A steam generator comprising: a steam outlet nozzle having a central axis; and a steam nozzle flow restrictor for restricting the amount of steam that can escape in case of a break of a steam line downstream the steam outlet nozzle, said steam nozzle flow restrictor comprising: a support web within said steam outlet nozzle having radial arms extending from the interior walls of the steam outlet nozzle and having a central opening concentric with the central axis; a shaft slidably supported and axially moveable within the central opening and having a stop at one end that prevents the one end from slipping into the opening, and a flow restrictor orifice plate at another end, said orifice plate having one or more openings and extending substantially perpendicular to the central axis, and the orifice plate being movable between an open position spaced from an input end of the steam outlet nozzle when the stop at the one end rests against the central opening, and a closed position with the orifice plate resting against the input end of the steam outlet nozzle when the stop is moved away from the support web central opening and said openings of the orifice plate restrict a flow of steam through the steam outlet nozzle as compared to when the orifice plate is in said open position; and a biasing mechanism for biasing the orifice plate into the open position. a steam outlet nozzle having a central axis; and a steam nozzle flow restrictor for restricting the amount of steam that can escape in case of a break of a steam line downstream the steam outlet nozzle, said steam nozzle flow restrictor comprising: a support web within said steam outlet nozzle having radial arms extending from the interior walls of the steam outlet nozzle and having a central opening concentric with the central axis; a shaft slidably supported and axially moveable within the central opening and having a stop at one end that prevents the one end from slipping into the opening, and a flow restrictor orifice plate at another end, said orifice plate having one or more openings and extending substantially perpendicular to the central axis, and the orifice plate being movable between an open position spaced from an input end of the steam outlet nozzle when the stop at the one end rests against the central opening, and a closed position with the orifice plate resting against the input end of the steam outlet nozzle when the stop is moved away from the support web central opening and said openings of the orifice plate restrict a flow of steam through the steam outlet nozzle as compared to when the orifice plate is in said open position; and a biasing mechanism for biasing the orifice plate into the open position. a support web within said steam outlet nozzle having radial arms extending from the interior walls of the steam outlet nozzle and having a central opening concentric with the central axis; a shaft slidably supported and axially moveable within the central opening and having a stop at one end that prevents the one end from slipping into the opening, and a flow restrictor orifice plate at another end, said orifice plate having one or more openings and extending substantially perpendicular to the central axis, and the orifice plate being movable between an open position spaced from an input end of the steam outlet nozzle when the stop at the one end rests against the central opening, and a closed position with the orifice plate resting against the input end of the steam outlet nozzle when the stop is moved away from the support web central opening and said openings of the orifice plate restrict a flow of steam through the steam outlet nozzle as compared to when the orifice plate is in said open position; and a biasing mechanism for biasing the orifice plate into the open position.