A method for determining a leaking nuclear fuel rod that remotely measures the internal pressure in the plenum region of the fuel rod by remotely measuring the thermal response of the rod when a localized heating is imposed on the outside of the rod in the plenum region. The temperature of the cladding at two symmetrically spaced points on either side of the location where the heating is imposed is remotely monitored as a function of time and compared to a standard to determine the internal pressure of the plenum.