JP2015090283A - Reactor installation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reactor installation capable of preventing damage to a containment vessel and preventing radiation leak due to it even if core meltdown occurs and then melted nuclear fuel falls and passes through a reactor vessel.SOLUTION: A reactor installation 100 comprises: a reactor vessel 106 that stores nuclear fuel 102 and a first metal member 200; and a containment vessel 108 that stores the reactor vessel 106 and a second metal member 202. The first and second metal members are respectively formed by arranging multiple metal balls, which have a melting point lower than that of the nuclear fuel, along each shape of a bottom in the reactor vessel 106 and a bottom in the containment vessel 108, and the first and second metal members can bury melted nuclear fuel. This configuration can prevent radiation leak from being caused by passage of the melted fuel through the containment vessel because the melted nuclear fuel is covered by metals and heat is radiated from the whole containment vessel even if core meltdown occurs and then the melted nuclear fuel falls and passes through the reactor vessel.

Description

  The present invention relates to a nuclear power plant for power generation in which countermeasures for core melting are taken.

  There are various types of nuclear reactors. In Japan, pressurized water reactors and boiling water reactors are used as commercial reactors. In both cases, low-enriched uranium is used as fuel, and heat generated by fission of uranium contained in fuel rods arranged in the reactor vessel is extracted by circulating light water (hereinafter referred to as water) and used for power generation. A nuclear reactor (hereinafter referred to as a water-cooled nuclear reactor). As a result, the fuel rods are cooled, and the extracted hot water is used to rotate the power generation turbine. That is, in the case of a boiling water light water reactor, water vapor taken directly from the reactor vessel is supplied to the power generation turbine. In the case of a pressurized water reactor, the high-temperature primary cooling water taken out from the reactor vessel is once supplied to the steam generator, and the steam generated from the secondary cooling water by the steam generator is supplied to the power generation turbine. The

  In a water-cooled nuclear reactor, if some kind of trouble occurs in the cooling facility and the cooling water is not circulated normally, the fuel rod cannot be cooled, the water boils, the water level drops, and the fuel rod Exposed. If such a state continues, the fuel rods become even hotter, and in the worst case, core melt (meltdown) occurs in which the fuel rods melt. When core melting occurs, hot molten fuel falls to the bottom of the reactor vessel and accumulates. The accumulated melt passes through the bottom of the reactor vessel and falls to the bottom of the containment vessel, and also penetrates the containment vessel to cause radioactivity leakage.

  Various proposals have been made as countermeasures for melting the core. For example, Patent Document 1 below discloses a holding device that is disposed below a reactor vessel and holds a core melt. The holding device includes a heat resistant layer and an impact relaxation layer having a compressive strength lower than that of the heat resistant layer. As the material of the heat-resistant layer, a material having a melting point higher than the temperature of the core melt, for example, aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, hafnium oxide, yttrium oxide, neodymium oxide, phosphoric acid Salt-based oxides, tungsten, tantalum, molybdenum, rhenium, and the like are disclosed. The material of the impact relaxation layer is lower in compressive strength than the heat-resistant layer, such as tungsten, tantalum, molybdenum, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, zinc, aluminum oxide, zirconium oxide Hafnium oxide, neodymium oxide, lanthanum oxide, yttrium oxide, magnesium oxide, phosphate compound, calcium oxide, silicon oxide and the like are disclosed.

  Patent Document 2 below discloses a mechanism for cooling the melt holding device by circulating a coolant such as water around a core melt holding device provided below the reactor vessel.

  Patent Document 3 below discloses a method for treating a nuclear reactor in which a control rod generates heat. Specifically, it is disclosed that a water injection zone is formed by surrounding a nuclear reactor with a retaining wall, and then filling concrete is placed after water injection.

  In Patent Document 4 below, when core melting occurs, the oxide and metal constituting the molten core deposited at the bottom of the reactor vessel may be separated and deposited in layers, and the heat of the molten core is heated. Techniques have been disclosed for solving problems that could concentrate on a highly conductive metal layer and damage the reactor vessel. Specifically, a configuration is disclosed in which a support plate provided with a flow path hole is horizontally disposed in the reactor vessel, and a heat path for transferring heat is provided below the core. When core melting occurs, the core melt falls to the bottom of the reactor vessel through the channel holes in the support plate. The heat of the fallen core melt is cooled by cooling water surrounding the reactor vessel and flooding it. At this time, the heat path contacts the melting core to transmit heat to the support plate, and the support plate melts and falls and mixes with the melting core, so that the amount of metal increases and the concentration of heat can be suppressed. This prevents damage to the reactor vessel due to heat concentration.

JP 2012-194120 A JP 2013-2963 A JP 2013-50395 A JP 2011-2332048 A

  As described above, various countermeasures against core melting have been proposed, but are not sufficient.

  In Patent Documents 1 to 4, it is necessary to configure a holding device using a highly functional member, or to provide a complicated structure, and there is a problem that the cost becomes high. Moreover, in patent documents 3 and 4, it does not become a countermeasure when a nuclear reactor vessel is penetrated by a molten core.

