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SUMMARY AND
The Aircraft Heactor Experiment
isec. 1) is now well into the transition
period between design and reality.
The design is essentially complete,
almost all the components areonorder,
end a substantial number of these
have been received and installed in
the ARE rjuilding. The significant
modifications during the past, quarter
include cornplet,ion af the off-gas
system design (incorporating holdup
tanks rather than charcoal adsorbers)
and the inclusion of a reactor hy-pass
(so that the fluid circuits may be
checked out independently of the
reactor). Coincident with the completion
of the reactor design, the
Aircraft Reactor Experiment Hazards
Summary Itspor t, ORNL-1407, was submitted
to the AEC for approval. It
is anticipated that even though the
experiment may be completely assembled
by the summer of 1953, a significant
and indeterminant period will be required
for shake-down operation before
the reactor becomes critical.
Val v e s , p ump s ,
i ns t rumen t a t i o n I
and other components of both the
fluoride fuel (NaF-ZrF4-UF, , 50- 46- 4
mole 7%) and reflector coolant (NaK)
circuits are being developed for the
Aircraft Reactor Experiment (sec. 2).
In most, instances, these components
have been tested on smaller than full-
scale prototypes of the actual ARE
components. Tests are now under way,
however, on the full-scale pumps,
valves, and some instrumentation
designed for the reactor experiment.
At this time, centrifugal pumps with
both gas seals and frozen seals have
operated satisfactorily for extended
periods at temperatures between 1280
and 1500°F. A combination packed and
frozen seal has been specified far
the ARE pump. Although a bellows type
of seal has been specified for the
ARE, a considerable program has been
undertaken on high-temperature, self-
lubr ic at in8 seal s.
INTRODUCTION
The rotameter type of flowmeter
and the modified Moore Nullmatic
pressure transmitter havebothoperated
satisfactorily at high temperatures
(-140OOF). Neither of these instru-
ments is affected by the ZrF, vapor
above the fuel. Vapor traps of the
type that will be required in the gas
system above the fuel surge tanks have
been satisfact,orily developed.
The heat transfer coefficient of
an aircraft type of sodium- to- air
radiator, in which the radiator fins
were sectioned every 2 in. i n the
direction of air flow, was increased
20% over that of the same radiator
with plain flat fins.
The general design studies Isec. 3)
were confined to performance analysis
of a Sapphire turbojet: engine in which
the engine radiator performance was
extrapolated from a sodium-to-air
radiator section tested at ORNL.
Performance data for both the radiator
and engine are presented. Arrange-
ments have been completed with the
Wright Air Development Center for
their participation in the development
of high-temperature liquid-to-air
aircraft radiators.
The several reactor physics studies
(sec. 4) include those of oscillations
in a circulating fuel reactor, a
technique for reactor calculations,
and the temperat ure-dependence of a
cross section exhibiting a resonance.
The damping influence of fuel circula-
tion has been demonstrated even when
the earlier assumptions are replaced
by more realistic conditions. With
regard to reactor calculations, it is
shown that the slowing down of neutrons
in parallel slabs of materials with
different properties can be described
in some instances by a set of images
of the original neutron source.
Critical assemblies of both the
Aircraft Reactor Experiment and a
ref 1 ec to r -mode rated re actor have been
tested (sec. 5 ) . Critical mass,