Patent Number: 039649652
Section: description

DETAILED DESCRIPTION OF THE INVENTION Having reference to the above drawing, the reactor pressure vessel 1 contains the core 2, the coolant main pipeline loop is shown at 3 and the direction of the coolant flow is indicated by the arrow 4. The coolant flows from the pressure vessel 1 to the steam generator 5 and is returned to the pressure vessel under the force of the pump 6 which maintains the circulation in the loop 3. The secondary coolant pipeline loop 3a is shunted around the pump 6 so as to pass from 10 to 20% of the coolant through the coolant water purification system 10 which included the degassing facility 11 where the coolant is decompressed and cooled so that its gases are separated. The degassed water coolant returns to the pressure vessel 1 via the pipeline 12 which is part of the secondary loop 3a. The separated gases flow through the pipe 14. As previously mentioned, these gases are mainly hydrogen, nitrogen and oxygen but they also include small amounts of the noble gases krypton and xenon making the disposal of the gases a problem as previously indicated. According to the invention, these gases are passed by the pipe 14 into a recombiner 15 which is of the catalytic type, the amount of oxygen relative to the hydrogen being insufficient to support flame combustion. In this way the oxygen is removed from the gases, the output from the recombiner 15 going through a dryer or water separator 16 from which the water flows via a pipe 17 for return to the water system of the reactor installation or disposed of. The gases leaving the recombiner 16 then go into a gas separation facility generally indicated by 18. This gas separation facility may be of the type which through condensation and step-wise evaporation of the different gases effected via suitable heat exchangers, effects the separation according to the liquification temperatures of the gaseous components. Known equipment is capable of separating the major part of the noble gases in the gas mixture leaving the recombiner 16, particularly krypton and xenon, and these are fed via a pipe 20 to the previously referred to gas storage facility 21. The latter can be a steel bottle containing for better absorption, activated carbon. Its volumetric capacity need not be greater than 1m.sup.3 and preferably it is of much smaller size, such as less than 0.1m.sup.3. Such capacities are sufficient for storing the noble gases produced in the course of a years operation of a pressurized-water powered reactor of 1000 MWe. The separated hydrogen is sent through a pipe 23 and to the water coolant gas-charging system 24 which normally also includes a storage facility for the hydrogen, permitting its use as required. This facility 24 feeds into the secondary loop 3a as required to maintain the water coolant' s hydrogen concentration, or possibly used elsewhere. It is important to note that the purity requirements for the hydrogen with respect to radioactivity components are so low that the gas separation facility 18 need not operate with great efficiency and, therefore, can be constructed and operated inexpensively as compared to the expense that would be required for the complete removal of the noble gases. The condensed nitrogen and possibly some remaining portion of the noble gases are fed from the facility 18 via a pipe 25 to a unit 27 of the type which by partial evaporation or rectification entirely separates the nitrogen from any remaining noble gases, the latter going through a pipe 28 to the previously described noble gas storage bottle 12. The separation here should be adequate to remove all remaining noble gases to a degree permitting discharge of nitrogen to the atmosphere if desired. As shown, the nitrogen leaves 27 via a pipe 30, a valve 24a serving to send the nitrogen either to the gas-charging facility 24 or to a gas stack 32 discharging the nitrogen to the atmosphere, this being entirely safe from the environmental pollution viewpoint as it now or may potentially in the future exist. Neither of the facilities 11 and 18 are required to separate completely all of the noble gases. This is required in the case of the facility 27 but here the content of noble gases is already very small as compared to the initial content and they must be separated only from the nitrogen. It follows that the previously described problem is solved by this invention in an economical way while meeting the environmental requirements which the previously described prior art system could not do satisfactorily.