DE3114060A1 - METHOD AND DEVICE FOR SOLIDIFYING A RADIOACTIVE WASTE LIQUID CONTAINING SOLIDS - Google Patents

Description

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SHIP ν. FONER STREHL SCHOBEL-HOPF EBBINGHAUS FINCK

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description

The invention relates to a method and a device for solidifying liquid radioactive effluents from nuclear power plants and especially for the solidification and coating of liquids Wastewater with a low or medium radioactive level from nuclear power plants, nuclear power research laboratories and treatment plants. The invention is particularly suitable for the concentration and solidification of relatively dilute liquid wastewater with a low level from light water reactors such as pressurized water reactors and boiling water reactors.

It is known to concentrate liquid waste from light water reactors to a certain extent and then the Encapsulating concentrates in different types of binding agents, for example cement, bitumen or synthetic resin polymers. The mixture The waste material and binder is then stored in containers. About the amount of waste and the corresponding number To be able to further reduce storage tanks has recently become proposed to dry the waste material completely and a dry product in the binder material or base material to include. The methods used and developed in order to obtain a dry product prior to encapsulation are generally referred to under "volume reduction".

In this specification, "dried waste" and "dry product" mean waste solids, which are essentially does not contain free water. Bound water, for example water of hydration or water of crystallization, can be present.

Because of the problems that arise with the volume reduction, which will be explained later, many of the existing waste treatment plants still encapsulate some form of liquid concentrate. This results in a large number of storage bins for radioactive waste, which are temporarily stored on the earth's surface

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they have to before they are either sunk or permanently in the sea buried on land.

An actual volume reduction can result in considerable savings result in both money and work for a number of reasons. The amount of used to encapsulate a lot of waste Required binder material is reduced when the waste is in dry solid form.

At the same time, the amount of waste material that is placed in each container can be increased, so that the number of containers required is also reduced. As a covering for the waste material in a protective cover, as described here, is either encapsulation in a base material or in a binding agent or the arrangement of the waste in containers. The final volume of the encased waste material can be carefully estimated from the outflows from energy systems with a low radioactive level by a factor of at least 5 to 15 the volume reduction process can be reduced. A reduction in the number of storage tanks produces a corresponding reduction in the space and equipment requirements for intermediate storage, container handling, container transport and the final storage as well as the manpower required for all these operations.

Another advantage of the volume reduction is that it is safer to handle and more economical to dispose of of the waste material is reached. Since smaller amounts of waste material are handled, stored, transported and finally can be permanently eliminated, there will be a corresponding reduction in spite of the danger to the staff and a corresponding Increase in device service life achieved. The security for the environment is enhanced by both the smaller Number of waste containers, thus also increased by the fact that there is no risk of the radioactive ions being released Water content is avoided.

Despite these well-known advantages of volume reduction,

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a number of difficulties in developing an effective one Result in volume reduction. So one tried thin film evaporator to be used as drying devices for volume reduction systems. However, as soon as a dry state is reached the waste concentrate becomes a heavy paste with solids contents in excess of 60% by weight. This paste dries relatively slowly as a film. In order to achieve drying in a thin film evaporator, a vacuum must be combined with a relative vacuum low speed can be used to advance material along the heated surface. Such systems therefore require expensive auxiliary equipment to generate the vacuum, so that the evaporator does not have a efficient throughput because the feed flow is limited by the rate at which the film dries. In addition, the feed rate must be monitored and controlled very closely, so that the drying at the evaporator outlet or occurs near it. Too early drying leads to blockage of the transport passages and clogging the evaporator rotor. Irrespective of such a control, the blockage often occurs after a relatively short period of time Operating periods have become harder due to the gradual build-up Layers of concentrate on the heated wall surface, this condition due to the low amount of material feed is aggravated. Such an arrangement therefore works far more effectively as a concentrator than as a dryer.

Other types of dryers, such as spray dryers, have been proposed for use in volume reduction systems and drum dryer. Such dryers generate large quantities of dust particles which are difficult to get out of the exhaust gas streams must be removed and which can lead to rapid erosion or clogging of the gas treatment device. Spray dryers have the further disadvantage that solids collect and settle in the spray nozzles and around the spray nozzles can lead to a blockage. Drum dryers have the disadvantage that it can be difficult to use on the heated drum to scrape off dry layers formed

or otherwise remove it.

