CN108053895B - Reactor core melt trapping device for split-charging enhanced cooling - Google Patents
Reactor core melt trapping device for split-charging enhanced cooling Download PDFInfo
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Abstract
The invention belongs to the technical field of nuclear safety control, and relates to a reactor core melt trapping device for sub-packaging intensified cooling. The trapping device comprises a reactor pit, a reactor pressure vessel, a melt retention vessel, a crucible, a retention water tank, a cooling water tank and connecting pipelines, wherein the melt retention vessel with an open top is positioned in the reactor pit, the lower part and the bottom of the reactor pressure vessel are placed in the melt retention vessel, and a space positioned below the melt retention vessel in the reactor pit forms a cooling space; a crucible is arranged below the bottom plate of the melt retention container in the pile pit; the retention water tank is positioned outside the pile pit and is connected with the pile pit through a connecting pipeline; the cooling water tank is positioned outside the pile pit and is connected with the cooling space through a connecting pipeline. By using the trapping device, the scheme of the reactor core trap with compact arrangement and high cooling efficiency can realize effective trapping and containing of the reactor core melt by temporary detention and split charging reinforced cooling of the melt, and the trapping device can cope with the severe accident condition of the nuclear power station.
Description
Technical Field
The invention belongs to the technical field of nuclear safety control, and relates to a reactor core melt trapping device for sub-packaging intensified cooling.
Background
A serious accident of a nuclear power plant begins with the large-area melting of the fuel components of the reactor, at the moment, the first barrier fuel cladding serving as a depth defense system fails, and if the reactor cannot be cooled in time, the related internals are also melted and form core melt, and the core melt falls into a Reactor Pressure Vessel (RPV) lower head. Under the condition that the external cooling of the RPV lower end socket is insufficient, the RPV lower end socket can be melted through, namely the pressure boundary of the primary loop of the second barrier is broken through, and the molten core enters the containment vessel. After the pressure vessel is melted through, the melt is directly sprayed onto the raft foundation of the containment vessel to interact with structural concrete (MCCI), the raft foundation of the containment vessel is gradually eroded downwards at a higher speed within a certain time, and if the thickness of the raft foundation is insufficient, the bottom plate may be melted through. This can result in the release of radioactive material on a large scale, as the last barrier of the containment vessel is breached, which in turn destroys the integrity of the containment vessel.
The existing strategies for dealing with the serious accidents are mainly divided into two types, namely, an in-pile melt retention technology (IVR) and an out-pile melt retention technology (EVR).
The IVR technology ensures that the RPV lower end socket is submerged mainly by continuously injecting water into the reactor pit, takes away decay heat of reactor core melt through boiling heat exchange at the outer wall surface of the RPV, and finally retains the melt in the RPV. IVR technology appears in Loviii VVER-440 nuclear power station in Finland for the first time, and is also successfully applied to the design of AP600, AP1000, APR1400, CAP1400 (1400 MWe PWR designed by national Nuclear technology Co., Ltd.) and Hualongyi (1000 MWe PWR designed by the joint research and development of Chinese Nuclear industry group and Chinese Guankari group) in China. However, in this technique, there is a large controversial in estimating the heat flux density of the molten core loaded on the inner wall surface of the RPV, and currently, the current international mainstream opinion suggests that the IVR technique is not suitable for a large power reactor type, such as a reactor type of 1000MWe or more.
EVR technology is primarily achieved by providing a smelt collection device outside the RPV, then cooling the smelt within the collection device, and eventually achieving retention. EVR technology has the advantage over IVR technology of larger operating space and more flexible cooling, especially in dealing with severe incidents of larger power stacks. At present, the EVR technical solutions with engineering conditions are mainly divided into the following 4 types: 1) before the molten material flows to the containment bottom plate, filling water into the reactor pit to form a deep water pool, then enabling the molten material discharged from the pressure container to fall into the water pool formed in the cavity of the pressure container, and cooling by continuously injecting water, wherein the technology is such as a Nordic boiling water reactor; 2) adopting a dry type reactor pit or a reactor pit with only a small amount of water (forming a shallow water pool), continuously injecting water after the molten material flows to the bottom plate and spreads, ensuring that the molten material is submerged, and realizing cooling, wherein the technology comprises the following steps of a majority of early second-generation pressurized water reactors and boiling water reactors; 3) the method comprises the following steps of temporarily retaining the melt in a pile pit for a certain time by a special device, then transferring the melt to a large space for spreading, and realizing effective retention of the melt by bottom partition wall type and/or top submerged type cooling, such as a reactor core catcher of EPR (ethylene propylene rubber); 4) this technique, such as the core catcher of VVER1000, ESBWR and EU-APR1400, confines the entire core melt within the collection vessel by placing the collection vessel directly within the pit, directly below the RPV, and then flood-cools the core melt with cooling water outside the collection vessel and/or cooling water at the top of the melt.
