JPH0341394A - Passive cooling system for nuclear-reactor containment structure - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to the invention in U.S. Patent Application No. 294,095, entitled "Natural Circulation Passive Cooling System for Nuclear Reactor Containment Structure," filed January 6, 1989. are doing.

FIELD OF THE INVENTION The present invention relates to liquid-cooled nuclear reactor plant facilities. More particularly, the present invention relates to a self-actuated passive cooling system for a containment structure housing a nuclear reactor containing nuclear fuel.

BACKGROUND OF THE INVENTION A typical power reactor is housed inside a containment structure as a safety measure. A reactor containment structure is a nuclear fuel core that generates heat and auxiliary components of a nuclear reactor system.
For example, part of a coolant pipe (or heat transfer pipe)]
designed and used to confine nuclear reactor pressure vessels containing Because their contents constitute a source and/or vehicle for radiation and radioactive fission products, the containment structure housing the reactor effectively isolates the reactor system confined within it. Must. This means that all contents, including water, water vapor, gases and steam, and accompanying fission products and other radioactive sources that may escape from the reactor pressure vessel, particularly its associated cooling system, must be contained. There is.

Achieving a structure that satisfies the above requirements with an effective fluid-impermeable containment structure that reliably isolates the confined contents from the outside world has technical and constructional aspects. Generally speaking, there are no major obstacles.

However, if certain types of accidents occur in a nuclear reactor system (eg, loss of coolant), large amounts of very hot pressurized water may be released from the reactor system into the interior of the containment structure. Such very hot pressurized water flash-evaporates to water vapor, which can carry radioactive fission products and substantially increase pressure and temperature within the containment structure. Such incidents can create extremely high pressures and temperatures inside "leak-proof" containment structures.

Therefore, stringent requirements are placed on the integrity and ability of containment structures to fulfill their intended role of retaining all potentially hazardous materials originating from a nuclear reactor system.

The large thermal energy inherent in nuclear reactors and the potentially harmful high pressures created by flash vaporized water vapor are
Release by simply removing debris from the containment structure,
or escape into the outside atmosphere by any other means. This is because such water vapor may entrain or carry radioactive fission products, which may also be released into the environment.

Various pressure suppression means have been proposed and devised in the past to address the problem of overpressure.

Among them are various measures and devices for condensing the generated water vapor and thereby reducing the overpressure responsible for the accident. Examples thereof are disclosed in US Pat.

In the absence of effective pressure suppression means to alleviate the high pressures created by water vapor, the containment structures must be designed and constructed at great expense and must withstand extremely high internal fluid pressures. It is necessary to carry out maintenance to maintain the quality.

However, no matter how hardened a containment structure is, there is no guarantee that it will not fail, given the temperatures and pressures that can occur in a typical power reactor plant.

Under accident conditions, the decay heat generated by the core of the nuclear fuel within the pressure vessel is released into the containment structure through the pressure suppression vent system or the pressure vessel's safety and pressure reducing valves. In conventional nuclear reactor plants, such excess thermal energy is typically removed by active cooling systems from motors, pumps, valves, and heat exchangers.

The operation of these active components is dependent on external power and/or proper operator intervention.

SUMMARY OF THE INVENTION The present invention relates to a natural circulation passive cooling system for a nuclear reactor plant containment structure. Such passive cooling systems provide a means for reducing the temperature of the internal environment of the reactor containment structure, relieving overpressure within the containment structure by condensing steam and lowering the ambient temperature. Or help eliminate it. Such passive cooling systems are based on natural circulation heat transfer mechanisms that allow thermal energy to be safely dissipated into the external environment without contaminating radioactive fission products.

OBJECTS OF THE INVENTION A primary object of the present invention is to provide a new and improved containment cooling system for a nuclear reactor plant.

It is also an object of the present invention to provide a natural circulation cooling system for a containment structure of a nuclear reactor plant.

