What was the principal nuclear reaction of Fermi's nuclear pile

[Villhelm]

I've known about the basic story of the first nuclear pile since before I can remember, but never found information on what the associated nuclear reaction actually was and was wondering if anyone here knew or could point me in the right direction.

 

[mathman]

The reactor fuel was Uranium, so I presume the reactions would be the same as any Uranium reactor.

 

[cmb]

From various sources, etc., as far as I have pieced together the following should address your question (and related factoids) regarding the first reactor pile, CP-1. (I trust I will be corrected if any of these have come from inaccurate sources.)

Principle reaction = Absorption of slow neutrons by U-235 in un-enriched uranium.

Fuel used = 40 tons of un-enriched uranium dioxide pressed into 17,000 'pseudospheres', plus 6 tons of "Spedding’s eggs", uranium metal in cylinders of 2 1/4" OD x 3" long.

Moderator = 4,000 x 6 lbs ultra-pure graphite blocks, drilled with holes to take the above uranium, plus a further 300 tons of graphite in layers.

Control rods = cadmium.

Safety moderator = buckets of boric acid to be poured in from above

Power output = 0.5 W