Regarding the research of the reactor core catcher, a plurality of related patents are generated at home and abroad. Foreign patents such as US4,113,560(Core catcher for nuclear reactor Core meltdown containment, university of massachusetts, 1978, which may be considered as a design prototype of EVR), US4,280,872(Core catcher device, french atomic energy agency, 1981, which advanced EVR technology to the level of engineering application), and later numerous principle, structurally different Core catcher patents US4,442,065, US4,113,560, US4,342,621, US 8,358,732, US6,353,651. Domestic patents such as CN201310005308.0 (large passive nuclear power plant core catcher with bottom water injection and external cooling), CN201310005342.8 (a large passive pressurized water reactor nuclear power plant crucible type core catcher), CN201310005579.6 (large passive pressurized water reactor nuclear power plant core catcher with smelt expansion chamber), CN201310264749.2 (device combining smelt in-reactor and out-of-reactor detention in large passive nuclear power plant), and CN201320007203.4 (large passive pressurized water reactor nuclear power plant core catcher with smelt expansion chamber).
However, the above EVR solutions have the following problems: the scheme of both a deep pool and a shallow pool has the risk of steam explosion; the cooling effect of the pure water injection and flooding at the top of the melt on the melt is poor; the reactor core catcher applied to EPR needs a larger expansion room, and the melt migration path is longer and has more links; the problem of requiring a large space for arrangement is found in the core catcher solution of ESBWR and EU-APR1400, whereas the arrangement of the relatively compact core catcher of VVER1000 takes at least 10 months to finally cool the melt after the melt retention is achieved.
Disclosure of Invention
The invention aims to provide a reactor core melt trapping device with split charging and enhanced cooling, which can realize effective trapping and containing of reactor core melt by temporary retention and split charging and enhanced cooling of the melt through a reactor core trap scheme with compact arrangement and high cooling efficiency, thereby coping with the severe accident condition of a nuclear power station.
To achieve this object, in a basic embodiment, the present invention provides a split enhanced cooling reactor core melt trapping device, which comprises a reactor pit, a reactor pressure vessel, a melt retention vessel, a crucible, a retention water tank, a cooling water tank and connecting lines,
said open-topped melt retention vessel (preferably in the form of a barrel) located within said pit and having the lower and bottom parts of the reactor pressure vessel located within said pit disposed therein, the space within said pit below said melt retention vessel forming a cooling space;
in the pile pit, the crucible is arranged below the bottom plate of the melt retention container;
the retention water tank is positioned outside the reactor pit and is connected with the reactor pit through the connecting pipeline so as to enable water stored in the retention water tank to enter the molten material retention container through the connecting pipeline, so that the lower head of the reactor pressure container is submerged, and the molten material in the reactor core is retained in the lower head of the reactor pressure container for a certain time;
the cooling water tank is positioned outside the reactor pit and is connected with the cooling space through the connecting pipeline, so that water stored in the cooling water tank can enter the cooling space through the connecting pipeline to cool the crucible for a long time (after the water is injected into the cooling space, effective retention and long-term cooling of the molten core in the crucible can be realized through boiling heat exchange and natural convection).
In a preferred embodiment, the present invention provides a split enhanced cooling reactor core smelt trapping device, wherein the outer layer of the crucible is made of metal, the inner layer is a protective layer (the protective layer is used for maintaining the integrity of the crucible),
the thickness of the protective layer is 10-50mm, the material is a refractory material selected from magnesia, alumina, zirconia or composite ceramic with a metal structure doped inside;
the composite ceramic with the metal structure doped inside is formed by mixing a massive refractory material made of magnesia, alumina or zirconia in high-melting-point metal or alloy or filling the massive refractory material in a high-melting-point metal or alloy frame structure (the metal or alloy is iron-based alloy, such as carbon steel with a melting point of 1500 ℃, stainless steel with a melting point of 1400 ℃, ferroboron with a melting point of 1400 ℃, ferrotungsten with a melting point of 1800 ℃ and the like), and the porosity of the composite ceramic is 25-75%.
In a preferred embodiment, the present invention provides a split enhanced cooling reactor core melt catcher, wherein the outer wall surface of the crucible is subjected to enhanced heat exchange treatment to increase surface roughness or turbulence as appropriate.
In a preferred embodiment, the present invention provides a split enhanced cooling reactor core melt catcher, wherein the crucible is a plurality of crucibles, including a main crucible with a larger diameter and an auxiliary crucible with a smaller diameter,
the single main crucible is arranged right below the melt retention container, the plurality of auxiliary crucibles are arranged below the side of the melt retention container and are uniformly arranged around the main crucible, and the total volume of free spaces of the main crucible and the auxiliary crucibles is slightly larger than the sum of the volumes of the core melt and all sacrificial materials. In a more preferred embodiment, the invention provides a reactor core melt trapping device with split intensified cooling, wherein the trapping device further comprises a flow guiding device arranged below the outer part of the main crucible and a flow disturbing mechanism arranged between the auxiliary crucibles along the circumferential direction and used for respectively intensifying heat exchange between the melt and cooling water outside the main crucible and the auxiliary crucibles,
the flow guiding device is used for narrowing the flow channel on the outer wall surface of the main crucible to 100-200mm to form a coolant accelerating channel;
the flow disturbing mechanism can be selectively provided with flow disturbing fan blades along the height direction, the outer edge of each fan blade is 100-400mm away from the outer wall surface of the auxiliary crucible, and the flow disturbing mechanism is used for enhancing the mixing between the cooling water with high enthalpy near the wall surface of the auxiliary crucible and the cooling water with low enthalpy of the main flow of the flow channel and sucking the water vapor on the heating wall surface to the center of the flow channel by virtue of centrifugal force;
the structure of the turbulent fan blade can be independent blades arranged at intervals (the height distance is 200-500mm), or a continuous spiral strip structure, the distance from the outer edge of the strip to the outer wall surface of the auxiliary crucible is 100-400mm, the thickness of the strip is 5-20mm, the climbing height of a single strip is 200-500mm, and the strip arrangement mode can select different height positions to arrange a single strip or continuously arrange a plurality of strips along the height direction.
