Q2Q- fermi's experiment (1 Viewer)

[freaking_out]

i have trouble with this dot point:

"describe Fermi's initial experimental obeservation of nuclear fission"

i have stuff on fermi, but what was his "initial" obervation?

 

[slyball]

from my notes...
Enrico Fermi achieved the first artificially induced nuclear fission reaction in 1934, although at the time he did not realise that fission had occurred. fermi bombarded uranium with neutrons and produced radioactive products that emitted b-particles. fermi assumed that he had produced a new isotope of uranium, U-239, and that this had undergone beta decay to form an isotope of the first transuranic element, atomic number 93, known today as neptunium-239. when the experiment was repeated in 1938, it was found to everyones surprise that not only was U-239 formed, but various other lighter elements.

 

[walla]

Yes it's a bit deceptive - he "observed" it but misunderstood what he was observing.

 

[Excalibur]

Umm slyball is prob right but as far as i understood that refered to the manhattan project and the reactor with which he actually intended to obserb stable fission

 

[xiao1985]

uhm, but i thought frish and meinter demostrated first nuclear fission???

 

[Viper]

Originally posted by xiao1985
uhm, but i thought frish and meinter demostrated first nuclear fission???

Who the hell are they?

Cheers

 

[Chand]

*Fermi bombarded many elements with neutrons. Doing this he created new isotopes.
*Some of these isotopes were unstable and emitted a beta particle.
*U-238 was bombarded and formed U-239, which underwent nuclear fission when bombarded by further neutrons.

thats all i have.

 

[Takuya]

Grrr do you think we need to memorise these equations? i.e. the fission products along with their mass #s and atomic #s?

 

[Constip8edSkunk]

to put it simply..

fermi did it, didnt recognise it properly
hahn and straussman redid it, didnt explain it
meitner and frisch redid it, explained it

also i dun think U-238 or 239 is fissile, U-238 when irradiated with neutrons will become U-239 which beta decays to form neptunium, and it will undergo beta decay to form plutonium (cant remember the particular isotopes)

U-235, occupying a small proportion of natural uranium is fissile and is what produced the multiple daughter products the above physicists observed


edit: there are many fission reactions that can occur, so i dun think u need to memorise any particular reaction eqn

 

[xiao1985]

ahhh thx Constip8edSkunk, dat dot pt hurts my forehead...... but i dunt fink i can cramp all those 2nite... so yea i am just gonna say that fermi did it all by himself..... =P

 

[freaking_out]

alright so that was the "first observation" dotpoint, in where he just observed nuclear fission, but did not state so???

anyways, what abt. the second dotpoint abt. fermi:
"describe Ferni's demonstration of a controlled nuclear chain reaction in 1942 "....r we meant to talk abt. his mouse trap experiment?

thanks.

 

[Constip8edSkunk]

1st dot pt, i got big discrepancies in sources here, i have 2 text books that says he did not recognise fission.. jacaranda even said that he didnt even perform the experiment and 1 text book that said he observed fission and lighter products but didnt investigate further....

so i think its safe to say that while his neutron irradiation experiment involving Uranium not only led to the transmutation in2 transuranic elements, but the minute concentration of U235 led to fission reactions to occur (although he did not recognise at the time) these products were varying beta decayers which indicated that there were multiple products. Fermi however did not investigate this any further.

Hahn and Straussman repeated this experiment and isolated lanthanum and barium in the products, confirming that lighter products were produce. Meiner and Frisch were able to explain this process by Bohr's water droplet model of the atom: Uranium undergone fission after it is destabilised by the neutron



Also Fermi's demonstration is with the chicago pile, the mouse trap thinf was not controlled

 

[freaking_out]

thanx.