Mark DeHart is a Senior Reactor Physicist and Directorate Fellow in the Nuclear Science and Technology Directorate at Idaho National Laboratory (INL). Over the past several years Dr. DeHart has led and directed a team of reactor physicists and computational methods staff performing applied multiphysics methods for numerous reactor types, including the Advanced Test Reactor (ATR), the Transient Test Reactor (TREAT) and advanced reactor concepts including micro-reactor, graphite reactor, molten salt reactor and nuclear thermal propulsion design concepts.  He has also led three Laboratory Directed Research & Development (LDRD) projects and participated in several others in projects related to reactor physics methods. DeHart joined INL in 2010  from Oak Ridge National Laboratory (ORNL) to assume a leadership role in reactor physics methods and applications.  Previously, during 17 years at ORNL, Dr. DeHart worked in both methods and analysis related to criticality safety, burnup credit, data validation, and reactor physics. He is the primary author of the NEWT lattice physics code and the TRITON depletion sequence within the SCALE code system and led development of modern lattice physics methods at ORNL. Prior to ORNL, Dr. DeHart worked at the Savannah River Laboratory (SRL) supporting K-Reactor restart physics; he completed his PhD at SRL in work related to K-Reactor lattice physics. Dr. DeHart has extensive experience in reactor physics, coupled multi-physics, criticality safety, depletion and spent fuel characterization, cross-section processing, and computer code verification and validation. He holds BS, MS, and Ph.D. degrees in nuclear engineering from Texas A&M University and is a Fellow of the American Nuclear Society (ANS).

I consider myself to be a reactor physicist, focused on analysis, methods development and validation.  At Savannah River Laboratory I focused on reactor kinetics calculations to support K Reactor restart, but while there I was able to complete my PhD in the development of a arbitrary-geometry discrete-ordinates radiation transport capability to improve lattice calculations for K Reactor. After the decision was made to shut down K Reactor I accepted a position at Oak Ridge National Laboratory.  I was very active in analysis supporting validation related to cross section libraries and to burnup credit (spent fuel validation).  I was able to move into a software development role, developing NEWT from my dissertation work and then TRITON to perform lattice depletion simulations.  This supported burnup credit, but grew into a lattice physics tool for the US NRC.  While I spent a lot of time doing training and support for lattice physics and spent fuel characterization, my preference was to work in analysis and validation.  An opportunity arose at INL to become more involved in validation and experimental measurements related to the ATR and later TREAT.  At present, I lead a team performing mutliphysics simulations of NASA nuclear thermal propulsion designs, but we are still using TREAT transient tests for validating our methods.  I now leak the International Reactor Physics Experiment Evaluation project (IRPhE), which is an international group chartered through to develop benchmarks from existing experimental data.