Community Research and Development Information Service - CORDIS


The project focussed on a series of two large-scale tests using the special facility developed at MPA Stuttgart. The test pieces were thick-walled cylinders of outer diameter 800 mm and wall thickness 190 mm, fabricated in a 17 MoV 8 4 mod steel with a two-layer austenitic cladding on the internal surface. The base material was heat-treated to produce a low toughness, high transition temperature condition, as could occur in an end-of-life RPV. The combination of shallow defect geometry, a different PTS transient and a low toughness material condition presented a distinct challenge from that addressed in the NESC-I experiment, while allowing the network to build on experience of the lessons learned for applying an integrated assessment approach.

The first experiment was performed in March 1999 using the NP2 test piece, containing a fully circumferential sub-clad defect with a depth of 8 mm. It produced a crack growth and arrest event; with a maximum extension of approximately 15 mm. Post-test metallography however revealed that the growth mode was intergranular. The second test was performed in September 1999 using the NP1 test piece, containing two shallow semi-elliptical through-clad defects of depth 21 mm and length 60 mm. Although the planned loading transient was achieved, no growth occurred.

The results of the two tests underline the conservatism of existing defect assessment procedures for shallow RPV flaws (code-based assessment routes indicated that a limiting defect size one order of magnitude below that used), and indicate the resistance of even degraded material containing simulated flaws to severe thermal shock loading. The extensive investigations by the NESC-II participants considered in particular the application of the Master Curve to this particular material and the consistency of fracture analyses using both simplified engineering methods and detailed cracked-body finite element models to predict defect behaviour under complex transients.

Additional information

Authors: STUMPFROCK L, MPA, Stuttgart (DE);SWAN D I, Rolls-Royce Ltd (UK);TAYLOR N ET AL, European Commission, Joint Research Centre, Institute for Energy, Petten (NL);SIEGELE D, Fraunhofer Institut für Werkstoffmechanik, Freiburg (DE)
Bibliographic Reference: EUR 20696 EN (2003), various paging. Free of charge
Availability: Available from European Commission, JRC Knowledge Management Unit, Ispra (IT) Tel: +39-033278-9843 or +39-033278-9864 Fax: +39-033278-9623 E-mail:
Follow us on: RSS Facebook Twitter YouTube Managed by the EU Publications Office Top