Water-cooled nuclear reactor with passive emergency shutdown and core cooling capability and on-line refueling

A water-cooled nuclear reactor is provided with a passive emergency shutdown and core cooling capability by providing it with emergency fuel element dispersal means operable from internal energy contained within the reactor pressure vessel for dispersing the core fuel content into an adjacent heat sink. In a preferred embodiment, the reactor is provided with especially designed fuel elements and fuel element guides to permit passive emergency core dispersal. The reactor shutdown mechanism also facilitates reactor refueling and permits selective on-line refueling during normal reactor operation