In a more preferred embodiment, the present invention provides a molten material trapping device for a divided enhanced cooling reactor core, wherein the trapping device further comprises a molten material guiding device,
the upper surface of the bottom plate of the melt retention container between the main crucible and the auxiliary crucible is paved with hill-shaped melt guiding devices so as to facilitate the transfer of the solid and liquid core melt falling on the hill-shaped melt guiding devices to the crucible;
the melt guiding device is made of high-temperature resistant material (such as high-temperature ceramic and ZrO)2Material, etc.) covered with a sacrificial material.
In a more preferred embodiment, the present invention provides a molten material trapping device for a divided enhanced cooling reactor core, wherein the structure of the molten material guiding device can be a simple form or a complex form,
the simple form is a funnel-shaped melt guiding device, and the high-temperature resistant material is laid in a slope form with the edge (the inner edge of the melt retention container) being high (the height is 50-300mm) and the middle (the edge position of the main crucible inlet) being low;
the complex form is a multi-curved surface type melt guiding device, which is composed of a plurality of funnel-shaped structures taking the positions of an auxiliary crucible inlet and a main crucible inlet as centers.
In a more preferred embodiment, the present invention provides a molten material collecting apparatus for a divided intensified cooled reactor core, wherein the collecting apparatus further comprises a sacrificial material, which is laid on an inner surface of the molten material retention vessel and/or on an innermost side of the crucible and/or on the molten material guiding device, and the sacrificial material laid on the innermost side of the crucible is used for reducing thermal shock of sensible heat of the molten material in the core to a wall surface of the crucible.
In a more preferred embodiment, the present invention provides a molten material trapping device for a reactor core with a split-type intensified cooling structure, wherein the sacrificial material is an oxygen-rich material selected from Al2O3(melting point temperature about 2050 ℃ C.), SiO2(melting point temperature: about 1720 ℃ C.), MgAl2O4(melting point temperature about 2100 ℃ C.), Fe3O4(melting point temperature about 1600 ℃ C.), TiO2(melting point temperature about 1840 ℃ C.), and the like.
In a preferred embodiment, the invention provides a reactor core melt trapping device with split intensified cooling, wherein the trapping device further comprises a melting plug, which is sealed at the inlet of the crucible, has a thickness of 20-100mm, is made of low-melting-point metal, low-melting-point alloy or vitreous material (the vitreous material floats on the inlet of the crucible after later melting to play a sealing role, and has a softening temperature of 400-1000 ℃), and is selected from magnesium-aluminum alloy (melting point 400-600 ℃), iron-based alloy (such as carbon steel melting point 1500 ℃, stainless steel melting point 1400 ℃, aluminum-iron melting point 1100 ℃, molybdenum-iron melting point 500 ℃, etc.), common glass softening temperature 400-500 ℃, quartz glass softening temperature 900 ℃, etc.
In a preferred embodiment, the invention provides a split intensified cooled reactor core melt trapping device, wherein the trapping device further comprises a damping device and/or a grid plate for damping mechanical shocks caused by dropping of large mass objects,
the shock absorption device is arranged between the bottom plate of the melt retention container and the bottom of the reactor pressure container;
the grid plate is arranged between the bottom plate of the melt retention container and the lower head of the reactor pressure container.
In a more preferred embodiment, the present invention provides a molten material trapping apparatus for a divided enhanced cooling reactor core, wherein:
the damping device and the grid plate are made of oxygen-rich materials selected from Al2O3(melting point temperature about 2050 ℃ C.), SiO2(melting point temperature: about 1720 ℃ C.), MgAl2O4(melting point temperature about 2100 ℃ C.), Fe3O4(melting point temperature about 1600 ℃ C.), TiO2(melting point temperature about 1840 ℃ C.), etc.;
the shock absorption device is a low pier with a trapezoidal section (the inner height is 100-300mm, the position of an inclined plane, which is 10-100mm closest to the heat insulation layer of the reactor pressure vessel, is 10-100mm, and the distance between the vertical outer boundary and the geometric center line of the pile pit is slightly larger than the outer radius of the heat insulation layer of the straight cylinder section of the reactor pressure vessel by 50-200 mm);
the square of the cross section of the grid plate is formed by splicing a plurality of square grid plates with the side length of 300-;
the fixing mode of the grid plate can select spot welding connection of certain gaps (5-20mm) maintained among grids or casting of concrete with the same quality of a sacrificial material as a whole.