It is also an object of the present invention to provide a functional improvement in containment structures of nuclear reactor plants from self-actuating passive cooling systems based on fluid convection heat transfer.

Furthermore, it is an object of the present invention to provide a passive pressure suppression system for a containment structure of a nuclear reactor plant, such as one based on heat transfer by natural convection.

Furthermore, it is an object of the present invention to provide a cooling system for a containment structure of a nuclear reactor plant, which is based on heat transfer by natural circulation.

DETAILED DESCRIPTION OF THE INVENTION Turning first to FIG. 1, a nuclear reactor plant facility 0 is shown. The nuclear reactor plant facility 0 includes a nuclear reactor consisting of a pressure vessel 12 containing a core 14 of nuclear fuel that generates heat. Nuclear fuel transfers the heat generated from nuclear fission to the surrounding coolant, usually water. Water as coolant serves as a heat transfer medium for the direct generation of steam in so-called boiling water reactors and indirectly for the generation of steam in so-called pressurized water reactors. With the coolant circulation lines 16 and 18,
Reactor pressure vessel 12 for transferring thermal power from nuclear fuel
It is possible to pump cooling water into the reactor pressure vessel 12 and to draw heated water and/or steam out of the reactor pressure vessel 12.

The water and/or steam thus extracted is used for applications such as power generation and then recycled through the circuit.

A nuclear reactor, consisting of a pressure vessel 12, a reactor core 14, and some associated components, is housed within a containment structure 20. Such a containment structure 20 includes a bottom or floor, vertical side walls, and a roof with fluid-impermeable surfaces on the surfaces designed to prevent radioactive material from escaping from the interior into the exterior atmosphere. A plastic liner 22 is installed.

In a typical water-cooled nuclear reactor plant, in addition to the reactor pressure vessel 12, the containment structure 20 also includes a plurality of compartments or compartments designed to serve specific functions or purposes. There is. For example, reactor pressure vessel 12 is surrounded by one or more drywell chambers 24 adjacent thereto. These dry well chambers 24 serve to receive and retain water, water vapor, or other vapors that may overflow due to leaks or other causes associated with nuclear reactor operation.

In addition, one or more compartments 26 partially filled with water serve as suppression pool chambers for cooling and condensing water vapor 2 below the surface of the internal water pool. Such suppression pool chamber 26 communicates with one or more dry well chambers 24 via conduits 28 . One end of conduit 28 opens into the top of dry well chamber 24, and the other end opens into suppression pool chamber 26. It opens into a suppression pool chamber 26 at a position below the water surface of the water pool contained therein. As a result, water vapor escaping from the high temperature, high pressure areas of the pressure vessel and its associated circuitry or flash evaporated from the hot water exiting is introduced into the dry well chamber 24.

Since the leaked water vapor or flash evaporated water vapor from the hot water exiting has an inherently high pressure, such water vapor is exhausted from the dry well chamber 24 through the conduit 28 and ultimately drains into the water in the suppression pool chamber 26. It is introduced into the suppression pool chamber 26 at a position below the water surface of the pool. Such water vapor condenses by contacting a pool of water below the surface.

As a result, the pressure within the containment structure 20, which has increased due to the leaked water vapor or the flash evaporated water vapor from the high-temperature, high-pressure water that has flown out, is reduced.

In accordance with a preferred embodiment of the present invention, one or more cooling pool chambers 30 are located above and adjacent to the suppression pool chamber 26, which are removed from compartments containing water pools.

The passive cooling system of the present invention uses one or more closed heat transfer vessels 32, and there are several embodiments depending on the manner in which they are used. The closed heat transfer vessel 32 used in the present invention is not limited to a closed tank-like vessel or vessel, but may also be an elongated vessel such as a closed pipe section. The inside of the sealed heat transfer container 32 is maintained at a suitable temperature range (for example, about 50 to 150'C).
) is enclosed in a fluid (e.g., water) that has a boiling point and a relatively large heat of vaporization or heat of vaporization. It is necessary that the fluid be chemically inert to the components and materials of the fluid, i.e. the fluid must not exhibit any chemical action or reaction on any part with which it may come into contact.

