METHOD FOR PREPARATION AND BURIAL OF RADIOACTIVE WASTE (RAW)

Abstract

 The object of the present invention is to increase the reliability of a long-term RAW isolation/burial, the efficiency of the burial and to reduce the cost of the burial. The process of the present invention utilizes an open-cut mine working with a completed cycle of mining minerals, in particular open-cut mines 3 with a rock base, having an equipped station 8 for RAW discharging and pretreating the same before the burial, a post 2 for retreating MRAW, a route network 6.
The RAW delivered for burial is pretreated on the equipped station 8, MRAW is retreated on the post 2 for recycling the metal decontaminated to a level allowing an unlimited use of the same in RF through "Vtorchermet" or as direct deliveries to metallurgical enterprises, the secondary RAW of the retreatment (disposable and solidified decontamination solutions, chips and fragmentation cuts, etc.) is enclosed into individual packages 12, closed, the upper covers 13 of IPs 12 are welded, and a cumulative flow of pretreated RAW is transported to a quarry for burial.

Description

[0001] The present invention relates to processes for pretreating and burying deep in the soil radioactive waste (RAW) generated and temporarily stored in the course of operation and while putting out of operation at objects and facilities of nuclear power plants and industries, at objects of costal service for nuclear submarine and surface marine fleets, at plants for uranium material mining and processing, for processing irradiated nuclear fuel at research and industrial nuclear reactors and installations, at common industrial enterprises and health facilities utilizing isotopic products, as well as at oil and gas extraction enterprises having a substantial amount of metal equipment irradiated by natural radioactive nuclides (RN) taken out from the earth interior together with extracted products.

[0002] The invention according to the present application creates a perspective of founding an active center (active centers) of handling RAW, which would provide for: a centralized collection, examination/pretreatment, repair, recovery and reinforcement of the external antirust protection for delivered packages and containers with RAW, repacking of defective packages into new ones, decontamination of reusable transportation containers and packages, processing of surface-contaminated metal radioactive waste with the return of decontaminated metal into the economic turnover, and a reliable and efficient final burying of radioactive waste in the bulk of exhausted open-pit and (or) open-cut mines.

[0003] There are known processes for a final isolation/burial of radioactive waste in geological formations of the crust where a natural or artificial cavity is filled with RAW comprised in various packages or containers in order to provide the RAW isolation from the environment for the period of said RAW potential danger of ∼1000 years, which is determined by the natural decay of the most of radioactive nuclides enclosed in the RAW, the main emphasis being laid on a long-term reliable isolation of RAW from underground water which can carry the radioactive nuclides and pollute the environment. That is why, cavities in the permafrost, in the layers of clay, mineral salt and in massive rocks are used to bury radioactive waste.

[0004] It is known a similar process of retreating equipment contaminated by radioactive nuclides, disclosed in the description of the RF patent for an invention No 2249056, Int. Cl. C22B60/00, C22B7/00, G21F9/30 of 18.04.2002, published on 27.03.2005, which comprises the decontamination of the assembly, dismantling, fragmentation, sorting by types of metals and by their activity, as well as the decontamination of fragments. After the fragmentation, the surface-contaminated fragments are separated, all the fragments are decontaminated by methods that do not modify the shape or the structure of metals, and are attested as mechanical and physical modifications; the attested fragments are submitted to decontamination by procedures that do not modify the shape or the structure of metals to the levels of a limited or non-limited use depending on the field of a further use of the same; and they are subdivided into fragments to be used for their designated purpose or reprocessed to get products of needed nomenclature products; and the fragments that do not satisfy the attestation requirements are sent for the use in metallurgical industry as radioactive metal waste scrap.

[0005] Drawbacks: said process cannot be implemented autonomously while distant from an equipped site for separating a secondary RAW that is generated by the same: chip, fragmentation scrap, used-up decontamination solutions, rejected scrap, etc. That is why, the remoteness of the site for retreating equipment contaminated by radioactive nuclides from the RAW burial site leads to a lower efficiency of the RAW retreatment and to a higher cost.

