Session: CS-10-01 Recent Developments in Japanese Codes and Standards

Paper Number: 61725

Start Time: Tuesday, July 13, 2021, 05:00 PM

61725 - Effect of Plastic Constraint and Cladding on Semi-Elliptical Shaped Crack in Fracture Toughness Evaluation for a Reactor Pressure Vessel Steel 

For the structural integrity assessment of reactor pressure vessels (RPVs) during pressurized thermal shock events, a semi-elliptical crack near the inner surface of RPV is postulated. The postulated crack has been revised from surface crack into embedded crack under the weld-overlay cladding, which is so-called as under-clad crack (UCC), in Japan electric association code (JEAC) 4206 in 2016. In the previous PVP2020 conference, we reported the fracture toughness test results of three-point bending specimens containing a straight shaped surface crack or an UCC. It was found that the apparent fracture toughness for the specimen with an UCC is higher than that for the specimen with a surface crack.

In this study, to investigate the effect of plastic constraint and cladding on the semi-elliptical shaped crack in fracture toughness evaluation, which shape is the same as that prescribed in JEAC4206-2016, we performed fracture toughness tests and finite element analyses (FEAs). We adopted the four-point bending fracture toughness tests for RPV specimens with a surface crack or an UCC. In the fracture toughness tests, the fracture toughness values at the deepest points of semi-elliptical shaped crack were derived from FEAs on the basis of JEAC 4206, in which the representative evaluation point is defined as the deepest point. From the test results, we found that the results of fracture toughness for the surface crack and the UCC were not significantly different at the deepest points of semi-elliptical shaped cracks. In addition, based on FEAs, plastic constraint parameters were evaluated, and the apparent fracture toughness was analytically predicted using the local approach. The results from FEAs showed that the plastic constraint at the crack tip of the UCC was lower than that of the surface crack, and the predicted fracture toughness for the UCC was higher than that for the surface crack.

Presenting Author: Masaki Shimodaira Japan Atomic Energy Agency

Authors:

Masaki Shimodaira Japan Atomic Energy Agency
Tohru Tobita Japan Atomic Energy Agency
Yasuto Nagoshi Mitsubishi Heavy Industries Ltd.
Kai Lu Japan Atomic Energy Agency
Jinya Katsuyama Japan Atomic Energy Agency