WO2015124773A1

WO2015124773A1 - Container for the storage of radioactive waste

Info

Publication number: WO2015124773A1
Application number: PCT/EP2015/053749
Authority: WO
Inventors: Ewald Risse
Original assignee: Cura Ingenieurgesellschaft Mbh
Priority date: 2014-02-24
Filing date: 2015-02-23
Publication date: 2015-08-27
Also published as: DE102014002390B3

Abstract

A container for storing radioactive waste is provided with: an inner casing (12) for holding the radioactive waste (14); a rigid outer casing (22, 28); and a flexible arrangement (16, 26) of compartments arranged between the inner casing (12) and the outer casing (22, 28), said compartments being filled with a swellable aluminium oxide material.

Description

Container for storage of radioactive waste

The present invention relates to a container for storing radioactive waste.

While nuclear energy has been used extensively worldwide for decades to generate energy, it has not been possible to satisfactorily solve the problem of storing the waste that occurs. For example, the storage of radioactive waste requires the provision of technical barriers that effectively and long term prevent the migration behavior of radioactive nuclides. The natural geological storage sites alone can not effectively prevent the migration of toxic solutions whose transport mechanisms are determined by the driving force of a high concentration gradient (diffusion) and / or by convection and dispersion (hydraulic gradient).

In EP 0 390 375 B1 there is shown a storage module for storing nuclear waste material, the module having an inner cavity formed of concrete defined by sidewalls and a floor and closed by a removable lid, a waste container in the cavity is included. A granular filler material is provided to at least partially fill a gap defined between the waste container and the module, the granular filler comprising 20% to 80% sand filler, 10% to 40% water-absorbing clay, and an organic liquid-absorbing material.

The present invention is therefore based on the object to provide a container for storage of radioactive waste, which provides not only effective radiation shielding for the radioactive waste, but also the transport mechanisms of the various nuclides contained in radioactive waste, such as. Co-60, Cs-137, Sr-90 and Zn-65, effectively inhibited.

According to the present invention, this object is achieved by a container for storing radioactive waste having an inner sheath for receiving the radioactive waste, a rigid outer shell, and arranged between the inner shell and the outer shell flexible chamber assembly, which is filled with swellable Tonerdewerkstoff. The inner shell may in this case be the shell of a receptacle for radioactive waste to be sheathed, eg the wall of a barrel or a barrel, or it may be its own be provided to receive radioactive waste. Since the inner shell serves only to fix the einzulagernden radioactive waste spatially, any rigid or flexible containers, such as metal, glass, ceramic, plastic, concrete or textile materials can be provided as an inner shell. The rigid outer shell acts as a boundary for the toner material when it swells after the beginning of storage by the decay processes taking place in the container. In addition, the outer shell acts as a stable protective body for the container.

The arranged between the inner shell and the outer shell flexible chamber arrangement is in this case designed so that the inner shell and thus the radioactive waste is completely surrounded by alumina material, but allows swelling of the Tonerdewerkstoffs and a concomitant shift of the Tonerdewerkstoffs in a targeted manner. The alumina material acts on the one hand as an absorber for radiation emitted by the radioactive waste, and on the other hand as an adsorber for any components of the radioactive waste, which succeeds to penetrate the inner shell. The provided in flexible chamber arrangement Tonerdewerkstoff, which could thus be briefly referred to as "ad-absorber", this is particularly suitable for receiving radionuclides, which are adsorbed on the alumina material and incorporated by ion exchange in the crystal lattice structure of the alumina material, where The resulting densification and mineralization of the alumina material ensures a long-term safe enclosure of the radioactive waste to be stored, by which the escape of free radionuclides is prevented in the best possible way by the thermodynamic and kinetic processes occurring here.

Preferred embodiments of the container according to the invention will be apparent from the dependent claims.

Unintentional displacement of the alumina material introduced in the chamber assembly can be avoided by providing a chamber assembly having a plurality of self-contained chambers.

The chamber assembly may include an array of tubing wrapped around the inner shell. Such an arrangement of filled with Tonerdewerkstoff hoses, which may for example be wound spirally around the inner shell, is particularly suitable for sheathing a radioactive waste receiving inner shell, the has an individual shape (shape and / or size), for example, if the radioactive waste to be stored is bulky components of broken power plants that can not be accommodated in standardized containers.

The placement of the chamber assembly around the inner shell can be simplified if the chamber assembly comprises a composite of a plurality of adjacent chambers. Such a composite of adjacent chambers may have a regular or irregular arrangement of chambers in which the adjacent chambers are arranged, for example, in a grid or honeycomb structure. Furthermore, the chamber assembly may be formed in the form of mats, which are placed around the inner shell, or as a preformed composite whose shape is adapted to the shape of the Innenhülie, which is particularly advantageous when a plurality of waste elements are stored should all have the same shape. For example, when radioactive waste is to be stored in the form of barrels of standardized size, the chamber assembly may be formed as a total barrel-shaped composite of a plurality of adjacent chambers in which the respective barrel is received.

