Mitsubishi Nuclear Fuel Co., Ltd.

Katsunori Ohuchi

Masashi Yoshida

Junichi Oyama

Taichi Koiwai

Akio Sando

Nobuo Miwa

Shuji Yamazaki

Akihiro Kato

Toshiyuki Kawagoe

Hitoshi Inada

Shunji Ono

A method of assembling a fuel assembly is presented so as to reduce radiation exposure to the assembly workers and to simplify the assembly procedure. Sleeves are pre-attached to an upper nozzle, and the guide pipes are inserted into respective grid cells through the sleeves of the upper nozzle and through the sleeves of the grids. The guide pipes are fixed in place to the sleeves of the upper nozzle and of the grids by bulging. There is no welding step necessary to join any of the assembly components while the assembly is in a semi-assembled condition. Therefore, the method is simple and efficient, and reduces the risk of radiation exposure to the assembly workers.

Method for assembling fuel assembly

An apparatus is presented for removing the keys smoothly and reliably from support grids of a fuel assembly. The apparatus performs the task of removing the keys, which had been inserted into the grid through the opening sections of the grid, and enables mechanization and automation of the key removal operation. The apparatus has a robotic arm including a pair of parallel grid support members freely movably disposed at the end of the robotic arm for clamping onto the side edges of the grid. The apparatus further includes a key rotation device disposed on the support arm for engaging with and rotating the keys; a key moving device disposed on the grid support members so as to hold the keys and move the keys in the direction of the key axis.

Apparatus for removing keys from support grid

An apparatus is presented for removing the inner and outer keys from a support grid of a fuel assembly automatically or by mechanical methods. The apparatus removes a line of keys from a loaded assembly inserted into a grid through an opening section of the grid to deflect the springs. Both ends of the keys are engaged with the engaging members, and one set of keys are rotated in one direction while the other set of keys are rotated in the opposite direction. The springs are then released to press on the fuel rods firmly in place between the springs and the dimples in the grid cell. The keys are removed from the grid by clamping or holding the keys and moving the keys together with the clamping/holding device in the key axis direction by operating the driving device until the keys are removed completely from the grid.

The present invention presents an apparatus to facilitate the loading of specific fuel rods into the specific grid cells of the grids of a fuel assembly. The loading apparatus utilizes air-pressure operated loading cylinders to push out the specific fuel rods from a fuel rod magazine into the corresponding grid cells. The loading apparatus operates in conjunction with a series of fuel rod support rollers which provide support to the fuel rods, being charged into the grids, from the underside of the fuel rods to prevent sagging of the tip end, thus avoiding scraping against the straps of the grids when entering the grid cells, and causing potentially harmful surface scratches on the fuel rods.

Apparatus for assembling nuclear fuel assembly

There are disclosed an assembling apparatus and an assembling method of a nuclear fuel assembly by which flaws or scratches to be formed on the surfaces of the fuel rods can be reduced. The fuel rods are inserted into the grid cells of the supporting grids under the state where the supporting grids are disposed in proximity to each other. Therefore, it is possible to remarkably reduce the fall-down movement of the tip portion of the fuel rod. Conventionally, the tip portion or lower surface of the fuel rod inevitably comes in contact with the grid cell of the supporting grid, so that the scratches might be formed on the surface of the fuel rod, which deteriorates the quality of the fuel assembly. However, according to the present method and apparatus, it is possible to avoid the interference between them so that the scratches to be formed on the surface of the fuel rods can be reduced remarkably.

Method for assembling nuclear fuel assembly and apparatus therefor

An apparatus for attaching a key member to a nuclear fuel assembly grid and detaching the same therefrom is disclosed. The apparatus includes a supply and recovery mechanism, an inserting and removing mechanism, and a rotating mechanism. The supply and recovery mechanism operates to supply the key member to a prescribed position adjacent to the grid and recover the same. The inserting and removing mechanism is disposed between the supply and recovery mechanism and the grid, and operates to insert the key member supplied from the supply and recovery mechanism into the grid and remove the key member from the grid to recover the same to the supply and recovery mechanism. The rotating mechanism is disposed adjacent to the inserting and removing mechanism, and operates to rotate the key member inserted in the grid in a prescribed direction about the longitudinal axis to attach the same to the grid and rotate the same in a direction opposite to the prescribed direction to detach the same from the grid.