[0006] It is known, as the closest prior art, a process for burying radioactive and toxic waste in the RF application for an invention No2008110312, Int. Cl. G21F9/24 of 17.03.2008, published on 27.09.2009, which comprises the steps of burying radioactive waste in a clay layer on sites of clay extraction, not only in wells, but also in open-cut mines or in subsurface workings; placing containers with radioactive waste into the last while establishing a pillar above the containers; filling the free space with plugging material, the same clay being used as the plugging material), the containers being placed at the central part of the clay stratum at a distance of 5-10 m from the bottom of the clay stratum and no less than 5-10 m from the roof of the clay stratum, and about 1 m overlaying clay layer is laid between the containers; sealing the mouth of the well.

[0007] Drawbacks: insufficiently reliable isolation, high cost, insufficient efficiency of the process.

[0008] The insufficient efficiency of the RAW isolation in subsurface workings in clay at the depth of 5-10 m from the bottom of the clay stratum to a level of 5-10 m from the roof is determined by the breaking of solidity in the stratum while carrying out the extraction operation, the placement of containers with RAW, plugging the voids with lumpy clay the water-proof properties of which do not exclude a contact of the RAW radionuclides with underground waters and their migration beyond the limits of the burial site.

[0009] The described placement of containers with radioactive waste is not a burial of radioactive waste but a burial of containers with RAW with the use of a 1 m barrier clay leads to a low efficiency of the burial process and to its high cost due to an irrational use of the volume of the burial cavity.

[0010] Technical result: improvement of reliability of a long-term isolation of the RAW burial, of the efficiency of the RAW burial and a lower cost of the burial procedure.

[0011] Said technical result is achieved thanks to the process for pretreating and burying radioactive waste RAW which comprises the steps of: RAW delivery from the producers of the same to a burial site; pretreatment of the delivered RAW including retreatment of metal radioactive waste MRAW surface-contaminated with radioactive nuclides; placement of the pretreated RAW into the burial volume; final isolation from the environment, wherein, for providing an efficient reliable and final burial of RAW, use is made of open cast mines with a complete cycle of mining minerals, in particular open-cut mines with a rock base, at which are equipped a site of RAW discharge and pretreatment for burying, a station for retreating metal RAW, a route network for RAW transport to the burial plate; as soon as the above mentioned works are over, RAW is delivered from the producers of the same to the burial site, with no limitations as to the origin (technogenic, natural radioactive nuclides NRAN), as to the activity level (low-active LA, medium-active MA, highly active HA), as to the structure, materials, shapes, dimensions, the period and conditions of previous storage of the RAW containers and packages, mainly in unified individual cube-shaped metal packages IP; the delivered RAW is pretreated to get it ready for burial, including repair of packages and containers, restoration of their anticorrosive coatings, repacking of containers and packages are pretreated, their anticorrosive coatings are repaired, defective packages are repacked into new ones; MRAW is processed while eliminating radioactive contaminants by a complex deep decontamination, after which the metal decontaminated and admitted to an unlimited use is withdrawn from the burial procedure and is returned into the economic turnover, while the secondary RAW that represents products of the retreatment process are compacted, solidified, packed into IPs and transferred to a quarry with the other pretreated packages, the ground bottom of said quarry is covered with supplied clay while covering and compacting the layer to get an even horizontal area surface on which the delivered RAW is arranged, using the particular structure of the IPs, in box units or container blocks, providing gaps between the blocks and the walls of the quarry with a height that does not exceed the calculated solidity of a unified IP, then the gaps are filled with clay, the clay is allowed to stand for a while to settle; after the clay depression the gaps are filled up, and the upper edge of the RAW blocks is covered with clay, together with all the gaps, completing the individual clay isolation of each assembled block of the first tier and forming a base site of the second tier, where the block-tier filling of the quarry is continued to the upper reference mark of the project, then the non-filled part of the quarry is filled with clay, completing the outline of the clay isolation in the volume filled with RAW, and then the soil from the dumps of overburden rock is used to cover the top, which completes the final stage of the RAW burial and the quarry recultivation to recover the initially existing natural landscape.

