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****Individuals requesting access to the source version of VERA 4.3 must provide the specific code/module that they are developing, the computing systems upon which they are developing the code, and the manner in which they will control access to the VERA package in the end use statement of the request. The individual must provide the name of the person on the VERA development team with whom they are collaborating as well. If this information is not included with requests for access to the source version of VERA 4.3, then the request will be denied. ****

1. NAME AND TITLE

VERA 4.3: Virtual Environment for Reactor Applications, Version 4.3

AUXILLARY PROGRAMS REQUIRED (Installed using omnus.sh)

CMAKE https://cmake.org/files/v3.14/cmake-3.14.2.tar.gz

GCC https://ftp.gnu.org/gnu/gcc/gcc-5.4.0/gcc-5.4.0.tar.gz

MPICH http://www.mpich.org/static/downloads/3.1.3/mpich-3.1.3.tar.gz

AUXILLARY LIBRARIES REQUIRED (Installed using vera_tpls/TPL_build/install_tpls.sh)

LAPACK/BLAS https://code.ornl.gov/casl/vera_tpls/-/tree/vera-tpls-4.3

BOOST https://code.ornl.gov/casl/vera_tpls/-/tree/vera-tpls-4.3

ZLIB https://code.ornl.gov/casl/vera_tpls/-/tree/vera-tpls-4.3

HDF5 https://code.ornl.gov/casl/vera_tpls/-/tree/vera-tpls-4.3

PETSC https://code.ornl.gov/casl/vera_tpls/-/tree/vera-tpls-4.3

SILO https://code.ornl.gov/casl/vera_tpls/-/tree/vera-tpls-4.3

QT https://code.ornl.gov/casl/vera_tpls/-/tree/vera-tpls-4.3

DATA LIBRARIES

mpact51g_71_4.3m2_03262018.fmt CASL’s MPACT-formatted 51g neutron subgroup library

origen_library/origen_casl2.2.def.bof The ORIGEN reaction data from ENDF

origen.rev01.jeff56g The ORIGEN JEFF data to supplement ENDF

origen_data/origen_casl2.2.yld.data The ORIGEN fission yield data

ENDF/B-VII.1 data for Shift:

ce_v7.1_endf(.xml) Description of continuous-energy (CE) data in cekenolib_7.1 directory

cekenolib_7.1 Directory containing CE data for each nuclide

Additional non-standard cross section and depletion libraries for testing and backwards compatibility are also included.

2. CONTRIBUTOR

The VERA Users Group (VUG), Oak Ridge, TN, USA

The core partners in the VERA Users Group include:

Electric Power Research Institute

Idaho National Laboratory

Los Alamos National Laboratory

Massachusetts Institute of Technology

North Carolina State University

Oak Ridge National Laboratory

Sandia National Laboratories

Tennessee Valley Authority

University of Michigan

Westinghouse Electric Company

This release also includes contributions from the following contributing partners:

Core Physics, Inc.

Pennsylvania State University

For more information, see: https://vera.ornl.gov/

3. CODING LANGUAGE AND COMPUTERS

Fortran, C/C++, Perl, Python; Linux (C00855PCX8602).

4. NATURE OF PROBLEM SOLVED

Neutronics analysis can be performed for 2D lattices as well as 2D core and 3D core problems for pressurized water reactor (PWR) geometries that can be used to calculate criticality and fission rate distributions by pin for input fuel compositions. MPACT uses the method of characteristics (MOC) transport approach for 2D problems. For 3D problems, MPACT uses the 2D/1D method, which uses 2D MOC in a radial plane and diffusion or Pn in the axial direction. MPACT includes integrated cross section capabilities that provide problem-specific cross sections generated using the subgroup methodology. The code can execute both 2D and 3D problems in parallel to reduce overall runtime, and it can also be used for eigenvalue, fixed-source, and time-dependent problems.

The Oak Ridge Isotope GENeration (ORIGEN) capability, from the SCALE nuclear modeling and simulation code, is used in MPACT to model the depletion, decay, and transmutation of hundreds to thousands of isotopes. It is integrated within MPACT to provide a complete neutronics capability.

A thermal hydraulics (TH) capability is provided with CTF (an updated version of COBRA-TF) that allows TH analyses for single and multiple assemblies using the simplified VERA common input. This distribution also includes coupled neutronics/TH capabilities to allow calculations using MPACT coupled with CTF. The integrated MPACT, CTF, and ORIGEN capability is generally referred to as the VERA Core Simulator (VERA-CS). This capability can be used in both quasi-static and transient mode to model reactivity insertion accidents. A simplified fuel model is provided with VERA: an approximate fuel model in CTF that can model the transient fuel temperature distribution.

The MAMBA code allows VERA to simulate the deposition of crud on the fuel rod surface. MAMBA solves the growth of the crud layer as well as the thermal solution, species transport, and chemical precipitation throughout the crud layer. MAMBA is tightly integrated into MPACT and CTF to provide direct feedback into the coupled simulation. MAMBA also includes a detailed mass balance capability that includes the generation of corrosion products from the steam generator and primary system piping, the deposition on core components, and removal from the coolant cleanup system.

Input/output capabilities include the VERA Common Input (VERAIn) script that converts the ASCII common input file to the intermediate XML used to drive all of the physics codes in the VERA. VERA component codes either read the VERA XML format directly or provide a preprocessor that converts the XML into native input for the component code. VERAView is an interactive GUI for the visualization and engineering analyses of output data from VERA. The Python-based software is easy to install and intuitive to use, and provides instantaneous 2D and 3D images, 1D plots, and alpha-numeric data from VERA multiphysics simulations.

