Design and Stress Analysis of Extraterrestrial ... - The Black Vault

other conditions being equal, the charge of fissionable material
is less. To moderate the neutron from the energy which they have
during fission (-2 MeV), moderating material (a moderator) is used
for example, hydrogen, which contains material mixed uniformly in
the core or separately from the fissionable material.
Reactors on Intermediate neutrons have a number of disadvantages
and advantages somewhere between the two previous types of reactors.
Thermal and intermediate reactors are divided into. homogeneous
and heterogeneous based on the principle of the core layout.
Homogeneous reactors have a moderator which is uniformly mixed with
the fissionable material; in
heterogeneous reactors the moderator
and the fisslonable material can be in different phases in the core.
BaseP on the physical state of the heat-transfer agent, reactors
are divided Into those with liquid and those with gas heat exchange.
Reactors in which the heat-transfer agent passes from liquid phase
to vapor phase are called "boiling." Reactors with liquid and gas
heat exchange are divided, based on the working medium's pattern
of motion, into direct-flow and loop reactors. In direct-flow
reactors the heat-transfer agent moves in the same direction in all
sections of the reactor. Communications, in this case, have a simple
form; the reactor is comparatively simple in construction. In
reactors with loop (or counter-current) flow the heat-transfer agent
is first used for cooling the housing of the reactor and then enters
the core. The loop pattern is sometimes determined by the location
of the reactor in the power plant.
Based on length of operation, reactors are divided into longuse
and relatively short-use reactors.
In addition, based on the character of the contact between the
wo:iking medium and the surface of the fuel elements of the core,
reactors are divided into reactors with solid, liquid, or gaseous
fuel element surfaces. The last two types of reactors allow the
working medium's temperature to rise beyond the limits of solid
state. However, they have r-t gone beyond the experimental or
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