[en] The problems of the manufacturers of nuclear actuators are discussed. The only significant demand for safety-related actuators is in the American designed PWR's. The design of the actuators must be updated to accommodate stricter and and constantly changing U.S. standards, which are guidelines rather than definitive parameters. The requirements for motorised valve actuators are discussed. The problem of effectively sealing off the motorized areas from possible steam leakage was overcome by a system of double sealing. The design was proved in the Marviken reactor test bed where 14 successive LOCA blowdowns were overcome. (U.K.)