QAIII,
Is NBIC applicable your area, if so jte is correct. Was this vessel PWHT? nozzles replaced without PWHT could be your culprit for cracked welds. Remember PWHT is also performed pending type of product that the vessel will handle (service conditions). Several factors can lead to cracked welds in a new vessel.. stress, use of inappropriate materials, weld defects not discovered during fabrication, the list goes on. I would be most concerned about the root cause of the cracked nozzles (i.e. fabrication, service requirements or design reasons) before proceeding with any type of repairs. You may find that the cracks are not just limited to the nozzle welds upon further inspection. At this stage the overall quality of the vessel is at question and should not be merely repaired and commissioned without determining the cause of the existing cracked welds.
Good luck
WBH