Patent Number: 
Section: claims

1. A protective screen for screening off a suction space and a suction duct connected to it, in an emergency cooling system of a nuclear power plant, said protective screen including at least one screen wall element having a suction side and an outflow side,wherein the screen wall element is built up of one or more modular cassette units for screening off a suction space and a suction duct connected to it in an emergency cooling system of a nuclear power plant, wherein the cassette units have rectangular sides,wherein the cassette units each contain:a plurality of screen pockets formed into rows which are open towards the suction side and which extend between two opposed rectangular sides of the cassette,two elongated lateral walls which extend between said two opposed rectangular sides of the cassette and which form lateral sides of the cassette, each lateral wall being formed from perforated sheet metal, andone or more elongated intermediate walls arranged between the lateral walls and formed as double walls with the double walls being open towards the outflow side, each intermediate wall extending between said two opposed rectangular sides of the cassette and being formed from perforated sheet metal, with the lateral walls and the one or more intermediate walls forming the lateral sides of the screen pocket rows,wherein each screen pocket is formed from an elongate portion of perforated sheet metal that is bent into a longitudinal valley, said longitudinal valley being transverse to the elongated lateral walls and the one or more intermediate walls, and said bent, elongate portion of perforated sheet metal spanning the distance between two consecutive intermediate walls or between one of the elongated lateral walls and an adjacent intermediate wall, with the screen pocket being open towards the suction side over said distance, and each screen pocket row has outflow gaps between said valleys on the outflow side, said outflow gaps being connected to the outflow side or open toward the outflow side,and wherein the cassette units are modularly configurable for placement in a row in order to assemble the screen wall element in the desired size. 2. A protective screen in accordance with claim 1, wherein the longitudinal valley comprises a substantially U-shaped form. 3. A protective screen in accordance with claim 1, wherein the screen pockets have a depth of greater than 0.1 m. 4. A protective screen in accordance with claim 1, wherein the spaced apart walls and the intermediate walls of the cassette units are clamped against one another by means of connection elements. 5. A protective screen in accordance with claim 1, wherein the suction pockets have a depth of greater than 0.2 m. 6. A protective screen in accordance with claim 1, wherein any of the spacings between the two sides of a double wall are determined by spacer elements disposed between the two sides of the double wall. 7. A protective screen in accordance with claim 1, wherein any of the spacings between the intermediate walls are determined by spacer elements disposed between the intermediate walls. 8. A protective screen in accordance with claim 1, wherein the plurality of screen pockets are directly open to, and in direct contact with, the suction side. 9. A protective screen in accordance with claim 8, wherein a pressure drop between the suction side and outflow side is determined by an effective screen area of the plurality of screen pockets. 10. A protective screen in accordance with claim 9, wherein the effective screen area comprises a flow-though resistance of the plurality screen pockets. 11. A protective screen in accordance with claim wherein the suction duct is located in a height restricted sump region. 12. A protective screen in accordance with claim 1, wherein the outflow gaps are closed to the suction side. 13. A protective screen in accordance with claim 1, wherein the plurality of screen pockets are structurally configured to supply water to the emergency cooling system of a nuclear power plant when material resultant from an incident is impinged against the plurality of screen pockets. 14. A protective screen in accordance with claim 13, wherein the material comprises concrete chunks and/or insulation debris.