Abstract: Anti-ejection device for nuclear reactor control rod.The reactor comprises a tight enclosure integral with the nuclear reactor vessel, the control rod being integral with the command bar. A system for manipulating the command bar comprises means for locking it. These means lock the command bar with respect to the tight enclosure for as long as the force exerted on this bar remains below a limit value. This limit value is at least equal to the force exerted on the command bar in the case of an accidental external cause urging the control rod to leave the reactor core. The device comprises means for obtaining a translation of the control rod, by exerting a force exceeding said limit value on the command bar.