JP7142134B2 - Core meltdown retention structure and reactor containment vessel - Google Patents

Description

The present invention relates to a core meltdown holding structure and a reactor containment vessel.

In a nuclear power plant, as a severe accident, an accident in which core meltdown material flows out from the reactor vessel is assumed. If core meltdown material falls into the cavity of the reactor containment vessel, the damage may increase if the structure forming the cavity is severely damaged. Therefore, it is necessary to take measures to suppress the occurrence of serious damage to the reactor containment vessel.

Conventionally, for example, in Patent Document 1, a structure having a bottom portion and a wall portion forming a cavity chamber below the reactor vessel is provided, and the wall portion includes a wall iron plate facing the cavity chamber and a wall portion facing the cavity chamber. A reactor containment vessel is shown having wall concrete provided on the outside of the wall steel plate and a wall liner provided on the outside of the wall concrete with respect to the cavity chamber.

Conventionally, for example, in Patent Document 2, a core meltdown holding device for receiving and holding meltdowns below a reactor vessel in the event of a core meltdown accident of a nuclear reactor is provided. A plurality of molten core holding blocks arranged to form an inclined bottom surface holding a core melt holding block, each of which has a through hole through which coolant can flow, and a support base that supports the molten core holding block , wherein through-holes formed in a plurality of core melt holding blocks communicate with each other, and a coolant introduction part for introducing coolant into the through-holes includes a coolant discharge for discharging the coolant from the through-holes. , and is arranged such that the height position of the through-hole gradually increases from the coolant introduction section toward the coolant discharge section. .

JP 2016-166833 A JP 2014-081212 A

In the reactor containment vessel shown in the above-mentioned Patent Document 1, core meltdown material flowing out of the reactor vessel is received in a cavity provided below the reactor vessel and dammed up by the wall of the structure. In addition, in the above-described molten core holding device shown in Patent Document 2, when the molten core falls onto the block holding the molten core, the upper surface of the block holding the molten core will melt. It absorbs heat from the object and dissipates heat to the side and bottom surfaces to cool the melted material. Thus, conventionally, core meltdowns are dammed or cooled where they fall.

However, if the core melt is dammed or cooled where it fell, it may remain thick where it fell, i.e., in a limited area, rather than spreading. If the core meltdown continues to fall, it will swell and be held in a limited area, delaying the cooling of the lower interior, resulting in a high rate of erosion of the structure that forms the cavity (e.g., floor concrete, etc.). There is a concern that the structure will melt and damage will occur.

SUMMARY OF THE INVENTION An object of the present invention is to provide a core meltdown holding structure and a reactor containment vessel that can prevent damage to structures caused by core meltdowns.

A core meltdown holding device according to an aspect of the present invention is provided between a reactor vessel and a floor portion that receives the core meltdown below the reactor vessel, and melts and mixes the core meltdown with the core meltdown. A sacrificial material is provided for lowering the melting point of the core melt to reduce the viscosity thereof, and the sacrificial material is formed into a plurality of granules.

Further, in the core meltdown holding apparatus according to the aspect of the present invention, it is preferable that the granular sacrificial material be stored in a container having a melting point lower than that of the core meltdown.

A core meltdown holding device according to an aspect of the present invention is provided between a reactor vessel and a floor portion that receives the core meltdown below the reactor vessel, and melts and mixes the core meltdown with the core meltdown. A sacrificial material is provided for lowering the melting point of the core melt to lower the viscosity, and the sacrificial material is arranged on the upper surface of the floor, and a region around the sacrificial material in which the sacrificial material is not arranged is provided on the floor. prepare.

Further, in the core meltdown holding device according to the aspect of the present invention, the molten core and the sacrificial material are made of a material having a lower melting point than the melted material of the sacrificial material, and are arranged on the upper surface of the floor surrounding the sacrificial material. preferably have a weir.

A core meltdown holding device according to an aspect of the present invention is provided between a reactor vessel and a floor portion that receives the core meltdown below the reactor vessel, and melts and mixes the core meltdown with the core meltdown. The sacrificial material is provided with a sacrificial material that lowers the melting point of the core melt to reduce the viscosity thereof, and the sacrificial material is collectively supported by a supporting member having a melting point lower than that of the core melt and the melt of the sacrificial material. It is provided so that it can be diffused as the member melts.

A core meltdown holding device according to an aspect of the present invention is provided between a reactor vessel and a floor portion that receives the core meltdown below the reactor vessel, and melts and mixes the core meltdown with the core meltdown. A cavity chamber provided with a sacrificial material that lowers the melting point of the core melt to make it low in viscosity, and is arranged below the reactor vessel in which the sacrificial material is arranged; and an adjacent chamber arranged around the cavity chamber. a communicating portion communicating between the cavity chamber and the adjacent chamber; and a material having a melting point lower than that of the melted material of the core and the sacrificial material, provided in the communicating portion and the cavity chamber. and a closing portion that secures and isolates airtightness from the adjacent chamber.

A core meltdown holding device according to an aspect of the present invention is provided between a reactor vessel and a floor portion that receives the core meltdown below the reactor vessel, and melts and mixes the core meltdown with the core meltdown. A sacrificial material that lowers the melting point of the core melt to reduce the viscosity is provided, and the sacrificial material is housed in a basket-shaped container made of a material having a higher melting point than the core melt.

A reactor containment vessel according to an aspect of the present invention includes a reactor vessel, a floor provided below the reactor vessel to receive core meltdowns, and any one of the above-described core meltdown holding systems. a structure;

According to the present invention, the sacrificial material melts and mixes with the core melt that has flowed out of the reactor vessel, thereby lowering the melting point and viscosity of the core melt. The low-viscosity core melt flows along the floor and spreads thinly, and is sufficiently cooled also in the thickness direction. Therefore, it is possible to prevent the molten core from remaining thickly on the floor, or to suppress the erosion of the floor even if the molten core reaches the floor. As a result, erosion of the floor can be prevented, and damage to the structure due to core meltdown can be prevented.

