US 4,363,780 AGranted

Boiling reactor

AssigneeAB Asea-Atom

InventorKare Hannerz

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Abstract

Boiling reactor comprising a reactor core (1) and a pressure vessel (2) enclosing said reactor core and being provided with at least one conduit for discharged steam and at least one conduit for feed water and during normal operation being filled with water up to a certain normal level (11), the steam pressure in the pressure vessel having a substantially constant value of at least 5 MPa. The pressure vessel (2) is surrounded by a water-filled pool (3) with a water volume above the reactor core (1) which is considerably greater than the water volume within the pressure vessel (2). The pressure vessel (2) is a concrete vessel having an internal thermal insulation (9). The reactor comprises emergency cooling pipes (19, 20) with valves (19', 20') connecting the reactor vessel (2) to the pool (3). The valves (19', 20') are normally closed. The pipes (19, 20) are positioned at different levels. The emergency cooling valves (19', 20') are adapted to be controlled in dependence on the water level (11) in the reactor vessel (2) in such a way that they are opened when the water level is below a certain minimum level. When the valves (19', 20') are opened, steam is flowing out of the reactor vessel (2) through the upper emergency cooling pipe (19), whereas water is flowing from the pool (3) into the reactor vessel (2) through the lower emergency cooling pipes (20) as soon as the difference in static pressure in the pool between lower emergency cooling pipe (20) and upper emergency cooling pipe (19) is greater than the pressure drop of the steam flux passing through the latter. Emergency cooling is achieved entirely without the use of pumps. (FIG. 1.)

Boiling water reactor comprising a reactor core (1) and a pressure vessel (2) surrounding said core and being provided with at least one conduit (14) for discharged steam and at least one conduit (16) for feed water and which, during normal operation, is filled with water up to a certain normal level (11), the steam pressure in the pressure vessel having a substantially constant value of at least 5 MPa, said pressure vessel being disposed with respect to a water reservoir (3) in such a way that a portion of the water-filled space of the reservoir positioned above the reactor core has a volume which is at least as large as the water volume present in the pressure vessel, characterised in that said pressure vessel is constructed as a substantially hollow-cylindrical body with a vertical axis and has an internal heat-insulating layer (9) and a metallic lining (10), arranged radially inside said layer (9), that at least one upper emergency cooling pipe (19), which in said pressure vessel (2) opens out above said normal level (11) is passed through said lining, said layer and through the wall of the pressure vessel, and arranged to open out into said reservoir via a corresponding, normally closed, first emergency cooling valve (19'), whereas at least one lower emergency cooling pipe (20), opening out into the pressure vessel, is arranged to open out into said reservoir via a corresponding, normally closed, second emergency cooling valve (20'), said lower emergency cooling pipe (20) penetrating said lining below the zone where said lining is penetrated by said upper emergency cooling pipe (19), said first (19') and second (20') emergency cooling valves being each individually controllable by first (23) and second (24) control means, respectively, which are both responsive to the output signal of a level transducer (22), said level transducer being arranged to give a signal for opening of said first and said second emergency cooling valves when, in said pressure vessel (2), the water depth is at least 10% smaller than the water depth at said normal level (11), but sufficient for keeping said reactor core under water.

Abstract

Claims7