High-strength Ni-based alloy tube for nuclear power use and method for manufacturing the same

The high-strength Ni-based alloy tube for nuclear power use consists, by mass percent, of C: 0.04% or less, Si: 0.10 to 0.50%, Mn: 0.05 to 0.50%, Ni: 55 to 70%, Cr: more than 26% and not more than 35%, Al: 0.005 to 0.5%, N: 0.02 to 0.10%, and one or more kinds of Ti: 0.01 to 0.5% and Nb: 0.02 to 1.0%, the balance being Fe and impurities. For this alloy tube, the grain size is as fine as grain size No. 6 or higher in JIS G 0551. It is preferable that the high-strength Ni-based alloy tube be manufactured by the process of preparing a Ni-based alloy stock through a remelting process, hot forging, heating to 1000 to 1160° C., hot extruding at a working ratio such that an extrusion ratio is 4 or higher, and performing solution annealing and thermal treatment.