The corrosion problem has been blown way out of corrosion, and I suspect, you're confusing it with the graphite swelling problem. Pure nickel won't corrode in

The corrosion problem has been blown way out of corrosion, and I suspect, you're confusing it with the graphite swelling problem. Pure nickel won't corrode in fuel salt, so to a first approximation, Hastelloy N works fine and lasts forever. Chromium is dissolved superficially, but this process is self-limiting. Two more corrosion mechanism were identified: some nickel transmutes and releases helium, which migrates to grain boundaries, and the fission product tellurium reacts with the metal. Solutions for both problems were identified by 1974, but never tested, because the MSR program was terminated. What is more likely to limit core life, is the graphite. Graphite, when irradiated, first shrinks, then swells. MSBR had a very complicated core made of precisely manufactured graphite pipes. These would crack and deform, and then they need to be replaced. Everyone who is considering a graphite moderated core seems to plan for a long life of the pot and a four year life of the graphite inside it. Copenhagen Atomics plans to use heavy water for moderation, so there is no graphite to worry about.