Nuclear reactor

A pressurized-water reactor comprising a reactor pressure vessel having an inside with an upper portion and a lower portion, said portions containing pressurized-water core coolant, a nuclear core in said lower portion, said core comprising fuel element and at least three substantially vertical control rod guide tubes therein, said guide tubes having top and bottom ends, a duct interconnecting said bottom ends, a guide tube adaptor positioned in said upper portion of said vessel and above said core, said adaptor comprising a substantially vertically high-pressure feed line tube having a bottom end releasably connecting with said top end of a first one of said guide tubes, said adapter also including a substantially vertical guide tube extension for each of said other guide tubes, each said guide tube extension having a bottom end registered with a top end of a respective one of said other guide tubes, said extensions each having a top end having a passage for said coolant, and which is open to said vessel's said upper portion, a control rod reciprocative in each of said other guide tubes and their respective guide tube extensions, said first one of said guide tubes being void of any control rod said feed line tube having a top end, and means for controllably removing a portion of said coolant from said vessel and increasing the removed coolant's pressure and returning the coolant to said top end of said high-pressure feed line.