terrapower/armi
Oct 2024 – Oct 2025
9 Months active
Languages Used
PythonRST
Technical Skills
Cross Section ModelingLattice PhysicsPhysics SimulationReactor PhysicsSoftware DevelopmentUnit Testing
Michael Jarrett
PROFILE
Michael Jarrett
Over nine months, Michael Jarrett engineered advanced reactor physics and data management features for the terrapower/armi repository, focusing on cross-section modeling, file system reliability, and simulation fidelity. He implemented enhancements such as heterogeneous assembly support, thermal expansion-aware mass conservation, and enrichment calculations, using Python and NumPy to optimize performance and memory usage. His work included robust bug fixes for symmetry handling and database loading, as well as improvements to MPI workload distribution and error handling. Through comprehensive testing, code refactoring, and detailed documentation, Michael delivered solutions that improved scalability, reliability, and accuracy for large-scale nuclear engineering simulations.
Overall Statistics
Feature vs Bugs
68%Features
Repository Contributions
28Total
Bugs
7
Commits
28
Features
15
Lines of code
3,045
Activity Months9
Your Network
15 peopleSame Organization
@terrapower.com7
Work History
October 2025
4 Commits • 2 Features
Oct 1, 20252025-10 Monthly Summary for terrapower/armi: Delivered two substantial features aimed at improving scalability, memory management, and reliability of cross-section computations and MPI workload handling. Updated tests and documentation to reflect changes. No user-reported critical bugs were identified in this period; stability improvements focused on edge-case handling and resource constraints.
4 Commits • 2 Features
Oct 1, 20252025-10 Monthly Summary for terrapower/armi: Delivered two substantial features aimed at improving scalability, memory management, and reliability of cross-section computations and MPI workload handling. Updated tests and documentation to reflect changes. No user-reported critical bugs were identified in this period; stability improvements focused on edge-case handling and resource constraints.
October 2025
September 2025
4 Commits • 3 Features
Sep 1, 2025September 2025 saw focused delivery across terrapower/armi, delivering key enhancements to enrichment calculations, smear density modeling, and axial expansion accounting, along with a robustness improvement in lattice physics writer. These changes improve modeling accuracy for fissile material inventories, support complex block configurations, ensure conservation of heavy metal moles and mass, and strengthen failure handling with targeted tests. The work advances reliability, test coverage, and readiness for next-generation reactor physics simulations.
September 2025
4 Commits • 3 Features
Sep 1, 2025September 2025 saw focused delivery across terrapower/armi, delivering key enhancements to enrichment calculations, smear density modeling, and axial expansion accounting, along with a robustness improvement in lattice physics writer. These changes improve modeling accuracy for fissile material inventories, support complex block configurations, ensure conservation of heavy metal moles and mass, and strengthen failure handling with targeted tests. The work advances reliability, test coverage, and readiness for next-generation reactor physics simulations.
August 2025
6 Commits • 3 Features
Aug 1, 2025Summary for 2025-08: The terrapower/armi codebase delivered robust neutronics and grid-geometry improvements, enhanced API surfaces for data handling, and safer initialization paths to reduce runtime errors during DB loading and snapshot restoration. Key outcomes include correcting configuration duplicates, improving nuclide density calculations, enabling hex lattice pitch representation, strengthening block filtering in the mesh generator, and stabilizing loading paths with clearer environment grouping tests. These changes improve reliability, accuracy of reactor core representations, and ease of testing, delivering business value through fewer production incidents and clearer data models.
6 Commits • 3 Features
Aug 1, 2025Summary for 2025-08: The terrapower/armi codebase delivered robust neutronics and grid-geometry improvements, enhanced API surfaces for data handling, and safer initialization paths to reduce runtime errors during DB loading and snapshot restoration. Key outcomes include correcting configuration duplicates, improving nuclide density calculations, enabling hex lattice pitch representation, strengthening block filtering in the mesh generator, and stabilizing loading paths with clearer environment grouping tests. These changes improve reliability, accuracy of reactor core representations, and ease of testing, delivering business value through fewer production incidents and clearer data models.
August 2025
July 2025
4 Commits • 2 Features
Jul 1, 2025July 2025 monthly summary for terrapower/armi: delivered performance-oriented data and geometry enhancements, with a focus on robustness, data integrity, and maintaining alignment with modeling requirements. The work emphasized upgrading core data storage and cross-section calculations, while also tightening merge workflows and geometry validation policies to reduce edge-case risks in production.
July 2025
4 Commits • 2 Features
Jul 1, 2025July 2025 monthly summary for terrapower/armi: delivered performance-oriented data and geometry enhancements, with a focus on robustness, data integrity, and maintaining alignment with modeling requirements. The work emphasized upgrading core data storage and cross-section calculations, while also tightening merge workflows and geometry validation policies to reduce edge-case risks in production.
