I. Introduction
NB3AL is an attractive strand material for the supercon-ducting coil in a fusion reactor. Generally, the longitudinal strain acting on Nb3Al decreases the critical current of the Nb3Al strand. In the cable-in-conduit (CIC) conductor, strands suffer thermal and bending strain. However, no decrease of the by bending strain of 0.4% after heat treatment was observed in a Nb3Al D-haped coil made by the react-and-wind (R&W) method in the R&D program for the National Centralized Tokamak (NCT) [1]. In the R&W method, the winding is carried out after heat treatment. The same tendency was also observed in the Nb3 Al-insert coil manufactured through ITER R&D [2]. These observations suggest that some cabling effect causes a relaxation of the bending strain in the strands.