Patent Number: 
Section: claims

1. A refueling apparatus for charging a nuclear fuel assembly in a reactor vessel, the refueling apparatus comprising:a refueling unit for loading new nuclear fuel to a reactor core or extracting spent nuclear fuel from the core; anda waveguide sensor unit including an ultrasonic wedge configured to form a Lamb wave, a waveguide with a first end connected to the ultrasonic wedge and with a second end configured to transmit the Lamb wave into liquid metal in the reactor vessel, and an ultrasonic sensor connected to the ultrasonic wedge and configured to sense a reflection signal reflected from an inside of the reactor vessel, the waveguide being formed in a plate shape and mounted in an end of the refueling unit,wherein the waveguide integrally moves with the refueling unit, and the waveguide sensor unit is configured to detect a condition of the inside of the reactor vessel, while the refueling unit refuels the fuel assembly in the reactor vessel, andwherein the refueling unit has a space for the waveguide, and at least a portion of the waveguide is mounted in the refueling unit. 2. The refueling apparatus of claim 1, wherein the waveguide sensor unit is configured to change a radiation angle of a radiation beam depending on a frequency change of an ultrasonic signal incident to the ultrasonic wedge, the radiation beam being radiated from the second end of the waveguide. 3. The refueling apparatus of claim 1, wherein a thickness of the second end of the waveguide transmitting the Lamb wave increases in a lengthwise direction. 4. The refueling apparatus of claim 1, wherein the ultrasonic wedge is made of a material capable of propagating a longitudinal wave velocity of about 1300 m/s to 2000 m/s, and configured to generate an A0 antisymmetric Lamb wave of an range of 0.5 MHz·mm to 2.5 MHz·mm which is a value obtained by multiplying an incident frequency of the Lamb wave and a thickness of the waveguide. 5. The refueling apparatus of claim 1, wherein the ultrasonic wedge is made of a polymer polytetrafluoroethylene wedge and filled with water or glycerin capable of propagating a longitudinal wave velocity of about 1300 m/s to 2000 m/s. 6. A refueling apparatus for charging a nuclear fuel assembly in a reactor vessel, the refueling apparatus comprising:a refueling unit including an extraction unit for extracting the nuclear fuel and a central axis connected to the extraction unit and transferring the extraction unit;a first waveguide sensor unit including a first ultrasonic wedge configured to form a Lamb wave, a first waveguide with a first end connected to the first ultrasonic wedge and with a second end configured to transmit the Lamb wave to a bottom of the extraction unit, and a first ultrasonic sensor connected to the first ultrasonic wedge and configured to sense a reflection signal reflected from an inside of the reactor vessel, the first waveguide being formed in a plate shape and mounted in an end of the extraction unit; anda second waveguide sensor unit including a second ultrasonic wedge configured to form a Lamb wave, a second waveguide with a third end connected to the second ultrasonic wedge and with a fourth end configured to transmit the Lamb wave to a side of the central axis, and a second ultrasonic sensor connected to the second ultrasonic wedge and configured to sense a reflection signal reflected from an inside of the reactor vessel, the second waveguide being formed in a plate shape and mounted in an end of the central axis,wherein the first waveguide sensor unit is configured to detect a condition of a bottom of the extraction unit and the second waveguide sensor unit is configured to detect a condition of the side of the central axis while the refueling unit refuels the reactor vessel, andwherein the extraction unit has a first space for the first waveguide, and at least a portion of the first waveguide is mounted in the extraction unit, and the central axis has a second space for the second waveguide, and at least a portion of the second waveguide is mounted in the central axis. 7. The refueling apparatus of claim 6, wherein the first and second waveguide sensor units are configured to change a radiation angle of a radiation beam depending on a frequency change of an ultrasonic signal incident to the first and second ultrasonic wedges, and the second waveguide sensor unit includes a plurality of waveguide sensor units, the radiation beam being radiated from the second end of the first waveguide and the fourth end of the second waveguide. 8. The refueling apparatus of claim 6, wherein the second and fourth ends have a respective thickness increasing in a lengthwise direction.