Worked on the terrapower/armi repository to enhance reliability in cross-section type handling by introducing explicit error validation in Python. Addressed a bug where invalid cross-section type numbers could be processed, implementing ValueError-based checks to ensure only values of 65 or greater are accepted. This approach reduced the risk of data corruption and runtime errors in downstream components. Refactored the relevant function to improve maintainability and updated unit tests to cover both valid and invalid input scenarios, ensuring robust error handling. Focused on error handling, refactoring, and unit testing, the work contributed to safer and more predictable code execution.