Reactor vessel annealing system

A system for annealing a vessel (14) in situ by heating the vessel (14) to a defined temperature, composed of: an electrically operated heater assembly (10) insertable into the vessel (14) for heating the vessel (14) to the defined temperature; temperature monitoring components positioned relative to the heater assembly (10) for monitoring the temperature of the vessel (14); a controllable electric power supply unit for supplying electric power required by the heater assembly (10); a control unit for controlling the power supplied by the power supply unit; a first vehicle (2) containing the power supply unit; a second vehicle (4) containing the control unit; power conductors (22) connectable between the power supply unit and the heater unit (10) for delivering the power supplied by the power supply unit to the heater assembly (10); signal conductors (20,24) connectable between the temperature monitoring components and the control unit for delivering temperature indicating signals from the temperature monitoring components to the control unit; and control conductors (8) connectable between the control unit and the power supply unit for delivering to the power supply unit control signals for controlling the level of power supplied by the power supply unit to the heater assembly (10). At least one of the vehicles is constructed to support comparatively heavy loads while being capable of being loaded and unloaded from essentially any location along either side of the vehicle. At least one vehicle is provided with a capable connecting unit which provides a stress-relief support for at least one set of cables. The system further includes apparatus for maintaining the interior of the vessel at subatmospheric pressure during annealing.