A Summary of the Low Upper Shelf Toughness Safety Margin Issue

Conference · Sun Jun 23 04:00:00 EDT 1991

OSTI ID:6005392

Merkle, J. G. ^[1]

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1. Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

The low upper shelf toughness issue has a long history, beginning with the choice of materials for the submerged arc welding process, but also potentially involving the use of A302-B plate. Criteria for vessels containing low upper shelf materials have usually been expressed in terms of the Charpy upper shelf impact energy. Although these criteria have had several different bases, the range of limiting values for wall thicknesses approaching 229 mm (9 in.) has remained between 54 to 68J (40 to 50 ft lbs). Allowable values for vessels with thinner walls and/or only circumferential low upper shelf welds might conceivably be less. A decision on criteria to be incorporated into the ASME Code is now being made. Choices to be made concern the method for estimating the decrease in upper shelf impact energy, flaw geometry for circumferential welds, statistical significance of toughness values, the choice between J_D and J_M, reference pressure, safety factors and the inclusion of tearing stability calculations by means of R curve extrapolation. NRC research programs have contributed significantly to the resolution of the low upper shelf issue. These programs embrace all aspects of the issue, including material characterization, large scale testing, analysis and criteria development.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE; USNRC
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 6005392
• Report Number(s): CONF-910602--25; ON: DE91010775
• Country of Publication: United States
• Language: English

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