Hitachi-Ge Nuclear Energy, Ltd.

Hitachi, Ltd.

Toshihiro Kodama

Hirokazu Akatsuka

Takahiro Tsuchiya

Kiyoshi Harada

Yuuichi Matsushita

Yoshimi Ishii

Noriaki Mase

Isao Kouga

Takeaki Suzuki

Noriaki Hattori

Kiyokazu Hosoya

Takahiro Konno

A control rod drive mechanism includes an outer tube and a guide tube which is arranged in the outer tube and is held by the outer tube. Furthermore, the control rod drive mechanism includes a spool piece with an inner magnet coupling and a rotary shaft connected to the inner magnet coupling arranged internally. The lower end portion of the outer tube is supported by the spool piece in the spool piece. The outside diameter of the outer tube, through the length of the outer tube, is smaller than the inside diameter of the spool piece and the outer tube, in the radial direction of the outer tube, is not projected outside the inner surface of the spool piece. Therefore, the installation places of the O-rings which are a seal member are reduced and the time required for maintenance of the control rod drive mechanism can be shortened.

Control rod drive mechanism

A control rod drive mechanism includes an outer tube, a guide tube disposed inside the outer tube, a ball tube, a hollow piston, and an electric motor. A gap between a ball traveling side of the screw shaft and the traveling balls and a gap between the traveling balls and a ball traveling side of the ball nut, having the gap coefficient (A) is given by: A=((2&#xd7;R&#x2212;L)&#x2212;D)&#xf7;(2&#xd7;R&#x2212;L). The diameter of the traveling balls is determined to satisfy the expression given by A, in which A has the value of more than 0.03 and less than 0.17.

Gap expanding method of ball screw and fine motion control rod drive mechanism incorporating gap expanded ball screw

It is an object of the present invention to provide a gap expanding method of a ball screw for preventing an increase in torque relative to an electric motor due to a protruding bulge caused by generation of a scar on the traveling side of the screw shaft of the ball screw, and to provide a control rod drive mechanism incorporating the gap expanded ball screw. In a ball screw disposed in a control rod drive mechanism, the ball screw has a screw shaft and a ball nut engaged with the screw shaft via travelling balls, and the balls are each configured to have a diameter smaller than that of the existing ball, thereby expanding a gap between a ball traveling side of the screw shaft and the ball and a gap between the ball and a ball traveling side of the ball nut.

A fine motion control rod drive mechanism handling apparatus attaches a fine motion control rod drive mechanism having a control rod drive mechanism body, a spool piece, a motor bracket and a motor unit to a reactor pressure vessel, and detaches it from the reactor pressure vessel. The fine motion control rod drive mechanism handling apparatus is provided with a bolt wrench assembly, a motor unit attachment mounted to the bolt wrench assembly, for meshing a first gear of a first gear coupling on a spool piece side with a second gear of a second gear coupling on a motor unit side, and a rotation mechanism mounted to the bolt wrench assembly, for rotating the motor unit attachment.

Fine motion control rod drive mechanism handling apparatus and method of handling fine motion control rod drive mechanism

A control rod grasped by a hook of a grasping equipment is moved down and is positioned at an upper end of a hollow piston of a control rod drive mechanism (CRD) in a state that the control rod is fully withdrawn from a core. Furthermore, the hook is inserted into an opening of a handle of the control rod. The hook is lifted up so as to make contact with the handle. The control rod grasped by the grasping equipment is rotated by a grasping equipment rotation apparatus. A state that gaps formed between joint convexities in a coupling socket of the control rod are positioned right above coupling spud convexities of the hollow piston occurs. At this time, the control rod falls by its own weight and the coupling spud convexities pass through the gaps. A grasping equipment movement apparatus suppresses the falling speed of the control rod. The control rod is rotated at 90&#xb0; and the control rod and CRD are connected. The time required for connecting the control rod and the hollow piston of the control rod drive mechanism can be shortened even further.

Method of handling control rod and control rod handling apparatus

A control rod handling apparatus and method for exchanging a control rod connected to a control rod drive mechanism by a bayonet coupling. The control rod handling apparatus comprises a member or connection to a fuel exchange apparatus, a fixing part having guides to be seated at the top face of an upper grid plate in a reactor vessel and to e supported by the upper rid plate, a body provided at the lower part of the fixing part, a control rod handling part having a control rod grasping instrument provided at the bottom part of the body, a fuel support piece handling part having a fuel support piece grasping instrument and means for positioning the fuel support piece grasping instrument, which is provided outside the control rod handling part, means for vertically moving the fuel support piece handling part along with the outside of the control rod handling part, and means for rotating the control rod handling part, the fuel support piece handling part, and the means for vertical motion.

Apparatus and a method for handling a control rod

An apparatus for handling a control rod driving mechanism (CRD) of a nuclear reactor. The apparatus has a turn carriage provided in a space within a reactor container where a pedestal is provided, and is adapted to turn on a rail provided on the inner peripheral wall of the container. The turn carriage carries a truck adapted to run along a rail on the turn carriage. A mast is provided on the truck and is driven by a mast driving means between an upright position and a horizontal position. The mast is designed for accommodating a CRD cart. The apparatus also has a CRD mounting/demounting means secured to the mast and adapted to be moved up and down by the CRD cart such as to mount and demount the CRD in and from a CRD housing.

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Hitachi, Japan

Toshihiro Kodama