FIG. 1 is a schematic configuration diagram showing an example of a nuclear power plant to which a reactor containment vessel according to an embodiment of the present invention is applied. FIG. 2 is a cross-sectional view showing a reactor structure of a pressurized water reactor applied to a reactor containment vessel according to an embodiment of the present invention. FIG. 3 is a schematic configuration diagram showing an example of a reactor containment vessel according to an embodiment of the present invention. FIG. 4 is a side cross-sectional view of the core meltdown holding structure according to Embodiment 1 of the present invention. FIG. 5 is a side cross-sectional view showing the action of the core meltdown holding structure according to Embodiment 1 of the present invention. FIG. 6 is a side sectional view of another example of the core meltdown holding structure according to Embodiment 1 of the present invention. FIG. 7 is a perspective view of a sacrificial material of the core melt holding structure according to Embodiment 2 of the present invention. FIG. 8 is a plan view of the sacrificial material of the core melt holding structure according to Embodiment 2 of the present invention. FIG. 9 is a side cross-sectional view of a core meltdown holding structure according to Embodiment 3 of the present invention. FIG. 10 is a side cross-sectional view of a core meltdown holding structure according to Embodiment 4 of the present invention. FIG. 11 is a side cross-sectional view of a core meltdown holding structure according to Embodiment 5 of the present invention. FIG. 12 is a side sectional view of a core meltdown holding structure according to Embodiment 6 of the present invention. FIG. 13 is a side cross-sectional view of a core meltdown holding structure according to Embodiment 7 of the present invention. FIG. 14 is a side cross-sectional view showing the operation of the core meltdown holding structure according to Embodiment 7 of the present invention. FIG. 15 is a side cross-sectional view showing the operation of the core meltdown holding structure according to Embodiment 7 of the present invention. FIG. 16 is a side cross-sectional view of a core meltdown holding structure according to Embodiment 8 of the present invention. FIG. 17 is a side sectional view of another example of the core meltdown holding structure according to Embodiment 8 of the present invention. FIG. 18 is a side cross-sectional view of a core meltdown holding structure according to Embodiment 9 of the present invention. FIG. 19 is a side cross-sectional view of a core meltdown holding structure according to Embodiment 10 of the present invention. FIG. 20 is a side cross-sectional view showing the action of the core meltdown holding structure according to the tenth embodiment of the present invention. FIG. 21 is a side cross-sectional view of a core meltdown holding structure according to Embodiment 11 of the present invention. FIG. 22 is a side cross-sectional view showing the action of the core meltdown holding structure according to the eleventh embodiment of the present invention. FIG. 23 is a side cross-sectional view of a core meltdown holding structure according to Embodiment 12 of the present invention. FIG. 24 is a side sectional view of another example of the core meltdown holding structure according to Embodiment 12 of the present invention. FIG. 25 is a side cross-sectional view of a core meltdown holding structure according to Embodiment 13 of the present invention. 26 is a cross-sectional side view of a sacrificial material of a core meltdown structure according to Embodiment 13 of the present invention. FIG.

EMBODIMENT OF THE INVENTION Below, embodiment which concerns on this invention is described in detail based on drawing. In addition, this invention is not limited by this embodiment. In addition, components in the following embodiments include components that can be easily replaced by those skilled in the art, or components that are substantially the same.

FIG. 1 is a schematic configuration diagram showing an example of a nuclear power plant to which a reactor containment vessel according to this embodiment is applied. FIG. 2 is a cross-sectional view showing the reactor structure of a pressurized water reactor applied to the reactor containment vessel according to this embodiment. FIG. 3 is a schematic configuration diagram showing an example of a reactor containment vessel according to this embodiment.

The nuclear reactor applied to the nuclear power plant of the present embodiment uses light water as a reactor coolant and a neutron moderator to make non-boiling high-temperature, high-pressure water throughout the primary system, and sends this high-temperature, high-pressure water to the steam generator. It is a pressurized water reactor (PWR) that generates steam through heat exchange and sends the steam to a turbine generator to generate electricity.

In a nuclear power plant having this pressurized water reactor, as shown in FIG. 1, a reactor containment vessel 11 houses a pressurized water reactor 12 and a steam generator 13 therein. The pressurized water reactor 12 and the steam generator 13 are connected via cooling water pipes 14 and 15 . The cooling water pipe 14 is provided with a pressurizer 16 . The cooling water pipe 15 is provided with a primary coolant circulation pump 17 . Therefore, in the pressurized water reactor 12, light water is heated as a primary coolant by the fuel constituting the reactor core, and the high-temperature light water is maintained at a predetermined high pressure by the pressurizer 16, and is passed through the cooling water pipe 14 to the steam generator 13. sent to In the steam generator 13, heat is exchanged between the high-temperature and high-pressure light water (primary coolant) and the secondary coolant, and the cooled light water is pumped through the cooling water pipe 15 by the primary coolant circulation pump 17 to form pressurized water. It is returned to reactor 12 .

The steam generator 13 is connected to a steam turbine 18 and a condenser 19 provided outside the containment vessel 11 via cooling water pipes 20 and 21 . The cooling water pipe 21 is provided with a water supply pump 22 . A generator 23 is also connected to the steam turbine 18 . The condenser 19 is connected to a water intake pipe 24 and a water discharge pipe 25 for supplying and discharging cooling water (eg, seawater). Therefore, the steam generated by exchanging heat with the high-pressure and high-temperature primary cooling water in the steam generator 13 is sent to the steam turbine 18 through the cooling water pipe 20, and the steam drives the steam turbine 18 to generate electricity. The generator 23 generates electricity. The steam that has driven the steam turbine 18 is cooled by the condenser 19 and then returned to the steam generator 13 through the cooling water pipe 21 .

In the pressurized water reactor 12, as shown in FIG. 2, the reactor vessel 41 includes a reactor vessel main body 42 and a reactor vessel body 42 mounted on the upper part thereof so that reactor internal structures can be inserted therein. It is composed of a lid (upper mirror) 43 . A reactor vessel lid 43 is fixed to the reactor vessel body 42 by a plurality of stud bolts 44 and nuts 45 so as to be openable and closable.

The reactor vessel main body 42 has a cylindrical shape whose upper part can be opened by removing the reactor vessel cover 43 and whose lower part is closed by a spherical lower mirror 46 . The reactor vessel main body 42 has an inlet nozzle (inlet nozzle) 47 for supplying light water (coolant) as primary cooling water and an outlet nozzle (outlet nozzle) 48 for discharging the light water. In addition to the inlet nozzle 47 and the outlet nozzle 48, the reactor vessel main body 42 is formed with a water injection nozzle (water injection nozzle) (not shown).

A reactor internal structure is inserted into the reactor vessel main body 42 . The core internals will be explained. An upper core support plate 49 is fixed above the inlet nozzle 47 and the outlet nozzle 48 , while a lower core support plate 50 is fixed near the lower mirror 46 below. The upper core support plate 49 and the lower core support plate 50 are disc-shaped and have a large number of communication holes (not shown) formed therein. The upper core support plate 49 is connected via a plurality of core support rods 51 to an upper core plate 52 in which a large number of communication holes (not shown) are formed.

A cylindrical core barrel 53 is arranged with a predetermined gap from the inner wall surface of the reactor vessel body 42 . The core barrel 53 has an upper core plate 52 connected to its upper portion, and a lower core plate 54 having a disk shape and having a large number of communication holes (not shown) connected to its lower portion. This lower core plate 54 is supported by the lower core support plate 50 .

A core 55 is formed by the upper core plate 52 , the core barrel 53 and the lower core plate 54 . A core 55 has a large number of fuel assemblies 56 arranged therein. Although not shown, the fuel assembly 56 is constructed by bundling a large number of fuel rods in a grid shape with a support grid. An upper nozzle is fixed to the upper end, and a lower nozzle is fixed to the lower end. A core 55 has a large number of control rods 57 arranged therein. A large number of control rods 57 are grouped at their upper ends to form a control rod cluster 58 that can be inserted into the fuel assembly 56 . A large number of control rod cluster guide tubes 59 are fixed to the upper core support plate 49 through the upper core support plate 49 itself. Each control rod cluster guide tube 59 extends at its lower end to a control rod cluster 58 within the fuel assembly 56 .

A reactor vessel cover 43 that constitutes the reactor vessel 41 is provided with a magnetic jack control rod driving device 60 at the top. A magnetic jack control rod drive 60 is housed in a housing 61 integral with the reactor vessel lid 43 . The numerous control rod cluster guide tubes 59 mentioned above extend to the control rod drive 60 at their upper ends. A control rod cluster drive shaft 62 extending from the control rod drive device 60 extends through the control rod cluster guide tube 59 to the fuel assembly 56 so that the control rod cluster 58 can be gripped.