The required flexibility of the chamber assembly, which permits swelling of the alumina material disposed therein, can be provided by various means that can be used individually or combined with each other. Thus, the ratio of the volume of the individual chambers with respect to the volume of the incorporated into this Tonerdewerkstoffs be sized so that there is sufficient space for the swelling of the Tonerdewerkstoffs available, for example by the amount of the Tonerdewerkstoffs is chosen so that this before the introduction of radioactive waste and thus before the start of the swelling process 20 to 50%, preferably about 30%, the inner volume of the chamber assembly fills. Furthermore, the chamber arrangement may have accommodation volumes for the alumina material which are made of a stretchable material and thus allow a volumetric expansion in the swelling of the alumina material. For this purpose, either the chamber arrangement can be made as such from a stretchable material, or else have a multi-layered structure in which the spatial arrangement of the individual chambers is determined by means of a non-stretchable cover material to which receiving volumes made of a stretchable material are attached. Also, flexible connecting elements can be provided between the individual chambers, the one allow for some transfer of adjacent caramers. Preferably, the flexible chamber assembly is configured to permit swelling of the alumina material by 300 to 1000%, ie, 3 to 10 times the initial volume. Finally, the chamber assembly may be made of a material which is subject to a predetermined decomposition over the duration of storage of the radioactive waste in the container, so that at the beginning of the storage of the loosely provided in the chamber arrangement Tonerdewerkstoff is held in a preselected spatial arrangement, the Chamber arrangement, however, with increasing mineralization and thus hardening of the clay material increasingly decomposed.

In preferred embodiments of the invention, the chamber arrangement has a plurality of layers, wherein the chambers in adjacent layers are preferably arranged offset from each other so that the overall toner material forms a closed layer which completely surrounds the inner shell. A multilayered staggered arrangement of the chambers filled with alumina material promotes the formation of a homogeneous layer of the alumina material, since swelling of the alumina material compensates for one layer of these less densely filled regions in adjacent layers, as encountered in particular at the connecting regions between adjacent chambers.

Suitable materials for forming the receiving volumes of the chamber assembly include thermoplastics, and in particular polyhalo-olefins. A particularly preferred material for the formation of the chamber assembly is PTFE, in particular microporous PTFE, in which a nested networks of open, labyrinthine pores has been formed by means of a special sintering process. The PTFE material may also contain additives such as copper, lead, carbon or nanosmectides, with which the radiation permeability of the PTFE material can be further reduced, in particular with respect to gamma radiation.

Between adjacent layers of the chamber assembly, flexible partitions may be provided. These can be made of similar materials as the chamber arrangement, or be designed as a special radiation-absorbing or radiation-reflecting layers.

The alumina material is preferably a mineral material selected from the group of smectites and zeolites and mixtures thereof. Smectites are swellable Three-layer clay minerals composed of two Si0 ₄ tetrahedral layers with an intermediate AlCvOctahedron layer. Smectites have a high adsorption and ion exchange capacity and can store large amounts of water. Zeolites are also skeletal silicates with a crystal lattice of Si0 ₄ and A10 ₄ , where here the crystal lattice of Si0 ₄ - and AlC tetrahedra is constructed, which are linked via oxygen bridges. The cavities formed in the crystal lattice form a uniform pore structure whose pores are wide, preferably at 0.3 to 0.5 nm. The zeolite provided in the chamber arrangement acts as an ion exchanger for metal ions released from the radioactive waste (Ag, Ba, Cd, Cr, Cs, Cu, Fe, Hg, Li, Sr, Zn) exchanged for cations of the zeolite and thus in the Crystal structure of the zeolite be bound. Preferably, the zeolite provided as the alumina material has a SiCVAlC ^ quotient of more than 4. Particularly suitable zeolites are thus clinoptilolites, calcium-sodium-potassium zeolite minerals of the heulandite group and AIumino framework silicates.

Preferably, the alumina material has a pH of 8 to 10, a micropore volume of about 0.4 cm ³ / g and an internal surface area of about 1000 m ² / g. The employed alumina material preferably has a Mohs hardness of from 2.0 to 4.0, a density of from 2.0 to 2.5 g / cm ³ , most preferably from 2.1 to 2.2 g / cm ³ , and a porosity of 32 to 40%. Particularly preferred alumina materials are clinoptilolite Ca and clinoptilolite Na, with clinoptilolite Ca having a high pH being preferred because of its greater cation exchange capacity. Preferably, the alumina material is filled with a bulk density of 750 kg / m ³ in the chamber assembly.

