Patent Number: 052934136
Section: claims

1. In a nuclear power plant having a containment, a system for pressure relief of the containment, comprising: a filter disposed inside the containment, said filter having a container, at least part of said container having two walls defining a chamber between said walls, and a heat-conducting fluid at least partly filling said chamber during a heating period and being at least half evaporated after attainment of an operating temperature. 2. The system according to claim 1, wherein said container has double-walled portions with said two walls, said double-walled portions having a heat-conducting resistance when not filled with said heat-conducting fluid being at least ten times higher than when filled with said heat-conducting fluid. 3. The system according to claim 1, wherein said two walls define a double-walled middle part of said container surrounding a vertical axis, and including a single-walled curved base firmly closing said middle part toward the bottom, and a curved cap firmly closing said middle part toward the top. 4. The system according to claim 1, wherein said middle part is cylindrical. 5. The system according to claim 3, wherein said double-walled middle part has a given height, said container includes a first inner chamber, said chamber between said walls is a second chamber having an annular cross section extending over the entire given height, and said second chamber communicates with said first inner chamber through openings formed just below said cap. 6. The system according to claim 5, including washing fluid filling substantially 30 to 80% of said first inner chamber, said second chamber having a lower part being filled with said heat-conducting fluid and an upper part, and filter mats filling at least said upper part. 7. The system according to claim 6, wherein said washing fluid fills substantially 50% of said first inner chamber. 8. The system according to claim 5, wherein said two walls have portions surrounding said heat-conducting fluid, and at least part of said second chamber has heat transfer fins increasing surface area in the vicinity of said wall portions. 9. The system according to claim 6, wherein both said washing fluid and said heating-conducting fluid are water. 10. The system according to claim 6, including a convection barrier in the form of a horizontal partition disposed in said second chamber above said heat-conducting fluid, said horizontal partition having at least one of a perforation and a slit formed therein. 11. The system according to claim 6, including mist separators disposed in said upper part of said inner chamber in front of said openings leading to said second chamber. 12. The system according to claim 5, including a vertical pipe disposed centrally in said first inner chamber for delivering a gas-steam mixture to be filtered, said vertical pipe having upper and lower ends, a horizontally extending segment through which the upper end of said vertical pipe communicates with the interior of the containment, radially disposed horizontal feed pipes into which the lower end of said vertical pipe discharges, and Venturi nozzles communicating with said horizontal feed pipes above said base. 13. The system according to claim 6, wherein said two walls are in the form of an inner wall and an outer wall, said outer wall has another opening formed therein leading to the outside, and including a pipe penetrating the containment and communicating with said other opening for carrying a filtered gas-steam mixture out of said second chamber through said outer wall at approximately half the height of said filter mats. 14. The system according to claim 1, including an overpressure line through which the interior of said filter communicates with a primary loop of the nuclear power plant, said overpressure line having an overpressure valve being closed during normal operation. 15. The system according to claim 1, including an overpressure line through which the interior of said filter communicates with the interior of the containment, said overpressure line having an overpressure valve being closed during normal operation.