The control rod drive unit 60 is vertically extended and connected to the control rod cluster 58. The control rod cluster drive shaft 62, which has a plurality of circumferential grooves arranged at equal pitches in the longitudinal direction on its surface, is magnetically driven. The output of the reactor is controlled by moving it up and down with a jack.

The reactor vessel main body 42 is also provided with a large number of instrumentation nozzles 63 penetrating the lower mirror 46 . Each instrumentation nozzle 63 has an in-core instrumentation guide tube 64 fixed to its upper end inside the furnace, and a conduit tube 65 connected to its lower end outside the furnace. Each in-core instrumentation guide tube 64 is connected at its upper end to the lower core support plate 50 . Upper and lower connection plates 66 and 67 are attached to each in-core instrumentation guide tube 64 to suppress vibration. A thimble tube 68 passing from the conduit tube 65 to the instrumentation nozzle 63 and the in-core instrumentation guide tube 64 can be inserted through the lower core plate 54 to the fuel assembly 56 . The thimble tube 68 is equipped with a neutron flux detector (not shown) capable of measuring neutron flux.

Therefore, by moving the control rod cluster drive shaft 62 by the control rod driving device 60 and inserting the control rod 57 into the fuel assembly 56, the nuclear fission in the core 55 is controlled, and the generated thermal energy The light water charged in 41 is heated and hot light water is discharged from outlet nozzle 48 and sent to steam generator 13 as described above. That is, the nuclear fuel that constitutes the fuel assembly 56 releases neutrons by nuclear fission, and the light water as a moderator and primary cooling water reduces the kinetic energy of the released fast neutrons and converts them into thermal neutrons. It facilitates nuclear fission and removes the generated heat for cooling. Also, the control rods 57 are inserted into the fuel assemblies 56 to adjust the number of neutrons generated in the core 55, and are rapidly inserted into the core 55 when the reactor is to be shut down in an emergency.

The reactor vessel 41 has an upper plenum 69 that communicates with the outlet nozzle 48 above the reactor core 55 and a lower plenum 70 below. A downcomer portion 71 communicating with the inlet nozzle 47 and the lower plenum 70 is formed between the reactor vessel 41 and the core barrel 53 . Therefore, the light water flows into the reactor vessel main body 42 from the inlet nozzle 47, flows downward through the downcomer portion 71, reaches the lower plenum 70, and is guided upward by the spherical inner surface of the lower plenum 70 to rise. , and after passing through the lower core support plate 50 and the lower core plate 54 , flows into the core 55 . The light water that has flowed into the core 55 cools the fuel assemblies 56 by absorbing the thermal energy generated from the fuel assemblies 56 that make up the core 55 . It rises to upper plenum 69 and is discharged through outlet nozzle 48 .

As shown in FIG. 3, the reactor containment vessel 11 of the nuclear power plant described above is erected on a solid ground 81 such as a bedrock, and is made of reinforced concrete or the like, and has a plurality of compartments inside, for example, an upper compartment 83 and a steam generator. A container loop chamber 84 is defined. A cylindrical structure 100 that defines a steam generator loop chamber 84 is formed in the center of the reactor containment vessel 11, and the reactor vessel 41 is suspended by the structure 100 containing concrete. Supported. The steam generator 13 is arranged in the steam generator loop chamber 84 and connected by cooling water pipes 14 and 15 .

The reactor containment vessel 11 has a cavity 150 defined therein by the structure 100 below the reactor vessel 41 . The reactor containment vessel 11 is provided with a fuel replacement water pit 88 . The refueling water pit 88 includes a reactor cooling path (cooling water supply device) 89 that supplies cooling water to the pressurized water reactor 12 to cool it in an emergency, and a reactor cooling water supply device that sprays the cooling water to the reactor containment vessel 11 for cooling. A reactor containment vessel cooling path (cooling water supply device) 90 is connected. The cooling water sprayed into the reactor containment vessel 11 is stored in the cavity chamber 150 from the steam generator loop chamber 84 via a drain line (not shown) provided in the structure 100 .

Although not shown, the reactor containment vessel 11 is provided with an external injection path for supplying cooling water to the cavity chamber 150, such as fire extinguishing water. The external injection route has a base end connected to external supply equipment such as fire extinguishing water installed outside the containment vessel 11 , while a tip end communicates with the cavity chamber 150 .

Thus, in the reactor containment vessel 11 , the cavity chamber 150 capable of supplying cooling water is provided below the reactor vessel 41 of the pressurized water reactor 12 .

Embodiments of the core melt holding structure will be described below.

[Embodiment 1]
FIG. 4 is a side cross-sectional view of the core meltdown holding structure according to the first embodiment. FIG. 5 is a side cross-sectional view showing the operation of the core meltdown holding structure according to the first embodiment. FIG. 6 is a side cross-sectional view of another example of the core meltdown holding structure according to the first embodiment.

As shown in FIG. 4, the core meltdown holding structure of Embodiment 1 includes a sacrificial material 1 provided between a reactor vessel 41 and a floor portion 150a of a cavity chamber 150 below the reactor vessel 41. Prepare. FIG. 4 shows a form in which the sacrificial material 1 is arranged on the upper surface of the floor portion 150a.

If a severe accident involving core meltdown damages the lower portion of the reactor vessel 41 (reactor vessel main body 42) and the core meltdown 10 flows out of the reactor vessel 41, the melted material 10 flows out from the lower portion of the reactor vessel 41. The molten core 10 falls toward the floor 150a of the cavity 150 of the containment vessel 11 provided below the reactor vessel 41 (see FIG. 5). That is, the floor 150 a of the cavity chamber 150 receives the core meltdown 10 . Core meltdown 10 includes a melted core and melted core internals accompanying the melted core.

The sacrificial material 1 is melted and mixed with the melted core 10, thereby lowering the melting point of the melted core 10 and making it less viscous. Therefore, the melted core 10 with reduced viscosity flows along the floor 150a of the cavity chamber 150 and spreads thinly, and is sufficiently cooled also in the thickness direction. Therefore, it is possible to prevent the core melt 10 from staying thick on the floor 150a. As a result, the floor 150a of the cavity chamber 150 made of concrete is prevented from being eroded, and damage to the structure 100 by the core meltdown 10 can be prevented.

The sacrificial material 1 contains one or more of compositions of an iron compound, an alkali compound, a silicate compound, calcium silicate (CaCiO ₃ ), and alumina (Al ₂ O ₃ ). Examples of iron compounds include carbon steel, stainless steel, Fe ₂ O ₃ , Fe ₃ O ₄ and iron ore. Examples of alkaline compounds include calcium-based Ca, CaO, Ca(OH) ₂ , CaCO ₃ and limestone; magnesium-based Mg, MgO, Mg(OH) ₂ , MgCO ₃ and dolomite; Na, _Na2O , NaOH, _NaHCO3 , _{Na2CO3 ,} sodium bicarbonate, trona and the like. Silicic acid compounds include, for example, SiO ₂ , sand, stone, calcium silicate, and magnesium silicate.

The core melt 10 and the sacrificial material 1 contact and react to form a mixture, which lowers the melting point. The main composition of the core melt 10 is UO ₂ and ZrO ₂ , which has a relatively high melting point and tends to solidify due to an increase in viscosity as the temperature drops. For example, the melting point of ZrO ₂ is about 3000K, but it drops to about 1600K when mixed with iron or calcium silicate, and drops to about 2500K when mixed with calcium oxide (CaO). The melted core 10 with a lowered melting point is made to have a low viscosity, thereby exhibiting the above effects.

