-i1- 
Fuel Arrangement: A second distinguishing feature is the fuel 
arrangement. The original and most developed type is the heterogeneous 
reactor in which fuel, moderator, coolant and fertile material are separated. 
A second type is the homogeneous reactors; in this system fissionable and 
fertile material are intimately mixed with a coolant and a moderator and 
circulated through a geometrical shape that will sustain a chain reaction 
in one section of a loop while removing heat with a secondary coolant in 
another section. 
Figure 6 illustrates a heterogeneous natural uranium graphite-water 
moderated, water cooled reactor. Figure 7 shows an aqueous homogeneous 
reactor which uses yo? fuel, has a thorium blanket and is heavy water 
moderated and cooled. The natural U reactor in Figure 2 illustrates the 
type of reactor used for Pu production and can be considered as the principle 
producer to date of fission product wastes. ; 
Heterogeneous reactors for mobile power, which use ue? as fuel, usually 
require a fuel element in which a metallic diluent is added to the uranium 
to provide adequate surface for heat removal. As will be shown later, this 
inecactive diluent plus a cladding material add large quantities of salts to 
waste solutions, thus materially increasing their volumes. 
Relation of Fission Products to Reactor Power 
Every time an atom of ue? fissions about 193 mev of energy are re- 
leased. Of this only 185 mev appears as sensible heat in a reactor. The 
principle energy is given off as kinetic energy of the fission products. 
The energy produced in the fission process can be related to the fission 
products by defining the decay energy after discharge from the reactor. 
Using y3? as the fuel, a theoretical calculation can be made in the 
following manner: 
DECLASSIFIED 
