A multi jack tensioner including: a body portion formed to engage an elongate fastening member or integrally formed therewith; a load bearing member for applying force to a workpiece to be fastened and arranged for location about said fastening member adjacent the body portion; a pressure chamber between the load bearing member and the body portion arranged to displace the body portion from the load bearing member in response to hydraulic pressure; and a plurality of jack bolts extending between the body portion and the load bearing member for further displacing the body portion from the load bearing member; wherein application of hydraulic pressure to the hydraulic chamber displaces the body portion from the load bearing member for tensioning said fastening member and whereby subsequent tensioning of the fastening member is applied by operation of the jack bolts.

A method for decommissioning a heavy water reactor facility includes: removing the plurality of guide tubes from a plurality of through-holes; installing a plurality of shielding stoppers in the plurality of through-holes; removing the shielding stopper installed in one through-hole of the plurality of through-holes, and inserting a cutting device into a lower portion of the reactivity mechanism deck through the one through-hole to cut a connection portion between the reactivity mechanism deck and the calandria vault by using the cutting device; and separating the reactivity mechanism deck from the calandria vault.

A jet pump plug and methods of forming a seal with a plurality of nozzles of a jet pump are disclosed. The plug has a plug body and a washer embedded within and bonded to the plug body. The washer has a center opening that cooperates with the plug body to define a central bore extending through the plug and the central bore can be configured to receive a fastener. A plurality of the disclosed plugs can be positioned in alignment with a respective nozzle, with each plug being sealed to the respective nozzle to form a seal.

The main purpose of the invention is a mitigation assembly (40) for a nuclear reactor comprising a box (41) with an upper portion (41) forming the head of the assembly housing an upper neutron shielding (UNS) device, comprising a head (105) comprising removable locking means (100) and a slug (101) installed free to move in translation relative over a given travel distance, the locking means (100) being configured such that locking/unlocking between the head (105) and the box (41) can be made by displacement of the slug (101) by means of an extraction grab with its pawls attached in the slug (101), characterised in that the lower part of the upper neutron shielding device comprises a cone-shaped sealing block (107) with the tip of the cone oriented downwards, cooperating with a cone-shaped internal surface (108) of the box (41), a sealing device (109) being formed between the two, the assembly created forming a removable sealing plug (110).

The main purpose of the invention is a mitigation assembly (40) for a nuclear reactor comprising a box (41) with an upper portion (41) forming the head of the assembly housing an upper neutron shielding (UNS) device, comprising a head (105) comprising removable locking means (100) and a slug (101) installed free to move in translation relative over a given travel distance, the locking means (100) being configured such that locking/unlocking between the head (105) and the box (41) can be made by displacement of the slug (101) by means of an extraction grab with its pawls attached in the slug (101), characterised in that the lower part of the upper neutron shielding device comprises a cone-shaped sealing block (107) with the tip of the cone oriented downwards, cooperating with a cone-shaped internal surface (108) of the box (41), a sealing device (109) being formed between the two, the assembly created forming a removable sealing plug (110).

A nozzle repair method and a nuclear reactor vessel include: removing a trepanning portion (208) as a connection portion with respect to an in-core instrumentation cylinder (204) in a groove-welding portion (206); removing the in-core instrumentation cylinder (204) from a lower end plate (66); forming a plug attachment opening (211) by removing the groove-welding portion (206); applying a pressing load to the lower end plate (66) by attaching a plug (212) to the plug attachment opening (211); and welding and fixing the plug (212) attached to the plug attachment opening (211). Accordingly, since a repair is easily performed, it is possible to improve the workability and to decrease a repair cost.

A bolt installation and removal (BIR) system is used for assembling and disassembling a nuclear vessel. The BIR system includes a platform with a stand for supporting the nuclear vessel. A track extends around an outside perimeter of the platform and multiple tool carts include wheels that roll on the track. Tool towers are located on the carts and include tool assemblies configured to install and remove bolts on the nuclear reactor vessel. Magazine towers also extend up from the tool carts next to the tool towers and include magazines that hold bolts for exchanging with the tool assemblies. Drive mechanisms move tool heads in the tool assemblies around a first vertical axis, vertically up and down, and laterally to more simply and reliably install and remove the bolts in a radioactive underwater environment.

A nuclear reactor is provided that includes a vessel; a core provided in the vessel; at least one plate heat exchanger provided in the vessel, with at least one duct for supplying a secondary fluid to the heat exchanger and a duct for discharging the secondary fluid from the heat exchanger, the discharge duct extending through the vessel. The nuclear reactor comprises a device for attaching the heat exchanger to an area of the vessel through which the discharge duct extends.

A system, method and apparatus for remotely installing a flange cover assembly on a fuel transfer tube fixed flange in a containment pit in a nuclear power plant is presented. In one example, the flange cover assembly includes J-bolt spring assemblies in which the feet of the J-bolt are rotated between a clamping and non-clamping orientation to engage with the rear face of the fixed flange. A tool frame is lowered into the containment pit to engage with the flange cover assembly to compress the J-bolt springs and extend the J-bolt foot toward and away from the flange cover. Dual acting cylinders move a spring compression frame on the frame tool to compress and relax the J-bolt spring assemblies.