SYMPOSIA PAPER Published: 01 June 2023

Experience with Embrittlement Trend Curves in Swedish PWRs


There are currently two operating pressurized water reactors in Sweden, currently planning for 60 years of operation until 2041 and 2043. The acceptance of operation time is continuously evaluated at least every 10 years in a comprehensive mandatory periodic safety review that requires the utilities to continuously update and implement the developments in science and technology. The RPV welds have been shown by the applied surveillance program to be the limiting material for operation. The welds are manufactured according to the same specifications with a chemical composition with high nickel and manganese content. The welds show a large increase in transition temperature shift with an almost linear relationship to neutron fluence that is underestimated by most of the established embrittlement trend curves (ETCs). The current regulations from the Swedish Radiation Safety Authority are in general not detailed and prescriptive and hence permit plant-specific ETCs if they are sufficiently justified and based on proper material and plant conditions. This paper describes the bases for the ETCs and an ongoing work to revise the ETCs to enable the use of a material-specific master curve for crack initiation, KIC, with compliance with the reactor vessel integrity analyses.

Author Information

Blomström, Johan
Dept. of Maintenance, Analytical Services, SE
Roudén, Jenny
Dept. of Maintenance, Analytical Services, SE
Efsing, Pål
Dept. of Maintenance, Analytical Services, SE Dept. of Solid Mechanics, KTH School of Engineering Sciences, Stockholm, SE
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Pages: 382–397
DOI: 10.1520/STP164720220067
ISBN-EB: 978-0-8031-7742-0
ISBN-13: 978-0-8031-7741-3