`Nuclear reactor bolt failures`

With experience you can tell a lot about the fracture of broken bolts. Back thirty years ago a nuclear reactor had a problem on some of its bolts, and I was working for a test lab — early 80s — and they said, we're going to send you a bolt, and we're not going to tell you anything about it. We want to know what you can tell us just from looking at it. They sent it, I looked at it, and I said: low cycle fatigue, moderate nominal stress, variable amplitude loading — because some of the fatigue cracks had different widths, telling you how fast it was growing. And it was operating at 600 degrees Fahrenheit. They were all surprised. You get blue coloring where the temperature was not uniform with time. Blue coloring in steel — they sometimes call it blue brittleness in carbon steels, but the temper colors. The steel forms a blue oxide around 600 degrees Fahrenheit; you can look it up on the internet. So I knew the temperature, in some cases I could see the different striations and the variability, I could tell the size of the high nominal stress, and I told them it didn't have a stress concentration — just by looking at the fracture. Sort of like reading tea leaves, except it's knowledgeable tea leaves.