Although some of the above problems could be solved by incompletely drying the concentrate, one would be more noticeable Moisture content in the waste product lead to problems with the properties of the encapsulated product. The presence of water in the radioactive fraction makes it difficult to determine the quality of the final product control from waste and binders. In other words, the amount of cement needed to produce the finished Mass must be used, depends on the total water content in the mixture of waste material and binder and that the amount of water in the wet concentrate or in the partially dried solids can vary and be difficult with any degree of accuracy is to be controlled. As a result, the previous methods turned out to be either too low or too high Water content in the encapsulated product. In a bitumen base or in a bitumen binder, water is extremely harmful, because this binder must be heated and water vapor is formed when the binder is heated, which leads to the encapsulation process disturbs. Water is also detrimental to most resin polymer binders because it stops the polymerization reaction. the end For these reasons, the presence of water in the waste fraction leads to a product which has a low water resistance low chemical due to the presence of unfixed radioactive ions that can dissolve Resistance and a poor structure, especially with regard to mechanical strength.

The object on which the invention is based is therefore to avoid these disadvantages and to obtain completely dried solid waste particles for coating in an unusually high amount, with the particles in a mass of high Should be encapsulated in a degree of wholeness.

To solve this problem, the waste effluent to be solidified, the chemical composition of which can change depending on the origin, subjected to a chemical treatment to remove the

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Adjust the pH to a basic range of more than 7.0 and / or insoluble compounds due to nucleation and / or deposition of the waste solids to form which are either suspended or dissolved in the waste liquid - if the effluent produced by a pressurized water reactor, it usually contains boric acid. In this case, lime is the preferred one chemical reagent to adjust the pH and to make the solids of such effluents insoluble. Others can too Metal hydroxides can be used, for example hydroxides of other alkaline earth metals. If the effluent from a boiling water reactor it usually contains sulfates, for which the preferred chemical reagent is barium nitrate. Other effluents that that can be treated according to the invention are processes from laboratory systems and other nuclear industry complexes or come from other nuclear reactor plants, for example in the form of liquid waste with low and medium radioactivity from processing plants for used fuel.

Many effluents are initially concentrated in a waste treatment system for at least some degree of initial concentration subjected to the waste generating plant, for example in a large volume evaporator, before the discharge takes place for intermediate storage in a storage tank. The storage tank liquid obtained can be dissolved and / or suspended Contain solids in amounts up to about 10 to 25 percent by weight. The chemical treatment of this storage tank waste takes place either in a mixing container to which the chemical reagent is added or by adding the chemical reagent directly to the special drying unit described below. Sufficient reagent is added to keep the pH above 7.0 preferably to a range of 10 to 12. This reagent is dissolved in water or added when dry. The chemical reagent chosen is intended to bind radioactive ions to a solid mass after drying and preferably generate insoluble salts that are capable of dissolving out of solution as suspended solids either immediately or after a

-IC-further concentration of the waste material to be deposited. Additionally, the dried waste solids must be compatible with the binder material and produce an encapsulated product, which has good mechanical strength and sufficient chemical resistance and is an essentially Form non-leachable solid mixture. When the reagent Is lime or burnt lime, it is preferably in an amount between 30 and 100 wt .-% based on the total solids added in the effluent. When the reagent is barium nitrate, it is preferably used in an amount between 20 and 50 percent by weight added to total solids. When the reagent is added through a separate mixing vessel, the waste liquid becomes preferably stirred for about 30 to 60 minutes to intimately mix the chemical reagent with the waste liquid. These There is no storage time for the reagent mixture when the chemical reagent is introduced directly into the special dryer unit.

Either after or before the chemical treatment becomes the waste material out into a concentrator, which is preferably a thin film evaporator and either can be built vertically or horizontally. Such evaporators have baffles or impellers attached to a rotor sit, which rotates at a relatively high speed in the range of 400 to 1000 rpm. Generated due to this speed the centrifugal force exerted on the waste material by the action of the blades forms a relatively thin film on an opposite one Wall heated to evaporate moisture from the film. Although the wall temperature increases over a wide area Can change range, these temperatures should preferably be between 150 and 300 ° C. Such vaporizers work extremely effective with an outlet concentration in the range of 30 to 70 wt% solids, preferably 40 to 60 wt%. The liquid retained in the concentrates enables the rotor to work at the optimum speed, which means that the Concentrate throughput is optimized and a drying of the concentrate film so far that a blockage of the delivery channel and a clogging of the rotor could occur, is avoided.

According to the concentration of the waste liquid in the evaporator will the concentrate obtained passed to a special drying unit, which consists of a mixing device, which a heated wall and a rotor with powerful impellers both for processing a heavy concentrate and for compulsory use Comprising advancing this concentrate and the resulting dry material. Since the energy supply level, the is required for the implementation of this function per rotor revolution, is much larger than with the thin-film evaporator, the mixer rotor rotates at a considerably slower speed, usually in the range of 25 to 75 rpm, preferably in a range from 40 to 50 rpm.

