Alan Cottrell: Magnox metallurgy

Alan Cottrell discusses discovering a metallurgical problem with the Magnox nuclear reactor design.

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In 1955 I was invited to go to the atomic energy establishment at Harwell, which I accepted, ‘cause I thought that they would have national problems there which fell into my field, and I was right. They were designing the Magnox reactors in those days, Magnox reactors for electricity production, and the uranium field rods were arranged to stand vertically, one above another, and they relied on the solidity of the metal to stop it bottling. But I – I predicted, and then I proved experimentally, that while it was being irradiated, the uranium, although it would remain solid, would behave actually as if it were a stiff liquid, like pitch, you know, pitch is a stiff liquid. ‘Cause of that it would gradually buckle and hit the sides of the channels and stick there and that would ruin the reactor. I calculated that the reactor would last two weeks before that happened, only two weeks, yeah. Well, they had to redesign it then, design the reactor so that – to support the uranium so that it was the supports that carried the weight, not the metal.

Did you do any experiments along the way to help you discover this would be a problem?

Yes, yes, that was – had all sorts of difficulties because – I had few facilities at Harwell and I had to irradiate uranium and then measure its distortion. And I did that by making uranium wire in the form of spring with a little weight on the end, all sealed up in a vacuum. Held it into the reactor on the end of a fishing line [laughs], my trout fishing, and then we could only look at it via mirrors because it was ferociously radioactive when it came out, of course. So we measured – with a theodolite onto a mirror onto the thing, so measured the increase in the spring length. That’s how we did that. It was a difficult and ingenious experiment but it worked, yes [laughs].

  • Interviewee Alan Cottrell
  • Duration 00:02:12
  • Copyright British Library Board
  • Interviewer Thomas Lean
  • Date of interview 3/15/2011
  • Shelfmark C1379/46

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