YAG LASER-WELDING OF NEUTRON-IRRADIATED STAINLESS-STEELS

Type 304L stainless steel plates of 8 mm thickness irradiated in a boi ling water reactor (BWR) to 1.2 x 10(25) n/m(2) (E > 1.0 MeV) containi ng 9 appm helium from transmutation have been successfully welded usin g a high power Nd-YAG laser under conditions of both continuous wave ( CW) and pulse modes. Unirradiated Type 316L stainless steel plate was lap welded to the irradiated Type 304L stainless steel plate under hea t inputs ranging from 240 to 540 J/cm. Bead on plate welding was carri ed out under the same welding conditions as lap welding, Tensile tests of lap welded joints were conducted at room temperature. All joints f ractured not in the irradiated materials but in the unirradiated mater ials and showed good mechanical properties. Based on these results it does not appear that helium affects the mechanical properties of joint s. Small grain boundary cracks were observed in HAZ of the weld made b y the CW YAG laser with heat inputs of 480 and 540 J/cm and crack leng th decreased with decreasing heat input. (C) 1998 Published by Elsevie r Science B.V, All rights reserved.