[0012] The improvement of reliability of a long-term isolation burial of RAW is achieved thanks to:

• the use of the rock base of a quarry, which possesses a high mechanical, structural and chemical stability, nuclear resistance, and for the majority of radioactive nuclides contained in RAW, the embedding rock acts like a geochemical barrier;
• the block/tier technology of filling the RAW containing quarry space; filling the gaps between the tiers, the RAW blocks and the walls of the quarry with soft, cushioning stratal clay, able to be self-healing and sorbing radioactive nuclides, compacted up under the effect of atmospheric precipitations and the weight of the upper filling levels, which builds, in association with the rock base of the quarry, a network of powerful barriers to the spread of radioactive nuclides beyond the limits of the burial site and provides for a stable burial in case of seismic activity and tectonic shoves;
• the burial of pretreated RAW into repaired packages and containers or repacked into new ones.

[0013] The improvement of efficiency of the process is achieved thanks to: the use of depleted quarries or open-cut mines with a high holding capacity for long-term isolation/storage of RAW, an existing route network, the unlimited durability which does not require high funding due to the reconversion of an object for extraction of minerals into a RAW burial site rather than to build a new burial object.

[0014] For example, the cost for building new RAW burial objects:

• Radioactive waste storage, III group, at the Kurskaya NPS (RF) -	2 500 mln RUR.
• Gorleben (Germany) -	3 350 mln. DM
• Konrad (Germany) -	2 735 mln. DM
• Yucca Mountain (USA) -	2 500 mln. USD
• Oncalo Center (Finland) -	3 000 mln. EUR

[0015] The object of RAW burial according to the claimed process is a depleted open-cut mine that does not require a high investment, which importantly reduces the cost price of the RAW burial.

[0016] The improvement of the process efficiency is reached thanks to the presence of MRAW surface-contaminated with radioactive nuclides of technogenic or natural origin, the decontamination pretreatment of which to a level of residual radioactivity enabling an unlimited use of the metal returned into the economic turnover and withdrawn from the burial procedure, without taking the expensive volumes of the burial site, while the RAW of the secondary retreatment is packed and buried. Therefore, the MRAW processing in the process of the present application becomes an effective component of retreating RAW before its burial, which excludes the metal good for use from being buried and eliminates the problem of the secondary RAW isolation/burial.

[0017] It is known that 1 t of hollow-bored MRAW (tubes, bends, branches, etc.) takes 3 m³, which means that the return of 1 t of decontaminated MRAW into the economic turnover saves 3 m³ of burial site volume capacity at the cost of 200,000 RUR / m³. The market price for NPS stainless steel scrap, depending on the nickel content of the same, fluctuates from 50,000 to 140,000 RUR per 1 t.

[0018] Therefore, the saving resulting from the retreatment of 1 t of MRAW according to the process of the present application with the retreatment expense of 30,000 RUR per 1 t, including the profit from commercialization and the economy of the volume capacity of the burial site, is as follows:

[0019] At the annual NPS MRAW retreatment productivity of 1000 t, the annual effect is: 670,000 RUR/t x 1000 t = 670 mln. RUR.

[0020] For MRAW from the oil and gas extracting industry, at the price for decontaminated metal of 4,000-5,000 RUR/t, at the annual retreatment productivity of 4000 t/year, the annual economy is

[0021] The total annual economic effect of the saving is

• direct deliveries of RAW from producers thus avoiding the stage and costs of building and exploitation of temporary overland RAW storage sites, particularly in case of decommissioning of radiation-dangerous objects and expiration of the project service life of buildings storing RAW;
• joining of the final stage of the RAW burying and the cultivation of a quarry, filling the empty volume of the upper part of the quarry with ground from the overburden rock dumps, damping ground and tailing dumps for ore and minerals processing waste.

[0022] The costs savings in the burial of RAW while implementing the process of the present application are the result of a minimized investment, economies obtained in the RAW retreatment and comparable in value with the expenses for building RAW burial objects, and the result of reduced expenses of RAW suppliers/producers thanks to the provision of the MRAW retreatment, to the RAW pretreatment and burying without limitations due to its origin (technogenic, natural radionuclides), to its activity level (low-active LAW, medium-active MAW, highly active HAW), to its structures, materials, shapes, dimensions, the period and conditions of the previous storage of the RAW containers and packages.

