Nuclear energy for the third millennium Page: 4 of 14
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two hundred meters underground in loose and dry earth. The reactor is designed to
function for thirty years, delivering electrical power on demand up to a level of
thousand electrical megawatts. From the time that the reactor is started to the time of
its shutdown thirty years later, the functioning is to be completely automatic. This is
an obviously difficult condition to fulfill. The most important factor in making it
possible is to design and operate the reactor without moving mechanical parts.
At the start, the reactor functions on thermal neutrons within a structure
containing uranium enriched in U-235 or having an addition of plutonium. That part
of the reactor is to deliver energy for approximately one year after which a
neighboring portion of the reactor containing thorium has been converted into Th-233
which rather rapidly decays into fissile U-233. This part of the assembly works on
fission by fast neutrons. It will heat-up if insufficient thermal energy is withdrawn
from the reactor's core, under the negative feedback action of engineered-in
thermostats. Indeed, these specifically designed thermostatic units absorb neutrons-
if excessive reactor core heating occurs-in order to decrease heat generation and to
act like automatic control rods. These units will be described below.
After the thorium in a given volume of the reactor's fuel charge is depleted, an
adjacent thorium-containing portion of the fuel charge will have been converted-
bred-into fissile material and is ready to continue the reaction. A schematic
representation of this concept is shown in Figure 1. Actually, the thorium "reactors" in
this Figure will be merged together into a single reactor system with the nuclear fuel-
burning reactions propagating down to the ultimate "reactor" U. (In practice, we
consider placing the fuel-igniting charge in the middle of the reactor system's "fuel
stick" and arrange breeding regions on both sides, shown in Figure 3.)
After all the thorium in the reactor's fuel charge has been used up, the reactor is
shut down by the first positive action of the operators in thirty years. The residual
radioactivity will be sealed within the reactor's core and thereafter allowed to decay in
place. The initially intense radioactivity will leave the reactor products inaccessible
and unusable for military purposes except if complicated, expensive and easily
observed large-scale operations are performed. Having thereby avoided
transportation of fission products and reprocessing significantly reduces cost and
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Teller, E. Nuclear energy for the third millennium, article, October 1, 1997; California. (digital.library.unt.edu/ark:/67531/metadc679862/m1/4/: accessed January 22, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.