Many nuclear power plants in Japan and overseas have experienced stress corrosion cracking in the weld portion of the apparatus made from stainless steel. To deal with this problem, a preventive maintenance method, which covers welding parts with thermosetting resin, has been used. By this method working time for coating in the plant is so long that it has made a serious problem for the workers' health. Thus we have developed a new method to cover the welding part with resin. This method can reduce the working time in the plant by preparing the composite sheets in the factory. Two thermosetting resins, epoxy and vinyl ester, were used for this system. In this method, thermosetting resin is fabricated into a sheet form at the shop. To estimate the adhesion strength from the measured hardness after application of the resin sheet, we conducted tests to evaluate the changes in the hardness and adhesion strength in the course of hardening in order to clarify the correlation between these parameters. We expect that the adhesion strength of the resin sheet can be estimated from the measured hardness after the application.
Comparisons of the functions and reliability of man-made and bio-materials were carried out and their life spans and reliability were also discussed. The protection levels of man-made and bio-materials were classified into 20 levels such as the materials themselves, energy consumption and self-protection, based on the materials used in both systems. Although the selection and the passive protection system of man-made goods are superior to those of living bodies, the total reliability of the latter is much better for their active protection and protection against invaders. The lack of these protections reduces the reliability of modern industrial goods. The adaptations by which goods or a living body can be adjusted to circumstances are listed and the short lives of industrial goods are discussed from the viewpoint of the materials used.