The rigid outer shell of the container preferably has a radiation protection layer made of concrete, wherein the radiation protection layer can be made in particular of hematite concrete, barite concrete or geopolymer concrete. The concrete radiation protection layer should have a low leaching rate, a high hardness, a small volume increase and a low diffusion coefficient. The leachability of radionuclides such as cesium or strontium, can be reduced by reducing the water / cement ratio, as well as by adding water glass or zeolite in the concrete preparation. For example, by adding the natural zeolite mordenite, the leaching rate for cesium can be reduced to about the fiftieth part. The rigid outer shell of the container may further comprise a collision and corrosion protection layer, in particular a layer made of ECC concrete.

The invention will be explained in more detail below with reference to the accompanying drawing, which shows a schematic sectional view of a container according to the invention.

The radioactive waste storage container 10 shown in the figure comprises an inner casing 12 for receiving radioactive waste 14. The inner casing may in this case be the casing of a radioactive waste receptacle to be covered, e.g. the wall of a barrel, or the outer wall of a fuel bundle, such as e.g. a Castor container. The inner shell 12 is surrounded by a plurality of tubular layers 16, which are filled with a swellable Tonerdewerkstoff, in particular KHnoptilolith. As indicated in the figure, in the exemplary embodiment shown, the chambers of the tube layers 16 are designed as tube layers extending vertically on the vertical walls of the inner envelope 12.

The tube layers 16 are surrounded by a partition 18, which is made in the embodiment as a double-walled layer of a high temperature resistant thermoplastic material, in particular polytetrafluoroethylene (PTFE), which surrounds the tube layers 16 sealingly.

In the space 24 formed between the partition wall 18 and the inner side 20 of a rigid outer wall 22 further layers 26 of a swellable Tonerdewerkstoff, in particular KHnoptilolith, filled chamber arrangement are provided. In the illustrated embodiment, the chambers of the tube layers 26 are designed as on the vertical walls of the inner shell 12 horizontally extending tube layers.

As explained above, the chamber arrangement is flexible in order to allow swelling of the toner material disposed therein. The total amount in the space between the inner shell 12 and the inner side 20 of the rigid outer wall 22 provided amount of Tonerdewerkstoff here is such that it fills up the space after complete swelling, so that in the course of mineralizing the toner layer between the inner shell 12th and the inside 20 of the rigid outer wall 22, a compact mineral layer is formed, which shields the radioactive waste 14 received in the inner shell 12 dense and radiation shielding. In the embodiment shown in the figure, a layer 28 of ECC concrete is provided around the rigid outer wall 22, which is made of Stratilenschutzbeton, which serves as Koilisions- and corrosion protection layer.

Claims

claims

ί. Containers (10) for the storage of radioactive waste (14)

- An inner shell (12) for receiving the radioactive waste (14);

- A rigid outer shell (22, 28); and

- One between the inner shell (12) and the outer shell (22, 28) arranged flexible chamber assembly (16, 26) which is filled with swellable Tonerdewerkstoff.

2. A container according to claim 1, wherein the chamber assembly (16, 26) comprises a plurality of self-contained chambers,

3. A container according to claim 1 or 2, wherein the chamber assembly (16, 26) comprises an array of tubes which are wound around the inner shell (12).

4. A container according to claim 1 or 2, wherein the chamber assembly (16, 26) comprises a composite of a plurality of adjacent chambers.

5. A container according to claim 3 or 4, wherein the chamber assembly (16, 26) comprises a plurality of layers.

6. A container according to claim 5, wherein the chambers are arranged offset in adjacent layers to each other.

7. A container according to claim 5 or 6, wherein between soft layers of the chamber assembly (16, 26), a flexible partition (18) is provided.

8. A container according to any one of claims 5 to 7, wherein the outermost layer of the chamber assembly (16, 26) on the inside (20) of the outer shell (22, 28) is fixed.

9. A container according to any one of the preceding claims, wherein the chamber assembly (16, 26) made of PTFE (polytetrafluoroethylene) is made.

A container according to any one of the preceding claims wherein the alumina material is a mineral material selected from the group consisting of smectites, zeolites and mixtures thereof.

11. The container of claim 10, wherein the alumina material comprises a zeolite material selected from the group consisting of clinoptilolites, heulandit group calcium-sodium-potassium zeolite minerals, and alumino skeletal silicates.

A container according to any one of the preceding claims, wherein the chamber assembly (16, 26) is arranged to permit swelling of the alumina material 3 to 10 times its original volume.

13. A container according to claim 12, wherein the soft earth material, the inner volume of the chamber assembly (16, 26) only partially, preferably 20 to 50%, and in particular about 30% fills.

14. A container according to any one of the preceding claims, wherein the outer shell comprises a radiation protection layer (22) made of concrete.

15. A container according to any one of the preceding claims, wherein the outer shell comprises a collision and corrosion protection layer (28).