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

The second end piece 5 fixes the fuel element to the lightweight
diaphragm 9 of the reactor.
The shell of the fuel element is the most loaded element in
the reactor and, consequently, in the entire power plant. The shell
operates under the highest possible temperature. It is subjected
to the action of gas forces arising as a result of uranium fission.
Gaseous fission products can collect under the shell. If the reactor
has various alternating modes of operation, this leads to cyclic
loading of the shell.
The fuel element unit of a thermal reactor (Fig. 2.7b) includes
end piece 1, part of end reflector 2, and the fissionable material
3.
Depending upon the heat-transfer agent and the temperature of
the fuel element, the end pieces are made from stainless steel,
for e~ample, Khl8N9T, molybdenum, niobium. The reflector can be
beryllium oxide, beryllium; the fuel in a homogeneous reactor can be
a blenid of uranium with graphite, beryllium oxide, hydrides.
A fuel element, thus, is a structure of various materials
assembled into one unit. A connection between the separate elements,
the steel end pieces, and tho outer shell, if there is one, is
accomplished by welding or soldering.
The fuel elements form the core of a homogeneous reactor. The
end piece 1 in the form of a tube then becomes hexagonal, which
ensures a tight fit for the core. The heat-transfer agent passes
through the openings inside the fuel element or between the uni's.
The fuel element is welded to the load bearing panel 4 through ring
5, providing a uniform wall for the welded parts. The second ring
of the fuel element rests on a diaphragm 6.
102