FR2583913A1 - WASTE STORAGE CONTAINER FOR DISPOSAL - Google Patents

Abstract

The invention relates to a storage container for waste to be disposed of. THE CONTAINER 10 INCLUDES A RECEPTACLE 11 CONTAINING RADIOACTIVE WASTE 12, AS WELL AS A POROUS MECHANICAL BARRIER 16. THIS BARRIER, ENCAPSULATING THE ENTIRE RECEPTACLE 11, CONTROLS THE PENETRATION OF WATER IN THIS RECEPTACLE BY DIFFUSION, AS WELL AS DIFFUSING, AS WELL AS WASTE ESCAPING FROM THE RECEPTACLE 11 IN CASE OF BREAKAGE. APPLICATION IN PARTICULAR TO LONG-TERM STORAGE OF RADIOACTIVE WASTE.

Description

WASTE STORAGE CONTAINER FOR DISPOSAL

  The present invention relates, in a manner

  general, to a waste storage container to be

  and, more particularly, to a container for storing hazardous and / or radioactive waste for long periods of time. periods. The Government of the United States of America holds rights in this invention under contract N DE-ACO6-77RL01030 between the US Department of Energy and the so-called

Rockwell International Corporation.

  Conventional non-destructive processes for storing hazardous and / or radioactive waste to be disposed of frequently involve the use of specially designed storage containers, which are either buried near the surface of the earth's crust (embankment), either in a deep geological formation. Because any type of single-walled container is likely to fail at some point, due to malfunction or mechanical damage, many containers for

  waste consists of two watertight barriers or

  double-walled designs, to prevent release of the contents of the receptacles. The inner receptacle or primary receptacle, usually consisting of a metal or a metal alloy, is surrounded by an external barrier or secondary barrier which may be either a second sealed metal receptacle or a layer of any absorbent material surrounding the receptacle. primary receptacle. Both types of barriers are intended to remove or reduce the extent of release of hazardous waste and / or

  radioactive in case of rupture of the primary receptacle.

  The essential problem inherent in using the conventional sealed metal container as a secondary barrier is its vulnerability to

  corrosion and other environmental conditions

  tites resulting in the rupture of the pro-

  and, consequently, by the release of

  that the primary receptacle is no longer able to contain. In order to avoid this problem, attempts have been made to fabricate weathertight secondary barriers made of a ceramic material, since the ceramics are extremely stable and resistant to corrosion. In addition, the ceramic materials do not chemically react with the metals constituting the containers or with the substances present in the landfill environment. One such process is described in an article by P. E. Ahlstrom, "Ceramic and Pure Metal Canisters in Buffer Material," NUREG / CP-0005, U. S. NucLear Regulatory Commission, Washington, D.C. 287-316, 1979. This article deals with

  the use of a ceramic coating deposited her-

  meticulously by hot isostatic pressing, around

  primary waste receptacle, to form a

  waterproof coat around this receptacle.

  Nevertheless, the above-mentioned ceramic encapsulation technique has certain disadvantages. First of all,

  because the protection is obtained only by

  finely, any breakage of the ceramic coating

  that renders its usefulness useless, and the extreme friability of ceramics renders them particularly prone to breakage either at the manufacturing stage or during transport to the storage site. Secondly, the equipment required for hot isostatic pressing is expensive, cumbersome and based on

constant evolution.

  The other type of secondary barrier mentioned

  above consists of a layer or zone of absorbing

  surrounding the primary waste receptacle. Such a layer of absorbent material acts as a diffusion barrier, and is intended to control and delay the release of the waste after a rupture.

  of the primary receptacle. In the most frequent process

  used to store hazardous and / or radioactive wastes to be disposed of, this absorbent material is a backfill consisting of crushed rock or clay, or even a mixture of two. The most commonly used clay is bentonite, a sodium montmorillonite that swells when it absorbs liquid, thus providing continuity and low permeability to barrier water. This

  swelling gives the bentonite a

  "self-sealing" property to fill and seal any voids or cracks found there, so as to form a virtually watertight barrier. Although clays generally have satisfactory swelling properties, they can

  become unstable during the geological times

  sages for the safe disposal of hazardous and / or radioactive wastes, these durations being between hundreds and thousands of years. For example, bentonite can deteriorate in the long run to a non-swelling form, either by chemical alteration or by

  thermal decomposition. In an aqueous medium containing

  With significant amounts of dissolved calcium, sodium bentonite is converted by ion exchange into calcium montmorillonite, a non-swelling clay. In the presence of potassium ions, the bentonite can be chemically converted into iLLite, another non-swelling clay. At approximately 370 C, bentonite irreversibly loses the water it

  encloses, and becomes a non-swelling form.

  Therefore, clays can not be considered

  derives as giving full satisfaction as

  barrier to control the clearance rate of

  radioactive waste-releasing heat.

  Therefore, a fundamental object of the present invention is to overcome the aforementioned drawbacks, by providing a new and useful waste storage container to be removed, which securely traps, for long periods, waste

dangerous and / or radioactive.

