  Radiation effects analysis of instruments operative in harsh radiation
environment is crucial for performance and functionality of electronic devices
and components. Engineering design of instruments is usually carried out in
Computer Aided Design (CAD) engineering software. Geant4-based Monte Carlo
codes are extensively used for particle transport simulation and analysis.
However, Geant4 is not prepared to accept CAD Standard for The Exchange of
Product data (STEP) format. MRADSIM-Converter is a new software for STEP to
Geometry Description Markup Language (GDML) format conversion, readable by
Geant4-based Monte Carlo codes. Its validation with two different converters
confirms its higher speed for importing CAD geometries with arbitrary size and
complexity having a user-friendly interface for modifying volumes properties.
