Primary pipeways in nuclear reactor

Purpose: To inhibit the glowing of columnar crystals in the welded portion thereby facilitate ultrasonic injury inspection in primary pipeways of BWR type reactors. Constitution: Upon welding a plurality of austenite type stainless steel pipeways, electric current is supplied from an alternating rectangular wave generating power source to exciting coils to apply an alternating magnetic field at 300 - 400 gauss of magnetic intensity and 1 - 5 Hz of magnetic frequency vertical to the molten pool. With the relation to the welding current flowing through the molten pool, the exerting direction of the Rorentz force is reversed, by which the inside of the molten pool can effectively be agitated and the columnar crystals tending to grow are divided finely and inhibited from growing. As a result, in the case of applying ultrasonic injury inspection, it is possible to effectively prevent the reduction in the SN ratio, generation of columnar echoes and locallized flow of ultrasonic waves thereby enabling to improve the injury detecting performance significantly and the reliability and safety of the primary pipeway can be improved. (Kawakami, Y.)