The first thing I see is that the nozzle to shell joint is not a fillet weld. The weld is a complete joint penetration groove weld with the joint geometry changing around the circumference.
The configuration of the groove, as shown, at the top of the sketch is nearly impossible to weld due to the limited access and the narrow groove angle. As a minimum, the groove angle at any point should be no less than 60 degrees, better yet if it is about 70 degrees.
The butt joint between the weldneck and the nozzle is a standard V-groove. Per B16.25 the groove angle should be 75 degrees and the weld should be complete joint penetration.
Best regards - Al