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View Diary: How Radioactive Is the Ocean? (100 comments)

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    Roadbed Guy
    I looked up your old diaries and saw one on modular reactors. That seems a much better idea than the current chaos.

    There are many people who think so these days. In my diary, I was just reporting the latest news. I'm hopeful that the idea of small modular rectors can get off the ground and make a substantial impact, but I'm not a fanatic. I just want the technology to work, and I'm open to any good ideas, should they pan out.

    The unit you described was light water. Why not D2O? I'm no expert, but doesn't the much better moderation (much less neutron absorption) allow less-enriched fuel?

    Yes, you are correct, and this is why Canada decided to go with their own technology of Heavy Water Reactors (the CANDU's), rather than purchase Light Water Reactor (LWR) technology from the US. The Canadian government realized that it would be easier for them, at the time, to produce heavy water than it would be to enrich uranium, an energy-intensive process, so that's the route they took. The CANDU design had other advantages for the Canadian infrastructure of the day as well, such as not requiring large forgings for a pressure vessel.

    It is a clever design, but as with all engineering efforts, there are tradeoffs. Compared to the light water reactor, Canada's heavy water reactor has certain advantages and certain disadvantages. I can't say that one is clearly superior to the other.

    And doesn't that give a better safety margin if there's a loss of moderator/coolant?

    Well, one of the disadvantages of the CANDU design is that most of the moderator is held in the calandria (a separate vessel). Thus, if you lose coolant, the moderator stays put, unlike a LWR, where the coolant is the moderator, so if you lose one, you lose both.

    If there are going to be a lot of modules around, it makes sense to do it as well as possible from the start.

    Well, that's one of the things that the designers of SMR's need to work out: what is the best way to cluster these modules to build a substantial power plant if that's what's wanted? There are people working on this today.

    An idealist is one who, on noticing that a rose smells better than a cabbage, concludes that it will also make better soup.
    -- H. L. Mencken

    by bryfry on Thu Jul 07, 2011 at 07:36:16 AM PDT

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