A VVER-1000 nuclear fuel assembly having a modified bottom nozzle with chamfers at the upper edge of the frustoconical transition from a hexagonal upper section of the nozzle to the lower circular end that mounts on a lower core support.

A flow distribution device (3) for a reactor, a lower internals (100) of a reactor and a reactor are provided. The lower internals (100) includes: a lower core support plate (2) defining a coolant hole therethrough; a flow distribution device (3) mounted on the lower core support plate (2) and including a distribution annular plate (8) and a distribution bottom plate (9); a vortex suppression plate (7) disposed below the distribution bottom plate (9); a support column (4) defining an upper end connected with the lower core support plate (2) and a lower end passing through the distribution bottom plate (9) to connect with the vortex suppression plate (7); an energy absorption device (5) defining an upper end connected with the vortex suppression plate (7); and an anti-break bottom plate (6) disposed on the lower end of the energy absorption device (5).

A fuel assembly includes full length fuel rods which contain a plutonium fissile (Puf) but do not contain a burnable poison, full length fuel rods which contain the fissile uranium and the burnable poison, and partial length fuel rods which contain Puf but do not contain the burnable poison in a channel box. The plutonium enrichment is decreased in an order of the full length fuel rods. The concentration of the burnable poison of the full length fuel rod is higher than the concentration of the full length fuel rod. In each side of a rectangular outermost periphery adjacent to the inner surface of the channel box in a horizontal cross-sectional view of the fuel assembly, two partial length fuel rods are adjacently disposed, and the full length fuel rod containing the burnable poison is disposed to be adjacent to each partial length fuel rod.

It is possible to achieve self-support of the fuel assembly without an upper grid plate when the fuel assembly is mounted or replaced, and it is also possible to prevent the fuel assembly from floating during a reactor operation. According to the present invention, the lower portion of the lower tie plate 7 as a part of the fuel assembly 3, which is inserted into the fuel support 9, extends, and a stable member 21 is provided around the extension portion 20, and thereby it is possible to achieve the self-support of the fuel assembly without the upper grid plate. In addition, since an increase in a weight due to extension of the lower portion of the lower tie plate 7 can prevent the floating during the reactor operation, a floating preventing mechanism using the upper grid plate is not necessary. Hence, it is possible to achieve the self-support of the fuel assembly without an upper grid plate when the fuel assembly is mounted or replaced, and it is also possible to prevent the fuel assembly from floating during the reactor operation.

It is possible to achieve self-support of the fuel assembly without an upper grid plate when the fuel assembly is mounted or replaced, and it is also possible to prevent the fuel assembly from floating during a reactor operation. According to the present invention, the lower portion of the lower tie plate 7 as a part of the fuel assembly 3, which is inserted into the fuel support 9, extends, and a stable member 21 is provided around the extension portion 20, and thereby it is possible to achieve the self-support of the fuel assembly without the upper grid plate. In addition, since an increase in a weight due to extension of the lower portion of the lower tie plate 7 can prevent the floating during the reactor operation, a floating preventing mechanism using the upper grid plate is not necessary. Hence, it is possible to achieve the self-support of the fuel assembly without an upper grid plate when the fuel assembly is mounted or replaced, and it is also possible to prevent the fuel assembly from floating during the reactor operation.

An improved retention system for retaining fuel rods in a fuel assembly is disclosed. The retention system includes a plurality of first engagement surfaces on the bottom nozzle of a fuel assembly. There is at least one engagement surface for each fuel rod. A second engagement surface is formed on the bottom end plug of each fuel rod. The first and second engagement surfaces are configured for engagement with each other for axially and laterally retaining each fuel rod within the fuel assembly. Debris deflectors may also be provided to deflect debris from coolant channels surrounding the fuel rods.

A nuclear reactor is designed to couple the load path of control elements with the reactor core, thus reducing opportunity for differential movement between the control elements and the reactor core. A core barrel can be fabricated in a manufacturing facility to include the reactor core, control element supports, and control element drive system. The core barrel can be mounted to a reactor vessel head. Movement, such as through seismic forces, transmits an equal direction and magnitude to the control elements and the reactor core, thus inhibiting the opportunity for differential movement.

A mounting assembly that has no threaded connections. A rod with pins or machined features radially extending from a distal end is configured to rotate until the pins align with grooves in a hole through a base plate. The rod is inserted through the hole until the pins are through an opposite surface of the base plate, compressing spring components on the rod. Then the rod is rotated until the pins are aligned with slots that partially extend through the second side of the base plate and the pins become seated in the slots. To remove the rod a tool that engages an articulated feature on the distal end of the rod is installed. The tool rotates the rod until the pins are disengaged from the slots, aligned with the through grooves and passed through the base plate.

A nuclear fuel assembly having lateral support provided by a bimetallic spring that extends from a side of the fuel assembly under certain core conditions to pressure against an adjacent component and withdraws under other core conditions, such as shutdown, to enable the nuclear fuel assembly to be aligned or withdrawn from the core and repositioned.

A nuclear fuel assembly having lateral support provided by a bimetallic spring that extends from a side of the fuel assembly under certain core conditions to pressure against an adjacent component and withdraws under other core conditions, such as shutdown, to enable the nuclear fuel assembly to be aligned or withdrawn from the core and repositioned.