[1C14-17] Reactor Pressure Vessel 2

[1C14] FY2017 Investigation for Improvement of Evaluation Methods of Irradiation Effects on Reactor Pressure Vessel and Core Internals

(1) Through-wall fracture toughness distribution of decommissioned Zion Unit 1 reactor pressure vessel material

*Masato Yamamoto¹, Tomohiro Kobayashi¹ (1. Central Research Institute of Electric Power Industry)

Keywords:Reactor pressure vessel steel, Decommissioned reactor pressure vessel material, Fracture toughness, The Master Curve method, Mini-C(T) specimen

Through-wall distribution of fracture toughness at ductile to brittle transition regime was studied for decommissioned Zion Unit 1 reactor pressure vessel steel base metal by means of very small size C(T) (Mini-C(T)) specimens and the Master Curve method. The material retrieved from near inner-surface location exhibited higher fracture toughness, in maximum 50 degree Celsius lower in Master Curve reference temperature T₀, than those of center materials despite of higher neutron fluence at near surface location. It is clarified that the fracture toughness at near surface location, where the PTS event is concerned, is governed by initial toughness distribution even after the full life operation of 15 years, and holds higher value than that in 1/4 thickness location, where the surveillance material is retrieved from.