In the mixer / dryer, the concentrate is heated ^{to a temperature of about 100 °} C., preferably in a range from 150 to 300 ^{° C.} At these temperatures and at solids concentrations above 50%, the concentrate forms a hardened layer or crust on the heated surface. The strength of the agitator blades and the speed of the rotor are dimensioned so that this crust can be broken up into particles and dried without the rotor sticking or the transport channels being blocked. The working means also include one or more helical members carried by the rotor for forcibly advancing the concentrate and the resulting dry particles. The helical part can consist of a blade or wing which is inclined with respect to the rotor axis in order to exert a positive axial thrust towards the mixer outlet. The mixing device can furthermore have self-cleaning devices for removing hard concentrate from the inner mixing elements.

By removing the concentrate from the thin film evaporator before it reaches a heavy, hard-to-work condition, much higher throughputs can be used. Instead, the heavy concentrate is placed in a heated mixer Dried with a robust construction, which can exert a strong mixing and shearing effect with a large throughput. Additionally we-

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ken the mixing elements and elements to move forward with each other and with stationary surfaces and other elements to achieve a self-cleaning effect, in which hard ones Solid layers are sheared off, removed and comminuted, so that the build-up of such layers on these elements and surfaces are prevented and a fine powdery product is produced. The mixer is thus used both for drying of the concentrate as well as breaking up the hardened and caked layers of the dried concentrate used. To carry out these functions and to complete the drying process with optimum efficiency are available on the market available mixers of relatively small size can be used. The heat capacity and the length of the mixer is dimensioned so that the dried solid waste enters the mixer outlet in the form of a free-flowing powder. Thus, the invention becomes more optimal Use made of the operating characteristics of both the thin film evaporator and a heated mixer to optimize a to produce dried waste product.

The term "thin film evaporator" includes drying devices, which can be used as a concentrator, provided that a relatively thin film is applied as a layer to the heated Surfaces is formed and that the film can not dry, but is removed before the moisture content is reduced to below 30% is. The thin film concentrator can be built either horizontally or vertically. The preferred thickness of the concentrate film in the evaporator is in the range from 0.5 to 5 mm, preferably in a range from 1 to 3 mm.

That from the moisture both in the concentrating section of the evaporator as well as steam generated in the drying section of the mixer is passed through a separator device to remove entrained solids and remove any transferred liquid droplets. Although the separator is either from the evaporator or from the mixer / May be dryer separated, the evaporator preferably has an integral particle separator section, wherein the steam

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from the mixer / dryer is returned to the evaporator, where it passes through the integral separator along with the vapor from the evaporator. With the removal of the particles will the overhead vapor stream, which also contain non-condensable gases can lead to an additional gas treatment system of conventional design. There the condensable part is cooled, to create a condensate. The non-condensable gases are filtered and released into a controlled ventilation system.

The dry particles of waste product coming out of the mixer / Dryer is discharged, can then be stored as such in a container jacket, for example a steel drum or first mixed with a binder material to encapsulate the dry particles. Encapsulation results a double jacket for the radioactive solids, the first jacket being the solidified binder material and the second Coat the container for holding a waste material and the Binder mix before the binder solidification is. However, a single covering can suffice, either the binder material or the container, depending on the regulations for handling and storage of the respective authorities. Mixing the dry waste powder with the binder or the base material for encapsulation can either be discontinuous in batch operation or take place continuously. When mixing in batches, a separate mixer takes a measured amount of the dry Waste particles and a measured amount of the binder material, the mixture being agitated until substantially one homogeneous mass is obtained. In the case of continuous encapsulation, a separate batch mixer can be used instead of the separate batch mixer Mixer can be used, which operates continuously. An essential feature of the invention, however, is that the last or downstream part of the mixer / dryer as an integral mixing section for continuous encapsulation the dry waste particles can be used in a coating compound. For this purpose the heated jacket is around the Split around the wall of the dryer into two or more coats.

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with the upstream mantle covering the first 50 to 70% the mixer / dryer length is heated normally. The downstream one Jacket encloses the binder mix section. In the present specification, a heated mixer is used without one Binder mixing section referred to as the "dryer", while the upstream heated section of the mixer with an integral Binder mixing section is referred to as the "drying section".

The binder mixing section can only be heated to the extent necessary to enclose the solid waste in a bitumen mass is. In this regard, the binder mixing section can be cooled rather than heated, so that the temperature of the copolymerization of a resin-polymer binder can be controlled, thereby improving the properties of the final encapsulated product can be beneficial. Enclosure of the waste in cement is usually carried out at ambient temperature or below.