March 2025
1 Commits • 1 Features
Mar 1, 2025March 2025 (2025-03) – Terrapower/armi: Delivered thermal expansion-aware improvements to number density and mass conservation, enhancing physics fidelity and ensuring mass balance during composition and temperature-driven changes. Implementations re-evaluate number densities after potential parent composition changes, refactor updates to properly handle thermal expansion–dependent volume changes, and maintain mass conservation across simulations. Added tests for composition-dependent thermal expansion to prevent regressions and support robust future changes. This work strengthens reliability of materials simulations under varying temperatures and compositions, enabling more accurate engineering decisions and risk reduction in reactor materials modeling.
1 Commits • 1 Features
Mar 1, 2025March 2025 (2025-03) – Terrapower/armi: Delivered thermal expansion-aware improvements to number density and mass conservation, enhancing physics fidelity and ensuring mass balance during composition and temperature-driven changes. Implementations re-evaluate number densities after potential parent composition changes, refactor updates to properly handle thermal expansion–dependent volume changes, and maintain mass conservation across simulations. Added tests for composition-dependent thermal expansion to prevent regressions and support robust future changes. This work strengthens reliability of materials simulations under varying temperatures and compositions, enabling more accurate engineering decisions and risk reduction in reactor materials modeling.
March 2025
February 2025
5 Commits • 2 Features
Feb 1, 2025February 2025 — terrapower/armi: delivered cross-section expansion, enhanced component sorting, and fixed symmetry-based physics corrections. These changes improve cross-platform usability, numerical accuracy, and simulation reliability, directly impacting model fidelity and user confidence.
February 2025
5 Commits • 2 Features
Feb 1, 2025February 2025 — terrapower/armi: delivered cross-section expansion, enhanced component sorting, and fixed symmetry-based physics corrections. These changes improve cross-platform usability, numerical accuracy, and simulation reliability, directly impacting model fidelity and user confidence.
January 2025
1 Commits
Jan 1, 20252025-01 Monthly Summary for terrapower/armi: Focused on improving numerical accuracy for edge assemblies in symmetric reactor models. Implemented a targeted bug fix that corrects the scaling of volume-integrated parameters for edge assemblies in 1/3 core symmetry by passing the core object (instead of the reactor object) to the relevant calculation routines, thereby increasing model fidelity and reliability in edge regions.
1 Commits
Jan 1, 20252025-01 Monthly Summary for terrapower/armi: Focused on improving numerical accuracy for edge assemblies in symmetric reactor models. Implemented a targeted bug fix that corrects the scaling of volume-integrated parameters for edge assemblies in 1/3 core symmetry by passing the core object (instead of the reactor object) to the relevant calculation routines, thereby increasing model fidelity and reliability in edge regions.
January 2025
November 2024
1 Commits • 1 Features
Nov 1, 2024November 2024 monthly summary for terrapower/armi focused on delivering reliable, data-safe file operations. Key achievement: introduced SafeMove utility to replace shutil.move, ensuring move operations complete successfully and improving data integrity for Database and DirectoryChanger. This change reduces risk of partial moves and data corruption during migrations, supporting robust data handling across ARMI workflows.
November 2024
1 Commits • 1 Features
Nov 1, 2024November 2024 monthly summary for terrapower/armi focused on delivering reliable, data-safe file operations. Key achievement: introduced SafeMove utility to replace shutil.move, ensuring move operations complete successfully and improving data integrity for Database and DirectoryChanger. This change reduces risk of partial moves and data corruption during migrations, supporting robust data handling across ARMI workflows.
October 2024
2 Commits • 1 Features
Oct 1, 2024Monthly summary for 2024-10: Delivered hetero-duct assemblies support for 1D cross-section models in terrapower/armi, enabling creation of partially heterogeneous assemblies via the ductHeterogeneous option in HexComponentsToCylConverter. This change improves memory usage and reduces runtime for lattice physics solvers, enabling more scalable and accurate simulations. Strengthened validation with targeted unit tests for heterogeneous averaging logic (CylindricalComponentsDuctHetAverageBlockCollection), increasing reliability and reducing regression risk. These efforts enhance modeling fidelity, performance, and overall impact for large-scale analyses, and demonstrate strong skills in modeling, testing, and performance optimization.
2 Commits • 1 Features
Oct 1, 2024Monthly summary for 2024-10: Delivered hetero-duct assemblies support for 1D cross-section models in terrapower/armi, enabling creation of partially heterogeneous assemblies via the ductHeterogeneous option in HexComponentsToCylConverter. This change improves memory usage and reduces runtime for lattice physics solvers, enabling more scalable and accurate simulations. Strengthened validation with targeted unit tests for heterogeneous averaging logic (CylindricalComponentsDuctHetAverageBlockCollection), increasing reliability and reducing regression risk. These efforts enhance modeling fidelity, performance, and overall impact for large-scale analyses, and demonstrate strong skills in modeling, testing, and performance optimization.
October 2024
Activity
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Quality Metrics
Correctness87.2%
Maintainability84.6%
Architecture82.6%
Performance72.6%
AI Usage20.0%
Skills & Technologies
Programming Languages
PythonRST
Technical Skills
Backend DevelopmentBug FixingCode OptimizationCode RefactoringConfiguration ManagementCross Section ModelingData StructuresDatabase ManagementDebuggingDocumentationError HandlingFile System OperationsFull Stack DevelopmentGeometry ConversionLattice Physics
Repositories Contributed To
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