JP2019132777A - Accident countermeasures, nuclear power plant, and radiation shielding method - Google Patents

Abstract

To provide nuclear power plant accident countermeasures which effectively prevent or minimizes the risk of steam explosion by minimizing deterioration of additives such as PEG caused by radiation from radioactive substances, and to provide a nuclear power plant with such accident countermeasures applied thereto, and a radiation shielding method.SOLUTION: A nuclear power plant accident countermeasures are disclosed, comprising providing a partitioning member 10 in a pedestal 3, a lower portion of a reactor pressure vessel, where the partitioning member is configured to partition a region from a level at least higher than a water level when water has been injected into the pedestal 3 to a level in the water or a level near the surface of the water into a plurality of sections 11 along a horizontal direction.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an accident countermeasure method for a nuclear power plant, a nuclear power plant for which an accident countermeasure is taken, and a radiation shielding method.

  Since the 2011 Fukushima Daiichi nuclear power plant accident, measures have been developed in the event of severe accidents at domestic nuclear power plants to improve safety. Among them, countermeasures are also required for MCCI (Molten Core Concrete Interaction) reaction in which the molten core penetrates the reactor pressure vessel and reacts with the concrete that constitutes the containment vessel outside the pressure vessel. As one of the countermeasures, in the case of a BWR (Boiling Water Reactor) plant, water is poured into the area (pedestal) in the lower part of the reactor pressure vessel in advance, and the melted and dropped core is cooled. It is considered that it is cooled with water.

  In addition, by injecting “polyethylene glycol (PEG)” as an additive to prevent or suppress the occurrence of a steam explosion in cooling water pre-watered on a pedestal, a measure for preventing or suppressing the occurrence of a steam explosion is also considered. (See Non-Patent Documents 1 to 3).

  Here, in the case where no measures are taken based on the pedestal dose evaluation when the reactor fuel is damaged and the rare gas is filled into the containment vessel via the wet well, the PCV (Primary Containment Vessel; containment vessel; The evaluation results of the dose effect on the pedestal water filling when the radioactive substance is filled in are shown in FIG. 22 and FIG. Here, as shown in FIG. 22, a model system focused on the vicinity of the pedestal 3 surrounded by the concrete member 1 and the lead member 2 was created, and the situation where the stored water 4 was accumulated due to water filling in the pedestal 3 was simulated. . Here, model creation and analysis evaluation were performed using the radiation transport calculation code PHITS (Particle and Heavy Ion Transport Code System) developed by the Japan Atomic Energy Agency (JAEA) ( Non-patent document 4). Located above the pedestal 3 is a pressure vessel 6 containing water vapor 5. At this time, it is assumed that the volatile radioactive material in the furnace (here, only Xe and Kr are assumed) has shifted to the total amount of PCV. In addition, the inventory is assumed to be conceivable from the information obtained by referring to various literatures, but the process, etc., in which the entire amount is transferred is a conservative evaluation. In addition, the height direction of the stored water 4 in the water filled portion is set such that the lower end is 550 cm and the upper end is 648 cm.

  From the results shown in FIG. 23, in the case of this evaluation condition, the dose is about 50 kSv / h in the space inside the pedestal 3, and the dose is about 10 kSv / h in water about 10 cm below the water surface. Therefore, the dose irradiated to the water below the surface to some extent is small. However, it has been found that there is a possibility of being affected by a relatively large dose in the vicinity of the surface of the water, which may reach about 20 kSv, which is likely to deteriorate the additive PEG, in a relatively short time.

Furuya et al., “Evaluation of Vapor Explosion Inhibition Effect by Addition of Viscous Agent and Surfactant”, Research Institute of Electric Power Research Institute: T99091, August 2000 Furuya et al. “SUPPRESSION MEASURES AND EFFECTIVE TRIGGERING RETARDANT OF STEAM EXPLOSIONS”, Central Research Institute of Electric Power, NURETH-16, 2015 Furuya et al., “Suppression Measures of Steam Explosions with and without External Pressure Pulse”, Central Research Institute of Electric Power Industry, ICMF-2016 T. Sato, K. Niita, N. Matsuda, S. Hashimoto, Y. Iwamoto, S. Noda, T. Ogawa, H. Iwase, H. Nakashima, T. Fukahori, K. Okumura, T. Kai, S. Chiba, T. Furuta and L. Sihver, Particle and Heavy Ion Transport Code System PHITS, Version 2.52, J. Nucl. Sci. Technol. 50: 9, 913-923 (2013)

  As described above, regarding the method of adding PEG when pre-watering the pedestal as a countermeasure against MCCI and a steam explosion, regarding the radiation resistance, assuming an accident at a nuclear power plant, rare gas is released. When the containment vessel is filled, there is a concern that PEG may be deteriorated by radiation from a radioactive substance such as a rare gas, and there is a problem that steam explosion may not be effectively prevented or suppressed.

  In view of such circumstances, the present invention provides a nuclear plant accident countermeasure method and accident countermeasure that can effectively prevent or suppress a steam explosion by suppressing deterioration due to radiation from radioactive substances such as PEG. An object of the present invention is to provide a nuclear power plant and a radiation shielding method.

  A first aspect of the present invention that achieves the above object is an accident countermeasure method for a nuclear power plant, in a pedestal that is a lower region of a reactor pressure vessel, from a position at least higher than the water level at the time of water injection to the pedestal. The present invention provides an accident countermeasure method characterized by providing a partition member that divides a region up to the water position or a position near the water surface into a plurality of sections in the horizontal direction.

