128 
Let me recall that in the uranium fission only 0.1 per cent of the 
mass of the uranium disappears when it is converted into its product 
nuclei. It would be optimistic to suppose that anything like this 0.1 pe 
cent is fully utilized. We know by burning coal in a suitable calorime 
ter how much energy it is possible to get out of a pound of coal. Mo- 
dern power plants deliver in the form of useful energy only about 30pe 
cent of the energy theoretically possible from the fuel. Engines made 
by James Watt two hundred vears aoro wprp far Ipos 
that the first atomic bombs exploded maj 
Watt stage of atomic energy and that, as 
efficient. It is 
one must gei an mcreasmgly larger fraction of the energy 
available. This could be the interpretation of the guarded i 
that the bombs exploded at Bikini were more effective than 
bombs . 
I have mentioned that the separation of the isotooe U-2; 
have the same 
easily separate 
suspected that 
tastically difficult job, far more difficult than any 
This led to the search for an element which might 
It was 
had seen, could be manufactured, and might well have the same fission 
properfaes as U-235. Plutonium is made by bombarding U-238, the 
pienniul isotope of uranium with neutrons. The Washington University 
cyclotron played a large part in producing the first bit of Plutonium 
Dig enough to be seen. Large quantities of uranium were placed close 
^PT^%T ?• , '^^ machine was set up to deliver neutrons, and these 
rnH nf fi, ""f"^ .^^"^^^^ ^^^"^ 'o'l'- hours a day, week after week. Atthe 
r^r^ ;>, "^ bombardment, a chemical procedure was used to sepa- 
held ^!«^''k1'°'''^*^'* ^^^*°^i^ ^'•oni the Uranium. Less than a pin 
buMt^^« i' "" w^*^*" ^^1 ^i^ ^°rk, the term "pinhead" is Smyth's, 
hpL Jo, ?°?^ ^^'^ ^^ chemists to verify that this "less than a pin- 
head of Plutonium" had the d^siT-oH « — «-*/^„ rpu„ 
i properties. The next step was 
Hanford, Washington to produce 
7 ""6^ •'-luionium plant at 
T, "l!*"^ ^^<l^ired amounts, 
make an 0^0^^''^^^' ^'^^^ ^"«^ P^» have the qualities necessary to 
s^n procef s C^"""^' ^""''^ '^ '^'^^'^ ^ ^^^^ of them by a fis- 
the Dr^urt t..! ^"^'"^ '^ released because the combined masses of 
loss L m^^r ^^\r^ ^^^^ "^" the mass of the parent nucleus, and the 
cZSS^cU.n^ " '^' °"ly 0-1 P" cent of the total mass, ac- 
KS^ago ^ ^^ '"^^^ evolved, as Einstein's theory predicted 
into^el^^^n^i' ^ "^'^^^ ^° emphasize again tiiat the conversion of ^f 
^re To^SyZ^lT" "^ ^-'^^ orPuisa very exceptional thing. There 
two S of U A. °P.^'t.^°^°^S ^^ 'pearly 100 elements. Only in fte 
e^erS bv I ch'J! ^^t^"" ^^ '^ been possible to convert mass into 
u^fau?- >, "^.^ Y^^^tion and this is because these two isotopes are 
^^^L^^"""^^ ^^ property of being fissionable bv neutrons and pos; 
. - -r *^o axi ui wni 
release nuclear energy 
properly used just make 