  Therefore, the present invention provides a nuclear reactor apparatus that can prevent damage to a containment vessel and leakage of radioactivity due to the melted fuel falling down and penetrating the reactor vessel. The purpose is to do.

  A nuclear reactor apparatus according to the present invention includes a nuclear reactor vessel containing a nuclear fuel, a containment vessel containing a nuclear reactor vessel, a first metal member disposed at a bottom portion in the nuclear reactor vessel, and a bottom portion in the containment vessel And a second metal member. The first metal member is formed by arranging a plurality of spherical metals having a melting point lower than that of nuclear fuel along the shape of the bottom in the reactor vessel, and the second metal member has a melting point lower than that of the nuclear fuel. A plurality of spherical metals are formed so as to be arranged along the shape of the bottom in the storage container. When the nuclear fuel is melted, the first and second metal members can bury the melted nuclear fuel.

  Preferably, the spherical metal is made of lead or tin.

  According to the present invention, when core melting occurs and molten nuclear fuel falls into the reactor vessel, the nuclear fuel is prevented from penetrating the reactor vessel. Because the molten nuclear fuel is covered with metal spread on the bottom of the reactor vessel, the heat from the molten nuclear fuel is used to melt the metal to cool the nuclear fuel and provide wide contact between the metal and the reactor vessel. As a result of transferring the heat of the nuclear fuel to the entire reactor vessel through the surface, heat is radiated from the entire reactor vessel. Therefore, molten nuclear fuel is prevented from penetrating the reactor vessel and causing radioactive leakage. Furthermore, when a situation occurs in which nuclear fuel penetrates the reactor vessel, the nuclear fuel debris that has fallen into the containment vessel is covered with metal spread on the bottom of the containment vessel, and is further cooled and rapidly heated. As a result of transmitting the heat to the entire containment vessel and dissipating heat, it is possible to prevent further melt-through from occurring even if the cooling water stops, and to keep the containment vessel healthy.

  In addition, a countermeasure against core melting can be realized with a very simple configuration and at a low cost.

It is sectional drawing which shows the outline | summary of the nuclear reactor apparatus which concerns on embodiment of this invention. It is sectional drawing which shows the structure of the 1st metal member of FIG. It is sectional drawing which shows the state which the melted nuclear fuel was covered with the 1st metal member, and was stable.

  In the following embodiments, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  Referring to FIG. 1, a nuclear reactor apparatus 100 according to an embodiment of the present invention includes a nuclear reactor containing a plurality of fuel rods 102 containing nuclear fuel (uranium), a plurality of control rods 104 and a first metal member 200. A vessel 106 and a containment vessel 108 containing a nuclear reactor vessel 106 and a second metal member 202 are provided. Although not shown in FIG. 1, the reactor apparatus 100 is provided with an apparatus for functioning as a power generation nuclear reactor.

  The control rod 104 is inserted between the adjacent fuel rods 102. The control rod 104 absorbs neutrons and is used to control the nuclear reaction of uranium in the fuel rod 102. Depending on the amount of insertion of the control rod 104, the amount of absorption of neutrons generated by the nuclear reaction changes. When the control rod 104 inserted between the fuel rods 102 is removed, the amount of neutrons absorbed by the control rod 104 is reduced and the nuclear reaction is promoted.

  In the nuclear reactor apparatus 100, primary cooling water (hereinafter, also simply referred to as cooling water) is accommodated in a reactor vessel 106, as in a known pressurized water light water reactor. The storage container 108 accommodates a circulation pipe that forms a circulation path of the cooling water, a pressurizer that pressurizes the cooling water, a steam generator, and the like (all not shown). The cooling water is pressurized and circulated as shown by the arrows in FIG. The primary cooling water heated to high temperature by the heat from the fuel rod 102 flows through the circulation pipe to the steam generator, and exchanges heat with the secondary cooling water supplied from the outside of the containment vessel 108 by the steam generator. To produce water vapor. The generated water vapor is used to rotate a power generation turbine.

  Cooling water is also a neutron moderator. The cooling water contains a neutron absorber (boron), and the nuclear reaction can be controlled by adjusting its concentration.

  Referring to FIG. 2, first metal member 200 disposed at the bottom of reactor vessel 106 has a plurality of spherical metals (hereinafter referred to as metal balls) 204, which is a reactor vessel 106 made of iron (steel). It is arranged and formed along the shape of the bottom part. Similarly to FIG. 2, the second metal member 202 is formed by arranging a plurality of metal balls along the shape of the bottom of the iron (steel) storage container 108. The metal sphere 204 is made of a metal having a melting point lower than the melting point of nuclear fuel (1132 ° C. for uranium, 2865 ° C. for uranium oxide), for example, lead.

