Patent Number: 
Section: claims

1. A nuclear reactor comprising:a pressure vessel having an interior sidewall:a core barrel disposed within the pressure vessel for circumferentially surrounding a nuclear core, the core barrel and the pressure vessel sidewall defining a downcomer region; anda plurality of circumferentially spaced apart neutron panels disposed in the downcomer region, each panel having a concave surface facing the core barrel and a convex surface facing the pressure vessel sidewall, with each panel having a variable thickness from a center to a side between the concave surface and the convex surface, wherein the thickness of the neutron panels varies in the circumferential direction and is greatest at the center and tapers to the sides. 2. The nuclear reactor of claim 1 wherein the thickness is approximately 3 inch, or 7.62 cm, in the center and tapers to approximately 1 inch, or 2.54 cm, on the side. 3. The nuclear reactor of claim 1 wherein the neutron panels are constructed of stainless steel. 4. The nuclear reactor of claim 1 wherein a top of the neutron panels is chamfered. 5. The nuclear reactor of claim 1 wherein the core barrel has a central axis that extends in a vertical direction and the neutron panels are constructed from a plurality of separate segments that are stacked vertically. 6. The nuclear reactor of claim 5 wherein each of the segments are rectangular having two longer sides with the longer sides extending in the vertical direction. 7. The nuclear reactor of claim 5 wherein each of the segments are approximately the same size. 8. The nuclear reactor of claim 5 wherein the number of segments is three. 9. The nuclear reactor of claim 5 wherein each of the segments is bolted to the core barrel. 10. The nuclear reactor of claim 5 wherein at least a portion of the concave surface of the neutron panel is spaced from an outside diameter of the core barrel by a standoff. 11. The nuclear reactor of claim 10 wherein the standoff is a washer. 12. The nuclear reactor of claim 5 wherein each neutron panel segment has a sloped opposing edge that inversely matches the slope on the opposing edge of the adjacent segment wherein the opposing adjacent edges are spaced from each other to permit reactor coolant to pass there between to cool the neutron panel segments. 13. The nuclear reactor of claim 1 wherein the neutron panels have grooves in the concave surface facing the core barrel that promotes cooling.