Referring now to FIG. 2, one embodiment of the present invention will be described in which at least one closed heat transfer vessel 32 is disposed within the suppression pool chamber 26. Specifically, the sealed heat transfer container 32A is placed submerged in the water pool, and the sealed heat transfer container 32A'' is placed above the water surface of the water pool. Thermal vessels 32A' and 32A'' are connected to the duct 3
6 to closed condensing vessels 34A' and 34A'', respectively, which are submerged in a pool of water in the cooling pool chamber 30. As a result, the excess water released from the reactor into the suppression pool chamber 26 is Thermal energy can be transferred to the outside by natural convection: the closed heat transfer vessel 32, the duct 36 and the closed condensing vessel 34 allow excess thermal energy to be transferred to the suppression pool chamber 26.
5 to the cooling pool chamber 30, without emitting any contaminating radiation or radioactive substances.

Moreover, such a cooling system is continuous and passive, as the cooled and condensed liquid flows back from the closed condensing vessel 34 through the duct 36 to the closed heat transfer vessel 32 under the action of gravity, so that it can be heated again. Can be used for transportation.

According to the natural convection heat transfer mechanism of the present invention, when excess thermal energy generated from the nuclear reactor is dissipated and contacts the closed heat transfer vessel 32, the thermal energy heats the liquid inside the closed heat transfer vessel 32. do.

When the temperature of the liquid reaches its boiling point, the liquid evaporates into vapor. As the steam containing thermal energy expands within the closed system, the steam travels through duct 36 and reaches a closed condensing vessel 34 submerged in a pool of water within cooling pool chamber 30 . In the cooling environment of the closed condensing vessel 34 submerged in water, the hot steam is cooled and the thermal energy it contains is released from the closed condensing vessel 34 into the water pool in the cooling pool chamber 30 to form a liquid. return. The thus cooled and condensed liquid flows back into the closed heat transfer vessel 32 under the action of gravity.

Although the water pool of the cooling pool chamber 30 is physically isolated from the reactor system and the cooling system described above, the thermal energy introduced into such water pool can be exhausted to the atmosphere by any suitable means. There is no risk that radioactive substances or radiation will be released during this process.

Further embodiments of the invention will now be described in connection with the two variants shown in FIGS. 3 and 4.

According to this embodiment, a closed heat transfer vessel 32 is placed within the suppression pool chamber 26. To be more specific,
The sealed heat transfer vessel 32B is disposed submerged in a water pool in the suppression pool chamber 26, and the sealed heat transfer vessel 32B'' is disposed above the water surface of the water pool.Reactor containment structure Corresponding hermetically sealed condensing vessels 34B and 34B' are arranged on the exterior of the article 20, and the internal hermetically sealed heat transfer vessel 32B or 32B' and the corresponding external hermetically sealed condensing vessel 34B or 34B'' have at least one It communicates via a duct 36. The heat transfer mechanism in this case is the same as in other embodiments.

That is, excess thermal energy entering the suppression pool chamber 26 vaporizes the liquid contained within the closed heat transfer vessels 32B and 32B'. The steam thus generated passes through the duct 36 to a closed condensation vessel 34B outside the containment structure.
and 34B°, and condenses in such a low temperature environment, releasing heat of vaporization. The cooled and condensed liquid flows under the action of gravity into closed condensation vessels 34B and 34B.
"The closed heat transfer vessels 32B and 3 pass through the empty duct 36.
2B' and utilized for new heat transport and heat dissipation cycles.

In the variation of FIG. 3, closed condensing vessels 34B and 34B' are placed in a flue-like gas passageway to induce an accelerated flow of air or other gas.

