Patent Number: 
Section: claims

1. A pressurized water reactor containment internal passive heat removal system with at least one cooling water circulation circuit, comprising:a heat exchanger located inside the containment and comprising an upper header and a lower header interconnected by heat-exchange tubes,a riser pipeline and a downtake pipeline connected to the heat exchanger,a cooling water supply tank located above the heat exchanger outside the containment and connected to the downtake pipeline, anda steam relief valve connected to the riser pipeline, located in the water supply tank and connected to the same hydraulically, wherein the heat exchanger is divided into heat exchanger sections each having an upper header section and a lower header section, each of the upper header sections and the lower header sections satisfying the relationship:L/D≤20,where L is the length of the respective upper or lower header section,D is the header bore of the respective upper or lower header section;wherein the riser pipeline is configured so that the riser section height hrs is no less than:hrs=(ΔPcres−Δρheghhe)/Δρrsg, ΔPcres=Δρrsghrs+Δρheghhe,where Pcres is the circuit total hydraulic resistance,hhe is the heat exchanger height,g is the gravity factor,Δρrs=ρcw−(ρ′(1−x)+ρ″x)Δρhe=ρcw−ρhw ρcw is the downtake pipeline water density,ρhw is the riser pipeline water density within the heat exchanger height range,ρ′,ρ″ are the water and steam saturation density, andx is the mean mass steam quality of the two-phase mixture in the riser section. 2. A system according to claim 1, wherein at least a part of the riser pipeline from the upper headers of the heat exchanger sections to the steam relief valve is inclined upwards from horizontal at an angle of at least 10°. 3. A system according to claim 2, wherein the riser pipeline includes sections with an inclination angle of less than 10° in relation to horizontal, the length of such sections is Lsec1 and the bore is Dsec1 meeting the following criterion:Lsec1/Dsec1≤10. 4. A system according to claim 1, wherein at least a part of the downtake pipeline has a downward inclination to an angle of at least 10° in relation to horizontal. 5. A system according to claim 4, wherein the downtake pipeline includes sections with an inclination angle of less than 10° in relation to horizontal, the length of such sections is Lsec2 and the bore is Dsec2 meeting the following criterion:Lsec2/Dsec2≤10. 6. A system according to claim 1, wherein the heat-exchange tubes have a height allowing to meet the criteria of turbulent convection on the heat exchanger outer surface, namely:Ra>4·1012,where            R      a        =                                        gl            3                    ⁢                      S            c                                    ν          2                    ·                                    ρ            w                    -                      ρ            c                                    ρ          c                      ,Ra is the Rayleigh criterion,g is the gravity factor,l is the heat exchanger tube height,ν is the steam-air kinematic viscosity coefficient,ρw is the steam-air medium density on the outer wall of the heat exchanger tubing,ρc is the steam-water medium density in the containment,      S    c    =      ν          D      dif      is the Schmidt number, andDdif is the steam diffusion factor. 7. A system according to claim 1, wherein the heat exchanger section has a single-row vertical bundle.