RU2293386C1 - Method for producing radiation-shielding packing block for placing in storage on shore - Google Patents

Abstract

FIELD: atomic engineering.

SUBSTANCE: proposed method for producing radiation-shielding packing block for placing in storage on shore includes comprehensive engineering inspection of reactor compartment on board large floating facility. Spent fuel assemblies are removed from reactor compartment whereupon the latter is disposed in equipment area premises, and hardening mixture is placed inside containment locations. Packing block is introduced in repair dock wherein nuclear steam-generating plant is cut out of reactor compartment, made floating, and conveyed to storage location. Assembled floating block is brought out of repair dock and upon temporary storage afloat it is entered in transportation-and-transfer dock whereon it is towed to storage location. Assembled radiation-safety packing block is conveyed for storage on shore.

EFFECT: unified available engineering means, enhanced stability of cut-out block holding steam-generating plant.

1 cl, 10 dwg

Description

The invention relates to nuclear engineering and technology, in particular to the integrated utilization, conservation, temporary and long-term storage of radiation-hazardous reactor compartments (RO) of large floating and other objects, for example large-tonnage surface ships (NK), cargo transport vessels, icebreakers and floating power plants with nuclear power plants (NPP).

A known method of decommissioning of nuclear submarines (NPS), followed by conservation and disposal of their radiation-hazardous reactor compartments, through which after unloading from the reactor spent nuclear fuel (SNF) carry out the following basic technological operations:

- placing the submarine on the slipway deck;

- dismantling, unloading of equipment and mechanisms;

- cutout of the reactor compartment (RO) as part of a three-compartment unit, otherwise the cutout of RO with two adjacent compartments giving buoyancy to the cut RO;

- conditioning of radioactive waste with the laying of concrete hardening mixtures inside the RO;

- towing for temporary storage of radioactive waste afloat for up to 10 ... 15 years in order to actively monitor the state of solid radioactive waste (SRW) in the premises of the radioactive waste and reduce the overall radioactivity of the facility;

- the subsequent towing of the three-compartment RO nuclear submarine and its storage at the onshore long-term storage site (PDH) through its infrastructure, consisting of a ship-lifting complex, including a transport and transfer dock, as well as a complex of ship and slipway equipment, sequentially transporting the nuclear submarine to the MP at the disconnection position (segments) of adjacent compartments and the final formation of the RO in the block packaging and its installation with the help of a transborder on the MPC (Collection of materials of the international workshop on contact e IAEA Expert Group (March 26-27, 2003) "Problems of the Utilization of Multipurpose Nuclear Submarines in the North-Western Region of Russia" (published by the Federal State Unitary Enterprise NIPTB Onega, Severodvinsk; Bulletin "Issues of Submarine Utilization" No. 2, 2004, ed . CJSC "Publishing House Atomenergoizdat" Moscow, p.13).

The disadvantages of this method are its limited use and insecurity.

The closest analogue to the claimed invention is a method of decommissioning, disposal, temporary storage and disposal of objects with radiation hazardous waste according to the patent of the Russian Federation No. 2133062, publ. 07/10/1999.

This method includes SNF unloading, a comprehensive engineering survey (CFC) of equipment, mechanisms, structures and facilities of the RO, radiation level verification, after which the equipment is dismantled. Then, hardening mixtures are laid in the reactor compartment, the cutting of PO in the transverse direction of the nuclear submarine together with two adjacent compartments in order to give the cut part buoyancy and, if necessary, for temporary storage of PO afloat. After that, adjacent compartments are separated in the dock and, with the help of a transport crane, the RO is transferred to onshore storage, for example, to a coastal storage site organized in a certain way.

However, the indicated method of disposal, in which the nuclear submarine is cut together with adjacent compartments for its subsequent installation on the MP, built to store radiation-hazardous nuclear submarines of utilized submarines and having the appropriate dimensions, is not suitable for utilized nuclear submarines of large tonnage, firstly, because differences in the design of the RO. In addition, the weight and dimensions of the ND RO are several times larger than those of nuclear submarines (see the Register of the Russian Federation (USSR) "Rules for the Classification and Construction of Nuclear Vessels", 1982, Leningrad, p. 13). Therefore, due to its limited capacity and size, the infrastructure of the nuclear storage facility designed to store the nuclear submarine’s ropes will not be able to accept the ND of the NK and ships with nuclear power plants utilized using the technology of this disposal method (for example, due to the limited width of the slipway deck of the transport and transfer dock PDH, distances between ship ways of slipways, positions of RO placement on PDH, etc.). In addition, the center of gravity will be located very high for RO NK cut using these methods, which will create the danger of it overturning during transportation.

