NOVELTY - Gastight reactor for separation of material included in composite raw material, comprises at least one reaction chamber and at least one rotor, the reaction chamber comprising at least one housing which is sealed in relation to the surroundings and has at least one inlet opening and at least one outlet opening and the rotor comprising at least one shaft, and at least a first part of the rotor being situated in the housing and the shaft extending from the first part through and out of the housing.    USE - The reactor is useful for separation of material included in composite raw material, where raw material comprises tires for cars and/or other vehicles; plastic; oil; nylon; polyester; digested sludge; wood; slaughterhouse waste; and oil plants (claimed).    ADVANTAGE - The reactor, which in operation, has less out-leakage of environmentally detrimental gases and less in-leakage of gases detrimental to the process in the reactor than known reactors of a comparable type.    DETAILED DESCRIPTION - Gastight reactor for separation of material included in composite raw material, comprises at least one reaction chamber and at least one rotor, the reaction chamber comprising at least one housing which is sealed in relation to the surroundings and has at least one inlet opening and at least one outlet opening and the rotor comprising at least one shaft, and at least a first part of the rotor being situated in the housing and the shaft extending from the first part through and out of the housing, characterized by at least one shaft seal, positioned directly or indirectly on the shaft, between the reaction chamber and the surroundings, the shaft seal only comprising at least one fluid channel which, in a first end, is connected to at least one fluid source which provides at least one inert gas, the fluid channel, in a second end, being in hydraulic communication with the reaction chamber, the fluid channel being partly in the form of at least one gap located between at least one first part rotating in the operation of the reactor and at least one second part non-rotating in the operation of the reactor, the gap extending around the shaft, and at least one remaining part of the fluid channel non-rotating in the operation of the reactor being directly connected to the gap for non-rotating supply of the gas to the gap in the operation of the reactor for the avoidance of pulsating gas pressure variations in the gap emanating from the supply. An INDEPENDENT CLAIM is included for a method of decreasing leakage of environmentally detrimental gases from a reactor and decreasing in-leakage of gases detrimental to the process in the reactor, which reactor is intended for the separation of material included in composite raw material and comprising at least one reaction chamber and at least one rotor, the reaction chamber comprising at least one housing which is sealed in relation to the surroundings and has at least one inlet opening and at least one outlet opening and the rotor comprising at least one shaft, and at least a first part of the rotor being situated in the housing and the shaft extending from the first part through and out of the housing, which involves providing the shaft with a shaft seal, positioned directly or indirectly on the shaft, between the reaction chamber and the surroundings, the shaft seal only comprising at least one fluid channel, the fluid channel being partly in the form of at least one gap located between at least one first part rotating in the operation of the reactor and at least one second part non-rotating in the operation of the reactor, and the gap extending around the shaft, and at least one remaining part of the fluid channel non-rotating in the operation of the reactor being directly connected to the gap for non- rotating supply of at least one inert gas to the gap in the operation of the reactor for the avoidance of pulsating gas pressure variations in the gap emanating from the supply; connecting the fluid channel in a first end to at least one fluid source which provides the inert gas; connecting the fluid channel in a second end to the reaction chamber; from the remaining part of the fluid channel, supplying the inert gas to the gap; and arranging so that the inert gas maintains a pressure which exceeds the pressure that prevails in the reaction chamber in the operation of the reactor.