In that the dry particles exiting the dryer or dryer section are essentially free of moisture it is possible to add an unusually high percentage of dry waste particles to the final binder encapsulated Include product. The weight percentage of the solid waste with respect to the total mixture preferably falls in the range of 40 to 70% and can go up to 75% without adversely affecting the properties of the encapsulated product to be influenced.

A variety of different materials can be used as binders to encapsulate such high percentages of solids will. These include bitumen, resin polymers and cement. The bitumen preferably has a point of penetration in the area from 40 to 50. Preferred resin polymers are thermosetting polyester resins. Thermosetting resins are preferably used, the polymerization reactions of unsaturated glycol monomers, such as propylene glycol can be formed with orthophthalic acid and a vinyl monomer such as styrene.

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A particularly economical binder per m ^{3 of} dry waste is cement, which costs around half less than bitumen and 1/10 to 1/15 less than synthetic resin polymers. Cement also has the advantage that the solids encapsulation can take place at ambient temperatures. A cement with a high aluminum oxide content is preferred.

Another essential feature of the invention is containment of the dry waste particles in cement and water. Volume reduction processes already in use resulted in a slurry of waste material that was only partially concentrated and contained a relatively high percentage of water. This water had to be either in dry form when adding cement or as a pre-mixed slurry. As a result The relatively unknown and variable amount of water in the waste material prior to adding the cement made it extremely difficult to find that Control the quality of the end product. The ratio of the cement added to the total waste material had to be relative narrow area to account for the area of water that may or may not be present in the waste material can be.

This is a special problem where, according to the prior art, cement is used as a binder with a wet concentrate has been mixed, which has at least part of the water, that is required for the final cement binder. There have been cases where the water content of the waste concentrate not sufficient during the refining process was fixed, whereby dissolved radioactive ions remained free, so that there was a possibility that these during the subsequent Handling or storage released.

In contrast to these measures are the solid waste particles according to the invention in a dry state when mixed with the inorganic cement and the water will. This then results in a product which is superior to the product in which some of the water is from the waste material

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was brought. The relative proportions of cement added and added water can vary over a relatively wide range without detriment to the superiority of this product is affected.

The water can be added to the dried waste material either with the cement or as a premixed slurry or separately as an independent one Component can be added.

Another essential feature of the invention is that a separate chemical treatment vessel eliminates or is bypassed and instead an upstream section of the dedicated dryer unit as a reactive mixing section used to mix the chemical reagent with the waste concentrate to adjust the pH and / or to make the waste materials insoluble. This way of working is particularly advantageous where lime or quick lime is being treated of borates from the pressurized water reactor is used. Calcium borate is a thixotropic gel-like material that attaches to the Walls of transport extensions can stick if it is added upstream of the thin-film evaporator, especially where it is in view of the distance is desirable, relatively long transfer lines between the evaporator outlet and the particular one To have drying unit.

The lime or another chemical reagent is preferably added in the dry state rather than as an aqueous solution, whereby an increase in the amount of water which must be evaporated by the solidification system is avoided. Through this, that chemical solutions are no longer required, the efficiency of the arrangement is improved and it can systems with smaller volume can be used, which results in savings in terms of operating and equipment costs.

The lack of moisture in the dry waste material allows bitumen and resin polymers to be used effectively. When the waste concentrate is little dried, the excess moisture

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te water vapor when it comes into contact with the hot bitumen, The resulting boiling mass creates an undesirable foaming effect. For effective use of resin polymers a well-dried waste product is preferred because any excess moisture adversely affect the polymerization of the resin monomers and prevent the formation of an effective encapsulating material can.

The further treatment of the dry is also in accordance with the invention Waste particles possible with regard to their final storage. Such a treatment can be a calcination and / or a Encapsulation in a glass mass.

The invention enables a relatively easy and flexible operational control, which is preferably based on a water mass balance between the stream supplied to the evaporator and the collected Condensate from the combined steam flows from the evaporator and the dryer. Through differential comparisons between the weight of the feed and the weight of the stored Condensate per unit of time, the amount of dry solids per unit of time can be determined using the average Knows the salt and / or solids content of the feed.

The amount of dried product discharged from the dryer can be measured continuously so that the Amount of encapsulation can be determined continuously. Alternatively, dosing funnels can be used for batch operation can be used to measure the weight of both dry waste and binder material that the separate binder mixing device is then fed. According to the invention this optimizes the speed with which relatively dilute solid solutions can be dried, thereby increasing the continuous operation of the process plant without breakdown or flow interruption; and a dry and powdery solid waste product can be generated. The properties of the dry waste product are such that it has high solids values due to

Mixing processes can be encapsulated, which are relatively flexible and easy to control and which in terms of proportions of water and cement in the binder material are relatively insensitive.

