WO1998055380A1

WO1998055380A1 - Method and device for the handling of bodies which have a reduced mechanical stability or are in a non aggregate status

Info

Publication number: WO1998055380A1
Application number: PCT/ES1998/000024
Authority: WO
Inventors: Joaquín PEREZ PALLARES
Original assignee: Hispano-Francesa De Energia Nuclear, S.A.
Priority date: 1997-06-06
Filing date: 1998-02-05
Publication date: 1998-12-10
Also published as: ES2115566B1; ES2115566A1

Abstract

The process comprises the placing of a flexible and adaptable pad or cushion over the object to be handled, the lower side of the cushion being wetted with a chillable liquid; then the cushion is placed onto the mass of the object to be manipulated with a predetermined pressure in order to adapt the cushion to the object, whereafter the liquid layer in simultaneous contact with the flexible mat and with the surface of the body to be handled is frozen; thereafter, the assembly formed by the mat and the body to be manipulated, which are joined by the frozen liquid layer, is lifted and moved to the location provided for its storage; thawing will separate the body to be manipulated from the mat.

Description

PROCEDURE AND DEVICE FOR THE HANDLING OF BODIES THAT PRESENT REDUCED MECHANICAL STABILITY OR NON-AGGREGATED STATE

DESCRIPTIVE MEMORY

The present invention is intended to disclose a method and its device for the manipulation of bodies that have reduced mechanical stability or non-aggregated state, that is, that they have insufficient mechanical resistance to allow manipulation similar to that of rigid objects or semi-rigid or even in an aggregate state, that is, in the form of several adjacent masses but not joined together.

The invention is especially applicable to physical and physical-chemical processes in which there are bodies that must be manipulated and have little physical consistency, being able to reach states of non-aggregation of the components. In these cases, conventional mechanical systems are not applicable since the bodies to be handled do not offer guarantees of physical stability since their mechanical resistance is not sufficient to guarantee the stability of the body against the stresses exerted during handling by the clamping or by the body's own weight.

One of the applications envisaged for the present invention is the handling of radioactive waste in which problems of selection and handling occur.

In the field of radioactive waste, as in any conventional waste mixture, it is necessary to make a selection to proceed to its final disposal, depending on its characteristics.

In the case of radioactive waste, the particularity that operations must be carried out with telecommanded media.

In the separation and selection of a mixture of radioactive waste, consisting of graphite, magnesium and uranium (metal and oxides), the problem arises of extracting uranium selectively without, when applying a clamping system, a dispersion or displacement occurs of the residue that progressively hinders the extraction, increasing the area affected by the mixture more and more, with the consequent increase in the volume of waste to be selected.

So far, the geometric characteristics, the arrangement and the densities of the different residues have made their correct extraction impossible with the available means.

In fact, the available and commonly used means are: telemanipulated arms equipped with mechanical clamping tools,

- vacuum cleaners.

In the case of telemanipulated arms, mechanical elements, such as tweezers, blades, claws, etc., are normally coupled at their ends, which, at an industrial and remote level, do not have the precision to selectively extract a residue clearly differentiated from the majority without preventing the dispersion or displacement of it, outside the initial work zone. In the case of the handling of radioactive waste, the non-dispersion or relative displacement of uranium is an indispensable condition that cannot be fulfilled with the use of telemanipulated arms.

With regard to vacuum cleaners, the fact of having a heterogeneous mixture not only in size, but also in densities, makes the aspiration preferentially extract the less dense residues, progressively penetrating the densest ones into volumes previously free of themselves, which unacceptably implies an increase in the amount of the waste to be processed, which can be understood taking into account that uranium and its oxides have densities ranging between 8 and 19 g / cm, instead graphite and magnesium have an order density of 2 g / cm.

The present invention is intended precisely to solve the aforementioned drawbacks, by disclosing a method and device to allow the safe handling of bodies that have the indicated mechanical stability deficiencies or even states with no aggregation.

The device is based on the adhesion that is revealed between two wet surfaces brought into contact, when freezing occurs, for example, by expansion of a cryogenic fluid.

If one of the two surfaces is sufficiently soft, it adapts to the irregularities of the other by applying light pressure on it.

In practical cases, since it is solid waste, it is the extraction device that is constructed presenting a soft surface. In this way, the loose residues are immobilized during the cooling of the assembly when the cryogenic fluid is injected. When freeze hardening has occurred, the assembly can be removed, avoiding dispersion or displacement of the waste.

