Containment internal passive heat removal system

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, and
• a 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, and
• x is the mean mass steam quality of the two-phase mixture in the riser section.