COATING PIPE

PURPOSE: To provide a clad tube capable of withstanding the accelerated corrosion. CONSTITUTION: A clad tube 17 having a section comprises an outer circumferential base layer 21 made of zirconium alloy having an inner surface and containing >=1 alloy element, a zirconium barrier layer 22 which is joined with the inner surface of the outer circumferential base layer 21 and allowed by above-mentioned >=1 alloy, and an inner circumferential liner 23 made of zirconium alloy which is joined with the inner surface of the zirconium barrier layer 22. The zirconium barrier layer 22 has the concentration distribution containing a diffusion layer extending from the inner surface of the barrier layer 22 (opposite to the nuclear fuel) to the inside of the barrier layer 22 (between the inside and the outside of the barrier layer). No alloy element is substantially present in an inner edge of the diffusion layer, while the alloy element of the maximum concentration is prevent in an outer edge (the inner surface of the barrier layer) of the diffusion layer.