NI-BASED ALLOY PIPE OR TUBE FOR NUCLEAR POWER

The purpose of the present invention is to provide an Ni-based alloy pipe for atomic power which has a low SCC crack propagation rate. The Ni-based alloy pipe for atomic power according to the present invention has a wall thickness of 15-55 mm, has a structure constituted only of an austenite phase, and has a chemical composition which contains, in terms of mass%, 0.010-0.025% C, 0.10-0.50% Si, 0.01-0.50% Mn, up to 0.030% P, up to 0.002% S, 52.5-65.0% Ni, 20.0-35.0% Cr, 0.03-0.30% Mo, up to 0.018% Co, up to 0.015% Sn, 0.005-0.050% N, 0-0.300% Ti, 0-0.200% Nb, 0-0.300% Ta, and 0% or more but less than 0.03% Zr, with the remainder comprising Fe and unavoidable impurities, and which satisfies the following relationship (1). -0.0020 = [N]/14-{[Ti]/47.9+[Nb]/92.9+[Ta]/180.9+[Zr]/91.2} = 0.0015 (1) For the symbols for elements in relationship (1), the contents in mass% of the corresponding elements are substituted.