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Leadership Team

Brief profiles of Oak Ridge National Laboratory's Leadership Team members are linked to each member's name. For more information about ORNL management, please contact us at


Stephen Streiffer
Laboratory Director

Dr. Stephen K. Streiffer became the director of Oak Ridge National Laboratory (ORNL) on October 16, 2023. As the twelfth director in ORNL’s history, Streiffer leads more than 6,500 staff in delivering on critical national missions by leveraging the laboratory’s world-leading facilities, tools, and signature strengths in neutron science, high-performance computing, advanced materials, biology and environmental science, energy technologies, nuclear science and engineering, isotopes, and national security research.

Susan Hubbard
Deputy for Science and Technology

Susan Hubbard guides one of the nation’s most extensive portfolios of research and development, spanning computing and computational sciences, materials science, environmental and biological research, energy science and technology, isotope research and development, fission and fusion energy, neutron sciences, and national security sciences. In concert with the Deputy for Laboratory Operations, she supports the Laboratory Director in the planning, integration, and execution of Laboratory-level initiatives.

Balendra Sutharshan
Deputy for Operations

Deputy for Laboratory Operations Dr. Balendra Sutharshan coordinates overall operations and support functions at ORNL: facilities operations; environment, safety, and health; business operations; security; human resources; communications; and technology transfer. In concert with the Deputy Director of Science and Technology, Sutharshan supports the Laboratory Director in the planning, integration, and execution of Laboratory-level initiatives as ORNL’s chief operating officer.

Lindsey Twardy
Chief of Staff

Lindsey Twardy is Chief of Staff at Oak Ridge National Laboratory. In this role, she serves as an advisor to the Laboratory Director and helps to integrate leadership across ORNL to advance the Lab’s vision, fulfill mission objectives, and ensure operational effectiveness.

Brian Arrington
Chief Human Resources Officer

Chief Human Resources Officer Brian Arrington oversees the lab’s talent recruitment and retention along with HR operations, labor relations, and benefits. Arrington, a highly accomplished executive who is especially skilled in all aspects of successful human resources management and operations, joined ORNL in 2023. Arrington is committed to attracting and retaining top talent. He does this by creating a culture in which team members are empowered with the confidence needed to execute and to succeed.


J. Scott Branham
Director, Business Services

As Chief Financial Officer, Mr. Branham leads the Laboratory's Business Services Directorate, with responsibility for directing the ORNL budgeting process and business management functions and delivering relevant and reliable financial analysis and reporting. The directorate's functions include procurement, accounting, business analysis, business systems, pension and savings operations, small business contracting, and prime contract administration. Mr. Branham also serves as Chief Financial Officer for UT-Battelle, LLC.

Jeremy Busby
Associate Laboratory Director, Isotope Science and Engineering

Dr. Busby is the Associate Laboratory Director for the Isotope Science and Engineering Directorate at Oak Ridge National Laboratory. His technical contributions range from light water reactors to sodium reactors and space reactor systems as well as research in support of the ITER project.

Jens Dilling
Associate Laboratory Director, Neutron Sciences

Jens Dilling, an experimental nuclear physicist and leader in the field of precision experiments for fundamental and applied nuclear physics, brings extensive experience to his role overseeing the neutron scattering and user research programs at the Spallation Neutron Source and High Flux Isotope Reactor. 

John Gearhart
Director, Environment, Safety, Health, and Quality

John Gearhart is the director of Environment, Safety, Health, and Quality (ESH&Q) at Oak Ridge National Laboratory. In this position, he leads the safety and operational infrastructure that enables the laboratory’s science missions while protecting workers, the public, and the environment. ESH&Q provides broad expertise and programs to support nuclear safety, promote occupational health, control work hazards, meet regulatory requirements, manage waste responsibly, and ensure quality performance.

Cynthia Jenks
Associate Laboratory Director,
Physical Sciences

Cynthia Jenks stewards ORNL's broad physical sciences portfolio, with particular emphases on quantum materials; structural materials and alloys; soft materials; nanoscience; and applications of materials and chemistry in energy and security.

David Keim
Chief Communications Officer

David Keim leads the Communications and Community Engagement Directorate at Oak Ridge National Laboratory. His responsibilities include media and community relations, internal communications, protocol visits and lab events, and he led the multi-site design team for the new American Museum of Science and Energy. His staff provides strategic support for Lab leadership and ensures the quality of science writing, technical editing, design, photography, and videography across ORNL’s diverse research portfolio.

