RU2012079C1 - Method of burial of ecologically hazardous objects - Google Patents

Abstract

FIELD: nuclear power engineering. SUBSTANCE: for decrease of harmful effects of emergency object on people and for increased reliability of burial underground burial ground is created under object where object is moved and heat liberated by object is withdrawn. Vertical shaft and horizontal adits towards center of object are constructed at safe distance from reactor. Cooling and heating sources are installed in adits, ground of foundation of object is reinforced in advance by drilling of inclined boreholes with placement of thick-walled casing pipes and by freezing of this ground with the aid of source of cold. Then underground working fixed with lining is created uniaxially to object above adit. Heat exchangers connected to specified sources of heat and cold are positioned inside working, internal space of working is filled and water is frozen, ground under object is unfrozen, casing pipes are removed out of inclined boreholes and vertical boreholes are drilled up to ice over perimeter of object. Then feed of coolant is stopped and heat-transfer agent is supplied into heat exchangers of foundation of working. As ice thaws and object sinks water created under these conditions is evacuated. EFFECT: improved safety of burial of ecologically hazardous objects. 2 cl, 1 dwg

Description

 The invention relates to special construction, namely, the technology for the disposal of environmentally hazardous facilities, mainly emergency units of nuclear power plants such as the fourth unit of the Chernobyl nuclear power plant.

 The experience of eliminating the consequences of the Chernobyl accident indicates the absence of effective ways to solve this urgent problem.

 Currently, it is believed that the most rational way this problem can be solved by creating around the emergency reactor a special protective shell - "sarcophagus".

 This method was implemented in practice, so it is taken as a prototype.

 A significant drawback of the selected prototype is its complexity due to the large size of the "sarcophagus" and the accompanying strong radiation exposure of people forced to work in the immediate vicinity of the emergency reactor.

 A significant disadvantage of this method is also the low reliability of the disposal of an environmentally hazardous facility. Internal heat release, as well as atmospheric variables affecting the design of the "sarcophagus" lead to its destruction.

 A known method of disposal of a nuclear reactor decommissioned [1]. After removing the fuel and coolant from the reactor core to be disposed of, it is filled with a binder solution and all openings are sealed to eliminate the risk of radiation exposure. A pit is dug in the ground right under the reactor and a bunker with concrete walls is built.

 There is a method of burying a nuclear reactor of a nuclear power plant in rocky soil, including removing fuel from the reactor, deactivating the reactor compartment, disconnecting adjacent structures to the reactor, moving to an underground repository, and removing heat [2]. From the surface, the main approach workings below the reactor room are located below the depth of the repository; from the lower elevation of the main approach workings under the reactor, a compensation uprising to the NPP foundation passes along its axis, and an outlet funnel is cut in the bottom of the compensation uprising, the axis of the outlet is located along the axis .

 The disadvantage of these designs is the insufficient reduction in the total dose of personnel during work, the reduction in the time of work.

 There is a known method for the disposal of an environmentally hazardous facility, namely, in the description of the example of using the claimed method as an environmentally hazardous facility, an emergency reactor similar to the fourth unit of the Chernobyl nuclear power plant, along with the Sarcophagus created after the accident [3], was adopted.

 An additional study of the materials of the Chernobyl accident showed that the efficiency of the disposal method can be many times greater if the environmentally hazardous object may not be the entire sarcophagus, but only a part of it — an emergency reactor together with the concrete mine where it is located. The size of this mine is 26x26 in plan and height is 35.5, together with the subreactor rooms, that is, it is much smaller than the outer dimensions of the entire Sarcophagus. The method allows to extract and bury only a concrete mine together with an emergency reactor, therefore, in this example, this particular structure should be considered an environmentally hazardous object.

 The purpose of the invention is to reduce the harmful effects on people, as well as improving the reliability of the disposal of an environmentally hazardous object.