  Another object of the present invention is

  to propose a radioactive waste storage container

  active with secondary barrier to control the rate of release of radionuclides upon rupture of the inner receptacle or primary receptacle

  containing radioactive waste.

  The present invention also aims to equi-

  per the aforementioned container of a secondary barrier providing physical protection to the inner receptacle,

  in order to extend its useful life.

  In addition, the present invention also aims to provide a secondary barrier which is a simple and robust, inexpensive, easy to manufacture, and which can be implanted on the storage site and which is stable and durable

  in service during the envisaged geological periods.

  The waste storage container according to the

  The invention includes a primary receptacle that contains hazardous and / or radioactive wastes and a secondary barrier that fully encapsulates the receptacle. The secondary barrier consists of an inert and porous ceramic material controlling the rate

  waste when the receptor breaks down.

  primary tackle. This secondary barrier comprises several interrelated parts with mutual interlocking

by means of subjection.

  The invention will now be described in more detail by way of nonlimiting example, with reference to the appended drawings in which: FIG. 1 is a perspective view of one of the embodiments of a waste storage container; designed according to the present invention;

  Figure 2 is a longitudinal section illustrating

  sensing the container of the present invention surrounded by a backfill in a buried storage place; Figure 3 is a cross section on the line 3-3 of Figure 2; and Figure 4 is a fragmentary perspective of

  one of the embodiments of a means of subjection

  used in the context of the present invention.

  Reference should now be made in detail to the exemplary embodiment illustrated in the accompanying drawings: FIG. 1 shows a storage container

  waste to be disposed of, generally designated by the reference

  10, and designed to store and store radioactive waste for long periods of time. Although the container according to the invention is particularly well suited to the long-term storage of radioactive waste, it is obvious that the invention is not limited to this field, but that it finds utility in the safe storage of any toxic or dangerous waste

  that are buried in the soil in the long run.

  As illustrated in Figure 2, the container

  comprises an internal container or receptacle 11 of

  designed to contain radioactive waste in the form of glass or other material 12. Receptacle 11

  consists of a cylindrical body made of a suitable alloy

  pried of stainless steel, provided with a side wall 13 and a closed end wall 14, concave or concave

  and forming a single piece with the side wall 13.

  The tightness of the receptacle 11 is adequately provided to exclude the release of the contents of this receptacle. It will be observed that the specific configuration of the receptacle 11, as well as the types of waste contained therein, may vary widely.

  measurement without departing from the scope of the invention.

  The receptacle 11 is integrally encapsulated to

  inside a cylindrical barrier of low permeability

  capacity, globally designated by 16 and comprising two

  shells or semi-cylindrical parts 17 and 18

  Lées. Part 17 has a semi-cylindrical side wall

  ending at the opposite ends, by

  end walls 21 and 22 substantially semi-circular

  lar. Similarly, the portion 18 has a wall

  semi-cylindrical side 23 ending at its ends.

  opposite sides, by extreme walls 25 and 26 globally

  semicircularly. Grooves 27 and 28 of sec-

  substantially rectangular, formed along the longitudinal edges of part 17, extend in the longitudinal direction of this part 17 and across

  the end walls 21 and 22 to receive Lan-

  elongated tracks 30 and 31 of further configuration

  Part 18, in order to establish a liaison

  between parts 17 and 18.

  Parts 17 and 18 have substantially greater wall thicknesses than the thickness of the wall of receptacle 11, and include

  wall areas 32 and 33 whose thicknesses are themselves

  even larger than the rest of those parts 17 and

  18, so as to conform overall to the shape of the receiver.

  11. The inner diameter of the composite barrier 16 is slightly larger than the outer diameter of the receptacle 11 to provide, between them,

  a radial gap 35 allowing any expansion

  temperature of the receptacle 11 resulting from the

  disintegration heat of radioactive waste.

  It is evident that the storage container 10 of the present invention is designed, as are the

  conventional radioactive waste storage containers

  to be buried in an excavation or tunnel in the rock or in the host air, either of a surface close to the ground (embankment) or of a deep geological formation. Once the waste is put in place, the excavation or the tunnel is filled by the crushed rock 37 or by the clay produced during the production process.

  digging, the waste container being completely

  closed in this filling material. In accordance with the federal regulations enacted by the Government of the United States of America, it is necessary that, in the event of a rupture of the primary receptacle, such commercial radioactive waste containers release slowly and uniformly the waste to the host rock, according to a low rate of 1 part per 100,000 contents

of the receptacle.

  For this purpose, the barrier 16 of the present invention is made of a porous ceramic material, preferably mullite, which is chemically and mechanically stable for long periods of the order of several thousand years. The corrosion rates of such an inert ceramic material are extremely low, even in boiling acids or alkalis. The low permeability of the porous ceramic barrier according to the invention has the effect of controlling the penetration of water into the primary waste receptacle to maximize its useful life;

  and, in case of breakage of the primary receptacle, of

  the release of hazardous and / or radioactive waste

  assets by reducing it to a controlled diffusion rate.