In a preferred embodiment, the invention provides a reactor core melt trapping device with sub-packaged intensified cooling, wherein the liquid level in a retention water tank is lower than a main loop pipeline, the bottom of the retention water tank is higher than a lower head welding seam of a reactor pressure vessel, and the volume of the retention water tank is 80-150m3。
In a preferred embodiment, the present invention provides a split enhanced cooling reactor core smelt trapping device, wherein:
the lowest operating liquid level of the cooling water tank is higher than the upper edge of the bottom plate of the melt retention container;
the bottom and the upper part of the cooling water tank are slightly lower than the liquid level and are respectively communicated with the cooling space through the connecting pipeline and the valve;
the connecting pipeline connected with the bottom of the side wall of the cooling space obliquely penetrates out of the side wall of the pile pit upwards, and an outlet on the inner side of the side wall of the pile pit is slightly higher than the bottom surface of the pile pit so as to prevent sundries from blocking a pipeline outlet.
In a more preferred embodiment, the present invention provides a molten material trapping device for a divided enhanced cooling reactor core, wherein the trapping device further comprises a filter disposed at a position of an interface between the bottom of the cooling water tank and the connection line.
In a preferred embodiment, the invention provides a reactor core melt trapping device with split intensified cooling, wherein a plurality of steam discharge ports are obliquely formed in the side wall of a reactor pit, and the outer outlet of the steam discharge ports is slightly higher than the liquid level of a cooling water tank, so that steam generated by boiling heat exchange is discharged into a containment vessel in time.
In a preferred embodiment, the invention provides a split intensified cooled reactor core melt trapping device, wherein the trapping device further comprises a filler filled in the inner bottom head area of the crucible, the filling height is higher than the equator of the inner bottom head,
the filler is made of a non-metal refractory material or a metal material with low melting point, high boiling point and high density, such as lead, so that the integrity of the lower end enclosure part is ensured and the overall heat exchange efficiency is improved.
In a preferred embodiment, the present invention provides a split intensified cooled reactor core smelt trapping assembly, wherein the trapping assembly further comprises a control system for monitoring the accident process under accident conditions and controlling associated equipment in the trapping assembly,
the control system comprises thermocouples arranged at different positions of the outer surface of the reactor pressure vessel, the melt retention vessel and/or the crucible along the height direction, and is used for tracking the current position of the melt, realizing the immediate or delayed opening of the valve through a remote signal or through the special design of the valve body (such as the valve is designed to be automatically opened in a power-off/gas-off mode), and the like.
The reactor core melt trapping device has the advantages that by the scheme of arranging the reactor core trap which is compact and has high cooling efficiency, the reactor core melt can be effectively trapped and contained by temporary detention and split charging reinforced cooling of the melt, so that the working condition of a severe accident of a nuclear power station can be met.
The beneficial effects of the invention are embodied in that:
(1) according to the invention, the molten material is retained for a certain time by the retention water tank, so that the molten material in the reactor core is fully liquefied, the decay heat power when entering the containment vessel is reduced, and the molten material in the later period is favorably shunted and cooled;
(2) when the lower end enclosure of the reactor pressure vessel fails, the melt can be rapidly guided into a plurality of crucibles, so that the area-volume ratio of the core melt is effectively increased, and the decay heat of the melt is favorably brought out;
(3) the heat exchange efficiency of the outer wall surface of the crucible is improved by filling the inside of the crucible (lower end enclosure filler) and performing enhanced heat exchange treatment on the outside (such as enhanced heat exchange treatment on the outer wall surface and a flow disturbing mechanism between a flow guiding device below the outside of the main crucible and the auxiliary crucible);
(4) the reactor core melt is transferred more directly and rapidly, the reaction (with water and sacrificial materials) in the period is less, the exposed area after the reactor core melt enters the crucible is smaller, and the radioactive substances are less released;
(5) the passive investment of cooling water and a natural circulation cooling mode are more reliable, and the long-term safety of the nuclear power plant after a serious accident is improved.
Drawings
FIG. 1 is a schematic diagram of the composition of an exemplary split enhanced cooled reactor core smelt trap apparatus of the present invention.
Fig. 2a is a schematic view of a structure of the melt guiding device 17 on the upper surface of the bottom plate 8 in fig. 1.
Fig. 2b is a schematic view of another configuration of the smelt guide means 17 on the upper surface of the bottom plate 8 of fig. 1.
FIG. 3a is a schematic view of a structure of the protective layer 19 (in this case, the protective layer 19a) on the surface of the auxiliary crucible 10 or the main crucible 11 shown in FIG. 1.
FIG. 3b is a schematic view of another structure of the protective layer 19 (in this case, the protective layer 19b) on the surface of the auxiliary crucible 10 or the main crucible 11 in FIG. 1.
FIG. 4 is a schematic view of the outer flow guide 12 and the flow perturbation mechanism 22 of the auxiliary crucible 10 and the main crucible 11 of FIG. 1.
Detailed Description
The following further describes embodiments of the present invention with reference to the accompanying drawings.
An exemplary sub-divided enhanced cooled reactor core melt containment apparatus of the present invention is shown in fig. 1-4, and includes a pit 1, a Reactor Pressure Vessel (RPV) 2, a retention water tank 3, a cooling water tank 4, a melt retention vessel 5 (including a floor 8), a vibration damper 6 (or a grid plate 6), a sacrificial material 7, a melt plug 9, an auxiliary crucible 10, a main crucible 11, a flow guide 12, a cooling space 13, a steam vent 14, a filter 15, a filler 16, a melt guide 17, a crucible inner bottom head 18, a protective layer 19 (which may be a protective layer 19a or a protective layer 19b), a refractory metal 20 (which may be a refractory metal or an alloy 20a or a refractory metal or an alloy frame structure 20b), a refractory block 21 (which may be a refractory block 21a or a refractory block 21b), and a refractory block structure 6, The spoiler 22, the connecting lines, and a control system (not shown).