  In such an aspect, by providing a partition member divided into a plurality of compartments, when the molten core falls, falling into the water through the compartments is allowed, but the radiation dose reaching the water is reduced. Can be reduced.

  In the second aspect of the present invention, the dimension A, which is the smaller dimension from the upper end in the vertical direction to the water surface of the partition member or the vertical dimension of the partition member, is greater than or equal to the dimension B in the horizontal direction of the partition. There exists in the accident countermeasure method as described in the 1st aspect characterized by there.

  In this aspect, the radiation dose can be reduced more reliably by the partition member.

  A third aspect of the present invention is the accident countermeasure method according to the first or second aspect, wherein the partition member is provided from a position higher than the water level at the time of water injection of the pedestal to the bottom.

  In such an embodiment, the partition member is relatively easily installed, and there is a secondary effect that the scale of the steam explosion when the molten core falls can be reduced.

  A fourth aspect of the present invention is the accident countermeasure method according to any one of the first to third aspects, wherein the partition member is partitioned in a lattice shape.

  In such an embodiment, the partition members are formed in a lattice shape, so that the partition member can be transported and installed relatively easily.

  A fifth aspect of the present invention is the accident countermeasure method according to any one of the first to fourth aspects, wherein the partition member is configured to be stacked in a plurality of stages from the bottom of the pedestal.

  In this aspect, the partition member can be provided relatively easily in the existing nuclear power plant.

  According to a sixth aspect of the present invention, in the accident countermeasure according to any one of the first to fifth aspects, the partition member is configured by arranging a plurality of partition member parts in parallel in the horizontal direction. Is in the way.

  In such an embodiment, it is relatively easy to carry the nuclear plant into the pedestal.

  According to a seventh aspect of the present invention, in any one of the first to sixth aspects, the partition member is configured by combining plate-like members having fitting portions that fit together. It is in the accident countermeasure method described.

  In this aspect, the seismic resistance of the partition member is improved, and the resistance is improved against the pressure during water injection.

  An eighth aspect of the present invention is the accident countermeasure method according to any one of the first to seventh aspects, wherein cooling water is injected into the pedestal.

  In such an embodiment, cooling water can be poured afterwards as a countermeasure against accidents.

  A ninth aspect of the present invention is the accident countermeasure method according to claim 8, wherein an additive for preventing or suppressing the occurrence of a steam explosion is injected into the cooling water in the pedestal.

  In such an aspect, by having the partition member, deterioration of the additive due to radiation can be reduced.

  A tenth aspect of the present invention is the accident countermeasure method according to any one of the first to ninth aspects, wherein the partition member is detachable and portable.

  In such an aspect, it is easy to install a partition portion in an existing nuclear power plant, and the influence on maintenance of the nuclear power plant is reduced.

  In an eleventh aspect of the present invention, in a pedestal that is a lower region of a reactor pressure vessel, a plurality of regions from at least a position higher than the water level to a position up to the water at the time of water injection to the pedestal are horizontally arranged. It exists in the nuclear power plant characterized by providing the partition member divided into division.

  In such an aspect, by providing a partition member divided into a plurality of compartments, when the molten core falls, falling into the water through the compartments is allowed, but the radiation dose reaching the water is reduced. Can be reduced.

  In a twelfth aspect of the present invention, the dimension A, which is the smaller dimension from the vertical upper end to the water surface of the partition member or the vertical dimension of the partition member, is equal to or larger than the horizontal dimension B of the partition. It exists in the nuclear power plant as described in the 11th aspect characterized by a certain thing.

  In this aspect, the radiation dose can be reduced more reliably by the partition member.

  A thirteenth aspect of the present invention is the nuclear power plant according to the eleventh or twelfth aspect, wherein the partition member is provided from a position higher than a water level at the time of pouring the pedestal to the bottom.

  In such an embodiment, the partition member is relatively easily installed, and there is a secondary effect that the scale of the steam explosion when the molten core falls can be reduced.

  A fourteenth aspect of the present invention is the nuclear power plant according to any one of the eleventh to thirteenth aspects, wherein the partition member is partitioned in a lattice shape.

  In such an embodiment, the partition members are formed in a lattice shape, so that the partition member can be transported and installed relatively easily.

  A fifteenth aspect of the present invention is the nuclear power plant according to any one of the eleventh to fourteenth aspects, wherein the partition member is provided by being stacked in a plurality of stages from the bottom of the pedestal.

  In this aspect, the partition member can be provided relatively easily in the existing nuclear power plant.

  A sixteenth aspect of the present invention is the nuclear power plant according to any one of the eleventh to fifteenth aspects, wherein the partition member includes a plurality of partition member parts arranged in parallel in the horizontal direction.

  In such an embodiment, it is relatively easy to carry the nuclear plant into the pedestal.

  According to a seventeenth aspect of the present invention, in any one of the eleventh to sixteenth aspects, the partition member is configured by combining plate-like members having fitting portions that fit together. Located in the described nuclear plant.

  In this aspect, the seismic resistance of the partition member is improved, and the resistance is improved against the pressure during water injection.

  According to an eighteenth aspect of the present invention, in the nuclear power plant according to any one of the eleventh to seventeenth aspects, the partition member includes a water passage opening through which water can move between the sections. is there.

