CTF 4.0 Theory Manual

Abstract

Coolant-Boiling in Rod Arrays-Two Fluids (COBRA-TF) is a thermal/hydraulic (T/H) simulation code designed for light water reactor (LWR) vessel analysis. It uses a two-fluid, three-field (i.e. fluid film, fluid drops, and vapor) modeling approach. Both sub-channel and 3D Cartesian forms of 9 conservation equations are available for LWR modeling. The code was originally developed by Pacific Northwest Laboratory in 1980 and had been used and modified by several institutions over the last few decades.COBRA-TF also found use at the Pennsylvania State University (PSU) by the Reactor Dynamics and Fuel Modeling Group (RDFMG) and has been improved, updated, and subsequently re-branded as CTF. As part of the improvement process, it was necessary to generate su cient documentation for the open-source code which had lacked such material upon being adopted by RDFMG. This document serves mainly as a theory manual for CTF, detailing the many two-phase heat transfer, drag, and important accident scenario models contained in the code as well as the numerical solution process utilized. Coding of the models is also discussed, all with consideration for updates that have been made when transitioning from COBRA-TF to CTF. Further documentation outside of this manual is also available at RDFMG which focus on code input deck generation and source code global variable and module listings.

BISON: A Flexible Code for Advanced Simulation of the Performance of Multiple Nuclear Fuel Forms

“…20)] and thermal hydraulics [e.g., CTF (Ref. 21)] codes, through the Virtual Environment for Reactor Applications (VERA) used in the simulations reported in Ref. 22.…”

Development of CTF modeling of interfacial drag, wall shear, and interfacial heat transfer for bubbly and annular-mist flow regimes

“…The wall heat transfer model in the subcooled nucleate boiling regime is based on one of two approaches which are hereby titled (1) the Hancox-Nicoll approach and (2) the Saha-Zuber approach. The Hancox-Nicoll approach is the base subcooled boiling wall heat partitioning model in CTF, and it is described in detail in the CTF Theory manual Salko et al [2017a] as Approach 1: Non-ONB model.…”

“…These terms are flow-regime dependent, as they depend on the structure of the two-phase flow. An assessment of the closure models used for these terms was not performed for this report; however, these terms are defined in more detail in the CTF Theory Manual Salko et al [2017a]. Other terms in these equations include C p (the specific heat for both liquid, l, and vapor, v) and the enthalpy, h, which can be for the saturated liquid (subscript f ), saturated vapor (subscript g), or the actual enthalpy (h l for liquid and h v for vapor).…”

Coupling MOOSE-Wrapped MPACT to BISON

“…These two components are coupled together and accelerated by the coarse mesh finite difference (CMFD) method. MPACT is also tightly coupled with CTF [6], an updated version of COBRA-TF, to provide thermal-hydraulic feedback. CTF is called by MPACT as a subroutine, so while CTF calculates the temperature and density distributions, it is not directly involved in the coupling implementations between Trogdor and BISON.…”

“…It consists of many codes that handle different physics and are coupled together, as shown in Figure1. The important codes for this work are MPACT for neutronics, CTF for thermal-hydraulics (TH)[6], MOOSE for coupling, and BISON for fuel performance.…”