Rattlesnake: A MOOSE-Based Multiphysics Multischeme Radiation Transport Application

TLDR

Advanced reactor concepts range from microreactors to pebble‑bed reactors, each presenting unique geometrical and multiphysics challenges, yet all require accurate neutron‑distribution predictions. The authors contend that existing single‑physics, single‑reactor coupling methods are too inflexible and introduce Rattlesnake, a MOOSE‑based radiation‑transport application designed to address these limitations. Rattlesnake, built on the MOOSE platform, employs shared data distribution and a flexible finite‑element framework to seamlessly integrate geometry and multiphysics for advanced reactors. The paper demonstrates Rattlesnake’s performance on a suite of test cases—including a microreactor, molten‑salt reactor, pebble‑bed reactor, the Idaho National Laboratory’s Advanced Test Reactor, and two benchmarks (C5G7 and LRA)—showing its capability across diverse reactor types.

Abstract

Advanced reactor concepts span the spectrum from heat pipe–cooled microreactors, through thermal and fast molten-salt reactors, to gas- and salt-cooled pebble bed reactors. The modeling and simulation of each of these reactor types comes with their own geometrical complexities and multiphysics challenges. However, the common theme for all nuclear reactors is the necessity to be able to accurately predict neutron distribution in the presence of multiphysics feedback. We argue that the current standards of modeling and simulation, which couple single-physics, single-reactor-focused codes via ad hoc methods, are not sufficiently flexible to address the challenges of modeling and simulation for advanced reactors. In this work, we present the Multiphysics Object Oriented Simulation Environment (MOOSE)–based radiation transport application Rattlesnake. The use of Rattlesnake for the modeling and simulation of nuclear reactors represents a paradigm shift away from makeshift data exchange methods, as it is developed based on the MOOSE platform with its very natural form of shared data distribution. Rattlesnake is well equipped for addressing the geometric and multiphysics challenges of advanced reactor concepts because it is a flexible finite element tool that leverages the multiphysics capabilities inherent in MOOSE. This paper focuses on the concept and design of Rattlesnake. We also demonstrate the capabilities and performance of Rattlesnake with a set of problems including a microreactor, a molten-salt reactor, a pebble bed reactor, the Advanced Test Reactor at the Idaho National Laboratory, and two benchmarks: a multiphysics version of the C5G7 benchmark and the LRA benchmark.