Investigation of Transition Fracture Toughness Variation within the Thickness of Reactor Pressure Vessel Forgings

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Abstract

An investigation has been conducted on the influence of the through-thickness sampling position on the tensile and fracture toughness properties of reactor pressure vessel forgings, using material from two actual pressurized water reactor vessels. The aim was to quantify the safety margins entailed by extracting surveillance samples from the 1/4T and 3/4T positions, as recommended by the current legislation. For each forging, seven layers have been considered: Inner surface, 1/8T, 1/4T, 1/2T, 3/4T, 7/8T, and outer surface; for each position, two tensile tests at room temperature and 16 fracture toughness tests in the ductile-to-brittle transition region have been performed. In terms of tensile properties, for both forgings the strength is higher at the surfaces than in the centre, while ductility (elongations and reduction of area) is substantially unaffected. For both materials, fracture toughness is better at the surfaces than in the central portion, although differences in terms of Master Curve reference temperatures are statistically not relevant at the 95 % confidence level. This effect is more pronounced for one of the materials, due to the larger amount of material removed with respect to the original heat-treated forging, and is qualitatively confirmed by metallographic observations.

Details

Original languageEnglish
Pages (from-to)1-9
JournalJournal of ASTM International
Volume7
Issue number1
Publication statusPublished - Jan 2010
EventJoint ASTM-ESIS Symposium on Fracture and Fatigue - ASTM, Vancouver, Canada
Duration: 1 May 20091 May 2009

Keywords

  • sampling position, fracture toughness, RPV forgings, PWR pressure vessel, Master Curve

ID: 169409