Fast nuclear reactor with axially adjustable neutron reflector - located inside the pressure vessel between the core and a neutron screen in the primary coolant flow

摘要

A fast nuclear reactor comprises a control, upright core of fissile material separated from the outer pressure vessel by a series of concentric sleeves defining annular spaces between them which are filled with primary coolant. Between sleeve, which immediately encloses the core, and the next outer sleeve is a space in which a neutron reflector is axially adjustable by power devices above the vessel to control the criticality of the core. Between sleeve and a lining of vessel is a space containing an array of neutron screen elements, between which the coolant flows downwards before passing up through the core. The vessel may also enclose electromagnetic pumps for the primary coolant (Na) and primary heat exchangers. Pref. the neutron reflector may be divided into six sections spaced circumferentially round the core and individually adjustable, by separate devices, within sections of an annular space which is closed at the bottom. ADVANTAGE - The overall size of the reactor is reduced and its control simplified. The neutron reflector has a reduced axial length, and consequently weight, compared with prior art reflectors located further outwards of the core.