PNNL

Over the course of his 20-year career at Pacific Northwest National Laboratory, Dr. Daniel Stephens has had significant impact on the national security missions PNNL supports. Dr. Stephens serves as the director of the Nuclear Nonproliferation and Security Sector within the National Security Directorate. In this role, he is responsible for a business portfolio that represents nearly one quarter of the total annual budget at PNNL ($1.64 billion in Fiscal Year 2024). He is a recognized thought leader who often engages internally and externally to drive and shape strategy of the nuclear nonproliferation and security missions of U.S. government agencies. 

Dr. Stephens spent four years as the technical group manager of the Radiation Detection and Nuclear Sciences group, where he was responsible for the management of more than 50 technical and administrative personnel; the safe and secure operation of 12,000 square feet of world-class laboratory capabilities; an active postdoctoral and student program; and research spanning basic nuclear and high-energy physics to sensitive nuclear security programs.

Previously, Dr. Stephens served the acting chief science and technology officer of the National Security Directorate, where he was responsible for the research and development investment strategy across the directorate. Dr. Stephens was also the chief scientist and manager of the project supporting deployments of radiation portal monitors at the nation’s borders for U.S. Customs and Border Protection within the Department of Homeland Security. Early in his career at PNNL, he served as a technical advisor during an off-site assignment to the National Nuclear Security Administration Office of Nonproliferation Research and Development for the Advanced Materials and Special Nuclear Material Movement Detection programs.

Dr. Stephens is an alumnus of the Oppenheimer Science and Energy Leadership Program, the premier leadership development program of the Department of Energy. He was a fellow in Cohort 6, in 2023. He has a distinguished history of scholarship, including several highly cited research papers, and was elected as a senior member of the IEEE Nuclear and Plasma Sciences Society in 2018. Dr. Stephens holds a PhD in nuclear engineering from the University of Tennessee.

• Nuclear nonproliferation
• National and homeland security applications of novel radiation detection instruments
• Advanced spectroscopic identification algorithms
• Alternate signatures for radioactive materials
• Sensor networking
• Operational testing and evaluation of sensor systems
• Space radiation environment modeling and experiment

• PhD in Nuclear Engineering, University of Tennessee
• MS in Nuclear Engineering, University of Tennessee
• MS in Physics, University of Tennessee
• BS in Physics, Georgia Southern University 

• Member, American Association for the Advancement of Science
• Elected Senior Member, Institute of Electrical and Electronics Engineers, Division of Nuclear and Plasma Science
• Appointment to the External Board of Advisors, Department of Nuclear Engineering, University of Tennessee, 2014 – 2019
• Member, Radiation Instrumentation Steering Committee, IEEE Nuclear and Plasma Science Society, 2014 – 2017 
• Short Course Instructor, for Nuclear Security: Instrumentation and Applications, IEEE Nuclear Science Symposium