Investigators: Roland deWit and Richard J. Fields

Technical Description:

Currently, industry predicts the fracture resistance of large structures and pressure vessels from measurements made on small samples with relatively large or deep flaws. Currently, industry uses scaling theories, that are controversial and mostly untested, to account for the difference in size between the sample and the structure. The goal of this project is to use NIST's unique 52MN (12-million lbf) testing facility to provide industry with test data on the fracture resistance of a pressure vessel wall with small flaws representative of actual service conditions. To accomplish this objective, samples 225mm wide (8.8in), 225mm thick (8.8in) and >1.2m (> 47in) long were cut from a nuclear reactor pressure vessel wall and realistic (shallow) flaws were created in the samples. Then, the fracture toughness was determined for the samples with these well characterized flaws. The results of these measurements will be used to evaluate new and existing scaling theories.

Technical Objectives:

• This research project is designed to assist the nuclear industry by providing a data base for evaluating controversial scaling theories for fracture toughness to assess the life of existing reactor pressure vessels.

Anticipated Outcomes:

• This research will enable industry to more accurately predict if a given flaw will cause catastrophic failure of pressure vessels such as nuclear and chemical reactors and this will result in improvements in the reliability and safety of nuclear reactors as well as any component where full-size testing is difficult or expensive.

Accomplishments for FY 1995:

• The tests were completed and the results reported to Oak Ridge National Laboratory for subsequent analysis.

Impacts and Technical Highlights:

• Oak Ridge National Laboratory is analyzing the results of these tests to enable the safer and more cost-efficient operation of nuclear reactors, but the impact will be beyond this industry to include any industry or government agency concerned with the performance of large structures where full-scale testing is impractical.

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Last modified: Mon Jan 06 09:46:15 1997 Metallurgy Webmeister