped carbon catalyst for the fuel cell and metal-air battery applications, 241st ECS Meeting, Vancouver, BC, Canada
  • Ratso et al. (2022), CO2turned into a bifunctional Ni and/or N doped carbon catalysts for the HER/ORR, ACS Fall 2022, Chicago, USA
  • Ratso et al. (2022), Lignin-based N-doped carbon nanomaterials for the ORR, ACS Fall 2022, Chicago, USA