Abstract: A method of subjecting a welded structure to heat treatment in which a tensile yield is produced on an inner surface of the welded structure and a compressive yield is produced on an outer surface of the welded structure by the steps of placing a cooling medium in the interior of the welded structure and heating the outer surface of the welded structure to cause a difference in temperature to exist between the inner surface and other surface of the welded structure. The method further includes the step of locally heating a weld by means of a heating member to improve residual stress in a localized area of the weld and repeating the improvement of the residual stress regarding another localized area of the weld.

Abstract: A rail apparatus for running an automatic ultrasonic flaw detector around a reactor pressure vessel for detecting any flaw in the weld beads on the reactor pressure vessel. At least two circumferential rails and vertical rails are connected through turn tables at their crossing points to form a rail unit. The rail unit has vertical rails extending upward from the uppermost circumferential rail. The vertical rails are secured to a gamma shield, so that the rail unit as a whole is suspended from the gamma shield by means of these vertical rails. The rail unit is provided with swing prevention devices for preventing swing thereof. In installation of the rail apparatus, the rail unit is temporarily mounted on the reactor pressure vessel before mounting the latter in a containment vessel. Then, after accurately placing the reactor pressure vessel together with the rail unit in a right place within the containment vessel, the rail unit is supported suitably by the gamma shield.

Abstract: A rail apparatus positioned around the surface of a reactor pressure vessel surfaces (1) for carrying equipment such as a flaw detector to permit the equipment to move along the surface of a reactor pressure vessel in the vertical and circumferential directions. The rail apparatus has a plurality of vertical rails (81) and at least one circumferential rail (82) connected to the vertical rails through turn tables (83) at respective points of intersection. Each vertical rail (81) is supported by a supporting member wall fixed at its one end to a gamma-ray shielding wall (2) surrounding the reactor pressure vessel. The vertical and circumferential rails as a unit are retained by the gamma-ray shielding member (84) through oscillation prevention means (86).

Abstract: A semi-automatic scanner for ultrasonic flaw detection comprises a carriage travelling on a guide rail, a guide arm extending in a direction transverse to the travel direction of the carriage and supported by the carriage so as to pivot in a plane transverse to the travel direction of the carriage, a probe holder slidably supported by the arm, and a probe mounted on said probe holder so as to pivot about two axes transverse to each other. One of the axes is generally in parallel to the travel direction of the carriage. The carriage is driven by a motor, and the probe is moved by manual or motor-driving operation in a direction transverse to the travel direction of the carriage while pressing the probe on a surface to be inspected, whereby the probe accurately follows the surface even if the surface is curved.