Patent Number: 046559922
Section: claims

1. A method of measuring coolant fluid temperatures, said fluid emerging from outlets of an array of generally parallel fuel/breeder sub-assembly wrappers forming a core of a nuclear reactor, said method comprising projecting a beam of pulsed ultrasound transversely across the core at glancing incidence to said outlets of the wrappers and scanning said beam in a direction perpendicular to the beam direction whereby the beam propagates across the wrapper outlets in the array and undergoes reflection at diametrically-opposed edge portions of each of a plurality of said outlets located in different zones of the array, detecting echo signals produced as a result of such reflections, recording the timing of the echo signals with respect to pulsing of the beam, analysing the echo signals to relate them with the edge portions of respective wrapper outlets, and translating the timings of the so related echo signals into a temperature value for the coolant fluid emerging from the respective wrapper outlet. 2. A method as claimed in claim 1 wherein analysing the echo signals includes identifying those echo signals obtained when the scanned beam is normal to the diametrically-opposed edge portions. 3. In a nuclear reactor, apparatus for measuring coolant fluid temperatures, said fluid emerging from outlets of an array of generally parallel fuel/breeder sub-assembly wrappers forming a core of the nuclear reactor, said apparatus comprising ultrasonic transmit/receive transducer means for projecting a beam of pulsed ultrasound transversely across the core at glancing incidence to said outlets of the wrappers, means for effecting scanning of said beam in a direction perpendicular to the beam direction whereby the beam propagates across the wrapper outlets in the array and undergoes reflection at diametrically-opposed edge portions of each of a plurality of said outlets located in different zones of the array, means for detecting echo signals produced as a result of such reflections, means for recording the timing of the echo signals with respect to pulsing of the beam, means for analysing the echo signals to relate them with the edge portions of respective wrapper outlets, and means for translating the timings of the so related echo signals into a temperature value for the coolant fluid emerging from the respective wrapper outlet. 4. An apparatus as claimed in claim 3 wherein said analysing means includes means for identifying those echo signals obtained when the scanned beam is normal to the diametrically-opposed edge portions.