Nuclear reactor pressure vessel

In a nuclear reactor system including structure defining a containment space, said structure including a structure floor at a topographical grade level, and a nuclear reactor core, a pressure vessel for housing said reactor core therein, said pressure vessel comprising,

• a metallic structured inner liner part, said inner liner part having a top region of reduced width relative to that of an inner liner lower major body part, said top region demarked in upward termination thereof by an inner liner part head, said inner liner part having an encircling compass and defining a fully enclosed space, said reactor core being situate in said enclosed space at a lower region therein adjacent a bottom boundary of said inner liner part,
• a pre-stressed concrete outer vessel part encasing said inner liner part in following contour therewith from the bottom boundary thereof upwardly to a location proximal merger of the inner liner part reduced width region with its relatively widened remainder structure,
• a concrete cover received on top of said outer vessel part, said cover having a central opening for upward pass through of the inner liner part reduced width top region but with a surface of the cover defining the opening in abutment with an external surface of said top region, the cover, the concrete outer vessel and the inner liner lower body major part being disposed below the grade level in an earth fill, and
• a circulation shroud in the pressure vessel located about the reactor core spaced therefrom and extending upwardly therefrom to a location proximal but below a normal level of a steam generating pool of water present in the vessel, the reactor core being squat comparative to a height of the pool whereby natural circulation of heated water in the pool is promoted in a convective flow path defined by the space between the shroud and the reactor core, upwardly towards a surface of the pool and then downwardly at the exterior side of the shroud to a shroud space reentry location defined by shroud openings adjacent a lower reach of the reactor core.