Pronghorn: A Multidimensional Coarse-Mesh Application for Advanced Reactor Thermal Hydraulics

TLDR

This paper introduces Pronghorn, a multiscale thermal‑hydraulic application that models pebble‑bed reactors using advanced physical models, multiphysics coupling, and numerical discretization. Pronghorn is built on the open‑source MOOSE framework, employing state‑of‑the‑art physical models, numerical methods, and nonlinear solvers to deliver fast, advanced reactor thermal‑hydraulic simulations in a modern software engineering environment. The authors demonstrate Pronghorn’s capabilities through diverse applications—including depressurization natural circulation, forced convection in pebble‑bed reactors, 3‑D/1‑D coupling with RELAP‑7 for loop analysis, and coupling with Griffin neutronics—showing verification, validation, and improvements over legacy tools in meshing, physics modeling, and multiphysics coupling.

Abstract

This paper presents an overview of Pronghorn, a multiscale thermal-hydraulic (T/H) application developed by Idaho National Laboratory and the University of California, Berkeley. Pronghorn, built on the open-source finite element Multiphysics Object-Oriented Simulation Environment (MOOSE), leverages state-of-the-art physical models, numerical methods, and nonlinear solvers to deliver fast-running advanced reactor T/H simulation capabilities within a modern software engineering environment. This work summarizes the physical models, multiphysics and multiscale coupling, and numerical discretization in Pronghorn with emphasis on our initial target application to pebble bed reactors (PBRs). A diverse set of applications are shown to depressurized natural circulation in the SANA experiments, forced convection in the Pebble Bed Modular Reactor, three-dimensional (3-D)/one-dimensional coupling of Pronghorn and RELAP-7 systems T/H for loop analysis in the High Temperature Reactor Power Module, and forced convection in the Mark-1 Pebble Bed Fluoride-Salt-Cooled High-Temperature Reactor. A multiphysics coupling of Pronghorn, RELAP-7, and Griffin deterministic neutronics for a gas-cooled PBR demonstrates the capability of the MOOSE framework for reactor design calculations. These applications highlight the verification and validation underlying Pronghorn’s software development while emphasizing features that improve upon capabilities offered by legacy tools in areas such as 3-D unstructured meshing, physics modeling, and multiphysics coupling.