Abstract: An opening and closing device that opens and closes an access port opened from a substantially cylindrical working platform disposed inside a reactor vessel and used to access a nozzle stub of the reactor vessel from the inside of the working platform, the opening and closing device includes: a cover that is slidable along an outer peripheral surface or an inner peripheral surface of the working platform from a closing position where the access port is closed to an opening position where the access port is opened; and moving device for sliding the cover.

Abstract: A reactor vessel that performs work inside a nozzle stub of the reactor vessel, including a platform unit that is provided at an upper portion inside the reactor vessel and includes a substantially cylindrical side wall portion and a bottom portion blocking the lower end of the side wall portion; an access window that is provided at the side wall portion of the platform unit an access window moving device that opens and closes the access window; a working device; and a control device that is provided at the outside of the reactor vessel and controls the access window moving device and the working device, wherein the control device drives the access window moving device to open the access window, drives the working device to perform work inside the nozzle stub, and then drives the access window moving device to close the access window after the performance of the work.

Abstract: Disclosed is a nozzle stub working system for a reactor vessel that performs work inside a nozzle stub of the reactor vessel, the nozzle stub working system for the reactor vessel including: a platform unit that is provided at an upper portion inside the reactor vessel and includes a substantially cylindrical side wall portion and a bottom portion blocking the lower end of the side wall portion; an access window that is provided at the side wall portion of the platform unit to allow the inside of the platform unit to communicate with the nozzle stub; an access window moving device that opens and closes the access window; a working device that advances from the inside of the platform unit to the inside of the nozzle stub to perform work inside the nozzle stub; and a control device that is provided at the outside of the reactor vessel and controls the access window moving device and the working device, wherein the control device drives the access window moving device to open the access window, drives the workin

Abstract: An opening and closing device that opens and closes an access port opened from a substantially cylindrical working platform disposed inside a reactor vessel and used to access a nozzle stub of the reactor vessel from the inside of the working platform, the opening and closing device includes: a cover that is slidable along an outer peripheral surface or an inner peripheral surface of the working platform from a closing position where the access port is closed to an opening position where the access port is opened; and moving device for sliding the cover.