Abstract: Contactless transmission of information about temperatures within a fuel assembly of a nuclear reactor by means of a thermoelement situated in the fuel assembly, the thermoelement generating a magnetic field the intensity of which is proportional to the temperature within the fuel assembly. A harmonic magnetic sensing element disposed outside the fuel assembly for registering the value of intensity of this magnetic field is employed, the sensing element being connected to an arrangement for the evaluation of such. The fuel assembly is provided with a sheath or housing which permits the passage of the magnetic field therethrough.