If Japan Had Bought CANDU REactors, Would They Be IN Better Shape?

All of the reactors that were destroyed by the tsunami (and subsequent failure of the cooling systems) were GE Mark-I design reactors.
This was a design from the 1960’s, and is in se around the world, so it must be a pretty reliable syste,
Wold the Canadian “CANDU” design reactors have behaved differently (under these conditions)? Or would any reactor design have the same issues , when the emergency cooling systems fail?

Yes. In CANDU reactors, if the heavy-water moderator drains away from around the fuel tubes, the reaction stops. The primary coolant is also heavy water.


I don’t know. In a Candu Reactor, as noted above, if you loose coolant it automatically shuts down, which is a good thing. But the Japanese reactors were easily and successfully shut down, so that advantage doesnt mean anything in this particular case.

The real question is, how does a Candu reactor behave when you can’t cool it properly, but its been shut down?

Good question.

Well, at least 3 of us think so :slight_smile:

I am having some vague recollection of they are better in this regard somehow but I cant quite recall it. Or if its more of just better engineered/designed, or some fundamental difference in the general physics of the things.

I don’t know about the CANDU reactor, but some modern reactor designs such as the AP1000 are designed such that the decay heat will be cooled through completely passive means if all power is lost after a core shutdown.

Oh, I think I now remember the big advantage of Candu. They can run off regular uranium ore. Given that enriching uranium is a PITA (and can lead to nuclear weapon proliferation), its a significant advantage. A downside is heavy water is pretty expensive, so that adds to your capital costs to build the reactor. But this doesnt have anything to do with safety or emergency cooling.

Its been a long day and my brain is working at 10 percent right now so take everything I say with a grain of salt.

It seems to be a much safer design…

The proliferation of the Mark I design is based more on cost than reliability. A former GE engineer resigned early on because he did not believe the design would survive a catastrophic event. It now appears he was correct.

I believe CANDU reactors can use non-enriched uranium as someone else has suggested. The heavy water slows down the neutrons so that even non-enriched uranium can reach a critical state.

While I can’t say anything about the radioactive byproducts that might build up over time in the fuel, I would assume that the non-enriched uranium isn’t nearly as dangerous when things go awry as it’s pumping out much less radiation.

This is what I remember from my basic understanding, but since I’m not a nuclear engineer I can’t really say.

Not significantly, no, it wouldn’t have made much of a difference. No matter what reactor design they used, they’d still have all of the death and destruction of a magnitude 8.9 earthquake.

I know what you are getting at; but it still would have been nice if the reactors had been able to shut down in a less self destructive fashion instead of becoming expensive scrap metal.

What’s the most recent economic estimate of loss? I heard around 100 billion. A new nuclear plant costs 5-20 billion. So if up to 20% of the losses due to this earthquake are due to the destruction of this one plant, then perhaps a CANDU reacter would have actually significantly reduced their losses.

Even a completely safe plant might still have been trashed, though. It’s like the old saying, “Any landing you can walk away from is a good one… And in a great landing, you can re-use the plane”. Just because something won’t cause any deaths, doesn’t mean that there won’t be any monetary damages.

But it seems likely it wouldn’t have been trashed as bad. If they hadn’t had to flood the interior with seawater, if there hadn’t been melting of internal components perhaps they could have repaired the plant, or at least the fuel might be salvageable. And the fact that they weren’t outright wrecked but just badly damaged enough that they underwent irreparable damage only after the main disaster was over implies to me that a safer design might well have only suffered repairable damage.

I got a reactor here, its name is Point Lepreau,

And here’s a guy who says the design is new,

CANDU, CANDU, the reactor is a CANDU…