Fracture Toughness of Submerged-Arc Weld Samples from a Decommissioned Magnox Reactor Pressure Vessel: Initial Results

摘要

BNFL Magnox Generation Group is sampling irradiated submerged-arc weld metal from the reactor pressure vessel at Trawsfynydd Power Station, which is currently being decommissioned. Chemical analysis has shown that the sampled weld is typical of previously sampled submerged-arc weld. There are no significant variations either through the weld thickness or along the weld, indicating high quality and uniformity of construction. Dosimetry measurements are in line with predictions, and show significant attenuation ghrough the vessel thickness. Fracture toughness measurements are being made using pre-cracked Charpy specimens machined from four different depths in the through-wall thickness, with reconstituted material from failed Charpy halves being used to augment the test data. The data from the layer of the first weld furthest from the reactor core have been compared with predictions made by the methodology used in assessing continuing RPV integrity, and support the methodology.