Abstract:
A gas charging device injects hydrogen into the pressurized water that cools the core of a nuclear power reactor through nozzles provided in a pressurized water flow pump. Conduit and valve combinations also are provided to permit solid matter to be flushed from the nozzles.

Description:
TECHNICAL FIELD 
     The invention relates to a procedure for injecting gas into liquids and, more particularly, to injecting hydrogen gas into the primary coolant for pressurized water nuclear power plants, and the like. 
     BACKGROUND ART 
     It is not uncommon in nuclear power plants, to inject hydrogen gas into water by spraying primary coolant (i.e. water) into an atmosphere that contains hydrogen, e.g., into the hydrogen gas blanket of the makeup tank, or by bubbling hydrogen gas in the water phase of the makeup take. The makeup tank, moreover, is used, among other things, to equalize primary coolant volume changes. Toward this end, the makeup tank contains primary coolant and a hydrogen-gas blanket. 
     These procedures have the disadvantage that due to the large hydrogen volume in the makeup tank, a release of relatively large hydrogen volumes into the space surrounding the makeup tanks cannot be precluded, and therefore the possibility of gas explosions must be considered. There is a further disadvantage in the fact that the liquid gas content cannot be precisely controlled. 
     There is a need, therefore, to find a procedure through which a preset gas content can be reached in the liquid that is to be gassed and in which a release of dangerous volumes of gas can be reliably avoided. 
     SUMMARY OF THE INVENTION 
     In accordance with the invention these disadvantages are solved in that a specific gas volume is channeled to a pump. The pump is in fluid communication with the liquid flow that is to be injected with gas, and the gas is mixed with the liquid inside the pump casing. 
     For multi-stage centrifugal pumps, the gas preferably is injected near the last stage, because optimum mixing occurs there. 
     The equipment for implementing this procedure includes a gas charging device that is installed in the gas injection conduit. The gas injection conduit is designed doubly redundant on the discharge side of the gas charging pump and the conduits are directly or indirectly connected with gas injection nozzles inside the pump casing. Hereinafter the term nozzles refers to gas injection nozzles only. 
     Preferably the nozzles are arranged on the inner wall of the casing, on the pump rotor, in the pump suction conduit or in some combination of these locations. The nozzles can be flushed through a bypass flow of the gas-injected liquid. The conduits of the bypass flow are connected to the gas injection conduits. Furthermore, the gas injection conduit conduit isolation valves and bypass flow conduits can be shut off to enable the nozzles alternately injest gas and be flushed with rinse water. 
     Upstream and downstream from the pump an analysis measuring device is coupled to the liquid flow in question. 
     The gas volume that is to be injected by way of this gas charging equipment depends upon the hydrogen content that is present in the liquid which is to be injected and the head of the liquid flow. 
     The procedure and the equipment for implementing this invention are explained in more complete detail by means of a schematic drawing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     Illust. 1 is a schematic representation of an embodiment of the invention; and 
     Illust. 2 is a section through a flow pump. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The primary coolant of a pressurized water reactor system (not shown) which is to be injected with gas, flows in conduit 1 in the direction of the arrow 12. This primary coolant is further channeled in the direction of arrow 13 through a flow pump 2 that is installed in the conduit for normal use in a nuclear reactor system. With the aid of a gas charging device, illustratively, gas pump 6, a certain gas volume of which hydrogen is typical, is injected into pump casing 14 in the direction of arrows 15, through a gas feed conduit 3 and then by way of two gas injection conduits 3a, 3b.  Analysis measuring devices 7 and 8 coupled to the conduit 1 upstream and downstream, respectively, of the flow pump 2, provide information concerning the hydrogen concentration, or content, of the primary coolant prior to and after the injection of gas. Control of the gas volume, which must be injected via gas pump 6, is a function of the hydrogen content measured in the primary coolant downstream of the point at which gas is injected into the volume of liquid flowing in the conduit 1. 
     As shown in FIG. 2, the gas injection takes place on the inside of the pump casing, via nozzles 16, 17, 18 which are arranged on the casing inside wall 19, the pump rotor 20 or in suction conduit 21. Because the design shown in illustration 2 represents a multi-stage flow pump, nozzles 16 are arranged on the inside wall 19 of multi-stage casing 24. The nozzles are respectively in communication with the gas injection conduit 3a or 3b . When injecting gas with the aid of pump rotor 20, the bores 25, 26 in pump shaft 27 and pump rotor 20 form an elongation or extension of the gas injection line 3a, 3b. 
     Flushing of the nozzles is required during injections of dry gases into salt solutions (primary coolant is a salt solution) because there is a danger that one or more of the nozzles will close as a result of local solubility excess. For this reason, a bypass flow conduit 11 (FIG. 1) branches from the discharge side of the flow pump 2 into conduits 22 and 23 which are coupled, respectively to gas injection conduits 3a, and 3b. If isolation valves 9a and 5 are now closed, and isolation valves 9 and 5a open, a gas flow runs through gas injection conduit 3a, to the nozzles connected with this conduit and the liquid rinse runs through gas injection conduit 3b to the nozzles connected with this conduit. Through a reverse manipulation of the valves, the nozzles connected to gas injection conduit 3a will be flushed, and the injection of gas will take place via the nozzles connected to gas injection conduit 3b. Check valves 4, 10 prevent a backflow of gas or liquid rinse. This process takes place automatically, so that as the nozzles associated with conduit 3a are being rinsed, the nozzles associated with conduit 3b are utilized for injecting gas and vice versa. 
     The injection of gas is possible according to this procedure and the associated equipment, in a simplified and advantageous manner. Nitrogen, moreover, can be used as a gas blanket for the makeup tank, so that the danger of a combustion gas explosion is precluded. 
     An additional advantage of the technique under consideration is the fact that the hydrogen content of the reinjected primary coolant can also be kept within the specified values during load change processes.