Here, Fe, CaCiO ₃ >CaO, MgO>SiO ₂ >Al ₂ O ₃ >UO ₂ , ZrO ₂ in descending order of the effect of lowering the melting point and lowering the viscosity. It is desirable to contain a large amount of a composition that has a large effect of softening, and the above effect can be obtained remarkably. Such compositional order can be found in the literature Sun Yong Kwon, "Thermodynamic Optimization of ZrO2-Containing Systems in the CaO-MgO-SiO2-Al2O3-ZrO2 system." pid=135720) can be used as a basis.

Further, the greater the ratio of the sacrificial material 1 to the core melt 10, the greater the effect of lowering the melting point and lowering the viscosity, and the molar ratio of the core melt 10:sacrificial material 1 satisfies at least 2:1. is desirable. It is desirable that the sacrificial material 1 has a mass of 10% or more with respect to the assumed mass of the core meltdown 10 in order to obtain the above effect remarkably.

In addition, the sacrificial material 1 may be placed at least below the reactor vessel 41. However, since the sacrificial material 1 is mixed with the melted material 10 spreading from below the reactor vessel 41 to the outer region to reduce the viscosity, 4 and FIG. 5, it is desirable that they are also arranged in an area outside the area below the reactor vessel 41. FIG.

In the form shown in FIG. 6, the sacrificial material 1 is formed in layers on top and bottom, and in the figure, it is composed of an upper layer sacrificial material 1a and a lower layer sacrificial material 1b. In this configuration, it is desirable that the lower sacrificial material 1b is made of a material having a lower viscosity-lowering effect than the upper sacrificial material 1a. Lowering the viscosity can be achieved by following the order of decreasing the melting point and lowering the viscosity, or by changing the mass of the same composition that lowers the melting point and lowers the viscosity.

Note that the number of layers is not limited to the two layers described above, and it is sufficient that the sacrificial material 1 is formed in layers above and below, and the lower layer is formed of a material having a lower viscosity-lowering effect than the upper layer. It also includes the fact that each layer is not strictly separated, and is composed of a composition that gradually lowers the viscosity-lowering effect toward the bottom.

Therefore, the core melt 10 whose viscosity has been reduced in the upper layer spreads along the floor 150a, and then in the lower layer, the effect of reducing viscosity decreases, that is, the viscosity increases, and the erosion speed (fluidity) decreases. Therefore, it is possible to hold the molten core 10 while preventing the molten core 10 spreading along the floor 150a from remaining thick on the floor 150a. As a result, the floor 150a of the cavity chamber 150 made of concrete is prevented from being eroded, and damage to the structure 100 by the core meltdown 10 can be prevented. By increasing the eutectic temperature, the viscosity and melting point can be increased without lowering the temperature, and a material that increases the eutectic temperature may be provided in the lower layer.

By the way, the sacrificial material 1 is not limited to the above composition. For example, sacrificial material 1 may include reducing materials that reduce the main composition of core melt 10 . Examples of reducing agents include carbon (coke, etc.), hydrogen, sodium sulfite, and the like. Specifically, the main composition ZrO ₂ of the core melt 10 is reduced by carbon C to CO ₂ and Zr. In this manner, the sacrificial material 1 containing the reducing material can lower the melting point of the core melt 10 and reduce the viscosity. Therefore, the melted core 10 with reduced viscosity flows along the floor 150a of the cavity chamber 150 and spreads thinly, and is sufficiently cooled also in the thickness direction. Therefore, it is possible to prevent the core melt 10 from staying thick on the floor 150a. As a result, the floor 150a of the cavity chamber 150 made of concrete is prevented from being eroded, and damage to the structure 100 by the core meltdown 10 can be prevented.

Moreover, the sacrificial material 1 is not limited to the composition described above. For example, sacrificial material 1 may include a coolant that cools the main composition of core melt 10 . The coolant is, for example, a material containing water of crystallization, such as MgCl ₂ ·6H ₂ O, Na ₂ SO ₄ ·10H ₂ O, CaSO ₄ ·2H ₂ O, or the like. In this way, the sacrificial material 1 containing the water of crystallization, which is a coolant, can be cooled by the latent heat of vaporization taken away when the water of crystallization is evaporated, thereby lowering the melting point of the core melt 10 and making it low in viscosity. Therefore, the melted core 10 with reduced viscosity flows along the floor 150a of the cavity chamber 150 and spreads thinly, and is sufficiently cooled also in the thickness direction. Therefore, it is possible to prevent the core melt 10 from staying thick on the floor 150a. As a result, the floor 150a of the cavity chamber 150 made of concrete is prevented from being eroded, and damage to the structure 100 by the core meltdown 10 can be prevented.

[Embodiment 2]
FIG. 7 is a perspective view of a sacrificial material of a core meltdown holding structure according to Embodiment 2. FIG. FIG. 8 is a plan view of a sacrificial material of the core meltdown holding structure according to Embodiment 2. FIG.

The core melt holding structure of the second embodiment is characterized by the form of the sacrificial material 1 of the first embodiment described above. Specifically, as shown in FIGS. 7 and 8, the sacrificial material 1A is formed in a plurality of blocks, and the blocks are arranged side by side on the upper surface of the floor portion 150a. 7 and 8 show an example in which the sacrificial material 1A is formed in the shape of a regular triangular prism, but it may be a polygonal prism such as a quadrangular prism, a regular quadrangular prism, a regular pentagonal prism, or a regular hexagonal prism. , so long as they are arranged side by side on the upper surface of the floor portion 150a. Moreover, the sacrificial material 1A is provided with a suspender 1Aa such as an eyebolt on its upper surface. One block-shaped sacrificial material 1A is designed to weigh, for example, from several kg to ten and several kg, and can be installed or removed by being hung by a crane or the like using a hanging tool 1Aa.

As described above, in the core meltdown holding structure of the second embodiment, the sacrificial material 1A is formed in a plurality of block shapes, so that the mass of each piece is reduced and the portability is improved. Therefore, installation can be easily performed. Further, in the core meltdown holding structure of the second embodiment, the sacrificial material 1A can be transported, installed, or removed by being suspended by a crane or the like by the suspending tool 1Aa. Therefore, according to the core meltdown holding structure of the second embodiment, it is possible to easily remove and reinstall the structure 100 (the floor 150a of the cavity 150) during periodic inspection.

Although not shown in the drawings, in the core meltdown holding structure of the first embodiment, the sacrificial members 1A may be arranged on the upper surface of the floor portion 150a so as to be fitted to each other by unevenness or the like. By doing so, it is possible to suppress mutual positional deviation when arranged.

[Embodiment 3]
9 is a side cross-sectional view of a core meltdown holding structure according to Embodiment 3. FIG.

The core meltdown holding structure of Embodiment 3 is characterized by the form of the sacrificial material 1 of Embodiment 1 described above. Specifically, as shown in FIG. 9, the sacrificial material 1B is formed in a plurality of granules, and the granules are provided on the upper surface of the floor portion 150a. FIG. 9 shows an example in which the sacrificial material 1B is formed in the shape of spherical particles, but the shape is not limited. One granular sacrificial material 1B is designed to weigh, for example, several grams to ten and several grams, and a plurality of them can be housed in a container such as a bag, transported, and installed or removed. Granular also includes powder.

