Patent Number: 
Section: claims

1. A nuclear power plant, comprising:a containment vessel includinga reactor pressure vessel for receiving fissionable nuclear fuel,an aerosol pre filter stage,an aerosol filter stage,an iodine filter stage, anda pressure relief conduit through which a gas volume flow which is filtered in the aerosol filter stage and the iodine filter stage is releasable to ambient through a pass through opening in the containment vessel,wherein the iodine filter stage is arranged within the containment vessel,wherein the gas volume flows through aerosol pre filter stage, then the aerosol filter stage then the iodine filter stage before being released to the ambient through the pass through opening in the containment vessel,wherein the gas volume flows between and through the aerosol pre filter stage, the aerosol filter stage and the iodine filter stage in a horizontal direction, andwherein the aerosol filter stage and the iodine filter stage are connected with one another so that transferring the gas volume flow from the aerosol filter stage to the iodine filter stage is performed passively. 2. The nuclear power plant according to claim 1, wherein the aerosol filter stage and the iodine filter stage are arranged within a filter housing so that a combined aerosol-iodine filter unit is provided. 3. The nuclear power plant according to claim 2, wherein an outlet cross section of the aerosol filter stage is equal to an inlet cross section of the iodine filter stage. 4. The nuclear power plant according to claim 2,wherein a depth in a flow direction of the combined aerosol-iodine filter unit is between 1400 mm and 2000 mm, andwherein a height perpendicular to the flow direction of the combined aerosol-iodine filter unit is between 2500 mm and 2900 mm. 5. The nuclear power plant according to claim 1,wherein the iodine filter stage chemically adsorbs iodine or at least one organic iodine compound, andwherein the adsorbable iodine or the at least one organic iodine compound can be radio-active. 6. The nuclear power plant according to claim 5,wherein the iodine filter stage includes a zeolith material as an adsorbent, andwherein the zeolith material is hydrophobic. 7. The nuclear power plant according to claim 1, wherein an outlet surface of the aerosol filter stage has a distance from an inlet surface of the iodine filter stage of less than 260 mm. 8. The nuclear power plant according to claim 1, wherein a bed depth of the adsorbent is less than 80 mm. 9. The nuclear power plant according to claim 1,wherein the iodine filter stage chemically adsorbs iodine and at least one organic iodine compound, andwherein the adsorbable iodine and the at least one organic iodine compound can be radio-active. 10. The nuclear power plant according to claim 9, wherein the at least one organic compound is iodomethane. 11. The nuclear power plant according to claim 9, wherein there is no expansion valve between the aerosol filter stage and the iodine filter stage. 12. The nuclear power plant according to claim 1, wherein there is no expansion valve between the aerosol filter stage and the iodine filter stage. 13. The nuclear power plant according to claim 1, wherein beds for the iodine sorption material are formed by perforated vertical sheet metal plates so that the gas volume flows in the horizontal direction through perforations of the perforated vertical sheet metal plates. 14. The nuclear power plant according to claim 1, wherein a pressure difference between the aerosol filter stage and the iodine filter stage is below 200 mbar. 15. The nuclear power plant according to claim 1, wherein a dew point spread in the iodine filter stage is zero or negative. 16. A method for providing pressure relief for a containment vessel of a nuclear power plant, comprising the steps:running a gas volume flow initially through an aerosol pre filter stage, thereafter through an aerosol filter stage and subsequently through an iodine filter stage beforereleasing a filtered gas volume flow through a pressure release conduit to an ambient,wherein the aerosol filter stage and the iodine filter stage are arranged within the containment including a reactor pressure vessel,wherein the gas volume flows between and through the aerosol pre filter stage, the aerosol filter stage and the iodine filter stage in a horizontal direction, andwherein in that the gas volume flow is run from the aerosol filter stage into the iodine filter stage so that the gas volume flow remains substantially constant. 17. The method according to claim 16, wherein the gas volume flow is introduced from the aerosol filter stage directly into the iodine filter stage so that the iodine filter stage is continuously dried by a heat generated in the aerosol filter stage. 18. The method according to claim 16, wherein the aerosol filter stage and the iodine filter stage are connected with one another so that transferring the gas volume flow from the aerosol filter stage to the iodine filter stage is performed passively. 19. The method according to claim 16, wherein beds for the iodine sorption material are formed by perforated vertical sheet metal plates so that the gas volume flows in the horizontal direction through perforations of the perforated vertical sheet metal plates. 20. The method according to claim 16, wherein a pressure difference between the aerosol filter stage and the iodine filter stage is below 200 mbar.