Preventative Measures to Ensure Against Fracture/Cracking of the Confinement Boundary welds in Carbon/Alloy Steel Casks

Most cask designs for storage and transportation of spent nuclear fuel use two lids, an inner shield lid and an outer structural lid. The structural lid may be attached to the cask body by either a fullpenetration weld, a partial-penetration groove weld or bolts. Weld flaws, such as cracks, can occur in carbon and low alloy steels from several reasons. These reasons could result from defects in the cask shell material, improper fit-up of lid and backing ring, moisture contamination of the weld, or hydrogen induced cracking. Testing and evaluations have shown that weld flaws can be prevented if certain measures are implemented during weld fabrication. This paper will discuss improvement techniques that should be considered from accrued cask design and fabrication experiences. Additionally, a discussion is provided on how measured values of charpy tests and dynamic fracture toughness of welds, heat affected zone and base materials should be used as a basis to confirm weld integrity.