For example, as shown in FIG. 3, a passage outer wall 44 is installed spaced apart from the outer wall of the reactor containment structure 20, thereby forming a passage 46 for inducing airflow. By providing the inlet 48 not only at the bottom of the gas passage 46 but also in the middle of the gas passage 46, the cooling air flow around the closed condensing vessels 34B and 34B' can be increased. It should be noted that the closed condensing vessels 34B and 34B' may be constructed from two or more interconnected smaller vessels as shown to increase cooling surface area and improve cooling efficiency.

In the variant shown in FIG. 4, a closed condensing vessel 34B'' located outside the reactor containment structure 20 is submerged in a relatively large amount of cooling liquid (e.g. water). can use, for example, a pond, lake or swamp.

The operation of the passive cooling system in the various embodiments described above is to maintain continuous cooling fluid circulation based on convective heat transfer and gravitational reflux.

The coolant circuit in this case consists of the fluid moving from the closed heat transfer vessel through the communicating duct to the closed condensing vessel and then following the reverse path to return. When the temperature around the closed heat transfer vessel increases, the water or other suitable liquid contained therein boils or evaporates, thereby absorbing thermal energy. The water vapor or other vapor thus produced travels through ducts to an elevated closed condensation vessel surrounded by a cooling environment or heat dissipating medium (eg, a cooling liquid). As a result, the water vapor or other vapor cools and condenses, thereby releasing the thermal energy it has absorbed.

The liquid that condenses by releasing the transported thermal energy,
Under the action of gravity, reflux flows from the closed condensing vessel through duct 1 to the closed heat transfer vessel.

The cooling mechanism in various embodiments of the invention is passive. That is, it starts and runs on its own and does not require manual or automatic control of valves, pumps, or other prime movers. Cooling is achieved by natural circulation of the heat transfer liquid, which is recirculated and self-replenishing under the influence of gravity. In this way, cooling of the reactor containment structure is achieved over long periods of time without the need for external power or operator intervention.

Furthermore, because the heat transfer liquid is completely confined within the cooling system, it is isolated from contaminants within the containment structure. Therefore, the hermetic cooling system of the present invention can extend through the reactor containment structure and into the external ambient atmosphere, thereby preventing leakage of radiation and radioactive materials while protecting the containment structure. It is possible to transport thermal energy to the outside.

[Brief explanation of drawings]

Figure 1 is a vertical sectional view of the containment structure that houses the nuclear reactor plant, Figure 2 is a partially enlarged sectional view showing the suppression pool chamber shown in Figure 1 and the cooling pool chamber above it, and Figure 3 The figure is a partially enlarged sectional view showing the suppression pool chamber and the flue-like gas passage provided outside the containment structure for inducing airflow for heat removal, and Figure 4 is a partially enlarged cross-sectional view of the suppression pool chamber and the containment structure. FIG. 3 is a partially enlarged cross-sectional view showing a cooling liquid such as water existing outside. In the figure, 10 is a nuclear reactor plant facility, 12 is a pressure vessel, 1
4 is a reactor core, 16 and 18 are coolant circulation pipes, 20 is a containment structure, 22 is a liner, 24 is a try-well chamber, 26
28 is a suppression pool chamber, 28 is a conduit, 30 is a cooling pool chamber, 32 is a closed heat transfer vessel, 34 is a closed condensation vessel, 3
6 represents a duct, 44 represents a passage outer wall, 46 represents a gas passage, and 48 represents an inlet. F: / ni, / F/ ni 2

Claims (1)