An open-topped, barrel-shaped melt retention vessel 5 is located within the pit 1 with the lower and bottom of the reactor pressure vessel 2 located within the pit 1 (the side walls of the melt retention vessel 5 are slightly higher than the lower head weld of the reactor pressure vessel 2). The space in the pit 1 below the melt retention vessel 5 forms a cooling space 13.
In the pit 1, a main crucible 11 having a large diameter and a plurality of auxiliary crucibles 10 having a small diameter are provided below the bottom plate 8 of the melt retention vessel 5. The main crucible 11 is disposed directly below the melt retention vessel 5, and a plurality of sub-crucibles 10 are disposed below the side of the melt retention vessel 5 and uniformly arranged around the main crucible 11. The total volume of free space of the main crucible 11 and the auxiliary crucible 10 should be slightly larger than the sum of the volumes of the core melt and all the sacrificial material 7. The outer wall surfaces of the main crucible 11 and the sub-crucible 10 are subjected to heat exchange enhancement treatment, such as processing by a special means to appropriately increase surface roughness or increase turbulence.
The top of the main crucible 11 and the auxiliary crucible 10 are connected to the bottom plate 8 of the melt retention vessel 5, and a mountain is laid on the upper surface of the bottom plate 8 of the melt retention vessel 5 between the main crucible 11 and the auxiliary crucible 10A hill-like melt guiding device 17 to facilitate the transfer of the solid, liquid core melt falling thereon to the main crucible 11 and the auxiliary crucible 10. The melt guiding means 17 is made of a refractory material (e.g. high temperature ceramics and ZrO)2Material, etc.) covered with a sacrificial material 7.
The melt guiding device 17 is constructed in a simple or complex form.
In a simple form, a funnel-shaped melt guiding means 17a (see fig. 2a), in which refractory material is laid in the form of a slope with a high edge (the inner edge of the bottom plate 8 of the melt retention vessel 5) and a low middle (the position of the inlet edge of the main crucible 11). The regions above the inlets of the main crucible 11 and the sub-crucible 10 are made of refractory materials instead of low-melting-point metal plugs.
The complex form is a multi-curved melt guiding device 17b (see fig. 2b), in which the refractory material is laid at the inlet of the auxiliary crucible 10 and the inlet of the main crucible 11 at local low points. Taking 1/6 slices (6 slices may be spliced during installation) as an example, the surface a1 and the surface a2 are respectively melt guiding surfaces of the main crucible 11 and the auxiliary crucible 10, and the two guiding surfaces are generated by the following method:
(1) selecting 1/6 slice shape (annular belt shape with certain height, the outer boundary is attached to the inner wall surface of the melt retention container 5, the inner boundary is flush with the edge of the inlet of the main crucible 11), and high temperature resistant material with thickness of 50-300 mm;
(2) generating an A2 surface, grooving from the edge of the 1/6 slicing shape to the edge of the inlet of the auxiliary crucible 10, reserving a high-temperature resistant material with the thickness of 5-10mm at the edge of the inlet of the auxiliary crucible 10, and rounding off to facilitate the molten material to move into the auxiliary crucible 10;
(3) an A1 surface is generated, the center of the inlet of the main crucible 11 is taken as the center of a circle, the half length of the connecting line of the centers of the inlets of the main crucible 11 and the auxiliary crucible 10 is taken as a radius to draw a circle, a groove is formed from the edge of the vertical projection of the circle on the upper surface of the 1/6 slice shape to the edge of the inlet of the main crucible 11, and the edge of the inlet of the main crucible 11 is kept with a high-temperature resistant material with the thickness of 5-10mm and is rounded, so that the melt can be conveniently transferred into the main crucible.
The flow guide 12 is arranged outside and below the main crucible 11, and the turbulence mechanisms 22 are arranged circumferentially between the auxiliary crucibles 10. The flow guide 12 is used to narrow the flow channel of the outer wall surface of the main crucible 11 to 100 and 200mm, forming a coolant acceleration channel. The turbulence mechanism 22 can be selectively provided with turbulence fan blades along the height direction, the outer edge of each fan blade is 100-400mm away from the outer wall surface of the auxiliary crucible 10, and the turbulence mechanism is used for enhancing the mixing between the cooling water with the high enthalpy value near the wall surface of the auxiliary crucible 10 and the cooling water with the low enthalpy value of the main flow of the flow channel, and absorbing the water vapor on the heating wall surface to the center of the flow channel by virtue of centrifugal force. The structure of the turbulent fan blades can be independent blades (with the height interval of 200 plus 500mm) arranged at intervals, or a continuous spiral strip structure, the outer edge of each strip is 400mm away from the outer wall surface of the auxiliary crucible 10, the thickness of each strip is 5-20mm, the climbing height of a single strip is 200 plus 500mm, and the arrangement mode of the strips can select different height positions to arrange a single strip or continuously arrange a plurality of strips along the height direction.
