Reactor Physics

Reactor Physics

Nuclear reactor physics R&D at ORNL focuses on reactor core modeling & simulation analysis and methods development in areas such as reactor core physics, lattice physics, cross-section processing, nuclear fuel cycle assessments, radionuclide inventories, source terms, and decay heat. A key characteristic of our work is the combination of methods/software development and applications expertise.  Development focus areas include the SCALE code system and the DOE Consortium for Advanced Simulation of LWRs (CASL) core simulator VERA-CS. Applications focus areas include core analysis of light water reactors (LWRs); advanced reactor concepts such as small modular reactors and molten-salt reactors; ORNL’s High Flux Isotope Reactor; spent fuel characterization for licensing and nuclear safeguards; and fuel cycle analyses for exploring future nuclear options.


High-Fidelity Modeling and Simulation for a High Flux Isotope Reactor Low-Enriched Uranium Core Design

A high-fidelity model of the High Flux Isotope Reactor (HFIR) with a low-enriched uranium (LEU) fuel design and a representative experiment loading has been developed to serve as a new reference...

Analysis of new measurements of Calvert Cliffs spent fuel samples using SCALE 6.2

High quality experimental data for isotopic compositions in irradiated fuel are important to spent fuel applications, including nuclear safeguards, spent fuel storage, transportation, and final...

Analysis of Key Safety Metrics of Thorium Utilization in LWRs

Thorium has great potential to stretch nuclear fuel reserves because of its natural abundance and because it is possible to breed the 232Th isotope into a fissile fuel (233U). Various scenarios exist...


Develop and apply state-of-the-art modeling & simulation capabilities to lattice and reacor physics, spent fueld, and fuel cycle applications.


Leverage expertise with SCALE, CASL, and other nuclear software tools and experience with reactors and fuel cycles to solve challenging nuclear system problems.

Major Sponsors:

DOE Office of Nuclear Energy

DOE National Nuclear Security Administration

U.S. Nuclear Regulatory Commission



Kevin Clarno Photo

Kevin T Clarno

Distinguished R&D Staff; Group Leader, Reactor Physics; Interim Director, CASL

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