The stress corrosion cracking(SCC)behavior f A508/52M part in dissimilar metal weld A508/52M/316L in simulated primary water environments at 290℃ was investigated by means of slow strain rate testing(SSRT)and electrode potential monitor/control.The work was focused on the effects of water chemistry factors and mechanical factors.The water chemistry factors were impurities contaminations,i.e.chloride and sulfate,and electrode potential which varied in the range from-720 to +400mV(SHE)that simulated the electrochemical conditions of the weld in the environments from ideal water chemistry to bad water chemistry with significant contamination of oxygen.The mechanical factors were strain rate and existence of notch as stress raiser.Results from the tests on smooth specimens in the water without impurities doping showed that,when tested within the potential range from-720 to +200mV(SHE),the specimens always failed in the bulk zone of 52M weld metal in mechanical ductile style,similar to the behavior when tested in nitrogen gas.When the potential was raised to +300 and +400mV(SHE),the weld failed in brittle style by significant SCC,with transgranular SCC happened both along the interface and in A508 heat affected zone(HAZ)and intergranular SCC in the Nickel-based weld metal close to the interface.The doping of 10ppm chloride or sulfate in the water raised the susceptibilities to SCC and pitting.The decrease of strain rate from 1x10-6 s-1 to 3.1 x10-7 s-1 raised the SCC susceptibility slightly.The existence of notch at the interface raised the SCC susceptibility significantly.The cracking mechanism and meaning in application of experimental results are discussed.