An apparatus for separating a gas from a liquid but truly suited for use in a zero gravity environment. The apparatus includes first and second closed vessels each of which are separated into a gas and liquid zone. The first vessel is separated by gas de-entrainment means and the second vessel by a plurality of elongated passageways for capillary containment of a body of liquid. The passageways provide the sole source of fluid communication between the gas and liquid zones. The gas zones of the first and second vessels are in fluid communication with one another as are the liquid zones of the first and second vessels. Means are provided for introducing a liquid containing entrained gas into the first vessel for impingement upon the gas of the entrainment means such that the liquid passes through the de-entrainment means and flows into the second vessel and the entrained gas is separated and flows into a gas storage space of the second vessel displacing the body of liquid metal contained in the passageways in said second vessel. The apparatus further includes means for withdrawing liquid from a liquid zone of the second vessel which has been freed of any entrained gas. The apparatus is particularly suitable for use in the separation of tritium and helium from the lithium coolant of a nuclear reactor.

BACKGROUND OF THE INVENTION 
The present invention broadly relates to the separation of a gas from a 
liquid. It particularly relates to an apparatus for the separation of a 
noncondensable gas from liquid metal in a zero gravity environment. 
There is currently a major, combined effort being made by certain 
government agencies to develop a high-power, light-weight nuclear reactor 
power source (SP-100 Reactor) for use on future spacecraft. The program 
will require the resolution of numerous technological challenges. One of 
those challenges will be to provide a means for removing tritium and 
helium gas from the reactor coolant. 
The SP-100 Reactor utilizes liquid lithium as the reactor coolant and heat 
transport medium. Under neutron irradiation (which occurs inside the 
reactor core) lithium fissions into tritium and helium atoms which form 
molecules of gas. The amount of gas generated under such circumstances can 
be reduced by using lithium which is enhanced in the isotope Li-6; 
however, even Li-6 fissions at a rate such that approximately one liter of 
gas would be generated in the coolant per year of operation at 100 KWa 
(net). This gas must be removed and maintained separate from the coolant. 
If it were allowed to accumulate it would interfere with the heat 
transport of the coolant and could result in overheating and failure of 
individual fuel pins within the reactor core. Furthermore, the reactor 
must continue to be cooled via circulation of the coolant for several 
years after ultimate shut-down or failure of the system in order to remove 
the heat of radioactive decay of fission products. Thus there must be 
provided some means for maintaining the gas separate from the liquid 
coolant which would continue to function reliably even after loss of 
electrical power and loss of control over the gas separation apparatus. 
Removing entrained gas bubbles from a liquid metal in a zero gravity 
environment is not an easy task. In the absence of a gravity gradient, the 
gas could be anywhere in the system. Nonetheless it is essential that some 
means be provided for separating the gas from the coolant and accumulating 
it in a continuous manner. Using moving parts such as a centrifugal pump 
which could separate liquid from a gas via centripetal acceleration would 
not be satisfactory due to reliability concerns; namely, mechanical 
devices can fail. 
In addition, once separated there also must be some means for keeping the 
gas separate from the liquid coolant. Venting the gas into open space 
would not be acceptable if valves were required since a valve failure 
(either open or closed) could result in overheating of the reactor core 
with the attendant loss of the power system. A gas permeable frit could be 
used to form a portion of the wall in the coolant system. The permeable 
frit would let the gas diffuse out of the system into space. This would be 
undesirable, however, because it would represent a structurally weak point 
in the coolant system. Accordingly, there should be some means of storing 
the gas in the system which would be capable of maintaining the gas and 
liquids separate throughout the life of the system. 
OBJECTS OF THE INVENTION 
It is an object of the invention to provide an apparatus which utilizes the 
surface tension of a liquid to continuously separate gas bubbles from the 
liquid. 
It is another object of the invention to provide an apparatus which will 
maintain gas separate in an internal storage device utilizing the surface 
tension of a liquid. 
It is still another object of the invention to provide an apparatus for the 
separation of gas bubbles from a liquid which requires no moving parts. 
It is still another object of the invention to provide such an apparatus 
which will separate a gas from a liquid and keep them separated in a 
substantially zero gravity environment. 
Another object of the invention is to provide an apparatus for separating a 
gas from a liquid and maintaining them separate for hundreds of years. 
These and other objects of the invention will be more apparent from the 
drawing and following description thereof. 
SUMMARY OF THE INVENTION 
The present invention provides an apparatus for effecting separation of a 
gas from a liquid containing the same. It is a particular advantage of the 
present invention that it is utilizeable in a substantially zero gravity 
environment as would be encountered in outer space. It is another 
advantage of the present invention that it requires no moving parts. 