[0023] The analysis of the prior art level showed that the combination of essential features of the present application, set out in the claims of the present invention is unknown. It has been found that the technical solution of the present application does not explicitly result from the known prior art. The invention is novel, it involves an inventive step and is industrially applicable.

[0024] The applied process is illustrated by the following drawings, in which:

Fig. 1 is the general layout of a complex for RAW pretreating, processing and burying.

Fig. 2 is a functional/traffic diagram of a complex for RAW pretreating, processing and burying.

Fig. 3 is a general view of a unified metal individual package (IP) for RAW.

Fig. 4 is a general view of a bind of the upper IP on the lower one with some IP structural elements to enable the bind,

Fig. 5 is a view of arranging blocks/container blocks with RAW on the n^th stand/tier,

Fig. 6 is a diagram of the temporary roof framework mounting on loading shanks of the upper row of individual packages,

Fig. 7 is a diagram showing the sequence of filling and of recultivation of the quarry for the RAW burial:

• preparing the bottom-base of the quarry for filling with RAW
• block-like forming of the first tier and the base of the second tier
• end of filling the quarry capacity with RAW, covering the last upper tier with clay and beginning of recultivation,
• final burying of RAW and recultivation of the quarry,

Fig. 8 is a general view of a container block assembled with IPs and presenting a cavity for placing RAW in irregular size packages.

[0025] The process of the present invention comprises:

The use of an open cut mine working with a finished mineral resources mining cycle, a cut mine quarry 3 with a rock base, at which a post 8 is arranged for unloading RAW and for pretreating the same before burial, a post 2 for retreating MRAW, a route network 6 providing for transport of pretreated RAW ready for burial in a quarry 3.

[0026] The delivery of RAW along the line 7 from the producers-suppliers to the RAW burial site by all types of transport with no limitations: as to the origin (technogenic, natural radioactive nuclides), to the activity level (low-active LAW, medium-active MAW, highly-active HAW), to the structures, materials, shapes, dimensions, the period and conditions of the previous storage of the RAW containers and packages, most of it in unified metal cube-shaped individual packages 12 (a storage device for solid radioactive waste according to the useful model patent No475643, Int. Cl. G21C19/06, G21F9/34, 03.02.2005, published on 27.08.2005). The reusable containers and the equipped rail cars contain surface-contaminated MRAW including oil and gas mining equipment and tubing elements contaminated with natural radioactive nuclides. After the MRAW discharge, the reusable containers are directed along the line 9 to the decontamination post 10, and after passing the post of radiation and contamination control 11 they are returned to the RAW suppliers-producers for loading and delivering the next lot of MRAW.

[0027] The RAW pre-burial treatment is carried out on the equipped post 8, where packages and containers integrity is checked, the defects found are eliminated, the damaged packages are repacked into new ones when necessary, the MRAW is retreated in the post 2 with the use of procedures and equipments for deep complex decontamination, that allows to return the metal to a level of decontamination allowing the unlimited use of the same on the territory of RF through «Vtorchermet» or as direct deliveries to iron and steel manufacturers, which enables to prevent the burial of 90-95% of the volume of the initial MRAW (Fig. 2), the secondary RAW of the retreatment (disposable and solidified decontamination solutions, chips and fragmentation cuts, etc.) is packed into individual packages 12, and transported in a cumulative flow of pretreated RAW to the quarry 3 for burial (Fig. 2).

[0028] The embodiment of the invention.

[0029] The burial of RAW is carried out as follows: the bottom of a quarry is covered with a layer of supplied clay 4 that is evened and compacted to get a flat horizontal site of Fig. 7, where RAW is placed into unified metal cube-shaped individual packages IP 12 (Fig. 3), the elements 13, 14, 15 (Fig. 4) of which allow to remotely assemble and to line up volume blocks 5 by means of hoisting machines with practically almost 100% filling; using the self-shielding effect, to build «contact» IPs 12 with low-activity RAW into an outward protection barrier for container blocks 16, 17, 20, the inner volume of which is filled with «remote» IPs 12 with RAW of a higher activity, which allows to free and to return the transportation containers to the RAW suppliers for their reuse, while replacing their radiation shielding by the protection of the block perimeter assembled with IPs 12 (Fig. 8), with one-piece large-dimension and long-length RAW, packages with RAW of other structures and materials, and everything is rendered monolithic by filling the gaps and cavities with a suitable hardening material, such as concrete, precast concrete, water glass, paraffin-bitumen, etc. The blocks and container bocks 5 are built up to a height, which does not exceed the calculated strength of IPs of ∼10 mPa; the length, the width and the quantity are determined by the free space in a considered point of a tier site.