 The goal is achieved by the fact that at a safe distance from the object pass a vertical trunk and a horizontal adit (pattern) under the center of this object; establish a cold source and a heat source; the soil of the base of the object is pre-fixed by drilling deviated wells with the installation of thick-walled casing pipes in them, as well as by freezing the specified soil using these wells; then, coaxially with the object above the adit, an underground mine is created whose internal dimensions, in plan and height, are greater than the corresponding external dimensions of the object; the production is fixed by a lining, inside which heat exchangers are mounted, connected by pipelines and shut-off and control valves to the aforementioned refrigerator and heat source; sealing the covering space of the mine, the top of which is connected by means of a well with the atmosphere, and filling the internal volume of the mine with water, then a coolant with a negative temperature is fed into the heat exchangers, turning the water into ice, then the soil under the object is thawed; thick-walled casing pipes are removed from deviated wells and vertical wells are drilled to ice along the perimeter of the object, then the coolant is cut off to the heat exchangers and instead of it the coolant is fed only to the base base heat exchangers; as the ice melts and the object sinks, the water that forms during this process is removed; after installing the object on the base of the mine, the latter is filled with a hydrophobic sealant mixed with well-heat-conducting material, for example, copper fiber, and again the coolant is fed into the heat exchangers, limiting the self-heating of the object.

 In this way, the environmentally hazardous object is slowly lowered underground into a specially created hermetic casing with a refrigerator.

 The invention is illustrated by the following example of a device that implements the claimed method.

 In this example, an emergency reactor similar to the fourth block of the Chernobyl nuclear power plant, along with the “sarcophagus” created after the accident, was adopted as an environmentally hazardous object. The device diagram is shown in the drawing, which shows: the emergency reactor in the initial position I and the same reactor in the final position Ia, deviated wells with thick-walled casing pipes 2, designed to freeze the soil under the reactor; located under the reactor and coaxially to it is an underground mine 3 with a lining 4, inside of which heat exchangers 5 are located on the lateral surfaces, and heat exchangers 7 are located at the base 6. Pipe-in-pipe designs can be used as heat exchangers. The same structures can serve as additional reinforcement, increasing the strength of the lining of the underground mine. Pipes with shut-off and control valves 8, 9 and 10 are provided for supplying coolant and coolant to the heat exchangers. A water conduit 11 is provided for supplying water to the generation. The same water conduit is used to remove water from the production after ice melts. For the same purposes, a pump 12 and shut-off and control valves 13-17 are provided. To obtain a coolant, a cold source (chiller) 18 is provided, and a heat generator 19 is provided. A cryogenic liquid, for example liquid nitrogen or liquid air, can be effectively used as a coolant for freezing water and soil.

 Construction and installation work is carried out through a special vertical barrel 20 and horizontal adits 21 and 22 (patterns). To weaken the connection of the reactor with the surrounding soil, drilling of vertical wells 23 is provided.

 The method is as follows. At a safe distance from the reactor 1, a barrel 20 and horizontal adits 21 and 22 are constructed that are suitable for the axis of the reactor. In one of the tunnels 22, a refrigeration machine 18 and a heat generator 19 are installed and the construction of production 3 is started. Preliminarily, in order to prematurely lower the reactor 1, inclined wells are drilled and thick-walled casing pipes 2 are installed in them and the soil is frozen directly under them, increasing thus its strength. For these purposes, liquid nitrogen can be used in the best way.

 As the mine 3 is drilled, a side lining 4 with heat exchangers 5 is installed, and the base lining 6 with heat exchangers 7. The height of the mine 3 should be greater than the height of the reactor 1 with the "sarcophagus". In addition, during the construction of mine 3, it is necessary to take into account the volume of soil frozen under the reactor 1. Then fill the aforementioned mine 3 with water through a water conduit 11 (valves 14 and 16 are open, 13, 15 and 17 are closed).

 For a complete and quick filling with water of mine 3, it is advisable to drill at least one well 23 to release air into the atmosphere. After the fillings 3 are completely filled with water, the refrigeration machine 18 is turned on and the coolant flows through the pipes to the heat exchangers 5 and 7, and water is converted to ice, as a result of which the reactor 1 receives a new support in the form of a production base 6, through the ice mass and soil remaining after freezing under the reactor. The formation of a new support allows you to remove the old support. To do this, stop the flow of coolant in thick-walled casing pipes of deviated wells 2 and serve there for thawing the soil coolant. After thawing the soil, casing from wells 2 is removed. To reduce the connection between the base of the reactor and the surrounding soil, vertical wells 23 are drilled around the perimeter of reactor 1. After that, the refrigeration machine 18 is turned on, the coolant is turned off in the heat exchangers 5 and 7 and the heat generator 19 is turned on, from which the heat carrier is supplied only to the heat exchangers 7 of the base 6. 5, only a short-term heat supply is possible to eliminate ice adhesion to the side walls of generation 3.