  It is preferable that the cooling water circulation pipe is disposed so as to avoid the lower part of the bottom of the reactor vessel 106. Furthermore, it is more preferable that parts and devices that impair the function and safety of the nuclear reactor apparatus 100 when damaged are not disposed between the bottom of the reactor vessel 106 and the second metal member 202.

  In the reactor apparatus 100, when the core melts, a part of the melted fuel rod 102 falls and deposits on the first metal member 200 disposed at the bottom of the reactor vessel 106. In the deposited melt, the nuclear reaction continues uncontrolled. When the melt falls on the first metal member 200, the heat of the melt is transferred to the first metal member 200 (metal sphere 204), the first metal member 200 is melted, and the melt is cooled. . The molten first metal member 200 comes into contact with the reactor vessel 106 over a wide area. Since the steel reactor vessel 106 has a high thermal conductivity, the heat from the melt is quickly transmitted to the entire reactor vessel 106 and efficiently radiated from the entire outer wall of the reactor vessel 106. When the metal sphere 204 is formed of lead, the melting point of lead is about 327 ° C., and the melting point of steel is about 1500 ° C. Therefore, it is possible to prevent heat from the melt from concentrating on a part of the reactor container 106 and melting that part and penetrating the reactor container 106.

  Should the melt penetrate the bottom of the reactor vessel 106, the molten debris will accumulate on the second metal member 202. Therefore, similarly to the first metal member 200, the second metal member 202 is melted so that heat is efficiently radiated from the outer wall of the entire storage container 108, so that the heat is concentrated on a part of the storage container 108. Then, it is possible to prevent the portion from melting and the molten debris from penetrating the storage container 108.

Density at uranium melting point is a heat source contained in the melt (about 17.3 g / cm ³⁾ is greater than the density (about 10.66 g / cm ³⁾ at the melting point of lead, the metal ball 204 In the case of being formed of lead, the molten material dropped onto the first metal member 200 (metal sphere 204) is, as shown in FIG. 3, the molten first metal member (reference numeral “206” in FIG. 3). Sinks inside). The heat generated by the nuclear reaction in the melt 110 is transferred to the reactor vessel 106 through the contact surface between the molten first metal member 206 and the reactor vessel 106 and is radiated from the outer wall of the entire reactor vessel 106. Therefore, the melt 110 is in an equilibrium state in a state where the melt 110 is buried in the melted first metal member 206.

For example, when uranium 100t is used, the heating value is 1 MW. The heat radiation amount of the reactor vessel 106 is 4 to 5 kW / m ² , and if the surface area of the reactor vessel 106 is 300 m ² , 1 MW heat radiation from the reactor vessel 106 is sufficiently possible.

  The amount of the plurality of metal balls 204 is preferably such an amount that the molten material can be buried and covered when all of the fuel rods 102 are melted. For example, the total volume of the plurality of metal balls 204 is preferably larger than the entire volume of the fuel rods 102 accommodated.

  The size of the metal sphere 204 is arbitrary. All of the metal balls having the same size may be arranged, or metal balls having different sizes may be arranged.

  Moreover, it is not limited to a spherical metal. The shape is arbitrary as long as the metal is large enough to be spread on the bottom of the reactor vessel 106 and the containment vessel 108. It may be a rod or a flat metal.

  In addition, since the shielding effect of radioactivity is high, it is preferable to arrange lead at the bottom of the reactor vessel 106 and the containment vessel 108, but part or all of lead is made of an alloy such as aluminum, tin, or solder. It may be replaced.

  Although the case where the nuclear reactor apparatus 100 was a pressurized water light water reactor was demonstrated above, it is not limited to this. The reactor apparatus may be a water-cooled nuclear reactor, and may be a known boiling water light water reactor. In this case as well, when the core melts, the fuel rod melt accumulates at the bottom of the reactor vessel, and when the reactor vessel penetrates, it accumulates at the bottom of the containment vessel. Therefore, a metal member (for example, a plurality of metal spheres) may be disposed in a portion of the reactor vessel and the containment vessel where the melt may be deposited.

  The present invention has been described above by describing the embodiment. However, the above-described embodiment is an exemplification, and the present invention is not limited to the above-described embodiment, and is implemented with various modifications. be able to.

DESCRIPTION OF SYMBOLS 100 Reactor apparatus 102 Fuel rod 104 Control rod 106 Reactor vessel 108 Containment vessel 110 Melt 200 First metal member 202 Second metal member 204 Metal ball 206 Molten first metal member

Claims (1)

A nuclear reactor vessel containing nuclear fuel,
A containment vessel containing the reactor vessel;
A first metal member disposed at the bottom of the reactor vessel;
A second metal member disposed at the bottom of the containment vessel,
The first metal member is formed by arranging a plurality of spherical metals having melting points lower than nuclear fuel along the shape of the bottom in the reactor vessel,
The second metal member is formed by arranging a plurality of spherical metals having melting points lower than those of nuclear fuel along the shape of the bottom in the containment vessel,
The nuclear reactor apparatus, wherein the first and second metal members are capable of burying the molten nuclear fuel when the nuclear fuel is melted.

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