At the same time, the construction of a new specialized MPH with an infrastructure intended only for RP surface ships and vessels will require large capital expenditures, which is economically inexpedient and will create an additional threat to environmental and radiation safety for the region where such MPH is located.

The objective of the present invention is to obtain a method of forming a radiation-protective block package containing the radiation-hazardous part of the RO of utilized large tonnage SCs and vessels, the mass and dimensions of which will correspond to the available MPs for the RO of nuclear submarines without changing their infrastructure, and at the same time maintaining an acceptable safe level of the outside radiation of such a block package.

The technical result obtained by the implementation of the proposed method is to unify the existing arsenal of technical equipment for the disposal of RO, as well as to increase the stability of the block cut from the RO with a steam generating unit by reducing the height of its center of gravity.

Obtaining the specified technical result is provided due to the fact that in the method of forming a radiation-protective block package for installation onshore storage, a comprehensive engineering survey of the reactor compartment of a large floating object is performed. The spent fuel assemblies are removed, the equipment is removed from the reactor compartment, followed by its placement in the zones of the equipment room, and the hardening mixture is laid inside the containment rooms. An object is introduced into a repair dock, where an atomic steam generating unit is cut out from the reactor compartment, made buoyant and transported to a storage location. The installation is cut vertically around the perimeter of the containment over its biological protection. Then, the upper part of the shell is cut with two horizontal cuts. At the same time, the distance between the cuts should not affect the protruding upper parts of the biological protection of the steam generating unit. The cut out middle part is removed, the upper part of the shell is welded to the lower one. After that, a temporary floating unit is mounted by installing and welding on four sides of the protective shell of the waterproof bulkheads, to the welded on parts of the adjacent structures remaining after performing longitudinal cuts, the waterproof bulkheads are attached flush with the parts remaining on the adjacent adjacent biological protection shell after vertically - transverse cuts, waterproof bulkheads buoyancy means - pontoons. In this case, the center of gravity of the installation should be located at the same distance from opposite bulkheads. A leak test is carried out, an anti-corrosion coating is applied. The mounted floating unit is removed from the repair dock and after temporary storage afloat is introduced into the transport and transfer dock, on which it is towed to the storage location. It is loaded onto the shore, the pontoons are disconnected, a radiation protective layer of shotcrete is applied to the outer surface of the remaining block, 20-30 mm thick, and the formed radiation protective block packaging is installed on shore storage.

To justify the prospects of the proposed solution, a comparative analysis of the mass and size characteristics of the currently disposed nuclear submarines of 1, 2, 3 generations and to be disposed of was made. As a result of the analysis, it was found:

- for a nuclear submarine RO, the maximum width (diameter) of a cylindrical strong hull, i.e. the width "B" is 13 m (which corresponds to the width of the slipway deck of the transport and transfer dock with an increase in side passages) with a maximum mass of nuclear submarines of not more than 2000 tons;

- it is characteristic of RC NK that the maximum width "B" reaches 42 ... 45 m with its maximum length l equal to 26 ... 32 m, and with a mass of RC NK no more than 4000 t, but the maximum width of the containment "b" is only ≈20 m with design structural ratios of the width and length _{of the} protrusion equal to b / l ₁ ≈1.6 ... 2, therefore, the length of the protrusion "l ₁ " does not exceed 10 ... 13 m (cm Fig. 4 and Fig. 5).

Thus, from the above ratios, we can conclude that the block packaging formed by the proposed method will be commensurate with the utilized nuclear submarine and allows the use of MPL infrastructure for nuclear submarines.

Reducing the height of the AU due to cutting out most of the equipment room will reduce the height of the entire package and bring the height of the AO closer to the dimensions of its width and length, which in turn will increase stability and buoyancy when towing and storing afloat, as well as increase safety against tipping over formulation of the block packaging at the MPC (the height of the ZO, until it decreases, reaches from the bottom of the tank to the upper hatches 35 ... 45 m or more).

The installation of watertight partitions on both sides of the cut-out spacecraft and the attachment of pontoons on both sides will ensure the buoyancy of such a unit, while the location of the center of gravity of the automatic control system at the same distance from the opposite bulkheads will provide sufficient stability against tipping over during transportation and storage afloat.

Ensuring the overall distance between long bulkheads is less than the width of the transport and transfer dock makes it possible to use the infrastructure of existing MPCs.

