This paper presents a practical, low-cost, and swiftly developed heterogeneous robotic system-comprising an aerial drone and a ground vehicle-designed for inspection and situational awareness in nuclear power plant (NPP) environments. Developed during the EnRicH 2025 competition in AKW Zwentendorf, our solution prioritized rapid prototyping using ROS2, off-the-shelf components, and open-source frameworks, achieving deployment within 3 weeks. We detail the design methodology: a 3D-printed airframe for the drone, an Ackermann-steering UGV, and a combined sensor suite composed of LiDAR, IMU, and radiation detection modules. Control and navigation algorithms were implemented using ROS2, leveraging SLAM and a hybrid autonomy paradigm to address GNSS denial inside containment structures. We also tackle communication challenges within shielded environments by integrating a modular mesh network and signal repeaters. Field trials in a real NPP demonstrated robust localization, reliable communication despite severe attenuation, and real-time radiation monitoring. Our contribution is a fully reproducible, low-cost air-ground inspection solution validated in a real NPP, together with a complete open-source release of mechanical designs, BOMs, firmware, and ROS2 software stacks.1