As described above, in the core meltdown holding structure of Embodiment 3, the sacrificial material 1B is formed in a plurality of granules, so that the individual mass is reduced and the portability is improved. Therefore, installation can be easily performed. Therefore, according to the core meltdown holding structure of the third embodiment, it is possible to easily remove and reinstall the structure 100 (floor portion 150a of the cavity chamber 150) during periodic inspection. In addition, the molten core holding structure of Embodiment 3 can be installed even in complicated shapes, irregularities, and gaps without being affected by the shape of the floor 150a to be laid, so that the degree of freedom in installation can be improved.

Further, in the core meltdown holding structure of the third embodiment, it is desirable that the granular sacrificial material 1B is divided and housed in a plurality of containers (for example, bags) having a melting point lower than that of the core meltdown 10. Therefore, it can be transported and installed or removed easily. Further, by installing the container as it is, the container can be melted by the molten core 10 and the sacrificial material 1B can be mixed with the molten core 10 . Alternatively, the container may be configured as a sacrificial material.

[Embodiment 4]
10 is a side cross-sectional view of a core meltdown holding structure according to Embodiment 4. FIG.

The core meltdown holding structure of Embodiment 4 is characterized by the form of the sacrificial material 1 of Embodiment 1 described above. Specifically, as shown in FIG. 10, the sacrificial material 1C is formed in layers, and the layers are provided on the upper surface of the floor portion 150a. Layered includes film, membrane, sheet, tile, panel, and the like. In addition, the layered sacrificial material 1C is flexible, so that it can be wound in a roll shape, transported, and installed or removed. The layered sacrificial material 1C is designed to have a thickness of, for example, several millimeters to ten-odd millimeters, and can be installed in multiple layers.

As described above, in the core meltdown holding structure of the fourth embodiment, the sacrificial material 1C is formed in layers, so that the mass of each piece is reduced and the portability is improved. Therefore, installation can be easily performed. Therefore, according to the core meltdown holding structure of the fourth embodiment, it is possible to easily remove and reinstall the structure 100 (floor portion 150a of the cavity chamber 150) during periodic inspection.

[Embodiment 5]
11 is a side cross-sectional view of a core meltdown holding structure according to Embodiment 5. FIG.

The core meltdown holding structure of Embodiment 5 is characterized by the form of the sacrificial material 1 of Embodiment 1 described above. Specifically, as shown in FIG. 11, the sacrificial material 1D is formed in a linear shape, and the linear shape is provided on the upper surface of the floor portion 150a. The term “linear” includes fibrous, cord-like, rope-like, and the like. In addition, the linear sacrificial material 1D is flexible, so that it can be wound in a ring shape, transported, and installed or removed. The linear sacrificial material 1D is designed to have a diameter of, for example, several millimeters to ten and several millimeters, and can be installed by intertwining, bending, or winding.

As described above, in the core meltdown holding structure of the fifth embodiment, the sacrificial material 1D is formed in a linear shape, so that the individual mass is reduced and the portability is improved. Therefore, installation can be easily performed. Therefore, according to the core meltdown holding structure of the fifth embodiment, it is possible to easily remove and reinstall the structure 100 (the floor 150a of the cavity 150) during periodic inspections. In addition, the core meltdown holding structure of Embodiment 5 can be installed even in complex shapes, irregularities, and gaps regardless of the shape of the floor 150a to be laid, and the degree of freedom in installation can be improved.

[Embodiment 6]
12 is a side cross-sectional view of a core meltdown holding structure according to Embodiment 6. FIG.

The core meltdown holding structure of Embodiment 6 is characterized by the form of the sacrificial material 1 of Embodiment 1 described above. Specifically, as shown in FIG. 12, the sacrificial material 1E is formed in a plurality of blocks, and the blocks are arranged or overlapped on the upper surface of the floor portion 150a. Moreover, the sacrificial material 1E is provided with a suspender 1Ea such as an eyebolt on its upper surface. One block-shaped sacrificial material 1E is designed to weigh, for example, from several kg to ten and several kg, and can be installed or removed by being hung by a crane or the like using a hanging tool 1Ea. In addition, the sacrificial material 1E has a recess 1Eb in the lower part thereof so as to avoid interference with the suspending member 1Ea of the lower sacrificial material 1E when stacked vertically.

As described above, in the core meltdown holding structure of Embodiment 6, since the sacrificial material 1E is formed in a plurality of block shapes, the mass of each piece is reduced and the portability is improved. Therefore, installation can be easily performed. Further, in the core meltdown holding structure of Embodiment 6, the sacrificial material 1E can be transported, installed, or removed by suspending it with a crane or the like by means of a suspending tool 1Ea. Therefore, according to the core meltdown holding structure of the sixth embodiment, it is possible to easily remove and reinstall the structure 100 (the floor 150a of the cavity 150) during periodic inspections. In addition, in the core meltdown holding structure of Embodiment 6, the sacrificial material 1E is provided with a recess 1Eb that avoids the lower suspending tool 1Ea, and mutual interference can be prevented even if the sacrificial material 1E is stacked vertically.

[Embodiment 7]
13 is a side cross-sectional view of a core meltdown holding structure according to Embodiment 7. FIG. FIG. 14 is a side cross-sectional view showing the action of the core meltdown holding structure according to the seventh embodiment. FIG. 15 is a side sectional view showing the action of the core meltdown holding structure according to the seventh embodiment.

The core meltdown holding structure of Embodiment 7 is characterized by the form of the sacrificial material 1 of Embodiment 1 described above. Specifically, as shown in FIG. 13, the sacrificial material 1F is arranged on the upper surface of the floor 150a, which is the region below the reactor vessel 41. As shown in FIG. The form of the sacrificial material 1F includes the forms shown in Embodiments 2 to 6 described above. Moreover, the sacrificial material 1F is not placed on the upper surface of the floor 150a, which is a region outside the area below the reactor vessel 41 around the sacrificial material 1F. Although the region where the sacrificial material 1F is placed is below the reactor vessel 41, this region includes at least the region directly below the reactor vessel 41. It may include a region that is not directly under the container 41 . That is, in the core meltdown holding structure of Embodiment 7, there is an area where the floor 150a is exposed around the area where the sacrificial material 1F is arranged.

As described above, in the core meltdown holding structure of Embodiment 7, a region where no sacrificial material 1F is arranged is provided around the region where the sacrificial material 1F is arranged. Therefore, the core melt 10 is made less viscous by the sacrificial material 1F, spreads along the floor 150a, and then cools while spreading to reach the area where the sacrificial material 1F is not arranged. When reaching the area where the sacrificial material 1F is not arranged, the molten core 10 spreads out, so that it is easy to cool and erosion of the floor 150a is suppressed. As a result, the floor 150a of the cavity chamber 150 made of concrete is prevented from being eroded, and damage to the structure 100 by the core meltdown 10 can be prevented. Moreover, since there is a region where the sacrificial material 1F is not arranged, periodic inspection of the structure 100 (floor portion 150a of the cavity chamber 150) can be performed without removing or reinstalling the sacrificial material 1F.

Further, in the core meltdown holding structure of Embodiment 7, as shown in FIG. 13, the weir 2 is arranged on the upper surface of the floor portion 150a surrounding the sacrificial material 1F. The weir 2 is made of a material having a melting point lower than that of the mixed melt of the core melt 10 and the sacrificial material 1F. The weir 2 may contain the composition of the sacrificial material 1 shown in the first embodiment.