Drawing on the outer surface of the block after separation of the pontoons by gunning with a radiation protective layer of shotcrete with a thickness of 20 ... 30 mm, which has high frost resistance and good protection against corrosion, provides an additional immobilization barrier to the main one created by filling the concrete inside the GZ, and , in addition, it is of very significant importance as a corrosion-resistant hermetic coating of the outer surfaces of the AO from the influence of climatic environmental factors (atmosphere ernyh precipitation, differential ambient temperature, etc.). All this as a whole creates a more reliable isolation of radioactive waste (RW) in the formed block package of RO PK.

The invention is illustrated by the following drawings:

Figure 1 - diagram of the cutout of the protective shell of the RO NK installed in the dock;

Figure 2 is a diagram of the separation and withdrawal from the dock of the on-board hull structures of the RO, fore and aft extremities of the PC;

Figure 3 - diagram of the connection of the pontoons to the welded short bulkheads in the dock;

Figure 4 is a section aa;

5 is a section bB;

6 is a section bb (reducing the height of the hardware room ZO);

7 is a section GG (reducing the height of the hardware room ZO);

Fig - remote node D with installed additional bulkhead;

Fig.9 - remote site E (section of an additional bulkhead formed block packaging with sprayed concrete);

Figure 10 is a sequence diagram of the transportation of a temporary floating unit for temporary storage and transfer to shore storage in the MPC.

The large-capacity NK to be disposed of after the SFA is unloaded and the superstructure is cut off is put into the floating repair dock 1, which is a unique large-size structure created in single copies for the repair and disposal of large-capacity nuclear ships in the Northwest and Pacific regions, and installed on its kilblocks (Fig .one). A comprehensive engineering and radiation survey of the premises, equipment and mechanisms of the reactor compartment 2 is carried out.

According to the results of a radiation survey, the possibility of the release and spread of radioactivity during long-term storage through the construction of AO 3 with biological protection 4 (Fig. 8) is assessed, the structural dimensions of the immobilization barriers are determined.

Many years of experience in operating and observing the radiation situation in the RC NK shows that its premises and equipment located outside the AO, especially those located on the side structures 5 (Figure 2) and strong transverse bulkheads 6 (Figure 1), as well as having an auxiliary purpose for the operation of reactor installations, in many cases are not radioactive, and only in some cases their γ-radiation dose rates slightly go beyond the background values, and according to the levels of radioactive contamination, they belong to categories, mainly , low activity and rarely to medium-level waste of SRW.

The levels of radioactivity in the equipment room 7 of the AO (Figure 4), which has a large amount of free space from the conditions of the features of SNF unloading, maintenance, repair of the reactor installation, etc., are many times lower than radioactivity than in the reactor room 8 (Figure 4) ), because these rooms are separated by biological protection.

They perform decontamination (including easily removable film decontamination for the purpose of fixing, isolation and localization of radioactive contamination), facilities and equipment of the RO, then dismantle the equipment, structural elements, mechanisms, pipelines. At the same time, certain types of equipment that are unloaded from the rooms of onboard structures 5 outside the AO, mostly related to low-level solid radioactive waste, are compactly mounted and fixed in the free zones of the lower part of the equipment room 7 (taking into account the alignment and mass of the floating module formed later). After that, the necessary hardening of the concrete hardening mixture is carried out in the premises for the creation of an immobilization barrier of sufficient power in accordance with the accepted technological process.

In accordance with the design and technical documentation of the ship's design, the optimal cutting lines of the AO are determined.

First, vertically transverse cuts 9 are performed outside the biological protection of the DA on adjacent structures, including the sides, deck and bottom of the RC NK, on the remaining parts of which waterproof bulkheads 10 will be installed and welded in the future to ensure that between long bulkheads of overall size "l ₁ " ( 5), which allows you to enter and install formed in the future temporary floating unit 11 on the slipway deck of the transport and transfer dock 12 and the long-term storage area for the nuclear submarine RO 13 (Figure 10). In this case, the cuts 9 are performed in such a way that the center of gravity of the formed block is located as close as possible to the middle of the size "l ₁ ", which will make it possible to tow it without heeling and with proper stability (with the same displacement and dimensions of the pontoons 14 connected to the block).

Next, the output from the dock of the bow 15 and stern 16 (Figure 2) of the extremities of the NK for their further cutting and disposal. Then, longitudinal cuts 17 are likewise performed on adjacent structures, on the remaining parts of which watertight bulkheads 18 will later be installed and welded, ensuring between the bulkheads of size "b", at which the center of gravity of the formed block will be as close as possible to the middle of size "b", which will make it possible to tow it without trim and with proper stability. After that, the onboard structures 5 cut off from the AO are taken out from the dock for cutting and disposal (see Figs. 2 and 4).

