Super Safe Small and Simple nuclear reactors for Japan?

Japan needs massive amounts of new power fast. Those damaged nuclear facilities will probably never come back online. Toshiba’s 4S (Super Safe Small and Simple) reactors are 10 MW each, buried in the ground, can survive an 8.9 earthquake, and appear to be quite safe. Obviously, they would need lots of them. The huge advantage here is they can be installed quickly.


4S’s are fueled at the factory, put in place to run for 20 years then returned to the factory for refueling. They are sodium-cooled and pretty darned impossible to melt down. If the cooling system is compromised they automatically shut down and just sit there in a block of sodium.

The biggest problem facing the 4S has been regulatory approvals, which would normally take in aggregate 100 times as long (and cost 100 times as much) if done the same way as a larger nuclear plant. That’s where this earthquake will probably change everything, at least in Japan, where the process will be streamlined almost to nothing with a 4S soon stashed under every power substation giving Japan a smart grid in the process.

Massively distributed power via 4S reactors everywhere means the grid would be able to withstand shocks to one part of the system much more robustly.

While many have qualms about nuclear power, Japan needs to find new sources of power very quickly. A highly industrialized nation simply can not allow rolling blackouts to go on for years.

From the comments to Cringeley’s article.

My inlaws in Tokyo are staying home today from work because the trains being run are going to limited due to the loss of power from the Nuclear plants. If Bob is right about the 4S reactors, I expect that a few will be deployed within 60-90 days at the outside with a testing period of 60-120 days. If they pass the test, expect wide-spread deployment just north of Tokyo (for Tokyo) and the Tohoku area to power the recovery process.


  1. Gee. What could possibly go wrong with a bunch of small nukes buried everywhere? Earthquakes, digging, water table intrusion, rot. How can Japan possibly guard all those nuclear sites from theft by terrorists (or profit-seeking cartels, or curious idiots)?

    You’re the big cheerleader for alternative energy, Bob. How about solar farms? Wind farms? Japan *is* an island, after all … why not tidal power?

    Please understand that the nuclear industry will say anything to justify its existence … including a recent statement I read that a small amount of nuclear radiation “is not harmful because the cells will heal themselves.”

    To which I would add … unless your cells *don’t* heal themselves, in which case, you’re dead from cancer. What’s the chance? … oh, gosh. They don’t say. They don’t know. Sounds like a big gamble to me.

    • The source for this is Cringely, a well-known tech journalist who has a serious nuclear background. He tends to be quite reliable.

      The only reasons they might go with mini-nuclear now is it can be installed fast. Wind and solar would take much longer. They need power now.

  2. “They are sodium-cooled and pretty darned impossible to melt down.”

    Almost sounds like satire! Sodium isn’t very reactive, right? I can’t imagine anything going wrong with that.

    This a time when many of the things the nuke industry promised could not happen, are happening. The promise of new nukes with “streamlined approval” does not increase my comfort level.

    • I hear you, however I’ve read Cringely for years and he tends to be quite reliable. And he’s not in the nuclear industry any more nor seems an apologist for it. In his first post about it, he slammed Japan’s response, saying they were less than truthful, and predicted those reactors would never be operational again.

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