 Due to the natural heat exchange of the production with the surrounding soil, this process will occur over time and spontaneously.

 As heat arrives at base 6, the ice on its surface will melt. By removing the formed water through the water conduit 11 by means of a pump 12 (valves 13, 15 and 17 are open, and 14 and 16 are closed), the height of the ice mass is reduced, while lowering into reactor 3 the reactor 1 standing on the ice mass. After complete melting of the ice, the reactor 1 becomes in its new constant position - pos. Ia. The lowering speed of the reactor, its inclination relative to the vertical axis is controlled by the flow of coolant using valves 9. Then the emergency reactor Ia is sealed by filling the outlet 3 with sealant. The type and properties of the sealant are taken according to the specific conditions of application of this method, including the actual heat generation, the presence and power of the surrounding 3 aquifers.

 As sealant can be used: cast concrete (with special additives that lower its viscosity), water glass, various resins and mastics. In the presence of aquifers, preference should be given to mastics consisting of hydrophobic materials, such as bimuth. To maintain the specified thermal regime of the emergency reactor Ia, heat exchangers 5 and 7 should be used together with the refrigeration machine 18. To improve the cooling of the reactor Ia, it is advisable to add fiber (finely cut wire) from a well-conducting material, such as copper, which will significantly increase the heat transfer coefficient of the said mastic.

 Burial according to this method of an environmentally hazardous object virtually eliminates being in the immediate vicinity of people from this object, and consequently, harmful effects on them.

 In addition, as a result of such disposal, an environmentally friendly system is obtained. Radioactive radiation is reliably absorbed by the earth, the thickness of which can be almost any, and the harmful effect on the underground aquifers is limited by the presence of a lining of the underground mine, the use of impermeable waterproofing, mainly from clay, created by injection of a clay solution into the surrounding soil, as well as using a hydrophobic sealant to fill the space between the lining of the mine and an environmentally hazardous object. An object buried in this way allows you to organize reliable control and maintenance of a given temperature by artificial cooling. In the presence of sufficiently powerful underground horizons, it is advisable to lower the temperature of the lining of the mine to negative temperatures.

 The layer of frozen soil formed around the mine will become an additional impenetrable barrier to the filtering of harmful substances into the underground aquifers.

Claims (2)

 1. METHOD OF DISPOSAL OF ENVIRONMENTALLY HAZARDOUS OBJECTS, including the creation of an underground repository beneath the object, the movement of an environmentally hazardous object into it and the removal of heat generated by the object, characterized in that a vertical trunk and horizontal adits from the trunk to the center of this object are carried out at a safe distance from the object adits of cold and heat are established in the adits, the soil of the base of the object is previously closed by drilling deviated wells with the installation of thick-walled casing pipes and freezing them of the soil with the help of a cold source, then coaxially with the object above the adit create an underground mine, the internal dimensions of which in plan and height are larger than the corresponding external dimensions of the object, the mine is fixed by a lining, inside of which heat exchangers are connected using pipelines and shut-off and regulating valves to the indicated sources of heat and cold, seal the under-lining space of the mine, which is connected with the help of the well to the atmosphere, and fill the internal volume of the mine in oh, with the help of a coolant with a negative temperature supplied to the heat exchangers, they freeze the water, after which the soil under the object is thawed, casing pipes are removed from the deviated wells and vertical wells are drilled to ice along the object’s perimeter, then the coolant is cut off and the coolant is fed into the heat exchangers of the production base, by as the ice melts and the object is lowered, the water formed during this process is removed, after installing the object on the base of the mine, the latter is filled with a hydrophobic sealant mixed with high cold-conductive material and again in the heat exchangers serves the coolant.  2. The method according to p. 1, characterized in that as a highly heat-conducting material using copper fiber.

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