Sunday, March 13, 2011


In Douglas Adam’s own words “the Hitchhiker's Guide to the Galaxy itself has outsold the Encyclopedia Galactica because it is slightly cheaper, and because it has the words "Don't Panic" in large, friendly letters on the cover.”  That advice seems particularly apropos in the week following the Japanese earthquake as we listen to the ongoing nuclear disaster that some would have us believe is occurring in that country.

The graphic above captured from illustrates the problem for those of us in North America and particularly those of us on the west coast of Canada.  Disregarding the two disturbances off the BC coast, the general flow of the wind is east to west from about La Paz and west to east starting at Japan and following the Aleutians around to Vancouver Island.  If something bad happens in Japan the wind is clearly going to bring it to us.  Those of you that are inland are likely OK because the rain will wash it out of the atmosphere as the wind comes over the coastal mountain ranges but those of us out here on the wet coast are going to get the radioactive fallout if the worst happens.

The big question though is what is really going on.  Leaving aside for a minute the distinct possibility that the Japanese government and their nuclear generating companies may be deliberately misleading the media, we are still subject to media misrepresentation and misunderstanding of the situation. 

“Nuclear” is such an emotional word which makes it hard to trust at face value any news report involving the word.  As near as I can tell the shutdown procedures at the reactors worked as they were designed to which means that the rods got inserted to shut down the reaction.  What I don’t completely understand is the physics and mechanics of the process after that happens.  Some talking head was on the radio this morning claiming that “7% of the reaction” continues indefinitely after the shutdown.  That was his explanation of why the core continues to generate heat even after a shutdown but it doesn’t make sense.  If that was really true then you could never stop a nuclear reaction, ever.  And that simply isn’t logical or consistent with history.  We know that reactors have been shutdown and decommissioned so that explanation is either just wrong or so over-simplified as to not be useful to me.

Actually the correct terminology for what happened in Japan is that the reactor was “SCRAMed”.  SCRAM has been adopted in engineering lexicon for any rapid shutdown but the original etymology is Safety Control Rod Axe Man (some sources say “Safety Cut Rope Axe Man”)Originally SCRAM referred to the guy standing above the Chicago Pile (the first nuclear reactor) with an axe.  His orders were to chop the rope holding the control rods out of the reactor if the shit hit the fan. 

According to Wikipedia the post-scram problem is the secondary products of decay which continue to emit neutrons.  Emitted neutrons striking a nucleus are what keeps the reaction happening.  A reaction becomes self sustaining or critical when the emitted neutrons are sufficient to generate new fissions which in turn generate sufficient newly emitted neutrons to split another nucleus.  Fission creates primary decay products which account for the bulk of the by products and much smaller amounts of secondary decay products.  As those secondary decay products live out their half lives eventually their neutron emissions will drop below a critical level which to my limited understanding would be the point where the reaction stops being self sustaining.

What I have gleaned from all this is that when the news reports that the reactor core has been “flooded with seawater”, rather than being the last ditch desperation measure that they make it sound like, it may actually be a very measured and reasoned response to a crisis.  The goal post SCRAM is to deal with those residual neutrons from the secondary decay products.  One way of doing that is to let them live out their brief little half lives until they finally dissipate themselves naturally.  In order to do that the operators need to keep cooling water flowing through the core because it is still generating a lot of heat.  That’s apparently where the talking head’s 7% number came from.  7% is evidently a good approximation of the amount of heat relative to full production in a reactor that has been in continuous service for some extended period of time.  And 7% of an unimaginably big amount of heat is still a lot of heat to deal with.  Since it appears that the backup generators got whacked by the tsunami, running the cooling pumps hasn’t been an option.  Actually it sounds like the cooling pumps worked just fine until their backup batteries went dead.  I can certainly relate to dead batteries, having woken up enough times to a cold RV after my batteries didn’t make it through the night.

The other way of dealing with those troublesome neutrons is to absorb them with something.  And seawater apparently is a pretty good absorbent for recalcitrant neutrons, hence the decision to flood the core when cooling was no longer an option.  So what I conclude out of all this is:

  • If the shit really does hit the fan we’re in big trouble here on the BC coast.
  • The news is as usual a spectacularly bad place to get information from.
  • The plant operators are likely doing exactly what their emergency response plan tells them to do, no matter how hard the media is trying to portray them as being in a state of panic.
  • Douglas Adams was right.  As usual.

(several days later) My brother-in-law just posted this link on his Facebook page.  This is likely as good a source of intelligent information about the situation as you will find.  Concurrently with posting this update I am listening to a news report that Canadian “Health Food” stores are running out of iodine as panic buying occurs.


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