Induced nuclear reactions: processes – systems – and elements – Reactor protection or damage prevention – Auxiliary heat removal structure
Patent
1996-08-05
1997-12-02
Wasil, Daniel D.
Induced nuclear reactions: processes, systems, and elements
Reactor protection or damage prevention
Auxiliary heat removal structure
376299, 376367, G21C 1518
Patent
active
056944420
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
This invention relates to a system for dissipating heat from the interior of a nuclear reactor containment building, in particular for dissipating any heat generated on the sudden occurrence of an incidental malfunction of the standard cooling arrangements;
As is known, nuclear reactors, along with their primary cooling circuit, are currently placed inside a primary containment structure made of steel or concrete which is usually constructed of several layers or walls. This primary containment structure is, in turn, placed inside a building whose side wails and roof are in communication with the external atmosphere.
In the event of an emergency situation, the heat generated by the nuclear reactor within the primary containment structure must be dissipated of necessity to the structure and the building outside, without releasing to the external surroundings any of the fluids contained in the primary structure.
It matters to observe that a nuclear reactor, even when shut down by reason of an emergency situation, continues to generate heat from the nuclear fuel decay. The amount of heat generated is initially quite large, and decreases over time, but never really comes down to zero. Heat shall, therefore, have to be dissipated even after shutting down the reactor.
In order to meet current safety requirements, the manner of dissipating the heat must be passive--i.e. must not rely on automatically or manually operated control arrangements, on the actuation of pumps or the like, the opening of valves, or the availability of power sources of any kind, and be inherently activated by natural physical phenomena related to structural features.
From French Patent No. 8216104, a heat dissipating method is known wherein an external heat exchanger in thermal communication with the interior of the enclosure to be cooled is employed. The external heat exchanger releases to the atmosphere heat from within. The heat exchanger utilizes a thermal carrier fluid in natural circulation for transferring heat from the inside out. In addition, it is located inside an open duct provided with a natural draft chimney, whereby a more efficient dissipation is promoted by increasing the velocity of the airflow in the neighborhood of the heat exchanger.
However, this prior approach involves the use of an outside heat exchanger having large transfer surfaces for transferring the decay heat generated during the initial stage of the emergency to the surrounding air. Accordingly, its cost is high. Furthermore, when water is to be used for a thermal carrier, gates must be installed in the chimney to prevent the water within the heat exchanger from freezing in a condition of low outside temperature. The provision of such gates is in conflict with the aforementioned requirement for passive operation.
It is the object of this invention to provide a system for dissipating heat generated within a reactor containment structure on the occurrence of an accident, which can overcome the above drawbacks with which the prior art is beset.
This object is achieved by a heat dissipating system according to the appended claims.
The features and advantages of a heat dissipating system according to the invention will become apparent from the following description of two embodiments thereof, as well as from the accompanying illustrative, and in no way limitative, drawings.
In the drawings:
FIG. 1 is a general view showing schematically a building and an containment structure accommodating a nuclear reactor therein, which incorporate the system for dissipating heat in case of accident according to this invention;
FIG. 2 is a scaled-up cross-sectional view showing schematically a top portion of the containment building in FIG. 1, with a heat dissipating system in a standby condition;
FIG. 3 shows the heat dissipating system of FIG. 2 while in operation;
FIG. 4 is a longitudinal section view of a tube nest element of the heat exchanger placed in the pool;
FIG. 5 is a perspective view showing schematically the heat exchanger in the pool;
FIG. 6 is a sche
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Cinotti et al., Liq. Metal Eng. and Tech. 3rd Int. Conf.-Oxford, Sep. 13, Apr. 1984, vol. 1, pp. 487-491.
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Cinotti Luciano
Proto Giuseppe
Enel S.p.A.
Wasil Daniel D.
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