The behavior of shallow flaws in reactor pressure vessels
- Kansas Univ., Lawrence, KS (United States)
Both analytical and experimental studies have shown that the effect of crack length, a, on the elastic-plastic toughness of structural steels is significant. The objective of this report is to recommend those research investigations that are necessary to understand the phenomenon of shallow behavior as it affects fracture toughness so that the results can be used properly in the structural margin assessment of reactor pressure vessels (RPVs) with flaws. Preliminary test results of A 533 B steel show an elevated crack-tip-opening displacement (CTOD) toughness similar to that observed for structural steels tested at the University of Kansas. Thus, the inherent resistance to fracture initiation of A 533 B steel with shallow flaws appears to be higher than that used in the current American Society of Mechanical Engineers (ASME) design curves based on testing fracture mechanics specimens with deep flaws. If this higher toughness of laboratory specimens with shallow flaws can be transferred to a higher resistance to failure in RPV design or analysis, then the actual margin of safety in nuclear vessels with shallow flaws would be greater than is currently assumed on the basis of deep-flaw test results. This elevation in toughness and greater resistance to fracture would be a very desirable situation, particularly for the pressurized-thermal shock (PTS) analysis in which shallow flaws are assumed to exist. Before any advantage can be taken of this possible increase in initiation toughness, numerous factors must be analyzed to ensure the transferability of the data. This report reviews those factors and makes recommendations of studies that are needed to assess the transferability of shallow-flaw toughness test results to the structural margin assessment of RPV with shallow flaws. 14 refs., 8 figs.
- Research Organization:
- US Nuclear Regulatory Commission (NRC), Washington, DC (United States). Div. of Engineering; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Kansas Univ., Lawrence, KS (United States)
- Sponsoring Organization:
- USNRC; Nuclear Regulatory Commission, Washington, DC (United States)
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 6366226
- Report Number(s):
- NUREG/CR-5767; ORNL/Sub-90-SH640/1; ON: TI92003575
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
36 MATERIALS SCIENCE
PRESSURE VESSELS
DEFECTS
STEEL-ASTM-A533-B
FRACTURE MECHANICS
DEPTH
FRACTURE PROPERTIES
REACTOR VESSELS
THERMAL SHOCK
THICKNESS
ALLOYS
CARBON STEELS
CONTAINERS
DIMENSIONS
IRON ALLOYS
IRON BASE ALLOYS
MECHANICAL PROPERTIES
MECHANICS
STEELS
220200* - Nuclear Reactor Technology- Components & Accessories
360103 - Metals & Alloys- Mechanical Properties