PWR that enables steam generator secondary fluid to flow into primary circuit and reactor vessel during a core melt

A pressurised water nuclear reactor, the reactor comprising:

• a reactor vessel accommodating a reactor core, the vessel comprising an inlet and an outlet,
• a primary circuit in which a water-based primary fluid is able to circulate,
• wherein the primary circuit comprises a first end connected to the inlet of the reactor vessel,
• wherein the primary circuit comprises a second end connected to the outlet of the reactor vessel,
• wherein primary fluid circulating in the primary circuit is able to flow into the reactor vessel through the inlet and flow out of the reactor vessel through the outlet after passing through the reactor core in order to extract heat produced by the reactor core,
• a secondary circuit in which a water-based secondary fluid is able to circulate,
• wherein the secondary circuit is fluidly isolated from the primary circuit, wherein the secondary circuit comprises a steam generator,
• wherein the secondary circuit is configured to absorb heat of the primary circuit and transform at least part of the heat into steam in the steam generator, and
• a safety system,
• wherein the safety system comprises a passage between the secondary circuit and the primary circuit,
• wherein the safety system comprises a safety device configured to control fluid flow in the passage,
• wherein the safety device is configured to place secondary fluid present in the steam generator in fluidic communication with the primary circuit, so that secondary fluid from the steam generator can flow through the passage, into the primary circuit, and then into the reactor vessel,
• wherein the inlet has a cross sectional area (Sinlet), the passage has a minimum cross sectional area (Streach), and Streach<0.05*Sinlet.