  In this aspect, water can be moved between the sections via the water passage opening, and water can be easily passed through all the sections.

  A nineteenth aspect of the present invention is the nuclear power plant according to any one of the eleventh to eighteenth aspects, wherein cooling water is injected into the pedestal.

  In such an embodiment, cooling water can be poured afterwards as a countermeasure against accidents.

  A twentieth aspect of the present invention is the nuclear power plant according to the nineteenth aspect, wherein an additive for preventing or suppressing the occurrence of a steam explosion is injected into the cooling water in the pedestal.

  In such an aspect, by having the partition member, deterioration of the additive due to radiation can be reduced.

  A twenty-first aspect of the present invention is the nuclear power plant according to any one of the eleventh to twentieth aspects, wherein the partition member is detachable and portable.

  In such an aspect, it is easy to install a partition portion in an existing nuclear power plant, and the influence on maintenance of the nuclear power plant is reduced.

  According to a twenty-second aspect of the present invention, there is provided a radiation shielding method from a radioactive substance, comprising: an existence space in which the radioactive substance is present; and a shielding space in which radiation is to be blocked while maintaining air circulation between the existence space In the radiation shielding method, a partition member that divides the boundary into a plurality of sections over the surface direction of the boundary is provided at the boundary.

  In such an aspect, by providing the partition member divided into a plurality of sections, the air flow through the sections is allowed, but the radiation dose reaching the blocking space can be reduced.

  In a twenty-third aspect of the present invention, the dimension A in the direction orthogonal to the surface direction of the boundary of the partition member is equal to or larger than the dimension B in the surface direction of the partition. The radiation shielding method.

  According to the present invention, by providing a partition member divided into a plurality of compartments in the pedestal of the nuclear power plant, when the molten core falls, it is allowed to fall into the water through the compartments, but reaches the water. The radiation dose can be reduced. In addition, by providing a partition member divided into a plurality of sections, air flow is allowed through the sections, but radiation shielding that can reduce the radiation dose reaching the blocking space is realized. Can do.

1 is a perspective view in which a part of a nuclear power plant according to Embodiment 1 is cut away. 1 is a cross-sectional view of a nuclear power plant according to a first embodiment. 1 is a plan view of a nuclear power plant according to a first embodiment. 10 is a cross-sectional view of a nuclear power plant according to Embodiment 6. FIG. 10 is a plan view of a nuclear power plant according to Embodiment 6. FIG. It is sectional drawing of the nuclear power plant which concerns on the comparative example 2. 6 is a plan view of a nuclear power plant according to Comparative Example 2. FIG. It is a figure which shows the result of an evaluation test. It is a figure which shows the result of an evaluation test. It is a figure which shows the result of Test Examples 1-3. It is a figure which shows the result of Test Examples 1-3. It is a figure which shows the result of Test Examples 4-6. It is a figure which shows the result of Test Examples 7-9. It is a figure which shows the result of Test Examples 10-12. It is sectional drawing of the nuclear power plant which concerns on Embodiment 2. FIG. 3 is a plan view of a nuclear power plant according to Embodiment 2. FIG. FIG. 10 is a perspective view of an example of a partition member component according to Embodiment 3. It is a perspective view of the other example of the partition member component which concerns on Embodiment 3. FIG. It is a perspective view of the other example of the partition member component which concerns on Embodiment 3. FIG. It is a perspective view of the example of the member of the partition member component which concerns on Embodiment 3. FIG. It is a figure which shows typically the radiation shielding method which concerns on embodiment. It is a figure which shows the evaluation result of the dose influence which acts on pedestal water filling. It is a figure which shows the evaluation result of the dose influence which acts on pedestal water filling.

  Hereinafter, the present invention will be described in detail based on embodiments.

(Embodiment 1)
FIG. 1 is a perspective view schematically showing a pedestal periphery of the nuclear power plant according to the first embodiment with a part thereof switched, FIG. 2 schematically showing a cross section, and FIG. 3 schematically showing a plane.

  As shown in FIG. 1, stored water 4 is provided at the bottom of a pedestal 3 surrounded by a concrete member 1 and a lead member 2, and a partition member 10 is provided above the stored water 4.

  The partition member 10 is a member that subdivides the upper space of the stored water 4 into a plurality of grid-like partitions 11. Each section 11 is provided so as to penetrate the partition member 10 in the vertical direction.

  Although the partition member 10 has the section 11 which subdivides the space, even if the molten core falls from above, the partition member 10 allows the drop into the stored water 4. This is to prevent or reduce the passage of radiation from a radioactive substance such as a rare gas in the space.

  Therefore, the partition member 10 needs to be formed of a material that can maintain its shape until the melting core falls. In other words, any material that can withstand the maintenance of its shape until the melting core falls, for example, a material such as concrete or iron may be used.

  Since the partition member 10 prevents or suppresses irradiation of the stored water 4 with radiation, the partition member 10 may be provided above the water surface of the stored water 4 and may be separated from the water surface. Moreover, if the upper part protrudes upward from the water surface, the lower part may be immersed in the stored water 4, but the part which prevents or suppresses radiation irradiation with respect to the stored water 4 is an upper part exposed from the water surface. .

  Although the size of the section 11 contributes to the effect of preventing or reducing the passage of radiation, simply, it is necessary to satisfy the condition that A ≧ B in the vertical dimension A and the horizontal dimension B of the section 11. There is.