Encapsulation or encapsulation with one of the three aforementioned binders produces a solid waste product, which is a has unusual chemical and leach resistance. If the binder is cement or a polymerizate, the solid waste product has an exceptionally high mechanical resistance. If the cement is used in the specified manner is, the mixture of binder and waste material have the advantage of rapid curing at ambient temperature, whereby an end product with high resistance to destruction under pressure, i.e. breaking, and to thermal Decomposition results, i.e. the product has fire resistance.

Further advantages of the invention are the possibility of radioactive To treat solids either in solution or in suspension, to carry out and control each process step independently, what about the setting of the process parameters in the event of a change in the feed composition or changes the. Environmental conditions Flexibility and simplicity results in dry waste solids for interim storage alone or to pack for permanent storage if encapsulation is not required by future waste treatment processes, Make changes to the encapsulation materials and facilities downstream of the dryer or dryer section; all process steps with the exception of chemical treatment and binder encapsulation without constant monitoring to be carried out by an operator and to provide remote operation and remote control without special problems, wherein normal operations that do not require operator activity are carried out within shielded areas can. The process allows commercially available equipment to be used with only minor adjustments and modifications. The equipment required for the process is easy to maintain and has minimal access requirements.

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possibility of shielded cells for maintenance and repairs. The device construction and arrangements do not require unusual design difficulties. The access options are not impaired. The device can be cleaned by rinsing the inner surfaces with commercially available cleaning complexes and / or solvents. Furthermore, the invention has all of the aforementioned Advantages of the volume reduction method.

The invention is explained in more detail, for example, with the aid of the drawings. It shows:

Fig. 1 schematically shows a flow diagram of the necessary for carrying out the method according to the invention Components as well as the lines for conveying the materials between these components and

Fig. 2 schematically in the flow diagram a modification,

in which a part of the dryer device for mixing dried solid waste with a Encapsulation binder material is used in place of the use of the separate mixer of FIG will.

In the arrangement shown in Fig. 1, a radioactive liquid effluent from a nuclear device is through a Device 20 is fed to an evaporator 22 with a large volume before it is passed through a line 24 to a storage tank 26 will. Through a line 28, purified water, which has been freed from impurities by the evaporator 22, becomes one controlled drainage system to release the purified water to the environment. The evaporator 22 reduces the liquid Amount of waste that must be stored on the spot. This evaporator and the storage tank 26 form a part a conventional waste treatment system for nuclear power plants or other nuclear devices. If the amount of dissolved solids in the effluent is already relatively high, so greater than about 10 wt%, the high capacity evaporator can can be omitted.

The liquid waste in storage tank 26 contains radioactive ions that are in the form of dissolved solids, suspended solids or as a mixture of both. This waste liquid then becomes a chemical through line 30 Treatment vessel 32 out, which has a stirrer 34 and a Has preparation tank 36 for a chemical reagent, over a sample line 38, a liquid sample can be removed to determine the amount of dissolved and / or suspended solids to be determined in the vessel 32. After adding lime or other suitable chemical reagent to the liquid waste suspended particles of insoluble salts can form in vessel 32 if they are not already present, and too coagulate a precipitate, which then settles at the bottom of the vessel by turning the stirrer 34 for the desired settling time settles. From the settled layer of the more concentrated solids the liquid can then be separated by pouring it off, leaving an upper liquid layer 40 of the evaporator feed line 20 is returned. The preferred working times for mixing a chemical reagent with the liquid waste are in the range of 30 to 60 minutes If it is desired to pour off the waste liquid, settling times are usually sufficient from 30 to 60 min.

When the pH of the waste liquid falls to the preferred range the solidification has been discontinued, the waste material is transferred to a vertical thin film evaporator 40 by means of a mud pump 52 in the connecting line 54 transferred. The thin film evaporator has a rotor 56 and a cylindrical wall 58, which is heated by a jacket 60, the one Heating medium, for example water vapor, is supplied through a line 62, which is discharged through a line 64.

Waste liquid is fed through an inlet to a manifold which circulates the liquid around the inner periphery of the heated Wall 58 distributed around. The liquid then flows downwards from the heated wall under the influence of gravity, where-

when it is wiped against the wall surface as a thin film or thin layer by blades or wings of the rotor 56. if the liquid waste flows downward as a thin layer spread over the cylinder wall, moisture is expelled, see above that the solids are concentrated and form a concentrate, which is collected in a lower chamber and out through a Concentrate outlet 66 is discharged. The concentrate outlet 66 is through a conduit 68 to the concentrate inlet of the dryer tied together.

Although separate particle separators can be used, the preferred thin film evaporator has a particle separator section 110 for removing both liquid and Solid particles that are carried away with the released moisture vapor have been.

