GB996512A - Nuclear fuel element - Google Patents

Abstract

996,512. Temperature measurement by acoustic resonace; telephone instrumennts; resonators. UNITED KINGDOM ATOMIC ENERGY. Aug. 23, 1963 [Aug. 30, 19621, No. 33302/62. Addition to 967,473. Headings H4D, H4J and H4X. [Also in Division G6] The temperature of a nuclear fuel element is deduced from the resonant frequency of an acoustic resonator in thermal contact therewith. The resonator comprises a stainless steel tube 16 (Figs. 2 and 3) mounted on the stub 17 of a cut-away heat transfer fin 11 and retained by an insert 18 welded to adjacent fins apertures 26 (Fig. 3) being provided in tube 16 to admit ambient gas which may be the reactor coolant gas (e.g. carbon dioxide or helium). Each end of tube 16 communicates with a fine bore stainless steel tube 21 the other ends of which communicate with respective electro-acoustic transducers 22, 23 mounted on adjacent axial splitter fins 14, the latter being interconnected by braces 15 to which they are welded. Each transducer comprises a stainless steel casing 27 (Fig. 3) containing a diaphragm 32 carrying a magnetic armature 33, a gas-tight partition 28 including a magnetic annular portion 38 and a stainless steel spacer 39, a magnetic core 35 carrying a winding 34 and a ring permanent magnet 36 surrounding coil 34 and in contact with a magnetic base plate 37. The electrical leads 24 from the coil may be led out of the reactor or may terminate in breakable contacts on the fuel element which co-operate with similar contacts on adjacent elements or on the reactor structure. In operation, one (input) transducer is fed from an oscillator the frequency of which is varied until resonance occurs in tube 16 this being indicated by a peak in the output signal received by the other (output) transducer. To ensure that resonance occurs only in tube 16 the diameter of the fine bore tubes 21 is chosen such that standing waves are not set up in them. The position of the ends of tubes 21 within tube 16 may be adjusted for optimum impedance matching and both tubes 21 may extend from the source end of tube 16. Also, the position of tubes 21 within tube 16 may be adjusted so that acoustic transmission through the latter tube occurs at a harmonic of the fundamental frequency of the tube thus allowing the output transducer which is responsive to the harmonic frequency to share common electrical leads with the input transducer which is energized at the fundamental frequency, the output signals from the two transducers being separated by electrical filters. In another arrangement the tube 16 may form the frequency controlling element in a self-running oscillator in which regeneration is provided by arranging for the output transducer to provide a measure of amplification: e.g. the transducer in this case could be constituted by a carbon microphone.