The outer layers of the main crucible 11 and the auxiliary crucible 10 are made of metal, and the inner layers are protective layers 19 (the protective layers 19 are used for keeping the integrity of the main crucible 11 and the auxiliary crucible 10). The thickness of the protective layer 19 is 10-50 mm. The material of the protective layer 19 is a refractory material selected from magnesia, alumina, zirconia or composite ceramic with a metal structure doped therein. The composite ceramic with the metal structure doped inside is formed by mixing a massive refractory material 21a made of magnesia, alumina or zirconia in a high melting point metal or alloy 20a (see fig. 3a), or filling a massive refractory material 21b in a high melting point metal or alloy frame structure 20b (see fig. 3b) (metal or alloy such as iron-based alloy, e.g., carbon steel with a melting point of 1500 ℃, stainless steel with a melting point of 1400 ℃, ferroboron with a melting point of 1400 ℃, ferrotungsten with a melting point of 1800 ℃ and the like), and the porosity of the composite ceramic is 25% -75%.
The sacrificial material 7 is laid on the inner surface of the melt retention vessel 5 and the inner side of the protective layer 19 (the inner surface of the sidewall of the melt retention vessel 5 is laid with a layer of the high temperature material first, and then the sacrificial material 7 is laid). The sacrificial material 7 laid on the inner side of the protective layer 19 serves to reduce thermal impact of sensible heat of the core melt on the wall surface of the crucible. The sacrificial material 7 is made of oxygen-rich material selected from Al2O3(melting point temperature about 2050 ℃ C.), SiO2(melting point temperature: about 1720 ℃ C.), MgAl2O4(melting temperature about 210%0℃)、Fe3O4(melting point temperature about 1600 ℃ C.), TiO2(melting point temperature about 1840 ℃ C.), and the like.
The inlets of the main crucible 11 and the auxiliary crucible 10 are sealed with melting plugs 9 with the thickness of 20-100mm, the materials are low-melting point metals, low-melting point alloys or vitreous materials (the vitreous materials float on the inlets of the crucibles after later melting to play a sealing role, the softening temperature is 400-1000 ℃), and the materials are selected from magnesium-aluminum alloys (the melting point is 400-600 ℃), iron-based alloys (the melting point of carbon steel is 1500 ℃, the melting point of stainless steel is 1400 ℃, the melting point of aluminum-iron is 1100 ℃, the melting point of molybdenum-iron is 500 ℃, and the like), the softening temperature of common glass is 400-500 ℃, the softening temperature of quartz glass is 900 ℃, and the like. The installation mode of the melting plug 9 can select a thread structure and a bottle stopper structure (the inlets of the main crucible 11 and the auxiliary crucible 10 are provided with grooves which are 20-60 degrees with the horizontal direction, the tail end of the melting plug 9 is provided with an inverted circular truncated cone-shaped matching groove, the front end is matched with the diameters of the main crucible 11 and the auxiliary crucible 10) or a boss structure (the diameters of the inlets of the main crucible 11 and the auxiliary crucible 10 are expanded by 10-30mm, the height of the expanded part is 10-100mm, the diameter and the height of the tail end of the melting plug 9 are matched with the expanded area, and the diameter and the height of the front end are matched with the diameters of the main crucible.
The filling 16 is filled in the lowest crucible inner lower end socket 18 area inside the main crucible 11 and the auxiliary crucible 10, and the filling height is higher than the equator of the crucible inner lower end socket 18. The filler 16 is made of a non-metal fire-resistant material or a metal material with a low melting point, a high boiling point and a high density, such as lead, so as to ensure the integrity of the lower end enclosure part and improve the overall heat exchange efficiency.
The damping device 6 or the grid plate 6 is selected for buffering mechanical impact formed by dropping of a large-mass object. The damper device 6 is provided between the bottom plate 8 of the melt retention vessel 5 and the bottom of the reactor pressure vessel 2. The grid plate 6 is arranged between the floor 8 of the melt retention vessel 5 and the lower head of the reactor pressure vessel 2. The damping device 6 or the grid plate 6 is made of oxygen-rich material selected from Al2O3(melting point temperature about 2050 ℃ C.), SiO2(melting point temperature: about 1720 ℃ C.), MgAl2O4(melting point temperature about 2100 ℃ C.), Fe3O4(melting point temperature about 1600 ℃ C.), TiO2(melting point temperature about 1840 ℃ C.)). The shock absorption device 6 is a short pier with a trapezoidal section (the inner height is 100-300mm, the closest position of an inclined plane to the heat insulation layer of the reactor pressure vessel 2 is 10-100mm, and the distance from the vertical outer boundary to the geometric center line of the reactor pit 1 is slightly larger than the outer radius of the heat insulation layer of the straight cylinder section of the reactor pressure vessel 2 by 50-200 mm). The square of the cross section of the grid plate 6 is formed by splicing a plurality of square grid plates with the side length of 300-. The fixing mode of the grid plate 6 can be selected from spot welding connection with certain gaps (5-20mm) maintained among grids or concrete pouring with the same quality of the sacrificial material 7 on the whole.