Testing within VUG has focused primarily on Westinghouse four-loop reactor geometries and conditions, with example problems included in the distribution.

Physics components included in VERA 4.3 EXE:

MPACT Neutron transport and cross section physics.

CTF Sub channel-resolved TH with fuel rod fuel heat transfer model.

ORIGEN Isotopic depletion and decay from a beta version of SCALE 6.3.

Shift Monte Carlo neutron transport

DAKOTA Software library for Optimization, Uncertainty Quantification, and Sensitivity Analysis.

Infrastructure components included in VERA 4.3 EXE:

TriBITS Enhanced CMake-based build system.

TRILINOS Software library for the solution of large-scale complex numerical problems.

VERAIn VERA common input processor.

VeraShift Utility code for coupling of MPACT and CTF with Shift.

5. METHOD OF SOLUTION

Details of the solution methods can be found in the included documentation and are briefly summarized below.

MPACT is based on the MOC transport approach for 2D problems, and cross section weighting is based on the subgroup methodology. The code can be executed in parallel to reduce overall runtime. For 3D problems, MPACT uses the 2D/1D method, which uses 2D MOC in a radial plane and diffusion or Pn in the axial direction. A 51-group library with subgroup parameters is provided. For simulating the time evolution of the reactor under operation, MPACT internally relies upon ORIGEN to solve the nuclide transmutation equations. ORIGEN provides isotopic information about the materials in the reactor as they undergo irradiation.

CTF (an updated version of the COBRA-TF code) is a sub channel TH code that uses a two-fluid, three-field (i.e., fluid film, fluid drops, and vapor) modeling approach. Both sub channel and 3D Cartesian forms of nine conservation equations are available for LWR modeling. CTF includes a wide range of TH models important to light-water reactor (LWR) safety analysis including flow regime–dependent, two-phase wall heat transfer; inter-phase heat transfer and drag; droplet breakup; and quench-front tracking. Due to its 3D capabilities and extensive array of reactor TH modeling capabilities, CTF has found much use in modeling of LWR rod–bundle transient analysis and PWR whole-vessel, loss-of-coolant accident (LOCA) analysis.

MPACT can call CTF to obtain fuel temperatures and moderator density. This is done by directly calling the CTF solver every outer iteration and passing the power distribution. After CTF converges on a given power shape, the temperatures and densities are passed back to MPACT and applied to the cross sections. A conditional check on the change in temperature and density is performed to determine whether the subgroup calculation needs to be rerun to obtain new shielding parameters for the cross section generation. This procedure continues until MPACT satisfies its internal convergence criteria on eigenvalue and fission source.

The MAMBA package simulates growth of crud, which refers to metal oxide corrosion products (primarily nickel ferrite, NiFe₂O₄) on fuel cladding and accumulation of boron in the porous crud. Precipitation of boron compounds, such as lithium tetraborate (Li₂B₄O₇), can lead to a crud-induced power shift (CIPS) in the nuclear fuel. In addition, the crud itself can lead to crud-induced localized corrosion (CILC) due to reduced thermal transport and thus increased temperatures, which can cause fuel mechanical failure.

The role of MAMBA is to simulate the buildup of crud and the precipitation of boron-rich compounds within the porous crud layer. Because the formation of crud is fundamentally a multiphysics problem, MAMBA is coupled to neutronic and TH solvers present in VERA to predict CIPS. MAMBA requires TH conditions as input—in particular, the cladding surface heat flux, turbulent kinetic energy, and the coolant temperature. Within VERA, TH conditions are provided by CTF. Additionally, the crud source term is modeled in MAMBA, which originates from corrosion of steam generators and primary loop piping.

Shift is a general-purpose radiation transport code that performs stochastic modeling of neutral particle physics using the Monte Carlo method. It can perform eigenvalue calculations as well as fixed-source calculations in neutron, photon, or coupled neutron–photon mode. Shift is integrated into VERA for both in-core reactor analysis using eigenvalue mode and ex-core dosimetry using fixed-source mode. The main modules of Shift include physics, tallies, geometry, source definitions, parallel decomposition, and variance reduction. Shift is also coupled to internal deterministic discrete ordinates and simplified PN solvers from the Denovo package. This enables the use of hybrid Monte Carlo methods for variance reduction. Shift is coupled to MPACT through VERA to enable source definitions for both fixed-source and eigenvalue problems.

6. RESTRICTIONS OR LIMITATIONS

The VERA Users Group reserves the right to pre-approve distribution of this release to non-VUG partners.

Other limitations and known issues with the software are documented in the Release Notes.

7. TYPICAL RUNNING TIME

Varies based on platform and complexity of the input being executed and ranges from minutes to hours to days depending upon the scope and complexity of the problem and the hardware systems on which it is executed.

8. COMPUTER HARDWARE REQUIREMENTS

Linux platforms are supported, and 32 cores or greater is recommended.

9. COMPUTER SOFTWARE REQUIREMENTS

Linux-based operating system with functioning gcc, g++ and gfortran compilers available, as well as X11 libraries.

Detailed system software and third-party library requirements are specified in the VERA Installation Guide. Specific OS versions tested are documented in the Release Notes.

10. REFERENCES

References and a list of supplied documentation are provided in the Release Notes.

11. CONTENTS OF CODE PACKAGE

The package will be transmitted on a DVD, which includes instructions for executable access, sample inputs, test problems, documentation, and reference material.

12. DATE OF ABSTRACT

12/20/2021 Rev 11/1/2023

KEYWORDS:

REACTOR PHYSICS, RADIATION TRANSPORT, THERMAL HYDRAULICS

RSICC CODE PACKAGE CCC-855