Broadly, the apparatus comprises a first closed vessel separated into a gas 
and a liquid zone by a gas de-entrainment means. Means are provided for 
introducing the liquid containing entrained gas into the first vessel for 
impingement upon the gas de-entrainment means. There also is provided a 
second closed vessel separated into a gas and liquid zone by an elongated 
member provided with a plurality of elongated passageways for capillary 
containment of a body of liquid. The passageways provide the sole means of 
fluid communication between the gas and the liquid zone. The gas zone of 
the first and second vessels are in fluid communication with one another 
and the liquid zone of the first and second vessels also are in fluid 
communication with one another. The second vessel also includes a means 
for withdrawing liquid free of gas from the liquid zone for recycle to the 
system from which it came, for example, a lithium-cooled nuclear reactor. 
In operation a liquid for example, lithium, is introduced into the first 
vessel and impinged upon the de-entrainment means whereby the liquid 
lithium passes through the de-entrainment means and flow into the second 
means. The entrained gas is separated and flows into a storage space (gas 
zone) of the second vessel displacing a portion of the body of liquid 
contained in the fluid passageways of the second vessel.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to the drawing therein is schematically depicted an apparatus 10 
constructed in accordance with the present invention. Broadly, the 
apparatus comprises a first closed vessel 12 separated into a gas zone 14 
and a liquid zone 16 by a gas de-entrainment means 18. Typically, the gas 
de-entrainment means will comprise a screen having a mesh size such that a 
liquid will pass therethrough but the surface tension of the liquid will 
be sufficient to prohibit the passage of a gas. In accordance with the 
particularly preferred embodiment wherein the liquid is lithium the screen 
will have a mesh size of from about 80.times.80 to 500.times.500 standard 
sieve size. 
Vessel 12 is also provided with a liquid inlet 20 for the introduction of a 
liquid containing an entrained gas. Inlet 20 is arranged such that the 
liquid and gas introduced into vessel 12 is directed in a manner to 
impinge rotationally upon the surface of gas de-entrainment means 18. 
Advantageously, gas zone 14 is also provided with a labyrinth or baffle 
22, the function of which will be described later. 
Apparatus 10 also includes a second closed vessel 24 which also is divided 
into a gas zone 26 and a liquid zone 28 by an elongated member 30 having a 
plurality of fluid passageways extending therethrough. The passageways 
provide the sole means for fluid communication between gas zone 26 and 
liquid zone 28. The passageways provide for the capillary containment of a 
body of liquid metal which forms a liquid gas interface 36. A lower 
portion of vessel 24 is provided with a discharge duct 38 from which the 
liquid, now free of entrained gas, is returned to the system from which it 
was originally withdrawn. 
The operation of the invention will be described with reference to its 
particularly preferred embodiment; namely, operation in a zero gravity 
environment for the separation of helium and tritium from the lithium 
coolant of a nuclear reactor. In operation a bleed stream of the lithium 
coolant is withdrawn for introduction into apparatus 10 via inlet 20. It 
will be appreciated that all of the primary coolant flow could pass 
through apparatus 10. In the interest of economics, only a portion would 
typically be withdrawn since that would be sufficient to maintain the 
entrained gas concentration at an acceptable value. The lithium containing 
entrained helium and tritium is impinged upon the gas de-entrainment means 
18 which typically will be a screen having a mesh size of from about 
30.times.30 to 500.times.500 standard sieve size. The surface tension of 
the liquid lithium is sufficient to prevent the gas molecules of helium 
and tritium from passing through thus they move upwardly through gas zone 
14 and labyrinth 22, the latter of which is provided to remove any 
entrained droplets of lithium. The gas then passes through a conduit 34 
into the gas space 26 of second vessel 24 displacing liquid lithium 
contained in member 30. 
Over a period of time the lithium gas interface 36 will move continually 
displacing additional liquid, however, the volume of member 34 can be 
selected to accommodate the required amount of gas for the life of the 
reactor. The lithium passing through gas de-entrainment means 18, now 
substantially free of any entrained gas, passes through a conduit 32 to 
liquid zone 28 of second vessel 24. From liquid zone 28 the liquid is 
withdrawn via discharge outlet 38 for return to the system. 
Typically, the passageways in member 30 will be formed from a plurality of 
small diameter tubes, the precise size of the tubes will vary depending 
upon the physical characteristics of the liquid being processed, however, 
the selection is well within the skill of those versed in the art. 
Typically, for the preferred application with lithium, the tubes will have 
an outside diameter within the range of from about 0.55 to 10.5 mm and an 
internal diameter within the range of from about 0.5 to 10 mm. In some 
instances it will be advantageous to cover the bottom ends of the tubes 
with a wire mesh or screen of the type previously described. The use of 
the screen will permit maintaining the interface under higher acceleration 
forces than would otherwise be possible. 
Obviously, many modifications and variations of the present invention are 
possible in light of the above teachings. It is therefore to be understood 
that, within the scope of the appended claims, the invention may be 
practiced otherwise than as specifically described.