The retention water tank 3 is located outside the reactor pit 1, and the bottom thereof is communicated with the upper space of the melt retention vessel 5 through a connection line so as to enable the water stored therein to enter the melt retention vessel 5 through the connection line, thereby submerging the lower head of the reactor pressure vessel 2 and enabling the core melt to be retained in the lower head of the reactor pressure vessel 2 for a certain time. The liquid level in the retention water tank 3 is lower than a main loop pipeline, the bottom of the retention water tank 3 is higher than a lower seal head welding line of the reactor pressure vessel 2, and the volume of the retention water tank 3 is 80-150m3。
The cooling water tank 4 is located outside the pit 1 and is connected to the cooling space 13 through a connecting line so that water stored therein can be introduced into the cooling space 13 through the connecting line to cool the main crucible 11 and the sub-crucible 10 for a long period of time. The lowest operating level of the cooling water tank 4 is higher than the upper edge of the floor 8 of the melt retention vessel 5. The bottom and the upper part of the cooling water tank 4 are slightly lower than the liquid level and are respectively communicated with the cooling space 13 through connecting pipelines and valves. The connecting pipeline connected with the bottom of the side wall of the cooling space 13 obliquely penetrates through the side wall of the pile pit 1 upwards, and the outlet of the connecting pipeline on the inner side of the side wall of the pile pit 1 is slightly higher than the bottom surface of the pile pit 1, so that the outlet of the pipeline is prevented from being blocked by sundries. A filter 15 is provided at the bottom of the cooling water tank 4 at the interface with the connecting line.
A plurality of steam discharge ports 14 are formed in the side wall of the reactor pit 1 in an inclined upward manner, and the outlets on the outer side of the steam discharge ports are slightly higher than the liquid level of the cooling water tank 4, so that steam generated by boiling heat exchange can be discharged into a containment vessel in time.
The control system is used for monitoring the accident process under the accident working condition and controlling related equipment in the capturing device. The control system comprises thermocouples arranged at different positions of the outer surfaces of the reactor pressure vessel 2, the melt retention vessel 5, the main crucible 11 and the auxiliary crucible 10 along the height direction, and is used for tracking the current position of the melt, realizing the immediate or delayed opening of the valve through a remote signal or through the special design of the valve body (such as the valve is designed to be automatically opened in a power-off/gas-off mode), and the like.
The above exemplary split enhanced cooling reactor core smelt capture device of the present invention operates as follows.
Under the accident condition, after the reactor core is melted in a large area, the molten reactor core is gradually migrated towards the lower end socket and accumulated in the lower end socket. The valve on the connecting pipeline of the retention water tank 3 and the melt retention vessel 5 is automatically opened before the molten material of the reactor core reaches the lower head, so that the lower head of the reactor pressure vessel 2 is submerged by injecting cooling water into the melt retention vessel 5 from the retention water tank 3. The cooling water in the melt retention vessel 5 is continuously boiled due to the sensible heat and decay heat of the core melt, and the steam is discharged into the free space in the containment vessel, during which the core melt is retained in the lower head of the reactor pressure vessel 2 until the cooling water in the retention water tank 3 is completely exhausted, and the lower head of the reactor pressure vessel 2 fails. The molten core flowing out from the lower head of the reactor pressure vessel 2 contacts and reacts with the damper 6 (or the grid plate 6) and the sacrificial material 7 in the molten material retention vessel 5, which lowers the temperature of the molten material and oxidizes metal substances therein, such as Zr and Fe. When the sacrificial material 7 is melted through, the core melt continues to melt through the melt plug 9 into the main crucible 11 and the auxiliary crucible 10.
Before the melt enters the main crucible 11 and the auxiliary crucible 10, the valve on the connecting line connecting the cooling water tank 4 and the cooling space 13 is automatically opened, and the two form a communicating vessel to submerge the main crucible 11 and the auxiliary crucible 10. After entering the main crucible 11 and the auxiliary crucible 10, the melt contacts the sacrificial material 7 in the main crucible 11 and the auxiliary crucible 10 and reacts to further lower the temperature of the melt. The molten metal oxidizes the metal substances in the sacrificial material 7, and meanwhile, the outer wall surfaces of the main crucible 11 and the auxiliary crucible 10 exchange boiling heat with the external cooling water. Steam formed by heat exchange is discharged into the safety shell through a steam discharge port 14 on the side wall of the reactor pit 1, and flows back into the cooling water tank 4 after being condensed, so that long-term cooling of the melts in the main crucible 11 and the auxiliary crucible 10 is realized.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is intended to include such modifications and variations. The above-described embodiments are merely illustrative of the present invention, and the present invention may be embodied in other specific forms or other specific forms without departing from the spirit or essential characteristics thereof. The described embodiments are, therefore, to be considered in all respects as illustrative and not restrictive. The scope of the invention should be indicated by the appended claims, and any changes that are equivalent to the intent and scope of the claims should be construed to be included therein.
