As the UK fleet of power plants changes technology from Advanced Gas Cooled Reactors to Light Water Reactors (LWR), the fatigue life of structural components in the primary coolant loop becomes of high interest. This is because of cyclic loading of LWRs caused by solid-liquid interactions which are less prominent in gas cooled reactors. Concurrently, modern welding techniques such as electron-beam (EB) welding are of great interest in LWR designs thanks to their benefits such as the ability to be automated, smaller heat affected zones and less material complexity as they can be deployed with no filler material (Horne et al., 2019). A common focus in studying weld fracture is the weld toe; this is because it has been observed that cracks often initiate in this region typically due to higher expected carbide deposition within the heat affected zone acting as stress concentrators. As EB welds have very narrow heat affected zone, the expected region in which cracks may initiate, is less obvious. This work compares three crack initiation sites taken from a modern reactor material (stainless steel 316L) pipe containing a circumferential EB butt weld and evaluates the fatigue crack growth rate (FCGR) within the linear region of the