PROCEDURE FOR THE PROCESSING OF RADIOACTIVE WASTES.

The available invention concerns a procedure for the recuperation of uranium and plutonium and other valuable material from firm, plastics containing raw wastes, in particular from processing places of nuclear fuels, and processing of the wastes released from uranium and plutonium to a space saving ultimate waste disposalable and/or again usable product. The Veranreinigungsgrad of these voluminösen wastes, which result within the controlled area of a production plant, is very different. Wastes with balancable, thus stronger impurities by nuclear fuel such as uranium and plutonium develop almost exclusively in the glove boxes and make for instance the Hãlfte of the entire waste aus.

Material-moderately seen this waste consists of PVC (polyvinyl chloride), rubber, polystyrene (HP), polymethyl metacrylate (PMMA), PL (PE), polytetrafluoroethylene (ptfe) and other one. Except these plastics also Zellstoffund other inflammable natural substances are in the waste material. Quantitatively PVC with a portion up to 70 Gew.%.<br outweighs/> in this mixture This fell off cannot in conventional way not be eliminated, there it long-lived radio-toxic nuclear fuel (plutonium) be contained. In order to achieve a safe dumping of the wastes, the objective of new treatment procedures is the Rüekgewinnung of the nuclear fuel, the decrease of the Pñmärabfallvolumens and production one ends storable Abfailproduktes.

So far one was limited in practice to fix such wastes cement blocks to finalstore in order to achieve a lowest possible leaching rate opposite water or salt caustic solutions, and in salt plugs. At this Verlo it drives is unfavorable that the waste volume extends substantially and a Plutonìumrückgewinnung at a later time no longer possible ist.

In order to switch off these disadvantages, primarily in the USA a set of burn procedures were developed, is with those apart from the volume reduction a concentration of the nuclear fuel on a small remainder volume, which ash portion should be achieved. Like the overview report KfK. - 2250 of the nuclear research center Karlsruhe to take is, has so far no procedure due to ungeiöster difficulties production-ready ones attain können.

Ais disadvantage is common to all burn procedures that with the mentioned Abfãllen with high PVC content the produced contaminated secondary quantity of waste in fixed ultimate waste disposalable form exceeds the output volume of the Primärabzs of case. With some Hoehtemperaturprozessoren ersehwerend that during the burn the plutonium is transferred into a very heavysoluble form, those is added the recuperation from ashes substantially erschwert.

Since so far no procedure admits is, with which a nuclear fuel feedback and a volume decrease are reached at the same time, placed itself the task to look for a way to the reaching of the put goal additionally in addition, generally the recovery nature not nuclear of valuable material 3s made possible. Such know for example precious metals or other rare materials sein.

The solution of this task exists according to invention in a procedure, which abiäuft according to the patent claims after the following steps:

a) Cut up the raw waste on approx. 5 mm grain size b) dissolution the same at increased temperature in an organic solvent under education of a polymer solution 4s C, suitable for plastics in the raw waste) separation of unresolved larger waste shreds d) separate the unresolved nuclear fuel portion from the polymer solution with the help of a centrifuge e) evaporation and condensation of the solvent to the Riickführung into the dissolution process according to b) under s0 remaining a polymer melt. The following supplementing Schñtte can be of advantage:

f) Imbedding of the waste portion to the c) into the remaining polymer melt g) racking of the polymer melt and solidification derss same in storage vessels to a Kunststoffblock.

Favorable way can be dissolved the raw waste in the organic solvent in step b) up to the reaching of a concentration of 10 Gew,%, wãhrend in step c) favourable-proves raw waste particles > 1 mm to be separated, those insolubly sind.

The basic principle of this erflndungsgemässen procedure exists thus in the dissolution of the before-cut up raw waste in an organic solvent, so that only after separation however form suspended by unsolvable plastic particles the unresolved impurities stay such as UO2 and PuOz in firmer. The raw wastes consist, as previously mentioned, primarily of thermoplastic plastics, for which several suitable organic solvents exist. There are also materials, how cellulose and wood interlaced or also strongly plastics like e.g. neoprene, which are insoluble to these solvents. The total portion of these unsolvable materials does not exceed however according to experience 25% of the total quantity of waste, it from there according to step c) from the polymer solution is separated, before this releases in centrifuges from firm nuclear fuel particles wird.

In the enclosed figure this procedure is schematically represented. In normal way out the wastes polluted in the working places, the work boxes in PVC bags welded with uranium and/or plutonium first instrumentation according to their plutonium content are thus e.g. sorted. Raw wastes with more than 5 gram per cubic meter nuclear fuel content are suitable for the procedure according to invention, there see with them a feedback of the nuclear fuel content are worth and empfiehlt.

