Filter medium for strainers used in nuclear reactor emergency core cooling systems

Abstract

A filter medium for strainers used in the emergency sump of a nuclear power plant ECCS. The filter medium is employed with double wall, concentric tube type strainer modules. The filter medium is preferably constructed of a woven or knitted stainless steel wire material and is shaped in a cylinder so that it can be inserted between an external and an internal strainer of a double wall, concentric tube type strainer in such a manner that water that passes through the strainer must pass through and be filtered by the filter medium before the water can be pumped to the reactor core. The filter medium is inserted through the bottom of the strainer module and is held in place by an x-shaped retainer.

1 . Filter medium for strainers used in nuclear power plant ECCS comprising: 
 filter medium secured immediately downstream of a strainer in a water flow path of an ECCS system for a nuclear reactor and located upstream in the water flow path of an ECCS pump so that water that has flowed through the strainer must first pass through the filter medium before it can reach the ECCS pump, and    said filter medium constructed of stainless steel wire material.    
   
   
       2 . Filter medium for strainers used in nuclear power plant ECCS according to  claim 1  further comprising: 
 said filter medium formed into the shape of hollow cylinders so that the cylindrical filter medium can be inserted into a space created on the downstream side of each double wall strainer module provided on the strainer.    
   
   
       3 . Filter medium for strainers used in nuclear power plant ECCS according to  claim 2  further comprising: 
 retention means associated with each cylindrical filter medium for securing the cylindrical filter medium within its associated strainer module.    
   
   
       4 . Filter medium for strainers used in nuclear power plant ECCS according to  claim 1  wherein said filter medium is constructed either of woven stainless steel wire or knitted stainless steel wire.  
   
   
       5 . A combination filter medium and strainer used in nuclear power plant ECCS comprising: 
 a strainer provided in an emergency sump for a nuclear reactor, said strainer provided with a plurality of strainer modules, each strainer module secured to a plenum box that communicates via a water suction line with an ECCS pump for supplying water to a reactor core, each strainer module provided with spaced apart double walls that form a cylindrical interior space on the downstream side of the double walls, and    a cylindrical filter medium secured between the double walls so that the filter medium is located within the cylindrical interior space.    
   
   
       6 . A combination filter medium and strainer used in nuclear power plant ECCS according to  claim 5  further comprising: 
 said cylindrical filter medium secured between the double walls of its associated strainer module by retention means, and said retention means secured to a bottom of said strainer module in such a way as to removably block the insertion in or removal of the cylindrical filter medium relative to its associated strainer module.    
   
   
       7 . A method for filtering water contained in a containment sump of an ECCS for a nuclear reactor through a combination filter medium and strainer comprising: 
 straining water from a containment sump through a perforated strainer in an ECCS to remove the larger particles of debris and other matter from the water,    filtering the strained water that has passed through the perforated strainer through a filter medium constructed of woven or knitted stainless steel wire material to remove the majority of the remaining debris and other matter from the strained water, and pumping the strained and filtered water that has passed through the filter medium to a reactor core by use of an ECCS pump.