STP1547

    Fracture Mechanics Characterisation of Forged Base Metal Ring of the Decommissioned Reactor Pressure Vessel of NPP Greifswald WWER-440 Unit 4

    Published: Jan 2013


      Format Pages Price  
    PDF Version (576K) 16 $25   ADD TO CART
    Complete Source PDF (11M) 16 $105   ADD TO CART


    Abstract

    The investigation of reactor pressure vessel (RPV) material from the decommissioned Greifswald nuclear power plant (NPP) representing the first generation of Russian type WWER-440/V-230 reactors offers the opportunity to evaluate the real toughness response. The Greifswald RPVs represent different material conditions, viz., irradiated, annealed and irradiated, and annealed and re-irradiated. This paper presents test results from measurements of the trepan taken from forged base metal ring 0.3.1. located in the reactor core region of the unit 4 RPV. This unit was shut down after 11 years of operation and represents the irradiated condition. The key part of the testing is focused on determination of the reference temperature T0 following ASTM E1921-10. The T0 of 11 thickness locations from the inner to the outer RPV wall varies between −112°C and −130°C, with a mean value of −121°C. These are very low values for WWER RPV steel irradiated with fluences between 5.4 and 1.2 × 1019 n/cm2 (E > 0.5 MeV) from the inner to the outer RPV wall. The fracture toughness values at cleavage failure KJc measured on LS oriented pre-cracked and side-grooved Charpy size SE(B) specimens from defined thickness locations of the forged ring show strong scatter. More than the allowed 2 % of the specimen size adjusted KJc-1T values lie below the fracture toughness curve for 2 % fracture probability. The application of modified master curve (MC)-based evaluation methods indicates that the material is non-homogeneous. Because of very low KJc values, the Structural Integrity Assessment Procedures for European Industry step 3 evaluation gave a maximum T0SINTAP of −40°C. The multimodal MC evaluation of KJc values from all thickness locations gives a T0MM of −118°C and a standard deviation of 25 K. The course of the fracture toughness curves evaluated via a multimodal approach also does not represent the measured KJc values, as more than 2 % lie below the fracture toughness curve for 2 % fracture probability. The reason for the occurrence of very low KJc values is intergranular planes detected on the fractured surfaces of the specimens.

    Keywords:

    reactor pressure vessel steel, neutron irradiation, fracture toughness, master curve approach, non-homogeneous steel, SINTAP, multimodal approach


    Author Information:

    Viehrig, Hans-Werner
    Helmholtz-Zentrum Dresden-Rossendorf, Dept. of Structural Materials, Institute of Ion-Beam Physics and Materials Research, Dresden,

    Houska, Mario
    Helmholtz-Zentrum Dresden-Rossendorf, Dept. of Structural Materials, Institute of Ion-Beam Physics and Materials Research, Dresden,

    Altstadt, Eberhard
    Helmholtz-Zentrum Dresden-Rossendorf, Dept. of Structural Materials, Institute of Ion-Beam Physics and Materials Research, Dresden,

    Kuechler, Roland
    Helmholtz-Zentrum Dresden-Rossendorf, Dept. Structural Materials, Institute of Ion-Beam Physics and Materials Research, Dresden,


    Paper ID: STP104056

    Committee/Subcommittee: E10.02

    DOI: 10.1520/STP104056


    CrossRef ASTM International is a member of CrossRef.