Abstract: The invention concerns a process for the production of a tubular zircaloy 2 blank which is internally clad with zirconium for use in producing composite cladding tubes for nuclear fuel. The internal zirconium cladding is rendered suitable for ultrasound monitoring of its thickness by an appropriate thermomechanical treatment which takes place during one or more of the production steps for said blank. The aim is to adjust the grain size to an ASTM index of between 9 and 12 for the zircaloy 2 and between 6 and 10 for the unalloyed zirconium, retaining a grain size difference between the zircaloy 2 and the unalloyed zirconium of at least 2 ASTM index numbers.

Abstract: According to the method of the invention concerning tubes, of which the plating to be checked is at least 0.4 mm thick and in which the acoustic impedance differs by at least 1% relative from that of the core of the tube, a properly dampened transducer is selected which has a frequency of 4 to 10 MHz. The position of the transducer in respect to the tube is adjusted experimentally, and its parameters of distance and orientation are differently adjusted in order to increase the "signal-to-noise" ratio. For determining the thickness of the plating, at least one double echo from the interface between the plating and the tube core is used, or alternatively, a triple echo from this interface. Also, there is a corresponding ultrasonic measuring apparatus as well as an application of the method to the ultrasonic measuring of the thickness of the plating of Zr alloy tubes. The tubes are plated with non-alloyed Zr or with some other Zr alloy.

Abstract: The electrolysis cell according to the invention is concerned with the preparation of Zr or Hf by electrolysis, from a molten mixture of alkali metal or alkaline earth chlorides and fluorides.It comprises a graphite collector which defines the anodic space and which is extended at the lower end below the level of the electrolyte by a metal wall made of metal to be deposited or coated with said metal.The wall may advantageously be made in the form of a porous diaphragm.