| 摘要 |
PROBLEM TO BE SOLVED: To provide an apparatus for measuring the size of clearance between upper grid plates, capable of miniaturizing and simplifying the constitution of measuring parts by eliminating the need to insert an inspection mechanism into a narrow portion, and making measurements through the movement of a sensor on the outside of a structure constituting the narrow portion, and a method capable also of reducing the measuring time including mounting time through the enhancement of handleability and of enhancing measuring accuracy, etc. SOLUTION: The apparatus includes a truck 20 movably mounted on the top of a core shroud inside the reactor pressure vessel 10 of a boiling water reactor; an arm 23 projecting downwards from the truck and positioned along the outer peripheral surface of the shroud; an ultrasonic measuring sensor movably provided on the arm to search without contact any objects present inside the shroud; and a measuring device located outside the core, for determining whether or not there is an object, by transmitting and receiving signals to and from the sensor, or for measuring clearance between the arrangement and the object, etc.
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