While the product remains adhered, the device is transferred to a container of confinement and transport (this in the practical case that is being contemplated), to which it will be introduced when the adhesion disappears by recovery of the temperature. The recovery of the temperature occurs naturally or forcedly, after the injection of cryogenic fluid ceases when it is used. The acceleration of defrosting can be done by means of a heating device associated with the device for handling. The shape and dimensions of the soft surface can be defined at will, depending on the disposition of the residue and affected area. Therefore, although the telemanipulated arm or the handling system of the extraction device does not offer the necessary precision, adhesion to the extraction device of only a limited portion of waste that is not dispersed by such manipulation allows the selection of the extracted product on a reduced amount thereof.

As indicated, the invention is fundamentally based on a device in which the adhesion that is revealed between two wet surfaces brought into contact is produced, causing the freezing of the wet sheet preferably by expansion of a cryogenic fluid. In detail the device to be used in the present invention consists of the following components:

A pad consisting of a moldable, flexible and porous element, which can absorb a certain amount of moisture and create a thin wet film between this element and the waste to be extracted. Latex has been used as a flexible material in the application.

The pad must also allow the expansion of a cryogenic fluid inside.

A cryogenic fluid, which must be able to produce the cooling of the assembly formed by the claw and the residues in contact, until the formation of an ice film between them. This ice film must be maintained during the movement of the pieces to a confinement and transport container.

A temperature sensor with a signal transmission cable, a digital converter and a reading device, for process temperature control. A pad support structure, consisting essentially of a metal plate.

A ballast to adapt the pad to the surface of the residue by a predetermined pressure.

This ballast can be suppressed if the claw assembly already has the weight that produces the desired pressure, or if the claw manipulator device directly transmits the force necessary for its correct pressure of adaptation to the material or residue.

A copper or stainless steel tube to drive the cryogenic fluid from storage to the pad.

A distributor of the cryogenic fluid in the entire extension of the pad to produce the expansion of the fluid in a homogeneous way and cause a uniform cooling.

A feeding tube of the pad moisturizer.

A heating system to supply heat to the pad and cause it to defrost (by electrical resistance, coil fed by heating fluid, etc.).

A thermal insulation of the pad, located on the opposite side from the one that comes in contact with the residue to be extracted, to improve the cooling rate.

The device can be manipulated with any maintenance element adapted to the needs, weight and size of the waste and the distance that these are.

The dimensions of the extraction device will be chosen according to the dimensions and weight of the product to be extracted, being a suitable option for the pad to cover the object to be collected with some excess.

The spatial precision of the handling element of the extraction device can influence the choice of the size of the device, so that poor precision will force the use of a larger extraction device.

Depending on the spatial location of the product to be extracted, the maintenance mechanism of the extraction device of the invention will be chosen, that is, a telemanipulated arm, hoist, crane bridge, etc.

Basically, the process object of the present invention will comprise the following phases: a) With the help of the maintenance device, place the extraction device with the pad previously moistened, with a freezing liquid, on the residue to be extracted. If the work area is outside the operator's direct field of vision, TV cameras may be available. Care must be taken that the portion of waste to be taken at once is completely under the pad, since the adhesion depends on the contact surface between the pad and the product to be extracted. However, if the pieces are not very heavy it is not necessary that they be completely covered by the pad. The adhesion limit depends on the quality of the pad. For pads constructed with commercial latex, this limit is 0.8 kg / cm. b) Once the extraction device is placed covering the residue, the freezing of the liquid occurs, for example, by opening the cryogenic fluid inlet to the pad and the temperature is controlled by the sensor. c) When the temperature reaches a regime value between -60 ° and -90 ° C, the extraction device can be lifted, since the contact residue will already be attached to the pad. At this time you can move the assembly to the place where you want to deposit the product and close the passage of cryogenic fluid. The temperature to be reached in the cooling depends on the environmental conditions in the environment of the waste and the type and size of the pieces to be extracted. d) To release the object or waste removed, the temperature must be recovered, so that the film of the frozen humectant between the pad and the adhered product melts. If the environment is not warm enough, and you want to speed up the operation, you can use the built-in heater.

Once deposited the waste extracted or object to manipulate when the collection pad reaches a temperature higher than the defrosting can start a new operating cycle.

When, due to its use, the pad loses its recovery characteristics, or due to the handling of contaminated materials the change is imposed, the pad replacement can be carried out keeping the rest of the extraction device.

The pad is attached to the support structure only by its perimeter, so that it is completely removable. Disassembly can be carried out remotely in case of handling contaminated products.

The clamping allows only the vacuum pad to be supported, since, when cooling is carried out, a sheet of frozen humectant is also established between the support structure and the pad, just as on its opposite face in contact with the product to adhere.