In the thin-film evaporator, the moisture is removed from the waste liquid removed, whereby the concentration of the dissolved and / or suspended solids is increased, so that a concentrate is formed, which has a relatively high percentage of solids compared to the supplied liquid in the Line 54 has. The heat supply and the charge flow to the evaporator are controlled so that the level of solids at outlet 66 remains below 70% by weight, as has already been done was explained.

The concentrate from the thin-film evaporator is discharged through a line 68 to a heated dryer 70, the inner one Has mixing elements, which are explained below. The dryer has a jacket 72 so that at least part of the inner wall can be heated by a heating medium which is introduced into the jacket through a conduit 74 and out of the jacket by a Line 76 is removed. In the preferred embodiment, the heat flux density and the heated surface are sufficient to the Moisture from the concentrate to form a dry solid completely remove waste material. The temperature of the heated surface of both the dryer and the thin

layer evaporator is chosen so that the desired amount the moisture to be removed is achieved in the respective units for an optimal range of charge flow rates, which are determined by the pump 52.

In one embodiment, dryer 70 has a pair of cooperating Rotors which are arranged in a housing for one revolution in a clockwise direction. The housing has a heating medium passage, which is formed by the heating jacket 72. Preferably there is only a small amount of clearance between the tips of the Mixing blades and the walls of the housing and between the slightest approximation of the interlocking blades present. the Mixing blades of the rotor can consist of a variety of blades and blades. In one arrangement, a helical moves Leaf or a helical wing forced the concentrate and dry particles that are obtained in the process forward to the dryer outlet. This wing is followed by a pair of mixing wings. There are also a couple arranged by mixing and advancing blades, which is to be processed Both mix and move material forward. A fourth pair of blades can also be provided along the length of the rotor to both mix and retard the material being processed.

Such delay blades work with the rest of the blades together to obtain a backward or forward working motion to effectively unravel the hardening material To subject and subdivide shear. A wide variety of combinations of helical wings and Mixing paddles are used. So dead straight wings can be used if a long dwell time is desired, while only helical blades are used if the dwell time is to be short. To meet the various requirements To satisfy the shear action time and dwell time, the respective number of straight, inclined and blades and feed blades inclined in the direction of delay

-23- as well as their arrangement can be changed in an appropriate manner.

Furthermore, the heat flow to the evaporator and to the dryer can be changed separately by means of remote control valves 78 and 80 in lines 74 or separately. In addition, another heating medium can be used for the evaporator and dryer, for example oil instead of steam. It can come from different sources at different Temperatures are supplied. An electrical heating device is also possible.

The operational flexibility of the system is further enhanced by a Bypass line 84 increased, which has a remotely operated control valve 86. This line can be used to run the vaporizer 50 to bypass, or to part of the waste liquid or all waste liquid straight from the chemical treatment vessel 32 to be transferred to the dryer 70. The bypass line 84 can be used to increase the flow of waste liquid through the dryer can be used without the flow sent through the evaporator 50 being reduced as is desirable. «® · μ sis relative high level of solids in the waste liquid from the treatment vessel 32 is present, so a solids content in the range from 20 to 50% by weight and even higher. Bypassing the evaporator with some of the working fluid can be desirable even if the dryer used has a considerably larger heated surface or noticeably higher temperature than the evaporator is working.

The drying and Durchsa + - ^T: apazität of the dryer can also be selected so that a dry waste product can be produced directly from the waste feed having concentrations of about 35% or more. Accordingly, if upstream evaporation or upstream evaporation is particularly effective and results in high solids concentrations in line 54, the entire output of pump 52 can be sent directly to the dryer without going through the thin film evaporator. Such solid concentrates in the waste liquid

however, these are unusual and difficult without special construction techniques or setting process to achieve. In addition, the feed speeds to the dryer are relative low so that this component cannot be used in the most efficient manner. The water vapor emerging from the dryer contains a high proportion of entrained dry particles, which means that a separate multi-stage particle separator is required what would be required, which is one of the less preferred alternatives. A thin film evaporator with an internal Particle separator and a downstream dryer of the construction described are considered to be the best mode of implementation considered the invention.

In a further embodiment of the invention are a Bypass line 87 is provided between the storage tank 86 and the pump 52 and a chemical addition line 88 to chemical Introduce reagents, preferably dry, directly into dryer 70 as shown in FIG. A similar chemical addition line 88a can also be used for introducing chemical reagents directly into the drying section of the one-piece dryer / mixer of FIG. 2 can be used. A valve 89 in line 87 and a valve 89a in the line between the mixing vessel 32 and the pump 52 allow the liquid effluent from the storage tank 26 flows past the vessel 32 for the separate chemical addition and directly to the thin-film evaporator 50 in front of the chemical Treatment is applied, as accomplished by the provided lines 88 and 88a. Lines 88 and 88a may feed into the same dryer inlet as line 68 or through a separate inlet on the circumference or is axially spaced from the inlet which receives the concentrate from the evaporator 50.

