HEAT TREATMENT FOR NOZZLE SAFE END PART OF VESSEL

PURPOSE:To improve the strength in the notched parts of both mounting parts by sticking one end of a thermal sleeve hermetically in a nozzle safe end part, and making the nozzle safe end part higher in temp. than the thermal sleeve part. CONSTITUTION:A cylindrical nozzle safe end part 3 projecting externally is provided in the opening part 2 at the inlet of a pressure vessel 1 for nuclear reactors and the preceding end part thereof is tapered 4 and is connected to a piping 5. A cylindrical thermal sleeve 6 of which one end opens into the vessel 1 is disposed in the part 3. The other end thereof is hermetically stuck by welding to the inside surface in the tapered part 4 of the part 3. Thereafter, cooling water 11 is supplied with a pump 10 into the sleeve 6, and the cylindrical part 8 of the part 3 is heated with a heater 9 to generate large tensile stress in a notched part 7, thereby yielding the same under tension. The heating is then stopped and the entire part is made uniform in temp., whereby residual compressive stress is applied in the part 7 and the strength thereof is improved.