Moe Khaleel
Associate Laboratory Director, National Security Sciences

Dr. Moe Khaleel guides the research and development of science-based solutions to counter critical threats to public safety, national defense, energy infrastructure and the economy. Leveraging the broad science foundation at ORNL, he oversees the work of multi-disciplinary research teams with signature capabilities in nuclear and uranium science, high-performance computing, geographic information science, cyber security science and advanced manufacturing.

Paul Langan
Associate Laboratory Director,
Biological and Environmental Systems Science

As ORNL’s Associate Laboratory Director for Biological and Environmental Systems Science, Paul Langan stewards a research portfolio targeting the convergence of biology, ecology, engineering, data discovery, physical sciences, and computing to advance U.S. competitiveness in the global bioeconomy and Earth system sustainability.

David Mandl
General Counsel

David Mandl is the General Counsel at Oak Ridge National Laboratory and Secretary of UT-Battelle, LLC. He leads a team of legal professionals with broad expertise in all practice areas relevant to ORNL’s mission, and oversees the Lab’s Privacy Program, Ethics Program, Intellectual Property Management, and Corporate Governance.

Kathryn McCarthy
Director, US ITER Project

Kathy McCarthy joined ORNL after serving as vice president for science and technology and director of the Canadian Nuclear Laboratories. She also held leadership roles at Idaho National Laboratory as director of domestic programs in INL’s Nuclear Science and Technology Directorate, director of the Light Water Reactor Sustainability Program Technical Integration Office, and national technical director for the Systems Analysis Campaign for DOE Nuclear Energy’s Fuel Cycle R&D Program.

Graeme Murdoch
Director, Neutron Upgrades Project Office

Graeme Murdoch is the director for the Neutron Upgrades Project Office. He has over 35 years of progressive experience working in technical and management capacities in a particle accelerator and fusion engineering environment. 

Tyler Owens
Federal Affairs Director

Tyler Owens is federal affairs director at ORNL. In this role, he serves as ORNL’s senior representative and chief liaison to government officials, industry, think tanks, and university representatives in Washington, D.C. He provides guidance to the laboratory director to develop and execute strategies that best position ORNL in the evolving federal policy environment. He is also responsible for presenting ORNL’s priorities to Congress, the administration, and federal agencies.

Fred Pieper
Chief Audit Executive and 
Director, Internal Audit

Fred Pieper, who has served as a chief audit executive for 14 years, leads the Internal Audit Directorate, which is responsible for all audit activities and the Employee Concerns Program at ORNL. The organization provides independent, objective assurance and consulting services to improve the effectiveness of risk management, internal control, and governance processes through evaluations of ORNL management systems, processes, and programs.

Kris Torgerson
Director, Information Technology Services

Kris Torgerson joined Oak Ridge National Lab in February of 2017 as Deputy Chief Information Officer and subsequently became Director of ITSD in October of 2017.  He was promoted to Chief Information Officer in September of 2018.  In this position, he is responsible for all commodity technology delivery as well as strategy, cyber security, and supports privacy program delivery for the Laboratory.

Gina Tourassi
Associate Laboratory Director, 
Computing and Computational Sciences

Georgia (Gina) Tourassi is the associate laboratory director for Computing and Computational Sciences at Oak Ridge National Laboratory. Dr. Tourassi has decades of research leadership leveraging AI, big data, and high-performance computing for scientific breakthroughs, most recently serving as the division director for the National Center for Computational Sciences and director of the Oak Ridge Leadership Computing Facility. 

Mickey Wade
Associate Laboratory Director,
Fusion and Fission Energy and Science

Mickey Wade was named Associate Laboratory Director for the Fusion and Fission Energy and Science Directorate in April 2023. Before that, he served as Division Director for Fusion Energy for three years. Wade recently served as deputy director of the Magnetic Fusion Energy Division for General Atomics and has extensive experience in fusion energy research, programmatic development, and strategic planning.

Robert  M Wagner
Associate Laboratory Director,
Energy Science and Technology

Dr. Robert Wagner is the Associate Laboratory Director of the Energy Science and Technology Directorate at Oak Ridge National Laboratory. In this role, he leads more than 450 researchers, technical professionals and other staff focused on developing and deploying advanced technology solutions in manufacturing, buildings, transportation, and electrical grid infrastructure. 

Ann Weaver
Director, Facilities and Operations

Ann Weaver manages seven divisions that provide critical laboratory support services. These include facilities management, laboratory protection (security, fire protection, emergency preparedness, and emergency management), engineering and construction management, materials fabrication, instrumentation, site services, logistical functions, and craft services. In addition, the Facilities and Operations Directorate includes laboratory modernization and facilities strategic planning functions.