Device for separating gaseous mixtures

An apparatus for the separating of isotope fractions, especially for the concentration of uranium 238 and uranium 235, which comprises a plurality of disks rotatable about a common axis and having central supply regions at which gas mixtures can be introduced. Outwardly from these supply regions, each disk is formed with a radial passage communicating with a chamber and opening into the latter through a constriction. Light fractions are removed from the edges of the gas flow radially through the chamber while a heavy fraction is passed centrally through at least one further constriction and into another chamber. The light fractions from one disk are fed to the supply region of another disk while the heavy fractions can be collected and fed to the supply region of still a third disk. Alternatively, or in addition, the light fraction delivery channels and the heavy fraction delivery channels for at least two disks are interconnected.

BACKGROUND OF THE INVENTION 
Various methods are known for separating or concentrating gas mixtures, in 
particular isotope mixtures. 
In practice, to obtain concentrations of U 235 from a uranium isotope 
mixture, the principal method is the diffusion technique. The so-called 
gas-centrifuge technique and separating nozzle technique have also been 
used. In all three methods, because of the low separating effect or the 
low throughput, a large number of separating stages must be provided in 
cascade in order to achieve the necessary concentration. Furthermore these 
methods have disadvantageously high energy consumption and high investment 
costs. 
Austrian patent No. 238 697 describes an apparatus for separating or 
concentrating gas mixtures. This apparatus comprises a disc rotating at 
high speed and having an annular supply or feed region for the mixture 
extending radially, this region communicating with at least one nozzle 
orifice extending radially of an annular nozzle and adjoining the nozzle 
orifice approximately in the plane of the nozzle orifice. The supply 
region comprises a delivery pipe for the heavy fraction of the mixture and 
on both sides of the nozzle orifice, delivery pipes for the light fraction 
of the mixture. However, in practice, this apparatus has not proved 
successful in isotope, particularly uranium isotope separation. 
Object of the Invention 
It is the object of the invention to provide an improved apparatus which is 
particularly suitable for uranium isotope separation or concentration. 
Summary of the Invention 
This object of the invention is achied disposing several discs 
substantially parallel to each other to be driven by a common shaft. The 
discs are preferably located under a vacuum bell jar with a vacuum of at 
most 150, preferably between 1 to 15 Torr. 
In an embodiment of the invention the delivery channels for the light 
fraction and/or heavy fraction of the mixture from several discs are 
interconnected. 
According to another feature of the invention a delivery channel of at 
least one disc is connected to the inlet of the supply region of another 
disc. 
Preferably, the vicinity of the outer edge of the rotating disc is a region 
in which the gaseous mixture leaves the disc with the formation of eddies, 
delivery devices being provided for discharge of the mixture from the 
central region and from a peripheral region of the eddies, independently. 
When a space free from flow restrictions exists along the outer 
circumference of the disc, the mixture leaving in the radial direction is 
set in turbulence at the edge of the disc. The light fraction accumulates 
in the central region of such turbulence while the heavy fraction 
preferentially accumulates in the outer circumferential area of the 
turbulence. 
According to the invention, a concentration results from this formation of 
turbulence. Under certain circumstances, a concentration of either 
fraction or separation of the two fractions can be achieved solely on the 
basis of this formation of turbulence, i.e. without providing radial 
nozzle inside the discs. 
In the apparatus according to the invention, internal cascading is effected 
by disposing several separating nozzles one behind the other per disc. The 
centrifugal forces serve for compression and not the actual separation. A 
radial pressure drop of approximately 4,000:1 prevails, i.e. the pressure 
drops across the disk to 1/4000ths of the pressure at the inlet to the 
disc space. An apparatus according to the invention, which maintains these 
pressure differences between the center and periphery, achieves a basic 
separating effect (separation factor) of 1.07 for the uranium isotope 
separation. With a nozzle orifice width of 0.2 mm and a nozzle ring 
diameter of 200 mm, a throughput of approximately 10 liters uranium 
hexafluoride gas per second is achieved. This means that a cascade of 22 
centrifuges produces an annual yield of 57 metric tons of U 235 enriched 
by 3%. For 1 kg of enriched material, only 9 KWH current are required in 
contrast to 300 KWH in the gas centrifuge. An installation which operates 
with an apparatus according to the invention is economically viable with 
an annual separating capacity of 100 metric tons enriched U 235. 
The separating effect is achieved according to the invention by the 
complicated alternating action of separating nozzles inside the disc, the 
formation of turbulence along the periphery of the disc, formation of 
turbulence in the stationary container, rotation of the gas in the free 
space between the disc and container and shock waves in this space.

