Nuclear reactor comprising a reactor lid and an additional inner lid

A liquid-metal-cooled nuclear reactor, comprising:

• a main vessel containing a primary fluid, said primary fluid being a liquid metal or alloy;
• a cylindrical separation structure extending vertically within the main vessel, separating a hot leg from a cold leg, the cold leg encompassing the hot leg;
• at least one opening provided in the cylindrical separation structure to enable the primary fluid to flow from the cold leg to the hot leg;
• a core submerged in the hot leg for heating the primary fluid;
• at least one heat exchanger having an inlet from the hot leg and an outlet to the cold leg for transferring heat from the primary fluid to a secondary fluid of an externally connecting circuit;
• at least one primary fluid circulation pump for circulating the primary fluid in the main vessel, wherein the at least one primary fluid circulation pump establishes a fluid level of the primary fluid in the hot leg lower than a fluid level of the primary fluid in the cold leg;
• and
• a reactor lid covering the main vessel;
• a gas plenum disposed beneath the reactor lid and above the hot leg;
• and
• an inner lid disposed beneath the reactor lid, wherein the inner lid covers the cold leg,
• wherein the hot leg is open ended towards the gas plenum.