  Here, in this embodiment, the section 11 has a lattice shape and a square shape in plan view, but this shape is not particularly limited. The planar view shape may be a rectangle or a polygon, or a circle or an ellipse. The dimension A in these cases is the distance between the opposing surfaces that are the maximum distance in the horizontal direction of the section 11, the dimension of each side in the case of a square, the dimension of the long side in the case of a rectangle, and the maximum facing in the case of a polygon. It is the distance between the surfaces, and it is the diameter for a circle and the major axis for an ellipse.

  According to an evaluation test described later, if A ≧ B, deterioration of the additive such as PEG in the stored water 4 due to radiation is prevented, but A ≧ 2B is more preferable.

Example 1
In this embodiment, the partition member 10 has a height (thickness in the vertical direction) of 102 cm (dimension A = 102 cm), the size of the compartment 11 is 20 cm square (dimension B = 20 cm), and the thickness of the wall separating the compartment 11 A concrete member having a length of 10 cm was used. The maximum arrangement number N of the partitions 11 in the horizontal direction is 17.

(Example 2)
In this embodiment, the partition member 10 is made of concrete having a height of 102 cm (dimension A = 102 cm), the size of the section 11 is 28 cm square (dimension B = 28 cm), and the thickness of the wall partitioning the section 11 is 2 cm. It was set as a member. The maximum arrangement number N of the partitions 11 in the horizontal direction is 17.

Example 3
In this embodiment, the partition member 10 is made of concrete having a height of 102 cm (dimension A = 102 cm), a size of the section 11 of 10 cm square (dimension B = 10 cm), and a wall thickness separating the section 11 of 20 cm. It was set as a member. The maximum arrangement number N of the partitions 11 in the horizontal direction is 17.

Example 4
In this embodiment, the partition member 10 is made of concrete having a height of 52 cm (dimension A = 52 cm), a size of the compartment 11 of 10 cm square (dimension B = 10 cm), and a wall thickness separating the compartment 11 of 20 cm. It was set as a member. The maximum arrangement number N of the partitions 11 in the horizontal direction is 17.

(Example 5)
In this embodiment, the partition member 10 is an iron member having a height of 102 cm (dimension A = 102 cm), the size of the section 11 is 10 cm square (dimension B = 10 cm), and the wall thickness separating the section 11 is 20 cm. It was. The maximum arrangement number N of the partitions 11 in the horizontal direction is 17.

(Example 6)
In the present embodiment, the partition member 10 is an iron member having a height of 102 cm (dimension A = 102 cm), a size of the compartment 11 of 34 cm square (dimension B = 34 cm), and a wall thickness separating the compartment 11 of 11 cm. It was. 4 and 5 are schematic views of cross sections and planes. The maximum arrangement number N of the partitions 11 in the horizontal direction is 11.

(Example 7)
In the present embodiment, the partition member 10 is an iron member having a height of 102 cm (dimension A = 102 cm), the size of the compartment 11 is 50 cm square (dimension B = 50 cm), and the wall thickness separating the compartment 11 is 15 cm. It was. The maximum arrangement number N of the partitions 11 in the horizontal direction is 7.

(Example 8)
In this embodiment, the partition member 10 is an iron member having a height of 52 cm (dimension A = 52 cm), a size of the section 11 is 34 cm square (dimension B = 34 cm), and a wall thickness separating the section 11 is 15 cm. It was. The maximum arrangement number N of the partitions 11 in the horizontal direction is 7.

Example 9
In this embodiment, the partition member 10 is an iron member having a height of 102 cm (dimension A = 102 cm), the size of the section 11 is 85 cm square (dimension B = 85 cm), and the thickness of the wall partitioning the section 11 is 15 cm. It was. The maximum arrangement number N of the partitions 11 in the horizontal direction is 5.

(Comparative Example 1)
A comparative example 1 was provided without the partition member 10.

(Comparative Example 2)
In Comparative Example 2, the partition member 10 is made of an iron member having a height of 102 cm (dimension A = 102 cm), a size of the section 11 of 155 cm (dimension B = 34 cm), and a wall thickness separating the section 11 is 15 cm. did. A schematic diagram of a cross section and a plane is shown in FIGS. The maximum arrangement number N of the partitions 11 in the horizontal direction is 3.

(Evaluation results)
As shown in FIG. 8, in Examples 1 to 5, the dose is reduced to 1 to 3 kSv / h or less at a water surface position of 648 cm in height, compared with Comparative Example 1 of about 35 kSv / h, The effect of the member 10 was confirmed.

  Moreover, as shown in FIG. 9, in Examples 6-9, in the water surface position of 648 cm in height, the dose is reduced to several kSv / h or less, compared with Comparative Example 1 of about 35 kSv / h, The effect of the partition member 10 was confirmed. In Comparative Example 2 where the height is 102 cm (dimension A = 102 cm) and the size of the section 11 is 155 cm (dimension B = 34 cm), the dose at the water surface position exceeds 10 kSv / h, and PEG degradation occurs. It turns out that there is a possibility.

  From this result, when the comparative examination is performed with the condition of Example 1 as an axis, the dose distribution until reaching the water surface changes at a low value when the size of the compartment 11 is reduced, and the water surface when the size of the compartment 11 is increased. The dose distribution up to 1 changes at a high value. Moreover, when the height of the lattice structure is lowered, the dose near the water surface is slightly increased. It can also be seen that when the material is changed from concrete to iron, the dose until reaching the water surface is low.

