The application of narrow gap hot wire TIG welding for welds in CPR1000 reactor pressure vessel import and export nozzle and the nozzle safe-end is summarized. Aiming at the unqualified problem of radiographic inspection of welds

the main causes of failure are found from the precision control of the positioner assembly

welding operation

atmosphere protection and control and other aspects. The welding process is improved from the close welding operation

weld clearance

environmental and other aspects. Through above measures

the welding quality and the primary qualification rate of radiographic inspection of weld are sharply improved

which provides valuable experience for the practical application of narrow gap TIG welding technology in domestic nuclear island main equipment.