Patent Number: 048428132
Section: claims

1. Nuclear reactor comprising: (a) a pressure resistant vessel for containment of a pressurized coolant,  (b) a removable cover for said vessel,  (c) coolant outlet nozzle means provided through said vessel in close proximity of said cover,  (d) a core located in said vessel arranged to be upwardly traversed by said coolant in operation and having a plurality of mutually adjacent fuel assemblies each having an upper end piece,  (e) a plurality of clusters of control elements, each having an upwardly expending drive shaft and each vertically movable into and out of said core by said drive shaft,  (f) upper internal equipments located in said vessel between said core and said cover, having:  wherein the upper internal equipments further comprise passage means for directing some of said coolant, introduced through said inlet nozzle means, above the plenum chamber and said guiding tubes for downwardly supplying a downward flow of coolant through said guiding tubes, whereby the pressure of the coolant in the guiding tubes and the cluster guides is higher than the pressure of the coolant flowing out of the core due to differential head losses.  (a) a pressure vessel for containment of pressurized water,  (b) a removable cover for said vessel,  (c) water outlet nozzle means opening through said vessel in close proximity to said cover to flow said pressurized water out of said vessel and water inlet nozzle means opening through said vessel at the same horizontal level as said water outlet nozzle means,  (d) a core located in said vessel and having a plurality of mutually adjacent upstanding fuel assemblies supported by a lower core plate, each of said fuel assemblies having an upper end piece arranged to laterally deflect a pressurized water flow which has been admitted into said fuel assembly through said lower core plate and has upwardly traversed said fuel assembly,  (e) a plurality of clusters of control elements, each cluster being vertically downwardly movable into a respective one of said fuel assemblies and upwardly out of said respective one of said fuel assemblies by a drive shaft projecting upwardly through the cover,  (f) internal equipments located in said vessel and supported by said vessel, having  (fa) a cylindrical external barrel radially spaced from said vessel, cooperating with said vessel to define an annular downward water flow path from said water inlet nozzle means to a space under said lower core supporting plate, and  (fb) flow separating means located above said core for collecting the water flowing out of said core and comprising:  a water volume defined by said cover and by a top part of the internal equipments, and vertical passage means by-passing the core, and communicating the water inlet nozzle means with the water volume,  whereby a water pressure prevails in said volume which is higher than the pressure of the water exiting the core. 2. Nuclear reactor according to claim 1 further comprising a cylindrical external barrel located within the vessel and spaced from an inner surface of said vessel, said barrel containing the core, the separating device and the plenum chamber, and being arranged to direct a major part of the coolant introduced into the vessel through coolant inlet nozzle means into a space under the core, 3. Nuclear reactor according to claim 2, wherein the cluster guides comprise, for each cluster of control elements, guiding transversal perforated plates disposed at a plurality of levels, some of said plates being held in radial abutment against the spacer tubes of said separating means. 4. Nuclear reactor according to claim 3, wherein the spacer tubes are vertical and distributed at nodal points of a hexagonal network therefore defining vertical spaces having a substantially hexagonal cross-section between each group of six adjacent ones of said spacer tubes, and wherein each of said vertical spaces contains one of said cluster guides and has a axis coinciding with the axis of said cluster guide, the transversal perforated plates thereof being held in radial abutment against each of the six spacer tubes defining said space. 5. Nuclear reactor according to claim 1, wherein the separating means form the lower part of the upper internal equipments and wherein said upper internal equipments are maintained inside the vessel by static clamping between the cover and the vessel. 6. Nuclear reactor according to claim 1, wherein the second holes comprise first connecting means for slidably connecting the lower plate to a respective one of said upper end pieces of fuel assemblies and second connecting means for connecting the corresponding cluster guide of said fuel assemblies to said lower plate. 7. Nuclear reactor according to claim 1, further comprising water coolant injection means including at least one pipe whose outlet is located in proximity of the lower part of the separating means and a medium pressure safety injection pump connected to said pipe. 8. Nuclear reactor comprising: 9. Nuclear reactor according to claim 8, further comprising: