U.S. Reactor Containment Technology: a Compilation of Current Practice in Analysis, Design, Construction, Test, and Operation, Volume 1 Page: 1-38
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Containment pressure requirements are not great if air is excluded
from the alkali-metal systems. This is accomplished at the Hallam Reac-
tor by locating the reactor vessel and radioactive sodium heat transfer
system in shielded compartments below the reactor room floor. A nitro-
gen atmosphere is maintained in these cells. The reactor building at
Hallam utilizes the negative-pressure containment concept. The capability
of using this concept indicates that the containment problem for this
type of reactor is less severe than for some other types.
220.127.116.11 Fast Reactors
Fast reactors must use liquid metals or other nonmoderating coolants
because of the moderating effect of either light or heavy water. Sodium
or sodium-potassium mixtures have been used exclusively, although gas
coolants are being considered. The excellent heat transfer properties
of the liquid metals are exceedingly valuable, since the core of a fast
reactor is usually small and as a consequence has limited heat transfer
The equipment is much the same as that required for a liquid-metal-
cooled thermal plant. Again it is necessary to use two heat transfer
systems so that the highly radioactive primary coolant will be separated
by an additional barrier from the steam system. There are fewer than ten
fast reactor systems operating throughout the world.
It may be possible to design fast reactor systems so that the nega-
tive pressure containment concept can be applied. However, high-pressure
containment is being used for the current fast reactors. The design basis
has been that of a severe nuclear excursion resulting from fuel element
meltdown. This excursion might assume some of the characteristics of a
TNT explosion, 40 producing high pressures and shock waves.
1.3.3 Gas-Cooled Reactors
Gases such as helium and carbon dioxide are used as reactor coolants.
In the gas-cooled concept shown in Fig. 1.7, the reactor heat is removed
from the fuel by the gas and is transmitted to a heat exchanger where
steam is generated to drive the turbine. The use of a gaseous coolant
allows attainment of high temperatures without the high pressures associ-
ated with water-cooled systems. The gas-cooled reactor has been popular
in several countries other than the U.S. because it can be designed to
use natural uranium as fuel. In fact, 33 gas-cooled power reactors, over
75o of the gas-cooled reactors in the world, are located in the United
Kingdom and France.
Graphite-moderated gas-cooled reactors, because of the nature of the
coolant, have, in general, less stored energy than pressurized-water re-
actors. It is possible to design gas-cooled reactors so that the after-
heat can be removed by natural convection. There are potential hazards,
however, because of the storage of Wigner energy in the graphite at lower
temperatures and graphite reactions with air and water at higher tempera-
tures. The former problem is usually avoided by designs that maintain a
graphite temperature at which Wigner energy releases do not present a
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Cottrell, William B. U.S. Reactor Containment Technology: a Compilation of Current Practice in Analysis, Design, Construction, Test, and Operation, Volume 1, report, August 1965; Oak Ridge, Tennessee. (https://digital.library.unt.edu/ark:/67531/metadc101033/m1/66/: accessed March 18, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.