Therefore, as shown in FIG. 14, the core melt 10 is stored by the weir 2 while being made low in viscosity by the sacrificial material 1F, so that melting and mixing with the sacrificial material 1F is promoted and the viscosity is further reduced. do. After that, as shown in FIG. 15, since the weir 2 is melted by the molten material in which the melted core 10 and the sacrificial material 1F are mixed, the melted core 10 with reduced viscosity spreads along the floor 150a. It reaches a region where the sacrificial material 1F is not arranged while being cooled in a state where the sacrificial material 1F is not arranged. When reaching the area where the sacrificial material 1F is not arranged, the molten core 10 spreads out, so that it is easy to cool and erosion of the floor 150a is suppressed. By arranging the weir 2 in this way, it is possible to promote melting and mixing of the core melt 10 with the sacrificial material 1F, thereby improving the viscosity reduction. As a result, the floor 150a of the cavity chamber 150 made of concrete is prevented from being eroded, and damage to the structure 100 by the core meltdown 10 can be prevented.

As shown in FIGS. 13 to 15, in the area where the sacrificial material 1F is not arranged, the floor 150a is formed with an inclined surface 150b that slopes down as it separates from the area where the sacrificial material 1F is arranged. is desirable. Therefore, the molten core 10 easily spreads along the inclined surface 150b, and the cooling performance of the molten core 10 can be improved.

[Embodiment 8]
16 is a side cross-sectional view of a core meltdown holding structure according to Embodiment 8. FIG. 17 is a side cross-sectional view of another example of the core meltdown holding structure according to Embodiment 8. FIG.

The core meltdown holding structure of Embodiment 8 is characterized by the form of the sacrificial material 1 of Embodiment 1 described above. Specifically, as shown in FIG. 16, the sacrificial material 1G includes a high sacrificial material 1Ga composed of a material having a high viscosity-lowering effect and a low sacrificial material 1Gb composed of a material having a low viscosity-lowering effect. and at least two types. The level of the viscosity reduction can be achieved by selecting the composition in order of magnitude of the effect of lowering the melting point of the core melt 10 and reducing the viscosity, as described in the first embodiment, or by increasing the mass. .

In the core meltdown holding structure of the eighth embodiment, the high sacrificial material 1Ga is arranged on the upper surface of the floor 150a which is the region below the reactor vessel 41, and the high sacrificial material 1Ga is surrounded by the floor 150a. A low sacrificial material 1Gb is arranged on the upper surface. The form of the sacrificial material 1G includes the forms described in the above second to sixth embodiments. Although the area where the high sacrificial material 1Ga is arranged is below the reactor vessel 41, this area includes at least the area directly below the reactor vessel 41. It may include a region that is not directly under the furnace vessel 41 . That is, in the core melt holding structure of the eighth embodiment, there is a region where the low sacrificial material 1Gb is arranged around the region where the high sacrificial material 1Ga is arranged.

Thus, in the core meltdown holding structure of the eighth embodiment, the high sacrificial material 1Ga is arranged on the upper surface of the floor 150a below the reactor vessel 41, and the upper surface of the floor 150a surrounds the high sacrificial material 1Ga. 1 Gb of low sacrificial material is placed in the . Therefore, the melted material 10 is reduced in viscosity by the high sacrificial material 1Ga, spreads along the floor 150a, and then cools in the spreading state to reach the area where the low sacrificial material 1Gb is arranged. When reaching the region where the low sacrificial material 1Gb is arranged, the melted core 10 spreads out, so it is easy to cool, and furthermore, the low sacrificial material 1Gb cools while reducing the viscosity. As a result, the floor 150a of the cavity chamber 150 made of concrete is prevented from being eroded, and damage to the structure 100 by the core meltdown 10 can be prevented.

In addition, in the core meltdown holding structure of the eighth embodiment, it is desirable to dispose the low sacrificial material 1Gb below the high sacrificial material 1Ga as well.

Therefore, the melted core 10 whose viscosity is reduced in the upper layer of high sacrificial material 1Ga spreads along the floor 150a, and then in the lower layer of low sacrificial material 1Gb, the viscosity decreases, that is, the viscosity increases and the erosion rate increases. (liquidity) decreases. Therefore, it is possible to hold the molten core 10 while preventing the molten core 10 spreading along the floor 150a from remaining thick on the floor 150a. As a result, the floor 150a of the cavity chamber 150 made of concrete is prevented from being eroded, and damage to the structure 100 by the core meltdown 10 can be prevented.

[Embodiment 9]
18 is a side sectional view of a core meltdown holding structure according to Embodiment 9. FIG.

The core meltdown holding structure of the ninth embodiment is characterized by the form of the sacrificial material 1 of the first embodiment described above. Specifically, as shown in FIG. 18, the sacrificial material 1H is configured as a facility structure or a part of the facility structure installed below the reactor vessel 41 . The facility structure includes, for example, a conduit support 160 that supports the conduit tube 65 (thimble tube 68) inside the cavity chamber 150. As shown in FIG. The facility structure also includes the outer surface member of the conduit tube 65 . In addition, the equipment structure includes walls and pillars that form the cavity 150 in the reactor containment vessel 11, although they are not shown in the drawings. That is, the equipment structure indicates a structure existing inside the cavity room 150 . In addition, the area below the reactor vessel 41 is an area including at least a part directly below the reactor vessel 41, and includes an area outside the area directly below the reactor vessel 41 following the area directly below the reactor vessel 41. You can stay.

In addition, when the sacrificial material 1H is provided on the equipment structure, the layered sacrificial material 1C of the fourth embodiment is wound around the outside of the equipment structure, or the linear sacrificial material 1D of the fifth embodiment is wound or entwined. It can be set by

Also, the sacrificial material 1H may be arranged on the upper surface of the floor portion 150a of the cavity chamber 150. FIG.

Thus, in the core meltdown holding structure of the ninth embodiment, the sacrificial material 1H is configured as an equipment structure installed below the reactor vessel 41 or a part of the equipment structure. The sacrificial material 1H melts and mixes with the core melt 10, thereby lowering the melting point of the core melt 10 and making it low in viscosity. It flows along and spreads thinly, and is sufficiently cooled also in the thickness direction. Therefore, it is possible to prevent the core melt 10 from staying thick on the floor 150a. As a result, the floor 150a of the cavity chamber 150 made of concrete is prevented from being eroded, and damage to the structure 100 by the core meltdown 10 can be prevented.

[Embodiment 10]
19 is a side cross-sectional view of a core meltdown holding structure according to Embodiment 10. FIG. FIG. 20 is a side cross-sectional view showing the action of the core meltdown holding structure according to the tenth embodiment.

The core meltdown holding structure of the tenth embodiment is characterized by the form of the sacrificial material 1 of the first embodiment described above. Specifically, as shown in FIG. 19, the sacrificial material 1I is supported by a supporting member 3 having a melting point lower than that of the melted material 10 and the sacrificial material 1I. Moreover, the sacrificial material 1I is provided so as to be able to diffuse as the support member 3 melts.

The support member 3 supports the sacrificial material 1I so that it does not spread all together, and may be configured as a weir as shown in FIG. may be configured. The support member 3 is made of a material having a melting point lower than that of the molten material in which the core melt 10 and the sacrificial material 1F are mixed. The support member 3 may contain the composition of the sacrificial material 1 shown in the first embodiment.