(Test Example 1-3)
In this test example, the height r (dimension A) of the partition member 10 from the water surface to the length L (dimension B) of one side of the section 11 is 1 cm above the water surface when the ratio r1 = A / B is changed. The change of the dose of the space of was compared.

(Test Example 1)
The partition member 10 of this test example has a height H of 52 cm (dimension A = 52 cm), a length L of one side of the section 11 is 52 cm square (dimension B = 52 cm), and a wall thickness D separating the section 11 is 13 cm. Then, an iron member (r1 = A / B = 1) having a maximum arrangement number N of 7 in the horizontal direction 11 is a basic member (Test Example 1-1), and r1 = 1.25 (Test Example 1-2) ), R1 = 1.5 (Test Example 1-3), r1 = 1.75 (Test Example 1-4), r1 = 2 (Test Example 1-5), r1 = 2.25 (Test Example 1-6) ), R1 = 0.75 (Test Example 1-7), r1 = 0.5 (Test Example 1-8), r1 = 0.25 (Test Example 1-9), r1 = 0.1 (Test Example 1) −10). In each test example, r2 = D / L = 0.25.

(Test Example 2)
In the partition member 10 of this test example, the height H is 52 cm (dimension A = 52 cm), the length L of one side of the compartment 11 is 104 cm square (dimension B = 104 cm), and the thickness D of the wall separating the compartment 11 is 6 An iron member (r1 = A / B = 1) having a maximum arrangement number N of 7 in the horizontal direction 11 is a basic member (Test Example 2-1), and r1 = 1.25 (Test Example 2) -2), r1 = 1.5 (Test Example 2-3), r1 = 1.75 (Test Example 2-4), r1 = 2 (Test Example 2-5), r1 = 2.25 (Test Example 2) -6), r1 = 0.75 (Test Example 2-7), r1 = 0.5 (Test Example 2-8), r1 = 0.25 (Test Example 2-9), r1 = 0.1 (Test) Example 2-10). In each test example, r2 = D / L = 0.25.

(Test Example 3)
In the partition member 10 of this test example, the height H from the water surface is 52 cm (dimension A = 52 cm), the length L of one side of the section 11 is 26 cm square (dimension B = 26 cm), and the thickness of the wall partitioning the section 11 An iron member (r1 = A / B = 1) in which D is 13 cm and the maximum arrangement number N of the partitions 11 in the horizontal direction is 7 is a basic member (Test Example 3-1), and r1 = 1.25 (Test Example) 3-2), r1 = 1.5 (Test Example 3-3), r1 = 1.75 (Test Example 3-4), r1 = 2 (Test Example 3-5), r1 = 2.25 (Test Example) 3-6), r1 = 0.75 (Test Example 3-7), r1 = 0.5 (Test Example 3-8), r1 = 0.25 (Test Example 3-9), r1 = 0.1 ( It was set as Test Example 3-10). In each test example, r2 = D / L = 0.25.

(Evaluation result of Test Example 1-3)
FIG. 10 shows the dose in the vicinity of the water surface (space with a height of 648 to 649 cm) in each test example. Moreover, FIG. 11 shows the reduction rate compared with the case where the partition member 10 is not provided.

  As a result, even if r1 is 0.1 or 0.25, the reduction rate can be reduced to near 0.8 or 0.6 to 0.7, but when r1 becomes 0.5, 0.5 or less It was found that 20 kSv / h or less can be realized, and that the reduction rate is about 0.3 or less when r1 is 0.75 or more. Further, it was found that when r1 is 1 or more, the reduction rate is 0.2 or less, and when r1 is 2 or more, it is 0.1 or less, which is an extremely high reduction rate.

  From the above, when r1 = 1, that is, H = L, the dose is reduced to at least one-fourth, and it is reduced to several kSv / h near the surface of the stored water designed to mitigate the steam explosion. It has been found that the radiation effects on the additives are sufficiently reduced. That is, it was found that H ≧ L (A ≧ B) is a preferable condition, and that r1 = 2 or more, that is, if H ≧ 2L (A ≧ 2B), a more desirable dose reduction effect can be expected.

(Test Example 4-12)
In this test example, the space 1 cm above the water surface when the ratio r2 = D / L of the wall thickness D separating the partition 11 of the partition member 10 to the length L (dimension B) of one side of the partition 11 is changed. The changes in dose were compared.

(Test Example 4)
This test example is a case where the dimension L of one side of the partition 11 of the partition member 10 is 104 cm (dimension B = 104 cm).

  The partition member 10 has a height H from the water surface of 104 cm (dimension A = 104 cm), the length L of one side of the compartment 11 is 104 cm square (dimension B = 104 cm), and the thickness D of the wall separating the compartment 11 Is an iron member (r2 = D / L = 0.01) having a maximum arrangement number N of 3 in the horizontal section 11 and a basic member (Test Example 4-1), and r2 = 0.025. (Test Example 4-2), r2 = 0.05 (Test Example 4-3), r2 = 0.1 (Test Example 4-4), and r2 = 0.15 (Test Example 4-5). In these, r1 = A / B = 1.

