Filter medium for strainers used in nuclear reactor emergency core cooling systems
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 two concentric strainer walls, 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. The filter creates varied approach velocity of the fluid and results in non-uniform fibrous debris accumulation on the strainer, insuring acceptable strainer debris hydraulic head loss.
1. In a nuclear power plant having an emergency core cooling system comprising at least one double wall concentric tube strainer defining an annular region between a first and second wall of said double wall concentric tube strainer, said annular region being closed at a first end, and open at a second end, said double wall concentric tube strainer being upstream of an intake of an emergency core cooling system pump, such that cooling water must first pass through said double wall concentric tube strainer before it can enter said pump intake, wherein, the improvement comprises:
a filter medium being located in said annular region in such a manner that cooling water that passes through said first and second walls must also pass through and be filtered by said filter medium before the water can be pumped to a reactor core; and
a retainer extending across said open second end to keep said filter medium in place.
2. The plant of claim 1 wherein said retainer is in the shape of an X.
3. The plant of claim 1 , wherein said filter medium is knitted or woven stainless steel.
4. The plant of claim 1 , comprising a plurality of double wall concentric tubes.