The sacrificial material 1I is formed in the form of granules or powder as shown in the third embodiment, and arranged together by the support member 3 so that it can be diffused as the support member 3 melts. Also, the sacrificial material 1I may be formed in a liquid state and supported by the support member 3 so that it can be diffused as the support member 3 melts. Also, the sacrificial material 1I may be formed in the form of granules or powder as described in the third embodiment, provided in the liquid, and supported by the support member 3 so that it can be diffused as the support member 3 melts.

Thus, in the core meltdown holding structure of the tenth embodiment, the sacrificial material 1I is collectively supported by the support member 3 having a lower melting point than the melted core 10 and the melt of the sacrificial material 1I. It is provided so as to be diffusible as it melts. As the supporting member 3 melts, the sacrificial material 1I melts and mixes with the molten core 10 as shown in FIG. Therefore, the melted core 10 with reduced viscosity flows along the floor 150a of the cavity chamber 150 and spreads thinly, and is sufficiently cooled also in the thickness direction. Therefore, it is possible to prevent the core melt 10 from staying thick on the floor 150a. As a result, the floor 150a of the cavity chamber 150 made of concrete is prevented from being eroded, and damage to the structure 100 by the core meltdown 10 can be prevented. Moreover, since the sacrificial material 1I can be collectively supported, inspection can be performed without removing or reinstalling the sacrificial material 1I at the time of periodic inspection of the structure 100 (floor portion 150a of the cavity chamber 150). .

[Embodiment 11]
21 is a side cross-sectional view of a core meltdown holding structure according to Embodiment 11. FIG. FIG. 22 is a side cross-sectional view showing the action of the core meltdown holding structure according to the eleventh embodiment.

The core meltdown holding structure of the eleventh embodiment is characterized by the form of the sacrificial material 1 of the first embodiment described above. Specifically, as shown in FIG. 21, the sacrificial material 1J is provided below the reactor vessel 41 and between the reactor vessel 41 and the floor 150a of the cavity chamber 150 that receives the core meltdown 10 . In FIG. 21, the sacrificial material 1J is arranged on the upper surface of the floor 150a. The form of the sacrificial material 1J includes the forms shown in Embodiments 2 to 10 described above and Embodiments 12 to 14 described later.

On the other hand, in the reactor containment vessel 11 , an adjacent chamber 151 is arranged around the cavity chamber 150 below the reactor vessel 41 . The adjoining room 151 forms a space that workers enter during normal operation of the nuclear power plant. A communication portion 152 communicates between the cavity chamber 150 and the adjacent chamber 151 . The communicating portion 152 is provided with a closing portion 4 that secures and isolates airtightness between the cavity chamber 150 and the adjacent chamber 151 . The closing part 4 is made of a material having a melting point lower than that of the core melt 10 and the melt of the sacrificial material 1J. The closing part 4 may contain the composition of the sacrificial material 1 shown in the first embodiment.

Thus, in the core meltdown holding structure of the eleventh embodiment, while the sacrificial material 1J is arranged in the cavity chamber 150 below the reactor vessel 41, the communicating portion 152 that communicates the cavity chamber 150 and the adjacent chamber 151 is airtightly closed by the closing portion 4 . The sacrificial material 1J melts and mixes with the melted core 10, thereby lowering the melting point of the melted core 10 and making it less viscous. Therefore, the melted core 10 with reduced viscosity flows along the floor 150a of the cavity chamber 150 and spreads thinly. After that, as shown in FIG. 22, when the closed part 4 is melted by the melted core 10 spreading along the floor part 150a, the melted core 10 spreads to the adjacent chamber 151 through the communicating part 152, and the heat transfer area is expanded. As a result, the cooling performance is improved and sufficiently cooled. Therefore, it is possible to prevent the core melt 10 from remaining thickly on the floor 150a. As a result, the floor 150a of the cavity chamber 150 made of concrete is prevented from being eroded, and damage to the structure 100 by the core meltdown 10 can be prevented.

[Embodiment 12]
23 is a side cross-sectional view of a core meltdown holding structure according to Embodiment 12. FIG. 24 is a side sectional view of another example of the core meltdown holding structure according to the twelfth embodiment. FIG.

The core meltdown holding structure of the twelfth embodiment is characterized by the form of the sacrificial material 1 of the first embodiment described above. Specifically, as shown in FIG. 23, the sacrificial material 1K is provided below the reactor vessel 41 and between the reactor vessel 41 and the floor 150a of the cavity chamber 150 that receives the core meltdown 10 . In FIG. 23, the sacrificial material 1K is arranged along the floor 150a. The form of the sacrificial material 1K includes forms shown in Embodiments 2 to 11 described above and Embodiments 13 and 14 described later.

A cooling mechanism 5 is arranged below the sacrificial material 1K. The cooling mechanism 5 is arranged on the upper surface of the floor portion 150a of the cavity chamber 150 and arranged along the floor portion 150a. In the cooling mechanism 5, a cooling pipe 5b is arranged inside a base material (for example, concrete) 5a laminated on the upper surface of the floor 150a. Coolant is circulated inside the cooling pipe 5b, thereby cooling the base material 5a and the surroundings of the base material 5a.

Thus, in the core meltdown holding structure of the twelfth embodiment, the cooling mechanism 5 is arranged below the sacrificial material 1K. The sacrificial material 1K melts and mixes with the melted core 10, thereby lowering the melting point of the melted core 10 and making it less viscous. Therefore, the melted core 10 with reduced viscosity flows along the floor 150a of the cavity chamber 150 and spreads thinly. Further, the core melt 10 spread along the floor 150 a is sufficiently cooled by the cooling mechanism 5 also in the thickness direction, and solidifies above the cooling mechanism 5 . Therefore, the molten core 10 can be held while preventing the molten core 10 from remaining thick on the floor 150a. As a result, the floor 150a of the cavity chamber 150 made of concrete is prevented from being eroded, and damage to the structure 100 by the core meltdown 10 can be prevented.

Further, in the core melt holding structure of Embodiment 12, as shown in FIG. and a low sacrificial material of 1 Kb. The level of the viscosity reduction can be achieved by selecting the composition in order of magnitude of the effect of lowering the melting point of the core melt 10 and reducing the viscosity, as described in the first embodiment, or by increasing the mass. .

The sacrificial material 1K is formed by laminating a high sacrificial material 1Ka in the upper layer and a low sacrificial material 1Kb in the lower layer of the high sacrificial material 1Ka. A cooling mechanism 5 is arranged below the low sacrificial material 1Kb. That is, the high sacrificial material 1Ka is arranged at the uppermost position, and the low sacrificial material 1Kb is arranged between the high sacrificial material 1Ka and the cooling mechanism 5 .

Therefore, the core melt 10 has a low viscosity in the upper high sacrificial material 1Ka and spreads along the floor 150a, and then the lower low sacrificial material 1Kb has a lower viscosity, that is, a higher viscosity and an erosion rate. (liquidity) decreases. Therefore, it is possible to hold the molten core 10 while preventing the molten core 10 spreading along the floor 150a from remaining thick on the floor 150a. As a result, it is also possible to prevent the core meltdown 10 from eroding the cooling mechanism 5 .

[Embodiment 13]
25 is a side cross-sectional view of a core meltdown holding structure according to Embodiment 13. FIG. 26 is a side cross-sectional view of a sacrificial material of a core meltdown holding structure according to Embodiment 13. FIG.