[Scope of Claims] 1. (a) A nuclear reactor plant including a containment structure surrounding a pressure vessel housing a core of nuclear fuel that generates heat; (b) A nuclear reactor plant provided adjacent to the pressure vessel; (c) a suppression pool chamber containing a cooling liquid for condensing steam and cooling hot water; (d) at least one containing a volatile liquid and disposed within said suppression pool chamber; sealed heat transfer vessels,
and (e) located outside the suppression pool chamber,
and at least one closed condensation vessel that communicates with the closed heat transfer vessel through at least one duct to form a closed circuit, so that thermal energy within the suppression pool chamber is transferred to the closed heat transfer vessel. A natural circulation passive cooling system for a containment structure of a nuclear reactor plant, characterized in that it is transported from the vessel to said closed condensation vessel, providing protection against overpressure in the containment structure. 2. (a) A nuclear reactor plant including a containment structure surrounding a pressure vessel containing a nuclear fuel core that generates heat; (b) a dry well chamber provided adjacent to the pressure vessel; ( c) a suppression pool chamber holding a cooling liquid for condensing steam and cooling hot water; (d) a cooling pool chamber; (e) excess thermal energy containing volatile liquid and entering said suppression pool chamber; (f) at least one closed heat transfer vessel disposed within the suppression pool chamber for trapping the heat transfer vessel; and (f) disposed within the cooling pool chamber and forming a closed circuit through at least one duct. at least one closed condensing vessel element in communication with the closed heat transfer vessel in such a manner that thermal energy leaking from the pressure vessel into the dry well chamber is transferred from the closed heat transfer vessel to the cooling pool chamber. Natural circulation passive cooling system for a containment structure of a nuclear reactor plant, characterized in that the system is transported to said closed condensation vessel of a nuclear reactor plant, providing protection against overpressure in the containment structure. 3. The natural circulation passive cooling system according to claim 2, wherein the closed heat transfer vessel is located in an area above the liquid level of the cooling liquid pool in the suppression pool chamber. 4. The natural circulation passive cooling system according to claim 2, wherein the closed heat transfer container is submerged in an area below the liquid level of the cooling liquid pool in the suppression pool chamber. 5. (a) A nuclear reactor plant including a containment structure surrounding a pressure vessel containing a nuclear fuel core that generates heat; (b) a dry well chamber provided adjacent to the pressure vessel; ( c) a suppression pool chamber containing a cooling liquid; (d) at least one seal containing a volatile liquid and disposed within said suppression pool chamber for capturing excess thermal energy entering said suppression pool chamber; a heat transfer vessel; and (e) at least one closed condensation vessel located outside the containment structure and communicating with the closed heat transfer vessel through at least one duct to form a closed circuit. As a result of the various elements, thermal energy leaked from the pressure vessel into the dry well chamber is transported from the closed heat transfer vessel in the suppression pool chamber to the closed condensation vessel outside the containment structure. A natural circulation passive cooling system for a containment structure of a nuclear reactor plant that provides protection against overpressure within the containment structure. 6. The natural circulation passive cooling system of claim 5, wherein said closed condensation vessel located outside said containment structure is exposed to the surrounding atmosphere. 7. The natural circulation passive cooling system according to claim 5, wherein the closed condensation vessel located outside the containment structure is submerged below the water surface of a water pool. 8. (a) A nuclear reactor plant including a containment structure surrounding a pressure vessel containing a nuclear fuel core that generates heat; (b) a dry well chamber provided adjacent to the pressure vessel; ( c) a suppression pool chamber containing a cooling liquid; (d) a plurality of sealed heat transfer chambers containing a volatile liquid and disposed within said suppression pool chamber to capture excess thermal energy entering said suppression pool chamber; (e) located outside the containment structure in a gas passage through which a cooling gas flow passes, and forming a closed circuit with each of the closed heat transfer containers via at least one duct; As a result of the plurality of communicating closed condensation vessel elements, thermal energy leaking from the pressure vessel into the dry well chamber is transferred from the closed heat transfer vessel in the suppression pool chamber to the outside of the containment structure and the gas passageway. Natural circulation passive cooling system for a containment structure of a nuclear reactor plant, providing protection against overpressure in the containment structure, characterized in that the system is transported to said closed condensation vessel located inside said containment structure.