(Test Example 5)
This test example is a test example 4 except that the dimension L of one side of the partition 11 of the partition member 10 is 104 cm (dimension B = 104 cm), the height H from the water surface is 52 cm, and r1 = 0.5. In the same manner, r2 = D / L = 0.01 (Test Example 5-1), r2 = 0.025 (Test Example 5-2), r2 = 0.05 (Test Example 5-3), r2 = 0 0.1 (Test Example 5-4) and r2 = 0.15 (Test Example 5-5) were used as partition members 10.

(Test Example 6)
This test example is a test in which the dimension L of one side of the partition 11 of the partition member 10 is 104 cm (dimension B = 104 cm), the height H from the water surface is 10.4 cm, and r1 = 0.1. As in Example 4, r2 = D / L = 0.01 (Test Example 6-1), r2 = 0.025 (Test Example 6-2), r2 = 0.05 (Test Example 6-3), r2 = 0.1 (Test Example 6-4), r2 = 0.15 (Test Example 6-5).

(Test Example 7)
In this test example, the dimension L of one side of the partition 11 of the partition member 10 is 52 cm (dimension B = 52 cm).

  The partition member 10 has a height H from the water surface of 52 cm (dimension A = 52 cm), the length L of one side of the compartment 11 is 52 cm square (dimension B = 52 cm), and the thickness D of the wall separating the compartment 11 Is an iron member (r2 = D / L = 0.01) with a maximum arrangement number N of 7 in the horizontal section 11 being a basic member (Test Example 7-1), and r2 = 0.025 (Test Example 7-2), r2 = 0.05 (Test Example 7-3), r2 = 0.1 (Test Example 7-4), and r2 = 0.15 (Test Example 7-5). In these, r1 = A / B = 1.

(Test Example 8)
This test example is a test example 7 except that the dimension L of one side of the partition 11 of the partition member 10 is 52 cm (dimension B = 52 cm), the height H from the water surface is 26 cm, and r1 = 0.5. In the same manner, r2 = D / L = 0.01 (Test Example 8-1), r2 = 0.025 (Test Example 8-2), r2 = 0.05 (Test Example 8-3), r2 = 0 0.1 (Test Example 8-4) and r2 = 0.15 (Test Example 8-5).

(Test Example 9)
This test example is a test except that the dimension L of one side of the partition 11 of the partition member 10 is 52 cm (dimension B = 52 cm), the height H from the water surface is 5.2 cm, and r1 = 0.1. As in Example 7, r2 = D / L = 0.01 (Test Example 9-1), r2 = 0.025 (Test Example 9-2), r2 = 0.05 (Test Example 9-3), r2 = 0.1 (Test Example 9-4), r2 = 0.15 (Test Example 9-5).

(Test Example 10)
This test example is a case where the dimension L of one side of the partition 11 of the partition member 10 is 26 cm (dimension B = 26 cm).

  The partition member 10 has a height H from the water surface of 26 cm (dimension A = 26 cm), the length L of one side of the compartment 11 is 26 cm square (dimension B = 26 cm), and the thickness D of the wall separating the compartment 11 Is an iron member (r2 = D / L = 0.01) having a maximum arrangement number N of 15 in the horizontal direction 11 and a basic member (Test Example 10-1), and r2 = 0.025. (Test Example 10-2), r2 = 0.05 (Test Example 10-3), r2 = 0.1 (Test Example 10-4), and r2 = 0.15 (Test Example 10-5). In these, r1 = A / B = 1.

(Test Example 11)
This test example is a test example 10 except that the dimension L of one side of the partition 11 of the partition member 10 is 26 cm (dimension B = 26 cm), the height H from the water surface is 13 cm, and r1 = 0.5. In the same manner, r2 = D / L = 0.01 (Test Example 11-1), r2 = 0.025 (Test Example 11-2), r2 = 0.05 (Test Example 11-3), r2 = 0 0.1 (Test Example 11-4) and r2 = 0.15 (Test Example 11-5).

(Test Example 12)
This test example is a test in which the dimension L of one side of the partition 11 of the partition member 10 is 26 cm (dimension B = 26 cm), the height H from the water surface is 2.6 cm, and r1 = 0.1. As in Example 10, r2 = D / L = 0.01 (Test Example 12-1), r2 = 0.025 (Test Example 12-2), r2 = 0.05 (Test Example 12-3), r2 = 0.1 (Test Example 12-4), r2 = 0.15 (Test Example 12-5).

(Evaluation result of Test Example 4-12)
FIG. 12 shows the doses of Test Examples 4-6, FIG. 13 shows the doses of Test Examples 7-9, and FIG. 14 shows the doses of Test Examples 10-12.

  As a result, when the height H (dimension A) from the water surface is a certain size, the wall thickness D does not affect the dose so much, and the height H becomes the dominant factor. In addition, the wall thickness D has an influence in a region that is thin to some extent, but it has been found that the effect of reduction is sufficiently exerted in the range of several centimeters of thickness assuming actual implementation. That is, the wall thickness D does not have to be a problem under normal conditions. A thicker one has a reduction effect, but is smaller than the relationship with the height H, and actual implementation is assumed. It is considered that there is a sufficient reduction effect in the order of several centimeters.

