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Nuclear Reactors

 18 Mar 2011

After the earthquake when the news stories reported the nuclear power plants went off line and then didn't have electricity to keep it cool I started to wonder if it could be possible to design an emergency back-up power system that would kick in using the pressure build-up of the containment vessel.  Last week I learned via NPR reporting that the heat  from the spent fuel rods in reactor 4 would break down water into hydrogen.  This got me wondering if spent fuel rods could be used for large scale hydrogen production.  

First let me plug NPR again.  America has no better media outlet to go to if they want to be educated about the issues of the day. Back to the main thoughts

It appears nuclear power plants use water to keep the fuel rods cool.  In order to keep the water cool there is some sort of radiator or refrigerator system to circulate the water.  This water cooling system uses electric pumps.  Without the electricity the water doesn't circulate and heats up.  Reporting of the first couple days makes it me believe there is a relief valve that initially released steam and kept the containment vessel from exploding.  However, this somehow produce the right conditions that when the remaining water heated up it actually caused the water to break down and produce hydrogen (I'm not really sure where the oxygen goes).  At this point the pressure builds up too fast for the relief valve or the oxygen combines with (or starts on fire) what is inside the containment vessel and explosions occur.  The first thing I wondered was if it was possible to design the containment vessel to use that pressure to pump water in and out of the containment vessel.

The next thing I found interesting was reactor 4 wasn't even active when the earthquake hit.  The rods that were in that reactor were in a cooling period.  It appears they need a cooling period that lasts almost a year.  Even these rods produced enough heat to break down the water.  A quick internet search and I found a DOE site the mentions hydrogen production using nuclear power.  In fact the nuclear hydrogen plan was published in 2004.  But this document seems to be considering designing new nuclear plants so they are capable of producing hydrogen.  This seems like an alright idea but I wonder if it might not be economical to design the spent fuel rod storage facilities in such a way that hydrogen is produced.  This type of development seems like it should be a lot cheaper than creating dedicated nuclear plants for this task.