  Since the ceramic diffusion barrier constitutes a mechanical or physical device rather than a chemical means for controlling the release of

  waste, its permeability may be calculated

  and it must remain constant throughout its intended useful life. Likewise, it is simpler to predetermine the chemical stability of ceramics since it is composed of typical metal oxides, such as aluminum oxide and / or silicon dioxide, which are common components. of

geological systems.

  Another advantage of the ceramic diffusion barrier of the present invention, as opposed to a chemical barrier or a clay barrier, is that it allows the use of crushed rock fill when the properties of the rock are present. host are an important or desirable factor

  in the isolation of waste. In the basatte, for example

  ple, the dissolved oxygen consumption by the phase

  The reactive glass of the host rock is an important parameter

  bearing to ensure a low corrosion rate of iron and iron alloys. The use of a crushed stone backfill, together with the porous ceramic diffusion barrier 16, makes it possible to draw

  advantage of these two materials.

  It is obvious that, if desired,

  physical barrier of the present invention may also

  be combined with chemical means to control the release of waste. For example, where high reliability of the control of the release of the waste is required and the clays whose use is envisaged are stable, the physical barrier 16 can be used in conjunction with such a barrier.

  clay, so as to minimize possible deficiencies

  running lances When clearing

of waste.

  Another advantage offered by the porous ceramic barrier 16 of the present invention is that a hermetic container shell is not necessary since said barrier is,

25839 13

  in fact, moderately permeable to water. Therefore, any simple mechanical securing device, such as that described hereinafter, may be employed. This allows an assembly of the barrier, that is to say a joining of the two halves 17

  and 18, near the storage point.

  As shown in FIG. 1, one of the securing means for holding the parts

  17 and 18 tight against each other may be

  ter in the form of at least one metal strip 38 resistant to corrosion, which is designed to surround

  parts 17 and 18 to maintain cohesion.

  The ribbons or collars 38 may advantageously be equipped with eyelets 40, to receive the hooks

  appropriate hoisting or handling equipment.

  In addition, or instead, necklaces 38, a cement

  Adequate ceramic may be deposited along the

  complementary marginal faces of both parties 17

and 18.

  Another means of securing is in the form of a key and groove system, having a pair of elongated keys 41

  extending longitudinally over the complete edges

  of Parts 17 and 18. As shown in part

  4, each key 41 includes

  takes a central region or soul 42, as well as

  protuberances 43 and 45 in the form of bulbs which extend

  longitudinally and engage in

  complementary grooves or grooves in Parts 17 and 18. The keys may extend the entire length of Parts 17 and 18,

  or only short distances to the

  from the opposite ends of these parts.

  ties. While FIG. 1 illustrates such a key and groove system in conjunction with collars 38, it will be appreciated that this system can be used alone or in combination with, or even combined with, an adhesive.

this adhesive and said collars.

  The description above shows that the objectives

  The present invention has been fully achieved.

  The invention provides an improved container of

  waste to be disposed of, which contains waste

  hazardous and / or radioactive for long periods.

  The container according to the invention has a porous and low permeability mechanical diffusion barrier, which raises the yield to a maximum by prolonging the useful life of the inner receptacle and limiting the transfer of masses from the container to that authorized by diffusion. The presence of a novel porous ceramic diffusion barrier provides physical protection of the primary waste receptacle to increase its longevity, and effectively controls the release of waste, within or with allowable parameters. , in case of rupture of the primary receptacle. Limiting the diffusion of mass from the cracked receptacle, and creating a porous flow environment around the container, promotes modeling of long-term performance even if storage takes place in the an environment of

fractured rock.

  It goes without saying that many modifications can be made to the container described and shown,

  without departing from the scope of the invention.

1 1

Claims (10)

  Container (10) for disposal of waste, characterized in that it comprises   a receptacle (11) for containing radioactive waste   active agents (12) and a porous metal barrier (16) which integrally encapsulates said receptacle (11)   to control the penetration of water into this receptacle   tackle and the release rate by diffusion of   escaping from said receptacle (11) in case of rupture of it.   Container according to claim 1,   characterized in that the barrier (16) is made of a ceramic material.   Container according to claim 2, characterized   terized by the fact that ceramics consist of mullite.   4. Container according to revendicaciorn 1, charac-   terized by the fact that the barrier (16) 'consists of   several parts (17, 18) joined together to prevent ring the receptacle (11).   Container according to claim 4,   characterized by the fact that the above-mentioned parts consist of a pair of opposed semi-cylindrical shells (17, 18).   Container according to claim 5,   characterized in that it has means (30, 31;   38; 41) to subjugate each other's predecessors cited (17, 18).   Container according to claim 6,   characterized in that the securing means is an adhesive interposed between the complementary ridges aforesaid parts (17, 18).   Container according to claim 6,   by the fact that the means of subjugation   consists of a cement interposed between the joint edges   elementary parts (17, 18).   Container according to claim 6,   The fact that the securing means consists of at least one belt (38) the parts joined together (17,18).   10. Container according to claim 6, characterized in that the means of subjection   includes grooves along the joint edges   of the abovementioned parts (17, 18) and removable keys (41) housed in said Gorges.