Masaru Ukai

Method and apparatus for measuring gap between adjoining fuel rods of fuel assembly

A gap between adjoining fuel rods arranged in a fuel assembly is measured by setting a measuring device into a fluid such as cooling water or a specific gas such as CF filling a container, placing a fuel assembly to be inspected to a predetermined portion the container, measuring a distribution of the fluid distributed in the fuel assembly by utilizing a nuclear magnetic resonance imaging system, and measuring the gap in accordance with the fluid distribution as an image. The measuring device includes a magnet unit and a coil unit for generating magnetic fields, and the coil unit includes a coil assembly for generating gradient magnetic fields and a coil assembly for generating a high-frequency magnetic field and detecting a nuclear magnetic resonance signal. The gap measuring apparatus utilizing nuclear magnetic resonance further includes a controlling device for controlling the magnetic fields generated by the magnet unit and the coil assemblies and a data processor for carrying out data processing in response to a signal transmitted from the controlling device, wherein the distribution of the fluid in the fuel assembly is processed as a sectional image of the fuel assembly to thereby measure the gaps between adjoining fuel rods or between the fuel rod and the water rod.