The core meltdown holding structure of the thirteenth embodiment is characterized by the form of the sacrificial material 1 of the first embodiment described above. Specifically, as shown in FIG. 25, the sacrificial material 1L is accommodated in the container 6. As shown in FIG. The form of the sacrificial material 1L includes forms shown in Embodiments 2 to 12 described above and Embodiment 14 described later.

The container 6 is made of a material having a higher melting point than the melted material 10 and is shaped like a cage. Specifically, as shown in FIG. 26, the container 6 is surrounded by at least a side plate and a bottom plate so that the sacrificial material 1L can be accommodated therein. The container 6 has at least side plates and a bottom plate formed with a large number of holes 6a such as a lattice or punching metal. In FIG. 26, the sacrificial material 1L is formed in a granular shape, and the holes 6a are formed in a size that does not allow the granular sacrificial material 1L to fall off. Further, the container 6 is provided with a suspender 6b such as an eyebolt on its upper surface. The container 6 includes 1 L of sacrificial material, is designed to weigh, for example, several kg to ten and several kg, and can be installed or removed by being hung by a crane or the like using a hanging tool 6b. In addition, the container 6 has a recessed portion 6c in the lower portion so as to avoid interference with the hanger 6b of the lower container 6 when vertically stacked.

As described above, in the core meltdown holding structure of the thirteenth embodiment, the sacrificial material 1L is housed in the basket-shaped container 6 made of a material having a higher melting point than the core meltdown 10 . The sacrificial material 1L is melted and mixed with the melted core 10, thereby lowering the melting point of the melted core 10 and making it less viscous. Therefore, part of the core melt 10 with reduced viscosity flows out through the holes 6a of the vessel 6, flows along the floor 150a of the cavity chamber 150, and spreads thinly. Therefore, it is possible to prevent the core melt 10 from staying thick on the floor 150a. As a result, the floor 150a of the cavity chamber 150 made of concrete is prevented from being eroded, and damage to the structure 100 by the core meltdown 10 can be prevented. Moreover, part of the melted core 10 whose viscosity has been reduced eventually solidifies while remaining inside the vessel 6 . Therefore, the core meltdown 10 can be recovered by removing the container 6 .

[Embodiment 14]
In Embodiment 14, the reactor containment vessel 11 includes a reactor vessel 41, a floor portion 150a provided below the reactor vessel 41 and receiving the core meltdown 10, and any one of the above-described embodiments. and a core meltdown structure.

Therefore, the core melt 10 that has flowed out of the reactor vessel 41 is melted and mixed with the sacrificial material of the core melt holding structure, thereby lowering the melting point and making it less viscous, and flows along the floor 150a to spread thinly. . Therefore, it is possible to prevent the core melt 10 from staying thick on the floor 150a. As a result, the floor 150a of the cavity 150 made of concrete can be prevented from being eroded, and the structure 100 forming the reactor containment vessel 11 can be prevented from being damaged by the melted material 10. FIG.

1 sacrificial material 1a upper layer sacrificial material 1b lower layer sacrificial material 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H, 1I, 1J, 1K, 1L sacrificial material 1Aa suspension tool 1Ea suspension tool 1Eb recess 1Ga high sacrificial material 1Gb low sacrificial material 1Ka high sacrificial material 1Kb low sacrificial material 2 Weir 3 Supporting member 4 Blocking part 5 Cooling mechanism 5a Base material 5b Cooling pipe 6 Vessel 6a Hole 6b Suspension tool 6c Recess 10 Core melt 11 Reactor containment vessel 12 Pressurized water type nuclear reactor 13 steam generator 14, 15 cooling water pipe 16 pressurizer 17 primary coolant circulation pump 18 steam turbine 19 condenser 20, 21 cooling water pipe 22 feed pump 23 generator 24 water intake pipe 25 drain pipe 41 reactor Vessel 42 Reactor Vessel Body 43 Reactor Vessel Lid 44 Stud Bolt 45 Nut 46 Bottom Mirror 47 Inlet Nozzle 48 Outlet Nozzle 49 Upper Core Support Plate 50 Lower Core Support Plate 51 Core Support Rod 52 Upper Core Plate 53 Core Barrel 54 Lower Core Plate 55 core 56 fuel assembly 57 control rod 58 control rod cluster 59 control rod cluster guide tube 60 control rod drive unit 61 housing 62 control rod cluster drive shaft 63 instrumentation nozzle 64 in-core instrumentation guide tube 65 conduit tube 66, 67 Connecting plate 68 Thimble tube 69 Upper plenum 70 Lower plenum 71 Downcomer part 81 Ground 83 Upper compartment 84 Steam generator loop room 88 Refueling water pit 100 Structure 150 Cavity room 150a Floor part 150b Inclined surface 151 Adjacent room 152 Communicating part 160 Conduit support

Claims (7)

A sacrifice that is provided between the reactor vessel and the floor that receives the core meltdown below the reactor vessel, melts and mixes with the core meltdown, lowers the melting point of the core meltdown, and reduces the viscosity of the core meltdown. with materials,
The core melt holding structure , wherein the sacrificial material is formed in a plurality of granular shapes, and the granular sacrificial material is housed in a container having a melting point lower than that of the core melt. A plurality of core melters provided between the reactor vessel and a floor portion that receives the core meltdown below the reactor vessel, and are melted and mixed with the core meltdown to lower the melting point of the core meltdown and reduce the viscosity of the core meltdown. comprising a sacrificial material formed into granules of
A molten core holding structure in which the sacrificial material is arranged on the upper surface of the floor and a region around the sacrificial material in which the sacrificial material is not arranged is provided in the floor. 3. The core meltdown according to claim 2 , comprising a material having a melting point lower than that of said core meltdown and said melt of said sacrificial material, and having a weir disposed on the upper surface of said floor surrounding said sacrificial material. holding structure. A plurality of core melters provided between the reactor vessel and a floor portion that receives the core meltdown below the reactor vessel, and are melted and mixed with the core meltdown to lower the melting point of the core meltdown and reduce the viscosity of the core meltdown. comprising a sacrificial material formed into granules of
The core meltdown holding structure, wherein the sacrificial material is collectively supported by a support member having a melting point lower than that of the core meltdown and the melt of the sacrificial material, and is provided so as to be diffused as the support member melts. A plurality of core melters provided between the reactor vessel and a floor portion that receives the core meltdown below the reactor vessel, and are melted and mixed with the core meltdown to lower the melting point of the core meltdown and reduce the viscosity of the core meltdown. comprising a sacrificial material formed into granules of
a cavity chamber disposed below the reactor vessel and in which the sacrificial material is disposed;
an adjacent chamber arranged around the cavity chamber;
a communicating portion communicating between the cavity chamber and the adjacent chamber;
a closing portion made of a material having a melting point lower than that of the melted material of the core and the melted material of the sacrificial material, and provided in the communicating portion to ensure airtightness between the cavity chamber and the adjacent chamber for isolation;
a core meltdown retention structure. A plurality of core melters provided between the reactor vessel and a floor portion that receives the core meltdown below the reactor vessel, and are melted and mixed with the core meltdown to lower the melting point of the core meltdown and reduce the viscosity of the core meltdown. comprising a sacrificial material formed into granules of
The core melt holding structure, wherein the sacrificial material is housed in a basket-shaped container made of a material having a higher melting point than the core melt. a reactor vessel;
a floor provided below the reactor vessel to receive core meltdowns;
A core meltdown holding structure according to any one of claims 1 to 6 ,
A reactor containment vessel with a

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