Apparatus for attaching key member to nuclear fuel assembly grid and

An apparatus for assembling a nuclear fuel assembly is disclosed. The apparatus includes a deflecting device which is disposed adjacent to the grid and deflects grid springs away from dimples opposing thereto. The deflecting device includes a tubular member, a rod member and a drive mechanism. The tubular member has a plurality of circumferentially divided sleeve pieces. The rod member is releasably inserted in the tubular member for sliding movement therealong. The drive mechanism is drivingly connected to the rod member and moves the rod member in the tubular member in a longitudinal direction thereof to bring the rod member into urging engagement with the sleeve pieces of the tubular member, whereby the sleeve pieces are deflected to be urged against the spring to deflect the same.

The present invention relates to a pull-in rod type loader for loading fuel rods efficiently and conveniently from a fuel rod magazine to a fuel assembly. The control rod pipes and fuel rods are held in assigned grid cells, respectively termed pipe-cells and fuel-rod-cells, in each quadrant section of a grid. The control rod pipes are disposed in a quadrant so that the locations of the pipe-cells assigned for the guide pipes in one quadrant are symmetrical with respect to a central rotational axis of the apparatus. The grid cells and the pull-in loader are both aligned with respect to a central rotational axis. To load the fuel rods into the fuel assembly, only the pull-in rods need to be operated for every 90 degree rotation of the loader about the central axis, because the locations of the pull-in rods correspond exactly with the grid cells assigned to hold fuel rods. This type of loader does not require complex switching devices required in the conventional pull-in rod type of loaders, and the assembling operation can be carried out efficiently and quickly.

Assembling apparatus for nuclear fuel assembly

The present invention is made to provide an assembling machine for nuclear fuel assembly, having a simple mechanical construction, in which the time required for inserting the fuel rod can be reduced. In the prior-art machine, the pull-in rod and its drive mechanism and the like are required to perform the operation for inserting the fuel rod into the supporting grid, thus, the mechanical construction must be complicated. Further, a relatively long time must be required to perform the operation for holding the fuel rod by the pull-in rod, which makes the whole working hours longer. In the machine according to the present invention, a drive mechanism is provided to drive a stopper, by which the regulation of the stopper for regulating the fall-down movement of the fuel rod can be released with ease. Thus, the fuel rod is fallen down by its own weight, so that the fuel rod can be inserted into the grid cell of the supporting grid which is supported by the supporting post. Therefore, the machine construction can be simplified, and it is not necessary to perform the prior-art operation for holding the fuel rod by the pull-in rod, so that the time required for performing the inserting operation of the fuel rod can be reduced.

Assembling machine for nuclear fuel assembly

The present invention presents a method and an apparatus for assembling a fuel assembly which is free of surface damage on the fuel rod surfaces, and of distortions caused by residual stresses. Such problems are introduced by the method of inserting the fuel rods into the grids, and the sequence of attaching the control rod guiding pipes. In the conventional method, the guiding pipes are attached to the respective grids first and the fuel rods are inserted in the grids while the holding mechanisms (such as spring force against a dimple formed on the grid wall) are active. In the invented assembling method, the sprigs are deactivated first and then the fuel rods are inserted into the grids. Once the assembly is made firm with all the fuel rods in place and fixed firmly to the grids, the control rod guiding pipes are inserted into the grids and the pipes are fixed rigidly to the respective grids. By performing the assembling operation in the above sequence, slight shifting of the grids which occurs on fixing the pipes to the grids, during the conventional method, is prevented. The final assembly produced according to the invented method is free of surface damage and the overall quality of alignment of the assembly is excellent.

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Ibaraki, Japan

Katsunori Ohuchi