  From the above results, by providing the partition member 10, the radiation effect on the stored water 4 is reduced, and the concern about the deterioration of additives (such as PEG) that prevents or suppresses the occurrence of a water vapor explosion is further reduced. Is clear. If dimension A ≧ dimension B, it is estimated that the deterioration of the additive such as PEG in the stored water 4 due to radiation is prevented. However, it is more preferable that dimension A ≧ dimension B × 2 is more preferable. 7 and the results of Test Examples 1 to 12 are also apparent.

  When A> B, for example, radiation inclined at 45 degrees or more seems to be blocked, and when A> 2B, it is clear that more radiation is blocked.

(Embodiment 2)
In the embodiment described above, the partition member is provided so as to partition the entire space of the pedestal 3, but it may be provided partially.

  FIG.15 and FIG.16 is a schematic diagram which shows the cross section and plane of the nuclear power plant which concern on this embodiment.

  In the present embodiment, a water storage tank 20 is provided immediately below the pressure vessel 6 of the pedestal 3, and a partition member 10A is provided as a lid member of the water storage tank 20, and only in a region immediately below the pressure vessel 6 of the partition member 10A. A partition 11A is provided.

  According to this, when the melting core falls from the pressure vessel 6, the melting core falls into the stored water in the water storage tank 20 through the partition 11 </ b> A of the partition member 10 </ b> A and is cooled. Moreover, most of the radiation from above is effectively blocked by the partition 11A of the partition member 10A, and the concern about deterioration of PEG or the like in the stored water is reduced.

(Embodiment 3)
Although the partition members 10 and 10A described above are provided above the stored water 4 and just below the water surface, it is clear from the above-described effects that the same effect can be obtained even if the partition members 10 and 10A are provided away from the water surface.

  Moreover, the partition members 10 and 10A may be provided so that at least a part thereof is submerged in the stored water 4, or may be provided so as to protrude from the bottom of the pedestal 3 onto the water.

  In consideration of providing the partition member 10 in an existing nuclear power plant, it is presumed that it is preferable to provide the partition member 10 from the bottom of the pedestal 3. In this case, the effective portion as the partition member is a portion protruding from the water, but by partitioning the stored water, the details will be described later, but there is also an effect of reducing the magnitude of the steam explosion, from the bottom to the water It is effective to provide a partition member.

  Moreover, it is preferable that the partition member 10 is detachable and has portability. Therefore, it is preferable that a small part of the partition member is laid from the bottom and is laminated in multiple stages.

  Examples of such a partition member are shown in FIGS. 17 and 18.

  This partition member component 100 is a combination of four members 101 in a cross beam shape, and has an opening 102 serving as a partition and a half opening 103 forming a partition by combining two. The partition member component 100 can be provided so as to protrude from the water onto the stored water by laying a plurality of partition member parts 100 in the plane direction and laminating a plurality of stages.

  The partition member component 100A is similar to FIG. 17 in that four members 101A are combined in a cross-beam shape to have an opening 102A that becomes a partition and a half opening 103A that forms a partition by combining two members. However, a water passage opening 105A is provided at the lower center of each member 101A. Thereby, movement of water between each division is attained. This assumes that the partition member parts 100 and 100A are laid and stacked to form the partition member, and then the cooling water is injected, and the stored water can enter each compartment. Theoretically, the partition member component 100A may be used so that the water passage opening 105A exists in a part of the wall of the compartment communicating in the vertical direction. The partition member part 100A may be used for the lower stage, and the partition member part 100 may be used for others.

  When such partition member parts 100 and 100A are used, a partition member can be provided relatively easily in an existing nuclear power plant, and accident countermeasures can be performed relatively easily.

  In addition, by using such detachable and portable partition member parts 100 and 100A, there is an advantage that the partition member can be easily disassembled and discharged at the time of equipment inspection and repair.

  When the partition member parts 100 and 100A are laid and stacked, a fixing member that can withstand earthquake resistance and water injection pressure but can be easily disassembled may be used.

  Moreover, you may provide the convex part 111 and the recessed part 112 which fit adjacently at the edge part of each member 101B like the partition member component 100B shown in FIG. Thereby, the resistance to the pressure by earthquake resistance and water injection improves.

  Here, the shape of the partition member parts 100 and 100A is not particularly limited, and may be a part having a plurality of, for example, two or four openings serving as partitions. Further, the partition member parts 100 and 100A may be disassembled themselves. For example, as shown in FIG. 20, a fitting part 121 that fits the members 120 may be provided to form the partition member parts 100 and 100A.

  By assembling the partition member parts using the partition member parts 100 and 100A described above, and in particular, the member 120, portability and operability are improved, leading to work efficiency. In addition, work is facilitated when carrying in and out in a narrow area such as a pedestal. Furthermore, when not in use, it is possible to store it in a compact and convenient space saving.

  In addition, when water is poured into the pedestal, water is poured from the MUWC system or the like, and the discharge pressure at the time of water injection may be about 1.3 MPa. If it is said lattice structure, it will be fixed by mutually contacting in a pedestal and a wall firmly, and it is thought that it is a structure which can endure a certain amount of water pressure without being pushed away. This is an important point in considering actual operation.

  Further, as a secondary effect, the stored water of the pedestal is decomposed into small parts in the partition member sections, so that the explosion caused by the reaction between the molten core and the cooling water when the molten core falls is also effective. This is due to the fact that a vapor explosion has a small explosion energy in a microscopic area, but generates a high pressure wave when it occurs simultaneously. By providing compartments such as a lattice structure, the timing of vapor film collapse can be shifted in each compartment. This is thought to suppress the occurrence of a large explosion. Since it is only necessary to shift the timing to the acoustic wave restraint time of the pressure wave, it is estimated that about 10 cm is sufficient.