The amount of humectant necessary for the proper functioning of the cryogenic claw is very small and will be defined according to the dimensions. From 100 to 200 cm are enough to perform several maneuvers with a claw of about 800 cm of pad surface.

There is a moisturizer feed tube for compensate for losses in successive maneuvers.

The consistency of the adhesion of the cryogenic extraction device depends on the temperature at which the wet part remains solidified, and on the density and surface shape of the waste to be extracted. In order to ensure adhesion in most cases, it is recommended that the working temperature in the gas expansion zone be lower than -60 ° C (60 ° C below zero). Therefore, all gases that, when expanded below this temperature, do not manifest solidifications thereof, which would obstruct the gas flow are valid.

Therefore the usable cryogenic fluids are:

- Liquid nitrogen or equilibrium gas.

- Argon liquid or gas in equilibrium.

- Liquid helium or gas in equilibrium.

The pad receives the cryogenic fluid from commercial pressure bottles, expanding to atmospheric pressure, from the bottle outlet to the inside of the pad.

As a pad material, a commercial latex sponge about 10 cm thick or expanded polyurethane may be used in an embodiment.

Regarding the application pressure of the pad, the following range can be indicated for guidance and not limited to 0.01 kg / cm to 0.1 kg / cm.

The wetting liquid, although it may be any freezing liquid, will preferably be water, with the chemical corrections that may be necessary due to the nature of the process, taking into account, however, the changes that could be introduced at the freezing point.

The field of use will be very variable, and we can cite as an example:

Handling of delicate elements, where there may be consistency problems or physical damage of these elements to be taken by other means. Remote manipulation of elements of difficult selective grip in situ.

Collection of pulverulent elements and this without also creating dispersions thereof. Maintenance of solid products of granulometry or various size, without producing disintegration, dispersion, physical damage or mixing in the ignited material.

Obtaining "replicas" of the state of aggregation of the material lit in the ideal zone for the subsequent processing of the same and maintaining the physical integrity of the material. Obtaining "replicas" of the relief or topography of the material lit by means of the "footprint" on a moldable surface, resulting from the application on it of the material in a state of cryogenic adhesion to its pad. Mixed cases to those mentioned above or based on their characteristics or principles. For your better understanding, there are attached, by way of example, drawings of an embodiment of the present invention by way of explanatory but not limiting example.

Figures 1 and 2 are respectively a schematic section of an extraction device according to the invention and a plan view thereof.

Figures 3, 4, 5, 6 and 7 are schematic views representing, respectively, different operational phases of the process object of the present invention.

For the realization of the present invention, an extraction device with a freezing surface layer is essential, for example, by cryogenic means that could be designated by "cryogenic claw", as schematically observed in Figures 1 and 2. Said collection device or "cryogenic claw" comprises an adaptable area or pad -1- consisting of a moldable, flexible and porous element, capable of absorbing a certain amount of moisture creating a thin film on the underside -2- and in the moment of application on an object to be handled, between the lower face of the pad and the adjacent surface of the object. In a preferred embodiment the pad will be made of latex. Given the characteristics of the process, the pad should allow the expansion of the cryogenic fluid inside.

The pad -1- will be coupled to a support -3- preferably made of a metal material, such as a steel plate. A ballast -4- adapted to adapt the pad to the surface of the residue or body to be manipulated when exerting a predetermined pressure will preferably be adapted on the support structure.

Said ballast may be suppressed in the case where the cryogenic claw or extraction device is of sufficient weight to give rise to the desired pressure, or in the case in which the claw handling device directly transmits the necessary force to it. for adaptation to the material to be handled.

The pad assembly with the support and eventually the ballast is incorporated into a central arm -5- provided superiorly with a handle -6- which can take any variable shape. The arm -5- will drive inside a conduit -7- preferably made of copper or stainless steel to drive the cryogenic fluid from the storage point to the pad inside which said duct -7- will communicate with some arms preferably in radial arrangement -8-, in variable number, provided with liquid distribution nozzles Cryogenic to the mass of the flexible pad -1-. Likewise, the arm -5- will contain the electric conductor -9- destined to feed a heating battery -10- integrated in the pad -1- and destined to allow a quick defrosting of the extraction device to release the object or mass of transported waste .

The arm itself -5- allows the passage of the conduit -11- destined to the feeding of moisturizing liquid that is connected inferiorly with some radial distribution arms -12- equipped with nozzles for the exit of the liquid.

Finally, the arm -5- also allows the passage of the conductor -13- for the connection to a thermocouple represented schematically with the numeral -14-, designed to control the temperature of the pad in the different phases of the process that make it necessary.

