[ RadSafe ] Fast neutron reactors, sodium etc.

[JPreisig at aol.com]

Dear Radsafe,
 
     This is from:    _jpreisig at aol.com_ (mailto:jpreisig at aol.com)    .
 
      Hope you all are well and are enjoying  barbecue season or whatever.
 
      Fall earthquake season is upon us (hurricane  season in the USA 
also):  Sept. 21, 2011
+/- 6 weeks.  Earthquakes (magnitude 7.5 or above):  about  2.  Earthquake 
locations:  Chile,
 Japan, Tonga/Kermadec, Taiwan, Indonesia.  
 
       Back to radstuff.  Bless the  crews of the Scorpion and the 
Thresher.  They gave their all.
Sodium metal in a submarine (surrounded by all that ocean water) would make 
 me nervous too.
Kudos to the Chinese for making that fast neutron reactor work on  land.
 
       So, when fast neutrons hit a hydrogen  atom or molecule, they give 
up much of their 
incident energy.  And when fast neutrons hit sodium atoms (or  something 
equally heavy), they
bounce off the heavy atom and don't lose that much of their incident  
energy.  So, sodium, if
heated somewhat is a good choice for the moderating fluid in a fast neutron 
 reactor.  Still, heating
sodium makes me nervous also.  Do I really want hot sodium metal in my  
fast neutron reactor,
with 95% enriched uranium (enriched in U235) --- do I want such a reactor  
that will be taking
a space crew to Mars or whatever???
 
      How about using another material of similar  heaviness (i.e atomic 
mass) instead???
Mineral oil???  Glass microspheres (SiO2) suspended in some water,  iron 
spheres suspended in some
water, any other suggestions????  I suspect mineral oil is a bad  choice 
because it will or could
break down upon neutron irradiation???  Can glass and/or iron small  
spheres remain in suspension
in water and also be pumped through a reactor primary loop (a pipeline as  
it were???).
Clearly, you need more glass or iron in such a slurry to keep the fast  
neutrons fast???
 
      Someone having MCNP (Monte Carlo Neutral  Particle Program} handy (or 
someone willing to
do a crude hand calculation) could probably tell us if alternatives to  
sodium metal would work.
Otherwise I'll eventually get to this problem via a big money research  
grant (guffaw and snickering
noises go here???). 
 
     Whose bright idea was it to drill holes in the  FFTF reactor core???  
Guess we'll have to buy
or order a whole new reactor.  Oh, don't let me leave out you  experimenter 
types out of all this.
Put a glass slurry in your small lab reactor and see what happens.
 
     As for the fusion people and/or migma people, the  NSTX, ITER etc. are 
plenty big and energetic.
The D,D  and D,T fusion reactions occur at 50 to 200 keV.  People  with 1 
MeV Van de Graaff's
around can work on fundamental fusion studies instantly (see my radsafe  
postings on warm
fusion).  Also many physics departments have 200 keV accelerators  around 
that are usually
used for ion implantation.  W. Michigan U. still has a 6-12 MeV van de  
Graaff.
 
      Or if you are all for library and/or web  searches, you can look back 
into when the original 
fusion studies were done and what the results were.  Some academic  posters 
on radsafe
(not radsafe lurkers!!!) may actually remember when such fusion studies  
were done.
 
     Guess I'd better dust off my copy of MCNP and get  back to work.
 
     Have a good week!!!!       Joseph R. (Joe) Preisig, PhD