Patent Number: 
Section: claims

1. A drive device for an in-core neutron instrumentation system, the drive device driving a neutron detector of the in-core neutron instrumentation system for measuring neutrons in a nuclear reactor, comprising:a winding drum for winding a cable having the neutron detector mounted at a tip end portion thereof;a drive motor for driving the winding drum for winding/extending the cable;a base member on which the winding drum and the drive motor are mounted;a cover member mounted on the base member and housing the winding drum and the drive motor therein; anda safety circuit provided between a power supply of the drive motor and the drive motor, and for switching between a conductive state in which power can be supplied to the drive motor and a cut-off state in which power cannot be supplied thereto depending on a mounted state of the cover member,wherein the cover member comprises a plurality of cover wall surface portions surrounding a periphery of the base member, and is equipped with a cover locking mechanism portion for defining an order of mounting the cover wall surface portions on the base member, and whereinthe safety circuit is provided on one of the plurality of cover wall surface portions, andthe cover locking mechanism portion is provided so that the one cover wall surface portion on which the safety circuit is provided is finally mounted in the order of mounting the plurality of cover wall surface portions on the base member. 2. The drive device for the in-core neutron instrumentation system according to claim 1, wherein the safety circuit is controlled to be in the conductive state in response to a state in which the cover member is mounted on the base member, and is controlled to be in the cut-off state in response to a state in which the cover member is not mounted on the base member. 3. The drive device for the in-core neutron instrumentation system according to claim 1, whereinthe cover member comprises a cover upper surface portion for covering an upper portion of a space surrounded by the plurality of cover wall surface portions,the cover wall surface portions and the cover upper surface portion are held by a frame which is fixed to the base member and provided in abutting regions between adjacent two of the cover wall surface portions and in abutting regions between the cover wall surface portions and the cover upper surface portion, andthe cover locking mechanism portion is mounted on the frame. 4. The drive device for the in-core neutron instrumentation system according to claim 1, whereinthe cover member comprises a cover upper surface portion for covering an upper portion of a space surrounded by the plurality of cover wall surface portions, andthe safety circuit is configured to include a series circuit which is brought into the conductive state in response to the whole cover member being mounted on the base member. 5. A drive device for an in-core neutron instrumentation system, the drive device driving a neutron detector of the in-core neutron instrumentation system for measuring neutrons in a nuclear reactor, comprising:a winding drum for winding a cable having the neutron detector mounted at a tip end portion thereof;a drive motor for driving the winding drum for winding/extending the cable;a base member on which the winding drum and the drive motor are mounted;a cover member mounted on the base member and housing the winding drum and the drive motor therein; anda safety circuit provided between a power supply of the drive motor and the drive motor, and for switching between a conductive state in which power can be supplied to the drive motor and a cut-off state in which power cannot be supplied thereto depending on a mounted state of the cover member,wherein the cover member comprises a plurality of cover wall surface portions surrounding a periphery of the base member, and is equipped with a cover locking mechanism portion for defining an order of mounting the cover wall surface portions on the base member, and whereinthe safety circuit is provided on one of the plurality of cover wall surface portions, andthe cover locking mechanism portion is provided so that the one cover wall surface portion on which the safety circuit is provided is first removed in an order of removing the plurality of cover wall surface portions from the base member. 6. The drive device for the in-core neutron instrumentation system according to claim 5, wherein the safety circuit is controlled to be in the conductive state in response to a state in which the cover member is mounted on the base member, and is controlled to be in the cut-off state in response to a state in which the cover member is not mounted on the base member. 7. The drive device for the in-core neutron instrumentation system according to claim 5, whereinthe cover member comprises a cover upper surface portion for covering an upper portion of a space surrounded by the plurality of cover wall surface portions,the cover wall surface portions and the cover upper surface portion are held by a frame which is fixed to the base member and provided in abutting regions between adjacent two of the cover wall surface portions and in abutting regions between the cover wall surface portions and the cover upper surface portion, andthe cover locking mechanism portion is mounted on the frame. 8. The drive device for the in-core neutron instrumentation system according to claim 5, whereinthe cover member comprises a cover upper surface portion for covering an upper portion of a space surrounded by the plurality of cover wall surface portions, andthe safety circuit is configured to include a series circuit which is brought into the conductive state in response to the whole cover member being mounted on the base member.