Abstract: A tubular blank (22) is rolled on a mandrel (14) in a pilgrim rolling mill. In a first rolling stage, a first part of the blank (22) is rolled on a first part (18,19) of the mandrel (14), with a reduction of the outside diameter of the blank (22) to the outside diameter of the guide tube and a reduction of the wall thickness of the blank (22) to one of a first wall thickness (e1) and a second wall thickness (e2) exceeding the first wall thickness (e1). The mandrel (14) is advanced in the axial direction. A second part of the blank (22) is rolled on a second part (20,21) of the mandrel spaced from the first part in the axial direction with a reduction of the outside diameter of the blank to the outside diameter of the guide tube and a reduction of the wall thickness of the blank (22) to the other of the first wall thickness (e1) and second wall thickness (e2).

Abstract: A substantial part of the water contained in the spent solution is evaporated under vacuum in an evaporator (7) and is then condensed, so as to obtain slightly acidic water and a concentrated acidic solution polluted by zirconium fluoride ZrF.sub.4. The polluted concentrated acidic solution is treated by evaporation under vacuum in a crystallizer (8), so as to obtain zirconium fluoride ZrF.sub.4 crystals and a purified concentrated acidic solution. The slightly acidic water and the purified concentrated acidic solution are mixed in desired proportions in order to obtain a regenerated pickling solution.

Abstract: A method of manufacturing a tube suitable for use as sheath of a nuclear fuel rod zirconium based alloy. The alloy contains 0.18% to 0.25% iron, 0.07% to 0.13% chromium, 0.35% to 1.70% tin, all percentages by weight, 900 ppm to 2300 ppm oxygen, 80 ppm to 200 ppm carbon, and 50 ppm to 120 ppm silicon. A drawn blank is subjected to successive passes of metallurgical treatment and of heat treatment. The Fe/Cr ratio by weight in the alloy lies in the range 1.6 to 3. The heat treatment includes, after at least one rolling pass, a plurality of annealing passes under an inert atmosphere such that the sum .SIGMA.A is greater than 1.5.10.sup.-17, and advantageously in the range 2.10.sup.-17 to 2.10.sup.-16. The first rolling pass is performed on the tube coming from the drawing operation, without an intermediate annealing. .SIGMA.A designates the sum of the products of the times t (in hours) multiplied by the exponential of --Q/RT, where T is the temperature in K.

Abstract: The tubular cladding (1) comprises an internal surface of substantially prismatic shape, having successive faces. An ultrasonic examination head (3) makes it possible to emit ultrasound waves in the form of pulses from the outside of the cladding (1), so that the ultrasound waves pass through the wall of the cladding (1) and scan the wall over its entire periphery. The frequency of the ultrasound pulses is adjusted as a function of the circumferential scanning speed of the cladding (1). An ultrasound signal reflected by the internal surface of the cladding (1) is recorded and the reflected signal is analyzed in order to examine the number and the amplitude of the faces and the variation in thickness of the tubular cladding (1) over one revolution.

Abstract: A nuclear fuel rod cladding for a water moderated and nuclear reactor comprises an inner portion of Zircaloy 4 and an outer portion of a zirconium-based alloy which contains by weight, besides zirconium and unavoidable impurities:0.35% to 0.65% tin0.18% to 0.25% iron0.07% to 0.13% chromium, and0.19% to 0.23% oxygen,with the sum of the iron, chromium, tin, and oxygen contents being less than 1.26% by weight. It may alternatively or additionally comprise 0.80% to 1.20% by weight niobium and then the oxygen content is in the range 0.10% to 0.16% by weight. The thickness of the outer layer is 10% to 25% of the total thickness of the cladding. In a modification, up to 0.5% of iron, chromium, niobium is replaced by an equivalent content of vanadium.

Abstract: The duplex tube (1) comprises a tubular core (2) and a cladding or covering layer (3) made from an alloy, the base metal of which is identical to the base metal of the alloy constituting the tubular core (2).

Abstract: The fuel rod comprises a sheath having an inner tubular layer and an outer surface layer composed of zirconium alloys which differ from each other. The surface layer, whose thickness is between 10 to 25% of the total thickness of the wall of the sheath, is constituted by a zirconium-base alloy containing by weight 0.35 to 0.65% tin, 0.20 to 0.65% iron, 0.09 to 0.16% oxygen and niobium in a proportion of 0.35 to 0.65% or vanadium in a proportion of 0.25 to 0.35%. The inner layer may be constituted by an alloy such as Zircaloy 4 or a zirconium-niobium alloy.