Stainless steel

When stainless steel is used as a structural material for the core of fast neutron reactor, neutron beam induces a nuclear reaction (n,α) with it to cause various helium damages including expansion, density decrease and embrittlement. A stainless steel largely saved from the helium damages is obtainable by preparing a Fe-Cr-Ni alloy having a small impact cross section in nuclear reaction (n, α). This can be realized by combining iron 58, chronium 54 and nickel 62 (each having the smallest cross section) or at least by excluding iron 57, chromium 53 and nickel 61 (each having the greatest cross section) from the starting material of the alloy. The stainless steel thus obtained is valuable as a structural material for use in neutron reactor and nuclear fusion reactor. In one example, a 18-8 stainless steel was prepared by combining iron 58, chromium 54 and nickel 62, isolated by the conventional ion exchange process, in a proportion of 74:18:8. The alloy obtained was identical with usual 18-8 stainless steel in tensile strength and elongation at varying temperature. After a simulate neutron irradiation (irradiation with helium ion followed by heavy ion) corresponding to 1x1023 n/cm3, volume expansion was found to be 0.1% in the sample of the invention, whereas it was 4% in usual 18-8 stainless steel sample. (Kaichi, S.)