Patent Number: 
Section: claims

1. A detection apparatus usable with a fuel rod from among a plurality of fuel rods of a fuel assembly, the fuel rod having a cladding that has an interior region, the fuel rod being situated within a nuclear reactor, the detection apparatus being cooperable with an electronic processing apparatus situated outside of the reactor, the detection apparatus comprising:a transmitter that is structured to be positioned outside the cladding and inside the nuclear reactor in the vicinity of the fuel rod and structured to generate an excitation pulse and to transmit the excitation pulse through the cladding and into the interior region;an electrical circuit apparatus having a resonant electrical circuit that is structured to be supported within the interior region and to generate a response pulse in response to the excitation pulse and to transmit the response pulse in the form of a magnetic field signal that is structured to travel from the interior region and through the cladding, a characteristic of the response pulse being indicative of a condition of the fuel rod; anda receiver structured to be supported within the nuclear reactor outside the cladding and in the vicinity of the fuel rod, the receiver being structured to receive the response pulse and to communicate to the electronic processing apparatus an output responsive to the response pulse. 2. The detection apparatus of claim 1 wherein the resonant electrical circuit is supported within a plenum of the nuclear fuel rod. 3. The detection apparatus of claim 2 wherein the characteristic of the response pulse is indicative of a center-line fuel pellet temperature. 4. The detection apparatus of claim 2 wherein the characteristic of the response pulse is indicative of a fuel pellet elongation. 5. The detection apparatus of claim 2 wherein the characteristic of the response pulse is indicative of a pressure in the interior region. 6. The detection apparatus of claim 2 wherein the characteristic of the response pulse is indicative of a plurality of conditions of the fuel rod. 7. The detection apparatus of claim 1 wherein the resonant electrical circuit comprises a plurality of circuit components whose values are selected to cause the response pulse to have a unique frequency that is usable to identify the fuel rod from which the response pulse emanated. 8. The detection apparatus of claim 1 wherein the electrical circuit apparatus further comprises a calibration circuit that is configured to be supported within the interior region and that is structured to generate a calibration signal in response to the excitation pulse and to transmit the calibration signal in the form of another magnetic field signal that is structured to travel from the interior region and through the cladding, the another magnetic field signal being receivable by the receiver and usable to correct the response pulse received by the receiver for any signal change associated with component degradation or temperature drift. 9. The detection apparatus of claim 1 wherein the resonant electrical circuit comprises a plurality of circuit components that comprise a capacitor, the capacitor having a capacitance which is structured to vary in response to the condition of the fuel rod and which, responsive to a change in the condition, is structured to cause the response pulse to have a frequency that varies with the condition. 10. The detection apparatus of claim 9 wherein the capacitor comprises a movable plate and a stationary plate, the movable plate being structured to move with respect to the stationary plate responsive to a change in an ambient pressure within the interior region to alter the capacitance and to resultantly cause the response pulse to have a frequency that varies with the ambient pressure. 11. The detection apparatus of claim 1 wherein the resonant electrical circuit comprises a plurality of circuit components that comprise an inductor having a coil, the inductor having a inductance which is structured to vary in response to the condition of the fuel rod and which, responsive to a change in the condition, is structured to cause the response pulse to have a frequency that varies with the condition. 12. The detection apparatus of claim 11 wherein the fuel rod has a number of fuel pellets situated within the interior region, wherein the condition is a center-line fuel pellet temperature of the fuel rod, and wherein the electrical circuit apparatus further comprises a temperature transmission apparatus comprising an element that is elongated and that is formed at least in part of a ferromagnetic material, at least a portion of the element being receivable in the coil, the at least portion of the element that is receivable in the coil varying with the condition to cause the inductance to vary in response to the change in the condition. 13. The detection apparatus of claim 12 wherein the temperature transmission apparatus further comprises an amount of metal, the element being engaged with the amount of metal, the amount of metal being structured to undergo thermal expansion and contraction as a function of an increase and a decrease, respectively, in the center-line fuel pellet temperature, the element being structured to be moved relative to the coil by the amount of metal undergoing thermal expansion and contraction to thereby cause the inductance to vary in response to the change in the condition. 14. The detection apparatus of claim 13 wherein the amount of metal is in a liquid state during operation of the nuclear reactor, wherein the element is floated on the amount of metal, and wherein the element is structured to be buoyantly moved relative to the coil by the amount of metal undergoing thermal expansion and contraction. 15. The detection apparatus of claim 11 wherein the condition is an ambient pressure within the interior region, and wherein the electrical circuit apparatus further comprises a pressure indication apparatus comprising an element that is elongated and that is formed at least in part of a ferromagnetic material, at least a portion of the element being receivable in the coil, the at least portion of the element that is receivable in the coil varying with the condition to cause the inductance to vary in response to the change in the condition. 16. The detection apparatus of claim 15 wherein the pressure indication apparatus further comprises a vessel having a hollow cavity that is sealed to resist fluid communication with the interior region, the vessel being structured to be supported within the interior region and being structured to undergo contraction and expansion in response to an increase and a decrease, respectively, in the ambient pressure within the interior region, the element being situated on the vessel being structured to be moved relative to the coil by the vessel undergoing contraction and expansion to thereby cause the inductance to vary in response to the change in the condition. 17. The detection apparatus of claim 16 wherein the vessel is a bellows having a number of corrugations formed therein. 18. A method of detecting a condition of a fuel rod from among a plurality of fuel rods of a fuel assembly, the fuel rod having a cladding that has an interior region, the fuel rod being situated within a nuclear reactor, comprising:employing a detection apparatus to detect the condition, the detection apparatus being cooperable with an electronic processing apparatus situated outside of the nuclear reactor, the detection apparatus having a transmitter that is positioned outside the cladding and inside the nuclear reactor in the vicinity of the fuel rod, an electrical circuit apparatus having a resonant electrical circuit that is supported within the interior region, and a receiver that is supported within the nuclear reactor outside the cladding and in the vicinity of the fuel rod, the employing comprising:generating with the transmitter an excitation pulse and transmitting the excitation pulse through the cladding and into the interior region;generating with the electrical circuit apparatus a response pulse in response to the excitation pulse and transmitting the response pulse in the form of a magnetic field signal from the interior region and through the cladding;generating the response pulse to have a characteristic that is indicative of the condition of the fuel rod; andreceiving the response pulse on the receiver and communicating to the electronic processing apparatus an output responsive to the response pulse. 19. The method of claim 18, wherein the electrical circuit apparatus further has a calibration circuit that is supported within the interior region, and further comprising:generating with the calibration circuit a calibration signal in response to the excitation pulse and transmitting the calibration signal in the form of another magnetic field signal from the interior region and through the cladding;receiving the another magnetic field signal on the receiver; andemploying the another magnetic field signal received on the receiver to correct the response pulse received by the receiver for any signal change associated with component degradation or temperature drift. 20. The method of claim 19, wherein the employing of the another magnetic field signal received on the receiver comprises:employing the characteristic of the response pulse and another characteristic of the calibration signal to determine a ratio; andemploying the ratio to retrieve from a storage a corresponding value for the condition.