A reactor pressure vessel comprising: a reactor pressure vessel cylindrical wall portion; a lower head closing off a bottom of the cylindrical wall portion; a core barrel substantially coaxially disposed within the cylindrical wall portion and defining a coolant downcomer annulus between the core barrel and the cylindrical wall portion; a lower core support plate capping a bottom of the core barrel; and a cylindrical flow skirt disposed below the lower core support plate in the lower head, the cylindrical flow skirt having a vertical wall with a plurality of holes extending therethrough and an upper edge being proximate the lower core support plate, the cylindrical flow skirt being supported on the lower head from circumferentially spaced support locations, the reactor pressure vessel being adapted such that a majority of coolant flow entering the reactor pressure vessel and travelling down the annulus passes through the holes in the vertical wall of the cylindrical flow skirt before passing through the lower core support plate, wherein a portion is directed upward and directly through the lower core support plate, while a second portion is directed to the lower portion of a plenum underneath a vortice suppression plate where this portion of the coolant turns upward through the holes in the vortice suppression plate to the lower core support plate, characterized in that said support locations are diametrically symmetrical and evenly spaced so that a circumferential distance between at least some of the support locations is different than the circumferential distance between other of the support locations and so that the support locations do not align vertically with attachment positions of the core barrel to the interior of the reactor vessel wall. a reactor pressure vessel cylindrical wall portion; a lower head closing off a bottom of the cylindrical wall portion; a core barrel substantially coaxially disposed within the cylindrical wall portion and defining a coolant downcomer annulus between the core barrel and the cylindrical wall portion; a lower core support plate capping a bottom of the core barrel; and a cylindrical flow skirt disposed below the lower core support plate in the lower head, the cylindrical flow skirt having a vertical wall with a plurality of holes extending therethrough and an upper edge being proximate the lower core support plate, the cylindrical flow skirt being supported on the lower head from circumferentially spaced support locations, the reactor pressure vessel being adapted such that a majority of coolant flow entering the reactor pressure vessel and travelling down the annulus passes through the holes in the vertical wall of the cylindrical flow skirt before passing through the lower core support plate, wherein a portion is directed upward and directly through the lower core support plate, while a second portion is directed to the lower portion of a plenum underneath a vortice suppression plate where this portion of the coolant turns upward through the holes in the vortice suppression plate to the lower core support plate, characterized in that said support locations are diametrically symmetrical and evenly spaced so that a circumferential distance between at least some of the support locations is different than the circumferential distance between other of the support locations and so that the support locations do not align vertically with attachment positions of the core barrel to the interior of the reactor vessel wall.