This waste, which is released before also still in actually well-known way from possibly existing metal parts, becomes according to the Fig. 1 with the help of a transport container 1 of a shredder 2 supplied. In this the wastes are cut up depending upon process engineering necessity up to approximately 5 mm of grain size and over a not-represented discharge snail into an intermediate shelter 3 gelagert.

From this intermediate shelter 3 arrive the cut up fill up with the help of the agitator 31 and the delivering snail 32 into a boiler 4, which is provided with an agitator 41. Over the line 43 in this boiler solvent from the tank 10 is added and at the same time an increase of the temperature on 60-80°C under, the Doppelmante142 of the boiler supplied heat distribution medium is made. This consists e.g. of water and with 44 zuund with 45 is exhausted. In this boiler 4 thereby as much material of the waste mixture is registered, until a 10%ige PoIymerlösung formed. The time needed for the solution procedure amounts to thereby about 30 Minuten.

The dissolution procedure then the separation step for the unresolved plastic shreds from the polymer solution heated up follows. For these rough parts in addition a drum filter 5 is intended, the solitary particles with solvent is washed afterwards, stripped and to a collector 51 supplied. The remaining solution with the suspended nuclear fuel particles arrives then at a centrifuge 6, which possesses a centrifuge effect between 15,000 and 20,000 g. In this the nuclear fuel collects as firm cakes in the centrifuge cylinder. By the structural design of this centrifuge cylinder on an inside diameter of approximately only 80 mm the nuclear criticality safety is ensured. The centrifuge pipe is replaced after a sufficient SpaltstoffansammIung and in a transport container of the Spaltstoffaufarbeitung 64 zugeführt.

The cleaned polymer solution arrives then from this centrifuge by means of a pump 62 at three Flashverdampfern 71.72 and 73 and afterwards at the snail evaporator 81 switched into row. While the Flashverdampfer increases the concentration of the polymer solution of 10 auf40 Gew,%, resulting after the centrifuge, the snail evaporator downstream evaporates the remainder portion of the solvent. As shown in this example, it is appropriate to connect the snail evaporator 81 a second Schneckenver647 at the outlet side of 553 steamers 82 with this the Restverdamplung of the solvent up to a remainder content of less than 1% durchzuffihren and into the polymer melt the insoluble solids separated withdrawing from the snail evaporator with approx. 160°C in the drum filter 5 to interfere at the same time. These arrive from the container 51 over the line 52 at this snail evaporator 82.

The fluid polymer melt with the embedded solids will then into a transport container, e.g. a l0 400-1-Rollreifenfass filled and forms after cooling a compact nonporous plastic block, in that perhaps also still different not inflammable fill up there like glass, ceramic(s) or metallic machine parts to be embedded to be able. This block represents a leach out-steady 1 bundle, so that a cementing is necessary no longer and thus a ultimate waste disposalable product vorliegt.

Solvent steams withdrawing from the evaporators are supplied to a condenser 9 by way of the lines 83, liquefied there and introduced into the solvent tank l 0, by which they are if necessary again supplied to the dissolution process in the boiler 4. It takes place thus a constant cycle guidance of the solvent, so that consumption of this is extremely small. As solvents tetrahydrofurane or 2s Methyläthylketon.<br is for example suitable/> This procedure can be simplified naturally from the beginning still by the fact further that in the processing plants only such materials use find, all can which be solved in a suitable solvent aufa0. Likewise it is for the recuperation of other perhaps radioactive and not soluble fine-grained valuable material geeignet.

In relation to well-known procedures this procedure according to invention the following advantages has that:

3S 1st Rfickgewinnung of plutonium and uranium without chemical Prozesse.

2. No change, i.e. degradation of the solubility of PuO2 and UO2 during the treatment process regarding their further treatment with Salpetersãure.

3. No Sekundärabfallerzeugung.

4. The final product of the treatment process is endlagerungsfähig.

The ultimate waste disposalable waste volume is based on the 4s raw waste volume around for instance the factor 5 kleiner.

6. By the exhaust air no Aktivitätsfreisetzung.<br is made/> 7. The necessary equipments are well-known and erprobt.

8. No material problems result from thermal stress, there the temperatures under 170°C bleiben.

s0 9. by appropriate geometrical dimensioning of the used apparatuses is the nuclear criticality safety gewährleistet.

Since no acids are used to develop or, there is also no Korrosionsprobleme.

ss for l of 1st no exhaust gases there, is also no off-gas treatment mechanism develops notwendig.

12. The radiolytic gasification during the process is very small, there only a short time of contact of the nuclear fuel with the solvent - approx. 1 hour - given ist.

13. Considering the relatively low temperatures and a heat cycle guidance is also the necessary energy employment gering.

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