The extraction device or cryogenic claw will also have an insulating mass -15- opposite the area of contact with the object to be handled, intended to improve the cooling rate.

In figures 3 to 7 an embodiment of the process object of the present invention is schematically represented, with the aid of the extraction device which is also the object thereof.

The example shown shows a cryogenic claw or extraction device that has been indicated with the joint numeral -16- that has the flexible pad -17- and that by means of a remote control system -18-, not shown in detail, has been arranged on a little stable mass -19- that you want to manipulate. In the case represented by way of example, the maneuver will consist of depositing the dough in an adjacent collector -20-. After placing the cryogenic claw by means of the maintenance device on the waste mass -19-, with the pad -17- previously moistened, It will then proceed to adapt the pad -17- on the mass to be handled -19-, as shown in Figure 4 at which time, given the flexibility characteristics of the pad -7- a good adaptation is achieved of said pad on the dough to be handled. After this phase, the cryogenic fluid will be entered by controlling its temperature by means of the sensor, reaching the expected temperature regime that may be preferably between -60 ° C and -90 ° C, which will cause the layer of humidification transformed into ice has resulted in the union of the unstable mass -19- on the underside of the pad -17-. The next phase consists of lifting the extraction device -16-, as shown in Figure -5- and moving the mobile assembly -18- to place it above the collection area -20-, in which At the moment, the previously formed frozen layer will be liquefied to allow the detachment of the dough to be handled -19-, which may consist of a total of the previously manipulated dough or only part of it, which would force Repeat the process until its complete completion. The liquefaction of the ice layer previously formed can be achieved simply by heating due to the atmospheric temperature if it is sufficiently high or with the help of the heating system formed by the heating battery -10- previously explained.

The wetting of the pad will be carried out with an easily frozen liquid, for example, water and the application of the liquid sheet can be carried out by impregnating the pad or by other means.

Once the mass to be handled has been detached, the device will be able to start another work cycle.

Claims

1. Procedure for the manipulation of bodies that have reduced mechanical stability or non-aggregate state, which is characterized by the placement of a flexible and adaptable pad above the object to be manipulated, by humidifying the lower face of the pad with a freezing liquid and the subsequent placement of the pad on the mass of the object to be handled with a certain pressure to achieve its adaptation, then freezing the layer of freezing liquid in contact simultaneously with the flexible mat and with the body surface to be handled and then proceeding to lift the assembly constituted by the mat and the body to be manipulated together by the frozen liquid layer, moving the assembly to the place provided for its deposit, at which time the liquid will be defrosted to allow the separation of the body to be manipulated with respect to the conveyor mat

2. Procedure for handling bodies that have reduced mechanical stability or non-aggregate state, according to claim 1, characterized in that the freezing liquid is water.

3. Procedure for handling bodies that have reduced mechanical stability or non-aggregate state, according to claim 1, characterized in that the contribution of freezing liquid to the lower face of the pad is produced by wetting the mass of the pad.

4. Procedure for handling bodies that have reduced mechanical stability or non-aggregate state, according to claim 1, characterized by the use of the expansion of a cryogenic liquid inside the mat to produce rapid freezing of the liquid layer frozen between the face lower pad and body to handle.

5. Procedure for the manipulation of bodies that have reduced mechanical stability or non-aggregate state, according to claim 1, characterized in that the defrosting of the frozen liquid occurs by means of heat input through the inside of the pad.

6. Procedure for handling bodies that have reduced mechanical stability or non-aggregate state, according to the preceding claims, characterized by placing the mat on top of the body to be manipulated so that the lateral dimensions of the latter exceed those of the object to be handled. .

7. Device for carrying out the process object of claims 1 to 6, characterized by comprising a flexible and adaptable pad assembly, of a moldable type and porous nature, which is supported by a plate optionally provided with a layer with insulation characteristics thermal and eventually equipped with ballast weights, means of distribution of the wetting liquid, means for the distribution of the cryogenic liquid as well as heating and temperature control means being incorporated into the pad.

Device according to claim 7, characterized in that the flexible and adaptable mat is incorporated through an insulating layer to a metal support plate which in turn receives an upper arm provided with suspension means for transport by means of a device for remote control that allows the passage of the inside of the pipes of moisturizing liquid, cryogenic liquids, electrical conductors for the heating system and conductors of the control devices.

9. Device according to claims 7 and 8, characterized in that the cryogenic fluid conduit it presents a series of distributing branches of the cryogenic liquid to the mass of the mat inside the mat mass.

10. Device according to claims 7 to 9, characterized in that the mat is constituted by a porous mass of latex.