Quote:
Originally posted by beepbeep
Certain graphite moderated designs have so called "positive void coeficient", but my question was about use of intermediate cooling medium.
I took some classes in nuclear energy physics, just for fun, so I still have interest left :-)
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I almost wish I did nuke power for fun, rather than profit. It's a lot more fun when you're not doing it for real.
US design reactors don't generally use an intermediate heat transfer substance. Typically, the moderator is the coolant, per se. You might expect to find a standard two loop design like you'll find in your college textbooks on a submarine -- the primary loop is both coolant and moderator, and supplies heat to the secondary, which is the steam that drives the engines and turbines.
Having taken some nuke classes, that's what I'd expect to find, but because it's classified, I can't obviously tell you what we actually have. (In all seriousness, there are a number of reactor design issues that affect sound propogation, which is way more secret than the nuclear props of the reactor). Graphite, as you know, has great heat transfer chars, but stupid nuclear properties, so American plants don't generally use it. There's other substances that are a lot cheaper, more readily available, and don't have the bizarre chars of graphite.
There are, btw, several notable exceptions to any of the standards. One prototype plant used liquid control "rods" for a while. There were big drain holes at the bottom of the core, and in the event of an emergency, the reactor would be "flushed," rather than "scrammed." I was waiting for someone to connect a dangling chain (a la vintage outhouse) to the scram switch.
Dan