[0030] The upper row of 19 individual packages 12, assembled into blocks, is tied up and locked by welding or any other way, the upper edge of the block is covered with a liquid heated paraffin-bitumen mixture (waste of oil and gas MRAW retreatment) to protect the volume of the blocks against atmospheric precipitations, by redirecting them beyond the limits of the blocks into gaps and floors filled with clay 4, helping the last to settle and to be transformed from lumpy to a bedded clay. A temporary easily mountable roof 18 is built over the blocks with the same goal during the stage of assembly (Fig. 6). The gaps between the blocks and the walls of the quarry are filled with clay 4, which is allowed to stand for settling; the cavities are filled up, and the upper section of the RAW blocks and all the gaps are covered with clay (Fig. 7), thus forming a base stage of the second tier and completing the clay isolation of the RAW blocks of the first tier (Fig. 7). Such a block-tier filling of the quarry 3 is continued to the upper project reference, after that the non-filled part of the quarry is covered with clay 4 to complete the outline of the clay isolation of the RAW-filled volume, and to fill up with the ground from overburden dumps 1, to combine the recultivation of the quarry and to complete the final stage of the radioactive wastes burying (Fig. 7).

[0031] The use of the invention according to the present application enables to improve the reliability of a long-term isolation/storage of RAW and to reduce the costs of the burial.

Claims

1. Process for pretreating and burying radioactive waste RAW which comprises the steps of:

- RAW delivery from the producers of the same to a burial site;

- pretreatment of the delivered RAW including retreatment of metal radioactive waste MRAW surface-contaminated with radioactive nuclides;

- placement of the pretreated RAW into a burial space;

- final isolation from the environment,
characterized in that,

- for providing an efficient reliable and final burial of RAW, use is made of open mine workings with a completed cycle of mining minerals, in particular open-cut mines with a rock base, having

∘ equipped sites for RAW discharging and pretreating before the burial,

∘ a station for retreating MRAW,

o a route network for RAW transport to the burial quarry;

- as soon as the above mentioned facilities are ready, RAW is delivered from the producers of the same to the burial site, with no limitations

∘ as to the origin - technogenic, natural radioactive nuclides NRAN,

∘ as to the activity level - low-active LAW, medium-active MAW, highly active HAW,

∘ as to the structure, materials, shapes, dimensions, the period and conditions of previous storage of the RAW containers and packages, mainly in unified individual cube-shaped metal packages IPs;

- the delivered RAW is pretreated to get it ready for burial, including the repair of packages and containers, restoration of their anticorrosive coatings, repacking of defective containers and packages into new ones,

- MRAW is processed while eliminating radioactive contaminants by a complex deep decontamination, after which the metal decontaminated and admitted to an unlimited use is withdrawn from the burial procedure and is returned into the economic turnover,

- while the secondary RAW that represents products of the pretreatment process is compacted, solidified, packed in IPs and transferred to the quarry along with the other pretreated packages, the ground bottom of said quarry is covered with supplied clay to provide coverage and compacting of the layer to get an even horizontal site surface on which the delivered RAW is arranged, using a particular structure of the IPs, in box units or container blocks, providing gaps between the blocks and the walls of the quarry with a height that does not exceed the calculated solidity of a unified IP, then the gaps are filled with clay, the clay is allowed to stand for a while to settle; after the clay depression, the gaps are refilled up, and the upper edge of the RAW blocks is covered with clay, together with all the gaps, completing the individual clay isolation of each assembled block of the first tier and forming a base site of the second tier, on which the block-tier filling of the quarry is continued to the upper reference mark of the project, then the non-filled part of the quarry is filled with clay, completing the outline of the clay isolation in the volume filled with RAW, and then

- the ground from the dumps of overburden rock is used to cover the top, which completes the final stage of the RAW burial and the quarry recultivation to recover the initially existing natural landscape.

Drawing