Nuclear reactor with flow guidance in the upper internals

A nuclear reactor having:

• a pressure resistant vessel;
• inlet pipes and outlet pipes all of which open substantially at a same horizontal level into said vessel, for delivery of a pressurized liquid coolant to said vessel and delivery of said coolant out of said vessel, respectively;
• a core consisting of fuel assemblies located vertically and side by side within said vessel at a horizontal level lower than said same horizontal level of said inlet and outlet pipes;
• and
• internals located within said vessel, having a barrel supporting the core and defining with said vessel a downward coolant path from the inlet pipes to a space under the core and having upper internals located above the core, including an upper extension of said barrel above the core, and defining an outlet flow path for said coolant flowing up out of the core towards said outlet pipes;
• wherein said upper internals further include:
• first water guides each carried by said upper extension and each formed with passage means opening radially outwardly into one of said inlet pipes and communicating it with said downward coolant path for directing the coolant flow which arrives through the inlet pipes of the vessel along said downward coolant path,
• second water guides each carried by said upper extension and each formed with passage means opening radially outwardly into a respective one of said outlet pipes and opening upwardly, and
• dividing wall means consisting of a plurality of sections each connecting two successive ones of said first and second water guides and separating an annular space defined by said barrel and said extension into a lower volume in communication with said coolant downward path, into which the passage means of said first water guides open, and an upper volume into which said second water guides open,
• and wherein said extension of said barrel defines additional passage means opening into said upper volume, whereby the flow lines of said coolant in said outlet flow path are successively vertical and bent into a radially outward direction into said second volumes through said passage means.

A nuclear reactor having:

• a pressure resistant vessel;
• inlet pipes and outlet pipes all of which open substantially at a same horizontal level into said vessel, for delivery of a pressurized liquid coolant to said vessel and delivery of said coolant out of said vessel, respectively;
• a core consisting of fuel assemblies located vertically and side by side within said vessel at a horizontal level lower than said same horizontal level of said inlet and outlet pipes;
• and
• internals located within said vessel, having a barrel supporting the core and defining with said vessel a downward coolant path from the inlet pipes to a space under the core and having upper internals located above the core including an upper extension of said barrel above the core, and defining an outlet flow path for said coolant flowing up out of the core;
• wherein said upper internals further comprise a support plate supporting cluster guides receiving coolant flowing out of said core,
• wherein said upper extension comprises a radially outer shroud in water-tight contact with said vessel about said inlet pipes and outlet pipes and formed with coolant inlet and outlet openings respectively aligned with the inlet and outlet pipes and a radially inner shroud defining a coolant collection space for the coolant flowing out of the core with said cluster guide support plate, said radially inner shroud terminating upwardly at a distance from said support plate, and
• wherein said upper internals further comprise dividing wall means connecting said radially inner shroud and said radially outer shroud and consisting of first circumferential sections situated at a level higher than the inlet and outlet pipes, second circumferential sections situated at a level lower than said inlet and outlet pipes and sections connecting said circumferential sections and fractionating an annular space between said inner shroud and outer shroud into angularly distributed first volumes and second volumes alternating around a vertical axis of said vessel, said connecting sections being so located that said first volumes are in communication with said inlet pipes and said downward cooling path while said second volumes are in communication with said outlet pipes, whereby said outlet flow path impresses flow lines to said coolant which successively are upwardly directed, radially between said support plate and inner shroud and downwardly between the inner shroud and outer shroud.