The dry powdery waste material produced in the dryer 70 is taken to a metering hopper 90 which is passed through a valve 92 is controlled. When the dosing hopper is at least partially filled with dry particles, the waste

material delivered in batches with a predetermined weight to a separate mixer 54, which has a stirrer 96.

Depending on the weight of the dry material to be removed, the desired amount of binder material is placed in a binder mix tank 98 processed and fed to the mixer 94 via a line 100. The binder mixing device can also be one Have metering hopper 102 which is arranged to automatically actuate a control valve 104 in line 100, so that a predetermined amount of mixed binder material is added to the binder mixer. The dry ones Solids and the binder material are then mixed for a sufficient time that the dry particles and the binder material are intimately mixed and form a substantially homogeneous mixture, which then to a storage container 106 is discharged in a conventional manner. The container 106 is optional. The mixture can instead be in a mold with The desired shape can be cast and hardened into a block which can be further handled without inclusion in a container can. The binding material encloses practically all radioactive particles in a leach-proof and chemically resistant one A coat. Even if the particles on the surface of the solidified binder are not completely enclosed in the binder material are, they are sufficiently fixed, depending on the binder composition, allowing subsequent handling is possible within the applicable regulations. As a further alternative, the mixer 94 can be omitted. the dry particles are then enclosed directly in container 106 which is sealed with a lid and stored can be.

The moisture removed from the concentrate in the dryer 70 is returned as vapor to the evaporator 50 via a line 68 in the Countercurrent to the concentrate. The steam from the dryer combines with the steam from the thin-film evaporator and then flows through an integral separator section 110 in the evaporator for removing entrained particles from

Solids and moisture droplets. The overhead steam from which the Entrained particles have been removed, is fed through a line 114 to a condenser 116 to remove the moisture from to separate the non-condensable gases. The line 114 can optionally include a particulate filter 118 to capture particulates, which have not been removed by the particle separator. The non-condensable gases go out of the condenser 116 via line 120 to a conventional vent system for controlled release to atmosphere. The vent system has a bank of high efficiency filters 122 and a chimney 125.

The particle separation function performed for both the dryer and evaporator by evaporator separator 110 reduces the entrainment of dry particles and water droplets in the steam exiting the dryer from about 50 to 100 g / m ³ in line 68 to less than about 0.001 g / m ³ in the evaporator vapor line 114. Although a completely separate particle separator unit can be used as mentioned, a relatively expensive multi-stage unit is required to achieve the same removal factor.

Condensate from the condenser 116 becomes a condensate tank 130 supplied to a suction lift for a pump 132 for removing the To create low activity condensate from the waste solidification system. Depending on its activity levels The condensate can be transferred to the controlled discharge system for purified fluids or via a line 134 to the feed line 20 of the evaporator 22 can be recycled with high capacity.

For operational control purposes, the condensate flow from the pump 132 is measured by a flow sensor 136. Of the The chemically treated waste liquid feed flow is sensed by a flow sensor 138 in line 54. The respective flow signals are sent through device lines 140 and 142, respectively, to a recording device and a control unit 144 transmitted, which compares the signals and a

Control signal for regulating the speed of the pump 52 via a device line 146 generated.

In Fig. 2 a modification is shown in which components are provided for continuous encapsulation of the dry waste powder. In this embodiment, the extends Heating jacket 158 of modified dryer 160 only part of the way along the actual length of the dryer, preferably over 50 to 70% of the effective length of the rotor of this component. The remaining 30 to 50% of the rotor length has a downstream lying binder mixing section 162, which is approximately at one imaginary line 163 begins, which marks the end of the heated dryer sector 164. The binder material becomes the mixing section 162 from the preparation tank 165 continuously through a screw conveyor 166 or any other with positive force Displacement working conveyor mechanism for the binder materials fed. The waste concentrate is complete dried and forms dry powdery particles at the time the waste solids enter the mixing section 163, which is bounded by the imaginary line 163. The rotor components of the binder mixing section preferably have the same configuration as the rotor components of the upstream dryer section, although the rotor and Mixing elements of these sections can be different. Although the dryer section jacket 158 is heated, the binder mixing section has preferably an independent heat exchange jacket 168 that can be either heated or cooled, in order to obtain the optimum temperature for the binder mixture. Thus, the jacket 168 can be used to form the mixing section wall to heat, if bitumen is used to maintain its flowability, or the mixing section wall to cool if cement or resin polymers are used to prevent premature hardening which would otherwise result which would result in heat being transferred from the dryer section will.

