178 
PRIMARY 
CHARGE 
FERTILE 
MATERIAL 
FISSIONABLE 
MATERIAL 
(FUEL) 
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"PARENT" 
MATERIAL 
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DISCHARGE 
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ANNUAL REPORT SMITHSONIAN INSTITUTION, 1948 
STEAM 
GENERATOR - 
ELECTRIC 
POWER 
FicurE 1.—Diagram of atomic power plant. 
Atomic Power 
As a preface to a discussion of the 
problems entailed by the use of 
atomic power, the following broadly 
reviews the operation of an atomic 
power plant. 
Figure 1 shows schematically a pos- 
sible atomic power plant. The heart 
of the plant is the nuclear reactor 
which generates heat by the conversion 
of mass to energy. The heat is con- 
verted to electric energy by extracting 
it from the nuclear reactor with a heat- 
transfer fluid which boils water in a 
heat exchanger to make steam for a 
conventional turbine-generator. 
The nuclear reactor must be sur- 
rounded by an adequate radiation 
shield to protect power-plant per- 
sonnel from lethal neutron, gamma, 
and other radiation. The heat ex- 
changer and primary heat-transfer 
fluid probably will need a moderate 
amount of shielding. 
Into the nuclear reactor goes the 
atomic fuel, one of the known fission- 
able materials such as U235, and if it 
is desired to generate new fuel at the 
same time that the charged fissionable 
material is being consumed, a fertile 
material, such as U238, also may be 
charged. A material is called fertile 
when it can be transmuted to a 
fissionable material by the capture of 
neutrons. 
Discharged from the pile are the 
partly burned fuel and the irradiated 
fertile material which contains some 
new fissionable material. Later use of 
the unburned fuel and the new fuel 
both require chemical separation from 
any other structural materials, con- 
tainers, and from the fission product 
wastes. 
An optional phase of operation of an 
atomic power plant is the production 
of radioactive isotopes. This is shown 
in figure 1 as the adding to the pile of 
a byproduct charge of some “parent” 
material such as nitrogen, from which 
a radioactive isotope such as carbon 
(C14) is produced by the capture of 
neutrons. 
PRINCIPLES OF THE NUCLEAR REACTOR 
Occasion frequently may arise for 
reference to some of the nuclear prin- 
ciples of the chain reaction in the 
nuclear reactor. They are reviewed 
briefly in the following. 
Energy is released by the fission of 
the nucleus of a fissionable atom, 
U235 for example. The two nuclear 
fragments vary in the number of 
protons and neutrons contained in 
each. In general, each fragment is the 