Specific Description 
The apparatus according to the drawings comprises a shaft 1 mounted in 
bearings 2 and 3, which shaft can be driven at high speed by a drive 4. 
Several discs, 5, 6, 7 and 8 are attached to the shaft 1. Each disc 5 to 8 
comprises an annular supply region 9, which opens through a nozzle orifice 
(construction) 10a into an annular chamber 11a. Approximately in the plane 
of the nozzle orifice 10a, the chamber 11a comprises an outlet pipe 12a, 
which is firstly enlarged radially and opens by way of a further nozzle 
orifice 10b into a chamber 11b. Adjoining this chamber 11b in a similar 
manner is a further outlet pipe 12b and a further chamber 11c. The last 
chamber 11c opens into a delivery pipe 13. Each chamber 11a to 11c has on 
its outer wall, a V-shaped cross section and on both sides of the nozzle 
orifice, a delivery pipe 14 respectively, which is connected to collecting 
pipe 20. The shaft 1 is constructed to be partly hollow and comprises 
three chambers 15, 16 and 17. The chamber 15 comprises two outlet pipes 21 
extending radially, which open into the supply region 9 of the two discs 5 
and 6. The original mixture is supplied to the chamber 15 by way of a pipe 
18 and an annular bore 19, possibly through a stationary ring (not shown). 
Due to the centrifugal forces occuring upon rotation of the discs 5 to 8, 
the original mixture is supplied through the pipes 21 and supply regions 9 
to the nozzle orifice 10a. Directly thereafter, the mixture enters the 
chamber 11a, which has a V-shaped cross section with an outlet nozzle 22a 
on the outer wall. The actual separation of the two fractions takes place 
between the outlet nozzle 22a and the V-shaped wall acting as a separator. 
Thus, the light fraction is urged outwards into the delivery pipes 14, 
whereas the heavy fraction passes through the outlet nozzle 22a. The 
separating process is repeated in the same manner in both subseqeunt 
annular chambers 11b and 11c. The delivery pipes 13 for the heavy fraction 
communicate via a common collecting pipe 23 with the chamber 16 of the 
shaft 1. From the latter the mixture is passed in a similar manner through 
the disc 7. Thus, the heavy fraction is conveyed outwardly through the 
delivery pipe 13 of the disc while the light fraction in the delivery 
pipes 14 of the disc is led by way of the pipes 20a and 20b and a 
collecting pipe 25 to the next stage. An optimum utilization of the 
original mixture is thus achieved. 
The delivery pipes 20a and 20b for the light fraction are connected by way 
of a collecting pipe 25 to the chamber 17 of the shaft 1 and from the 
latter to the individual nozzle orifices 10a-10c and annular chambers 
11a-11c of the disc 8. The light fraction of the mixture is conveyed 
outwards by the delivery pipes 20a and 20b of the disc 8 by way of a 
collecting pipe 26. The heavy fraction of the mixture leaves the apparatus 
according to the invention by way of the delivery pipe 13 of the disc 7. 
FIG. 3 shows a removal device for the two fractions of the mixture on the 
outer edge of the disc 5. This removal device consists of stationary discs 
31 to 34, which are supported by an outer stationary ring (not shown). 
FIGS. 4 and 5 show the outlet region of a preferred embodiment of a disc 35 
according to the invention. When the mixture leaves the disc 35, it passes 
into the enlarged region 36 to form eddies 37. Since these eddies 37 
rotate at high speed, the heavy fraction is urged outwards, so that due to 
a controlled removal of the mixture in the central region of the eddy, 
possibly by a tube 38, an additional separating or concentration effect is 
achieved.