The jacket 168 is provided with a heating or cooling system via a line 171

-28-medium, for example water vapor or water, supplied.

If the binder material is cement, the dry one can Cement and water premixed in tank 165 and used as a slurry through a line 167 for one-step mixing with the dried waste in the mixing section 162. In another preferred embodiment, however, dry cement is separated into mixing section 162 via line 167 fed directly from the water. The water is also fed directly to the mixing section 162 via a separate water supply line 169 supplied. The outlet of the line 169 into the mixing chamber of the dryer 160 is axially downstream and / or in the distance At a distance in the circumferential direction from the outlet of the line 167.

In the same way, separate systems can be used for successive Addition of dry cement first and then water can be used in the batch encapsulation arrangement of FIG. In this arrangement, the binder tank 98 and the related ingredients are modified so that dry cement is fed into the separate mixer 94 in batches. For the batch feed of water are a separator feed hopper, not shown, and a water feed line to the Mixer 94 is provided.

Separate systems for adding various chemical components can also be used in the embodiments of Figures 1 and 2 when the binder material is a resin polymer is.

-Z9-.

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Claims (11)

Patent to sayings Method for solidifying a radioactive material containing solids Waste liquid, characterized in that the waste liquid is thereby chemically treated is that at least one chemical reagent is added to adjust the pH of the liquid so that it is greater than 7.0 is that the solids are concentrated in a thin film evaporator with a heated wall by that the waste liquid is spread as a film on the wall in order to remove some of the moisture from the waste liquid and to form a liquid concentrate which has a greater concentration of solids than the waste liquid has that the concentrate is dried in a mixing device which has a heated wall and rotor devices wherein the heated wall is contacted with the concentrate to remove the remaining liquid from the waste material to remove and form a solid waste residue, and the solid waste residue one after the other in the mixing device is subjected to shear to form dry particles, and that the dry particles of waste material be wrapped in a second material. 2. The method according to claim 1, characterized in that with the wrapping, the dry particles
intimately mixed with the second material to form a substantially homogeneous mixture. 3. The method according to claim 2, characterized in that the second material bitumen, a synthetic
Resin or inorganic cement. 4. The method according to claim 1, characterized in that during drying the concentrate is continuously dried until the waste particles are substantially free of free water, the waste particles being mixed with a binder material for wrapping
to form a substantially homogeneous mixture and then solidifying the binder material. 5. The method according to claim 4, characterized in that that both the continuous drying and the continuous mixing are carried out in the mixing device will. 6. The method according to claim 5, characterized in that the base material comprises at least two different components, wherein at least these two different components are added separately to the waste particles at different feed points for the wrapping,
which are separated from one another on the circumference or axially. 7. The method according to claim 1, characterized in that particles entrained in the moist steam are removed by the moist steam leaving the mixing device is discharged through the thin film evaporator, the means for removing the particulate solid. having substances. 8. The method according to claim 2, characterized 31U060 net that the substantially homogeneous mixture in a Container is discharged, which has a wall made of a water-impermeable material. 9. The method according to claim 1, characterized in that that the chemical treatment is carried out after the solids are concentrated in the thin film evaporator have been. 10. The method according to claim 1, characterized in that that the dry particles of waste material are calcined before being encased in a second material will. 11. Device for solidifying a radioactive waste liquid which has solids, in particular for carrying out the method according to one of claims 1 to 10, characterized by devices for treating a waste liquid with at least one chemical reagent for adjusting the pH of the liquid by a thin film evaporator for concentrating the waste liquid, which has a heated wall and rotor means to distribute the waste liquid as a thin layer on the wall, to evaporate the moisture from the waste material and to form a liquid concentrate which has a greater concentration of solids than the waste liquid , Behe through a heated mixer with ^a:; ^ th wall for drying the concentrate and having a rotor device for contacting the concentrate with the heated wall in order to remove the residual liquid from the waste material and to form a solid waste residue, the rotor devices having a plurality of mixing blades for the solid waste residue between the blades and subjecting the heated wall and between the various blades to a shear action so that dry particles are formed, and with an advancing device which adjoins the dry parts. 31H060 engages to forcibly move them to an outlet on the mixer forward, by means for
Discharge of the concentrate from the thin-film evaporator to the mixing device, through devices that ensure
that the waste liquid through the thin film evaporator
passes through and the concentrate is discharged to the mixing device so that the concentrate received by the mixing device contains at least 30% by weight moisture and by means for encasing the dry particles of the waste solids in a second material.