Self-compensating level control for sump suction pumps

A liquid cooled nuclear reactor including a reactor vessel, said reactor vessel being partially filled with reactor coolant and having a cover gas above the level of reactor coolant in said reactor vessel, a heat exchanger connected to an outlet of said reactor vessel, a coolant circulating pump connecting an outlet of said heat exchanger to an inlet of said reactor vessel, said pump being of a type classified as a sump suction pump having an integral sump tank and including inlet and outlet nozzles attached to said sump tank, an impeller disposed within said sump tank, a flow manifold connecting said pump impeller to said pump outlet nozzle, a drive shaft extending within said sump tank and attached to said impeller therein, a divider plate immersed within said reactor coolant within said sump tank, said divider plate being located above said impeller and said pump inlet nozzle so as to divide said sump tank into an upper chamber and a lower chamber, and orifice means for maintaining said cover gas in the tank at a pressure substantially equal to the pressure of said cover gas in the reactor vessel during all speeds of pump operation, said orifice means comprising a flow restricting tube member connecting said manifold to said upper chamber, and said flow restricting tube being sized such that reactor coolant flow through said tube member from said flow manifold to said upper chamber substantially equals reactor coolant flow passed said divider plate from said upper chamber to said lower chamber whereby the reactor coolant level in said pump tank remains substantially constant for all speeds of operation of said pump.