Then, two horizontally parallel cuts 19 are made along the perimeter of the SC in the zone of its free internal space of the equipment room remaining after laying the concrete hardening mixture inside the SC. At the same time, the distance between the cuts should be the maximum possible, but not affecting the protruding upper parts of the biological protection of the APPU.

After that, having previously sprinkled with a crane the upper part 20 of the protective shell and removed the middle part 21, for example, by cutting it into separate fragments and, if necessary, loading them in the form of SRW into the lower part of the hardware room of the GZ 7, the upper and lower parts are joined and welded together ZO 7 (see Fig.6, 7, 8).

At the end of the work on the formation of a temporary floating block 11, waterproof bulkheads 10 (long) and 18 (short) are installed and welded together along the contour, as well as to adjacent structures of the AO, they are tested for leaks, anti-corrosion coating is applied and flush to the short bulkheads 18 with long bulkheads 10 buoyancy means - pontoons 14 (Fig.3, 8).

Further, in the case of unavailability of the onshore long-term storage site 13, the formed temporary floating unit 11 is withdrawn from dock 1 and towed to the temporary storage facility afloat (PVC) 23, formed for receiving and storing afloat three-compartment RO submarines, and it is moored to the berth next to moored three-compartment RO NPS 24 (see Figure 10).

As soon as the onshore long-term storage platform 13, organized to store the nuclear submarine’s block-packages, is ready, the temporary floating unit is towed again and introduced into the transport and transfer dock 12 of the MPC, while the size “l ₁ ” of the block formed from the PC PC allows it to be installed on the slipway deck of the dock 12. Next, in a known manner from the dock 12, the block 11 with the help of the slipway and ship equipment PDH is transferred to the position (slipway) 25 of the disconnection of the pontoons and external concreting.

After disconnecting the pontoons and cutting off the outer protruding parts and elements, they begin to shotcrete the outer surface of the remaining part of block 11. First, a steel mesh is laid on its surface in one layer, tacking it by welding to the block surface, then, according to the developed technology and recipe, they are laid on the mesh by the known method of shotcrete using a cement gun, a layer of shotcrete 26 with a thickness of "a" equal to 20 ... 30 mm.

Upon completion of the complete cure (curing period of 28 days) of the concrete-preservative mixture, as well as checking its quality, the radiation-protective packaging unit 27 of the reactor compartment of the NK will be fully formed.

Further, as the appropriate storage location at the position (slipway) 28 of the MPC is prepared using the ship's equipment and transborder 29, the packaging unit 27 is transported to the appropriate storage location next to the radiation protective packages 30 of the nuclear submarines transferred for storage.

Due to the storage in one place of the reactor compartment compartments from all types of floating objects, the environmental and radiation situation will be improved in the regions allocated for the storage of utilized radioactive waste. In addition, the creation of unified radiation monitoring services, emergency prevention services, environmental monitoring, the creation of immobilization barriers, etc. will also contribute to this.

Claims (1)

A method of forming a radiation-protective block package for installation onshore storage, in which a comprehensive engineering survey of the reactor compartment of a large floating object is carried out, spent fuel assemblies are removed, equipment is removed from the reactor compartment with its subsequent placement in the areas of the equipment room, and a hardening mixture is laid inside the containment shell, an object is introduced into the repair dock, where an atomic steam generating plant is cut from the reactor compartment they are buoyant and transported to a storage place, characterized in that the installation is cut vertically along the perimeter of the protective shell over its biological protection, then the upper part of the shell is cut with two horizontal cuts, while the distance between the cuts should not affect the protruding upper parts of the steam generating biological protection installation, remove the cut out middle part, weld the upper part of the shell to the bottom, and then mount the temporary floating unit by installing and welding with even the sides of the protective shell of the waterproof bulkheads, to the welded on the parts of the adjacent structures remaining after performing longitudinal cuts, the waterproof bulkheads are flush with the parts welded on the adjacent to the biological protection of the protective shell of the vertically transverse cuts, the waterproof bulkheads of the buoyancy means pontoons, the center of gravity of the installation should be located at the same distance from the opposing bulkheads; tightness, anti-corrosion coating is applied, the mounted floating unit is taken out of the repair dock and after temporary storage afloat is introduced into the transport and transfer dock, on which it is towed to the storage place, loaded onto the shore, the pontoons are disconnected, the radiation protective is applied to the outer surface of the remaining block a layer of shotcrete with a thickness of 20-30 mm and establish the formed radiation-protective block packaging for onshore storage.

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