Post mortem investigations of the NPP Greifswald WWER-440 reactor pressure vessels


Post mortem investigations of the NPP Greifswald WWER-440 reactor pressure vessels

Viehrig, H.-W.; Rindelhardt, U.; Schuhknecht, J.

The investigation of reactor pressure vessel (RPV) materials from decommissioned NPPs offers the unique opportunity to scrutinize the irradiation behaviour under real conditions. Trepans taken from the whole RPV wall enable a comprehensive material characterisation. The paper describes the trepanning technology applied to the decommissioned WWER-440/230 RPVs of the Greifswald NPP. The Greifswald RPVs represent different material conditions such as irradiated, irradiated and recovery annealed and irradiated, recovery annealed and re-irradiated. The working program is focussed on the characterisation of the RPV steels (base and weld metal) through the RPV wall. The key part of the testing is aimed at the determination of the reference temperature T0 following the ASTM Test Standard E1921-05 to determine the fracture toughness of the RPV steel in different thickness locations. In a first step the material of the core welding seam was investigated. It could be shown that the Master Curve approach as adopted in E1921 is applicable to the investigated original RPV weld metal. The weld metal located in a distance of about 22 mm from the inner surface of the RPV wall yielded a T0 of 50°C which is about 40K higher than T0 close to the inner surface. This outcome is important for the assessment of results retrieved from so called boat samples taken directly from the RPV surface after the recovery annealing. It shows that boat samples do not represent the material with the lowest toughness.

Keywords: nuclear power plant; WWER type; reactor pressure vessel; weld metal; integrity assessment; neutron embrittlement; mechanical testing; fracture toughness; Master Curve concept

  • Contribution to proceedings
    19th International Conference on Structural Mechanics in Reactor Technology (SMiRT-19), 12.-17.08.2007, Toronto, Canada
    Proceedings of the 19th International Conference on Structural Mechanics in Reactor Technology
  • Lecture (Conference)
    19th International Conference on Structural Mechanics in Reactor Technology (SMiRT-19), 12.-17.08.2007, Toronto, Canada

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Publ.-Id: 9716