NL7808732A - METHOD FOR OPERATING A SEPARATION CASCADE FOR SEPARATING GASEOUS MATERIAL MIXTURES, IN PARTICULAR ISOTOPE MIXTURES. - Google Patents

Description

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__ J, "" VO 5918

Uranit Uran-Isotopentrennungs-Gesellschaft mbH,

Julich - Federal Republic of Germany

Method for operating a separation cascade for separating gaseous material mixtures, more particularly isotope mixtures.

The invention relates to a method and apparatus for operating a separating cascade for separating gaseous material mixtures, more in particular isotope mixtures, in a light and a heavy fraction, wherein the material mixture is cascaded via the ground step and light fraction - a number of enrichment and depletion stages are separated and fed to the light and heavy cascade output.

Uranium enrichment is normally performed in one or more | cascades. A cascade consists of a ground staircase, to which the 10 | material mixture is added, and a number of enrichment and! | depletion stages, the individual stages consisting of a number of parallel connected separating devices, for example gas centrifuges. For example, a cascade circuit of this type is shown in FIG displayed.

15 | Centrifuge cascades for enriching natural uranium have the property, in a particular characteristic of the centrifuges, that the composition of the isotope mixture at the light cascade outlet (product concentration P) through a variation of the material mixture feed (cascade feed F) over a wide area. can be arranged.

1, while the composition of the isotope mixture at the heavy cascade outlet (tail concentration T) varies only slightly. This makes it possible to meet the wishes of the customer with regard to different product concentrations. In the figure, the! feed flow with a solid line, the product flow with a broken dashed line and the tail flow indicated by a dotted line.

Centrifuge cascades are normally sized so as to obtain an optimum value for tail concentration at certain separation and natural uranium costs. It is now economically advantageous if, irrespective of the required product concentration, the price variations for the natural uranium can also be adjusted for the corresponding optimum tail concentration. That is, for example, at a price increase of the natural uranium, the tail concentration for the lighter uranium isotope U 235 can be lowered accordingly. Therefore, a cost increase for the crude uranium can be at least partially offset by better utilization of the material U 235 contained therein.

The object of the invention is to improve the operation of a separation cascade of the above-described type in such a way that a variation of the tail concentration is also possible.

For this purpose, the material mixture to be separated is split into two controllable partial flows and one partial flow is supplied to the ground stage and the other to an enrichment or depletion stage located in the vicinity thereof, in accordance with the concentration to be maintained at the heavy cascade output. fraction occurring, while the total current to be supplied is adjusted depending on the concentration of the light fraction 20 to be maintained at the light cascade output.

As a result, the tail concentration can also be infinitely adjusted. For example, if a portion of the cascade feed is fed to the adjacent enrichment stage in addition to the ground stage, the tail concentration in terms of its proportion of the light components is reduced, while the desired product concentration can be maintained by an appropriate adjustment of the total feed .

The invention will be explained in more detail below with reference to the drawing, in which in Fig. 2 a centrifuge cascade is found, which consists of a ground step 1 and a number of enrichment and depletion steps 2a to 2n, respectively. 3a to 3n, in which the stages are built up from different numbers of individual centrifuges connected in parallel or from centrifuge units grouped together.

Normally, the material mixture of uranium hexa-35 fluoride (UFg) to be separated is fed via lines 5 and 5 to the ground step 1 and split into light and heavy mixtures, after which the light mixture β 7808732/3 is added to the first enrichment stage 2a and the heavy mixture. the first depletion stage 3a is supplied, etc. The number of stages and the size of the stages is chosen so that the light cascade output 6 is obtained, a product of which the U 235 concentration is, for example, between 1 and h 2. can be set at approximately constant U 235 concentration of, for example, 0.25 $ at heavy cascade output 7

If, for the reasons already mentioned, it is now desired, for example, to lower the 235235 tail concentration at the heavy cascade output 7, at least part of the material mixture to be supplied is branched off over the conductor 8 and the first enrichment step 2a is supplied. This increases the number of impoverishment steps. Conversely, at least a partial current is fed via line 9 to the first depletion stage 3a. With the control valves 10, 15, 11, 12 and the pressure measuring devices 13, 11 · 15, the partial flows can be infinitely adjusted and checked.

This method allows the tail concentration to be steplessly between 0.2 $ and 0.3 $ with a suitable centrifuge characteristic, for example at a product concentration of 2.5 $ U, 235 desired by the customer, practically without losses. U 235.

7808732 /

Claims (1)

Device for applying the method according to claim 1, characterized in that three feed lines (5, 8, 9) are provided in parallel for supplying the material mixture and provided with flow control valves (10, II, 12). one leads to the cascade floor (1) and the other two lead to an enrichment and an impoverishment (2,3). \, 78 0 87 3 2