Claims (8)
1. A split-type enhanced cooling reactor core melt trapping device is characterized in that: the trapping device comprises a reactor pit, a reactor pressure vessel, a melt retention vessel, a crucible, a retention water tank, a cooling water tank and connecting pipelines,
the melt retention vessel with an open top is positioned in the reactor pit, and the lower part and the bottom of the reactor pressure vessel positioned in the reactor pit are positioned in the reactor pit, and a space below the melt retention vessel in the reactor pit forms a cooling space;
in the pile pit, the crucible is arranged below the bottom plate of the melt retention container;
the retention water tank is positioned outside the reactor pit and is connected with the reactor pit through the connecting pipeline so as to enable water stored in the retention water tank to enter the molten material retention container through the connecting pipeline, so that the lower head of the reactor pressure container is submerged, and the molten material in the reactor core is retained in the lower head of the reactor pressure container for a certain time;
the cooling water tank is positioned outside the pile pit and is connected with the cooling space through the connecting pipeline so as to enable water stored in the cooling water tank to enter the cooling space through the connecting pipeline to cool the crucible for a long time;
the crucible is a plurality of crucibles, and comprises a main crucible with a larger diameter and an auxiliary crucible with a smaller diameter, a single main crucible is arranged right below the melt retention container, and a plurality of auxiliary crucibles are arranged below the side of the melt retention container and are uniformly arranged around the main crucible;
the trapping device also comprises a flow guiding device arranged below the outer part of the main crucible and a flow disturbing mechanism arranged between the auxiliary crucibles in the circumferential direction,
the flow guiding device is used for narrowing the flow channel on the outer wall surface of the main crucible to 100-200mm to form a coolant accelerating channel;
the flow disturbing mechanism is flow disturbing fan blades arranged along the height direction, the distance between the outer edges of the fan blades and the outer wall surface of the auxiliary crucible is 100-400mm, and the flow disturbing mechanism is used for enhancing the mixing between the cooling water with high enthalpy near the wall surface of the auxiliary crucible and the cooling water with low enthalpy of the main flow of the flow channel and sucking the water vapor on the heating wall surface to the center of the flow channel by virtue of centrifugal force;
the structure of the turbulent fan blades can be independent blades arranged at intervals or a continuous spiral strip structure, the distance between the outer edge of each strip and the outer wall surface of the auxiliary crucible is 100-400mm, the thickness of each strip is 5-20mm, the climbing height of a single strip is 200-500mm, and the strip arrangement mode is that a single strip is arranged at different height positions or a plurality of strips are continuously arranged along the height direction.
2. The trapping device according to claim 1, characterized in that: the outer layer of the crucible is made of metal, the inner layer is a protective layer,
the thickness of the protective layer is 10-50mm, the material is a refractory material selected from magnesia, alumina, zirconia or composite ceramic with a metal structure doped inside;
the composite ceramic with the metal structure doped inside is formed by mixing a massive refractory material made of magnesia, alumina or zirconia in high-melting-point metal or alloy or filling the massive refractory material in a high-melting-point metal or alloy frame structure, and the porosity of the composite ceramic is 25-75%.
3. The trapping device according to claim 1, characterized in that: the trapping device further comprises a melt guiding device,
the upper surface of the bottom plate of the melt retention container is laid with a hill-shaped melt guiding device between the main crucible and the auxiliary crucible, so that the solid and liquid core melt falling on the hill-shaped melt guiding device is transferred to the crucible;
the melt guiding device is made of high-temperature resistant materials.
4. The trapping device according to claim 3, characterized in that: the trapping device further comprises a sacrificial material which is laid on the inner surface of the melt retention vessel and/or the innermost side of the crucible and/or the melt guiding device, and the sacrificial material laid on the innermost side of the crucible is used for reducing thermal shock of sensible heat of the core melt to the wall surface of the crucible.
5. The trapping device according to claim 1, characterized in that: the trapping device also comprises a melting plug which is sealed at the inlet of the crucible, has the thickness of 20-100mm and is made of low-melting-point metal, low-melting-point alloy or vitreous material.
6. The trapping device according to claim 1, characterized in that: the trapping device also comprises a damping device and/or a grid plate for damping mechanical impact formed by dropping the large-mass object,
the shock absorption device is arranged between the bottom plate of the melt retention container and the bottom of the reactor pressure container;
the grid plate is arranged between the bottom plate of the melt retention container and the lower head of the reactor pressure container.
7. The trapping device according to claim 1, characterized in that: the trapping device also comprises a filler which is filled in the area of the inner lower end socket of the crucible and has the filling height higher than the equator of the inner lower end socket,
the filler is made of a non-metal refractory material or a metal material with low melting point, high boiling point and high density so as to ensure the integrity of the lower end socket part and improve the overall heat exchange efficiency.
8. The trapping device according to claim 1, characterized in that: the trapping device also comprises a control system which is used for monitoring the accident process under the accident condition and controlling the relevant equipment in the trapping device,
the control system comprises thermocouples arranged at different positions of the outer surface of the reactor pressure vessel, the melt retention vessel and/or the crucible along the height direction, and is used for tracking the current position of the melt and realizing the immediate or delayed opening of the valve through a remote signal or through the special design of the valve body.
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| CN110391030B (en) * | 2019-06-27 | 2023-12-15 | 中国核电工程有限公司 | Partitioned crucible melt out-of-pile catcher |
| JP7182521B2 (en) * | 2019-06-27 | 2022-12-02 | 日立Ｇｅニュークリア・エナジー株式会社 | Reactor system |
| CN113409966A (en) * | 2021-04-29 | 2021-09-17 | 中国核电工程有限公司 | Reactor melt is collected outside pile, partial shipment, is detained system |
| CN115662662B (en) * | 2022-09-09 | 2023-06-13 | 中国核动力研究设计院 | Reactor core melt trapping cooler and parameter calculation method thereof |
| CN116386910B (en) * | 2022-11-28 | 2024-02-13 | 上海核工程研究设计院股份有限公司 | Reactor pressure vessel and method for improving retention effectiveness of reactor core melt |
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