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Topics: Nuclear Science and Technology Nuclear Systems Modeling, Simulation and Validation

Problem Statement

CTF has been adopted for use in the Virtual Environment for Reactor Applications Core Simulator (VERA-CS) being developed by the Consortium for Advanced Simulation of Light Water Reactors (CASL).  This requires improvements to software quality assurance measures, code testing, closure models, integration into the VERA-CS environment, and coupling to other VERA-CS physics packages.

Technical Approach

CTF is a subchannel thermal-hydraulics tool built from the legacy code, COBRA-TF.  This project has led to numerous improvements to CTF, including:

  • Implementation of new closure models and user features in support of CASL challenge problems including departure from nucleate boiling (DNB), crud-induced power shift (CIPS), and reactivity insertion accident (RIA)

  • Extensive verification and validation testing of the code

  • Coupling to the neutron transport code, MPACT, the crud-chemistry code, MAMBA, and the fuel performance code, BISON

  • Code performance improvements, including a domain decomposition parallelization of the code using the Message Passing Interface (MPI)

  • Integration into the VERA-CS environment, allowing CTF models to be developed from the VERA common input file and CTF results to be visualized in the VERAView visualization tool

  • Expansion of the code documentation suite to include a software assessment manual, software requirements, lifecycle process, and a training and change control plan

  • Integration of an automated code build and testing system

ORNL jointly maintains CTF with North Carolina State University (NCSU) and participates in the CTF User Group, which is responsible for distributing the code to users outside of CASL, providing user support, and providing a forum for users of the code to share code-related research and improvements.


This work has resulted in a modernized and improved version of COBRA-TF that has been used in support of CASL challenge problems and for various activities outside of CASL.  Code users include members of academia, nuclear vendors, utilities, and regulatory institutions. 


Consortium for Advanced Simulation of Light Water Reactors (CASL)


North Carolina State University 

Project Details

Principle Investigator