Disclosed are a voltage drop measurement system and methods for measuring resistivity of a nuclear reactor cladding. The system includes a short cladding sample of a nuclear reactor cladding. Two electrically conductive plugs are attached to the short cladding. A power supply is electrically coupled to the each of the two electrically conductive plugs and is configured to apply an electrical current to the short cladding through the two electrically conductive plugs. Two needle like probes are electrically coupled to a surface of the short cladding between the two electrically conductive plugs. The needle like probes are spaced apart by a distance L. Resistivity and heat flux are determined in accordance with Equations (1)-(4).