ASME Boiler & Pressure Vessel Code Requirements for Prevention of Brittle Fracture

Abstract

Ferritic materials used in the fabrication of both nuclear and non-nuclear pressure vessels are required to be ductile and resistant to brittle fracture over the entire range of expected service temperatures. One fundamental approach for ensuring such resistance is an implicit procedure based on two principles. First, ferritic materials are characterized by a transition from brittle behavior at relatively low temperatures (i.e., the lower-shelf temperature) to ductile behavior at relatively high temperatures (i.e., the upper-shelf temperature). Second, experience has shown that, generally, inexpensive tests (e.g., Charpy V-notch or drop weight tests) can be used to establish that materials of construction have sufficient temperature margin between the lowest service temperature (LST) expected during vessel operation and a reference temperature that guarantees ductile behavior during service.