(Other embodiments)
In the above embodiment, an example in which a partition member is used as an accident countermeasure method for a nuclear power plant has been shown. However, it is clear that a partition member can be used as a radiation shielding method from radioactive substances in consideration of the effect of the partition member. It is.

  In FIG. 21, the example which used the partition member for the radiation shielding method from a radioactive substance is shown.

  As shown in the figure, the outside of the intake / exhaust filter 32 of the nuclear facility 31 may have a radioactive substance attached thereto, and the surrounding space is an existence space 33 in which the radioactive substance exists. By providing the partition member 10 </ b> B between the existence space 33 and the blocking space 34 where it is desired to block radiation while maintaining the circulation of air with this space, the radiation dose in the blocking space 34 can be reduced.

  In addition, the partition member 10B is the same as the partition member 10 mentioned above, and detailed description is abbreviate | omitted.

  The accident countermeasure method described above has been described by taking the BWR as an example. However, the accident countermeasure method is not limited to the reactor type, and is applicable to, for example, a PWR (Pressurized Water Reactor) in a situation where this countermeasure method is effective. Is done.

  In the above-described embodiment, the nuclear plant accident countermeasure method using the partition member has been mainly described. However, the partition member is intended to block radiation from radioactive materials such as nuclear waste facilities and nuclear plant related facilities. It can be used for applications.

3 Pedestal 4 Reserved water 10, 10A, 10B Partition member 11, 11A, 11B Partition 100, 100A Partition member parts

Claims (23)

An accident countermeasure method for a nuclear power plant,
In the pedestal, which is the lower area of the reactor pressure vessel, the area from at least a position higher than the water level to the position under water or near the water surface at the time of water injection into the pedestal is divided into a plurality of sections in the horizontal direction. An accident countermeasure method characterized by providing a partition member.   The dimension A, which is the smaller dimension from the upper end of the partition member in the vertical direction to the water surface or the smaller dimension in the vertical direction of the partition member, is equal to or greater than the dimension B in the horizontal direction of the partition. The accident countermeasure method described.   The accident countermeasure method according to claim 1 or 2, wherein the partition member is provided from a position higher than a water level at the time of pouring the pedestal to a bottom.   The accident countermeasure method according to any one of claims 1 to 3, wherein the partition member is partitioned in a lattice shape.   The accident countermeasure method according to any one of claims 1 to 4, wherein the partition member is configured to be stacked in a plurality of stages from the bottom of the pedestal.   The accident countermeasure method according to any one of claims 1 to 5, wherein the partition member is configured by arranging a plurality of partition member parts in parallel in the horizontal direction.   The accident countermeasure method according to any one of claims 1 to 6, wherein the partition member is configured by combining plate-like members having fitting portions that are fitted to each other.   The accident countermeasure method according to any one of claims 1 to 7, wherein cooling water is injected into the pedestal.   9. The accident countermeasure method according to claim 8, wherein an additive for preventing or suppressing the occurrence of a steam explosion is injected into the cooling water in the pedestal.   The accident countermeasure method according to any one of claims 1 to 9, wherein the partition member is detachable and has portability.   In the pedestal, which is the lower region of the reactor pressure vessel, a partition member is provided that divides the region from at least a position higher than the water level to the position in the water into multiple compartments in the horizontal direction when water is injected into the pedestal. A nuclear plant characterized by that.   12. The dimension A, which is the smaller dimension from the upper end in the vertical direction of the partition member to the water surface or the smaller dimension in the vertical direction of the partition member, is equal to or greater than the dimension B in the horizontal direction of the partition. Nuclear power plant as described in   The nuclear power plant according to claim 11 or 12, wherein the partition member is provided from a position higher than a water level at the time of water injection of the pedestal to a bottom.   The nuclear power plant according to any one of claims 11 to 13, wherein the partition member is partitioned in a lattice shape.   The nuclear power plant according to any one of claims 11 to 14, wherein the partition member is provided by being stacked in a plurality of stages from the bottom of the pedestal.   The nuclear power plant according to any one of claims 11 to 15, wherein the partition member includes a plurality of partition member parts arranged in parallel in the horizontal direction.   The nuclear power plant according to any one of claims 11 to 16, wherein the partition member is configured by combining plate-like members having fitting portions that are fitted to each other.   The nuclear power plant according to any one of claims 11 to 17, wherein the partition member includes a water passage opening through which water can move between the compartments.   The nuclear power plant according to any one of claims 11 to 18, wherein cooling water is injected into the pedestal.   The nuclear power plant according to claim 19, wherein an additive for preventing or suppressing the occurrence of a steam explosion is injected into the cooling water in the pedestal.   The nuclear power plant according to any one of claims 11 to 20, wherein the partition member is detachable and portable.   A radiation shielding method from a radioactive substance, wherein a boundary between an existing space where the radioactive substance exists and a blocking space where radiation is to be blocked while maintaining air circulation between the existing space and a plane direction of the boundary A radiation shielding method, comprising: a partition member that is divided into a plurality of sections.   23. The radiation shielding method according to claim 22, wherein a dimension A in a direction orthogonal to the surface direction of the boundary of the partition member is equal to or larger than a dimension B of the partition in the surface direction.