Studsvik Material Integrity Life Extension (SMILE) Project
Joint project

Studsvik’s pool facility for storage and inspection of SMILE materials, left: 29 tonnes transportation flask, three pools each about 8 meters deep; and right: pool-in-pool for cutting and inspections. Photo: Studsvik.


The Studsvik Material Integrity Life Extension (SMILE) Project was launched in 2021 with the aim to provide the nuclear industry, mainly light-water reactors (LWRs) plant operators and national nuclear safety regulators with an improved understanding of materials’ ageing mechanisms in support of plant ageing management, life extension programmes, and operating licence renewals. This project will address priority topics highlighted by various international studies such as the investigation of ageing mechanisms of structural, metallic alloys used in the primary coolant systems of LWRs due to metal fatigue, corrosion-related mechanisms, thermal ageing, and neutron irradiation damage.

SMILE is a 5-year joint project conducted by Studsvik Nuclear AB, Sweden, based on experimental examinations and testing of aged materials that will be harvested from Swedish LWRs that are being decommissioned after more than 40 years of operation: Oskarshamn 1 and 2 (BWRs) and Ringhals 2 (PWR). Material replaced 30 years after operation is already available and will also be investigated, e.g. RPV upper head and pressuriser from Ringhals 3 and 4.

The project is structured into four main tasks. The objective of the first task is to build a material library by retrieving the materials and documents to the greatest extent possible with all known information on the materials selected to be harvested from the three retired Swedish LWRs and the major replaced components from Ringhals 3 and 4. All data collected and generated within SMILE will be organised and structured as such that the information can be easily transferred to a database, in case the necessary resources to create such a comprehensive database become available in the future. The second task investigates irradiation and thermal embrittlement of low alloy steels used for reactor pressure vessels and other large vessels in the primary coolant circuits of LWRs. The third task is addressing stainless steel alloy of core support structures and internals and is divided into two subtasks focusing on irradiation embrittlement including welds and irradiation assisted stress corrosion cracking and corrosion fatigue susceptibility. The fourth task is addressing the evaluation of pressure boundary stainless steels, nickel base alloys and their welds, where irradiation effects do not play a significant role. The task is divided in two subtasks focusing on dissimilar metal welds and stainless steel welds, stress corrosion cracking (SCC) resistance in BWRs and PWRs and alloy 690/152/52 primary water stress corrosion cracking (PWSCC) resistance and thermal stability in PWRs.

The Project will focus on establishing a mechanistic understanding of ageing phenomena and on validating or improving existing ageing models for life extension to 60 or 80 years. Co-operation and interaction with universities active in the study of ageing of materials and known international experts in the field will be undertaken to benefit from their insights and to facilitate knowledge transfer.

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Belgium, China, Czechia, Germany, Japan, Sweden, Switzerland and the United States.

Project period

January 2021 - December 2025

~ EUR 17 million