The ECC-SMART is oriented towards assessing the feasibility and identification of safety features of an intrinsically and passively safe small modular reactor cooled by supercritical water (SCW-SMR), taking into account specific knowledge gaps related to the future licensing process and implementation of this technology. The main objectives of the project are to define the design requirements for the future SCW-SMR technology, to develop the pre-licensing study and guidelines for the demonstration of the safety in the further development stages of the SCW-SMR concept including the methodologies and tools to be used and to identify the key obstacles for the future SMR licencing and propose a strategy for this process. To reach these objectives, specific technical knowledge gaps were defined and will be assessed to achieve the future smooth licensing and implementation of the SCW-SMR technology (especially the behaviour of materials in the SCW environment and irradiation, validation of the codes and design of the reactor core will be developed, evaluated by simulations and experimentally validated). The ECC-SMART project consortium consists of EU, Canadian and Chinese partners to use the trans-continental synergy and knowledge developed separately by each partner. The project consortium and project scope were created according to the joint research activities under the International Atomic Energy Agency, Generation-IV International Forum umbrella and as much data as possible will be taken from the already performed projects. This project brings together the best scientific teams working in the field of SCWR using the best facilities and methods worldwide, to fulfil the common vision of building an SCW-SMR in the near future.

One of the critical issues of long-term operation (LTO) of mainly pressurised water reactors (PWRs) is the embrittlement of the reactor pressure vessel (RPV) caused mainly by neutron irradiation. Substantial research has been performed in various international collaborative research projects, such as LONGLIFE, PERFORM60, SOTERIA, etc., which have helped to improve the understanding of many open issues in RPV ageing phenomena, such as flux effect and influence of chemical/microstructural heterogeneities on RPV embrittlement. Despite all the previous research on RPV embrittlement, there are several open issues. E.g. there are contradicting viewpoints on underlying mechanisms that lead to accelerated embrittlement (e.g. formation of new phases or accelerated growth of existing clusters) at high fluence conditions in certain low Cu RPV steels. Further research focussing on understanding unfavourable synergy between Ni, Mn and Si on microstructure and mechanical properties of RPV at high fluences is needed to elucidate the late irradiation effects. Existing embrittlement trend equations (ETEs) tend to underpredict RPV embrittlement at higher fluence regimes. Therefore subsequent efforts are needed to validate/adapt the ETEs accordingly. In addition, the applicability of master curve approach at high fluences and small/sub-sized specimens to characterize irradiation induced shifts in reference curves needs to be further investigated. To provide more insight into these issues NRG and JRC jointly conducted an irradiation campaign in the High Flux Reactor Petten, called Lyra-10. Within Lyra-10 a variety of different RPV steel specimens resembling VVER-1000 and western type PWR RPV steels with systematic variations in Ni, Mn and Si contents have been irradiated to high fluences resembling reactor operation above 60 years. The goal of STRUMAT-LTO is to address above mentioned scientific gaps in RPV embrittlement by exploiting the Lyra-10 specimens i.e. post irrad. examination.

The aim of the project is to determine the most affected and threatened components from the point of view of the long-term operation (LTO) and describe the effect of the LTO on the material properties as well as develop a simulation tool able to predict the non-acceptable state of the material. The project is specifically focused on the Water-Water Energetic Reactor (VVER), nevertheless, the approach is to maintain the easy transferability to other light water reactor technologies, as well. The outputs of the project will lead to the increase of operational safety at the extended lifetime due to the in-time prediction of the potential failure. The basic approach of the project is to combine the development of the simulation tools, experimental work (material analyses), in-service and/or non-destructive inspection techniques to develop the effective “early warning” tool for the assessment of the system integrity for the LTO of the current LWR with a specific focus on the VVER technology. The project's aim specifically focuses on the thermal aging and swelling of the loaded constructional materials. One of the most affected components from the LTO´s point of view are the heat exchanging tubes of steam generators (thermal ageing) and reactor internals (swelling). The experimental material was screened and selected with the main criteria: to support and validate the proposed methods in the most accurate way, and to be “on stock” and available at the expected start of the project, the latest. The experiments are planned to be performed at the available material with clear and well-described operational history as well as the material from the original batch in the “as-received” state to gain the most relevant and valuable information with high impact to the community.

The Long-Term Operation of Nuclear Power Plants (NPPs) calls for innovative methods to monitor the ageing of safety systems. New instrumentation will also lead to improve decision-making in accidental conditions thanks to additional information, complementing the material and organisational modifications decided after the Fukushima accident. The project FIND aims first to adapt innovative technologies deployed in other industries to prevent the failure of metallic pipes. FIND will work on Structural Health Monitoring technologies (ultrasonic guided waves and acoustic emission) to detect defects in real time during plant operation, even in inaccessible locations. In addition, Digital Twins will be developed to better predict degradation phenomena, with combination of detailed mechanical models and real plant data (strain, temperature and vibration measurements). Tests in experimental and industrial conditions (including NPPs) will be performed, representative of the following phenomena: - Local corrosion and large deformations of raw service water pipes, - Stress corrosion cracking and fatigue on the primary circuit, - Flow accelerated corrosion on the turbine extraction line. Concerning accidental instrumentation, FIND will first develop systems to track water movements during a loss-of-coolant accident. This will include localisation of breach thanks to heated thermocouples and data science approaches. FIND will evaluate feasibility to monitor progression of severe accidents, thanks to analysis of fission products in containment, either by gamma ray spectroscopy or physicochemical analysis. Technologies developed in FIND are low intrusive and cost effective. They will help to anticipate maintenance, and will complete or replace some Non-Destructive Testing. This will result in higher availability of NPPs, lower operator dosimetry, and reduced costs, which will foster their adoption. FIND is led by IRSN, French public expert for nuclear risks and encompasse

In the EU, most of the nuclear power plants (NPPs) are currently in the second half of their designed lifetime, making lifetime extension an important aspect for the EU countries. One of the most limiting safety assessments for long term operation (LTO) is the reactor pressure vessel (RPV) integrity assessment for pressurized thermal shock (PTS). The goal is to demonstrate the safety margin against fast fracture initiation or RPV failure. To verify safe operation of existing NPPs going through LTO upgrades, advanced methods and improvements are necessary. In the EU, currently used PTS analyses are based on deterministic assessment and conservative boundary conditions. This type of PTS analyses is reaching its limits in demonstrating the safety for NPPs facing LTO and need to be enhanced. However, inherent safety margins exist and several LTO improvements and advanced methods are intended to increase the safety margins of PTS analysis. Additionally, the quantification of safety margins in terms of risk of RPV failure by advanced probabilistic assessments becomes more important. The main objectives of this project are establishing of state-of-the-art for LTO improvements having an impact on PTS analysis: NPP improvements (hardware, software, procedures), development of advanced deterministic and probabilistic PTS assessment method including thermal hydraulic (TH) uncertainty analyses, quantification of safety margins for LTO improvements and development of best-practice guidance. After establishing the LTO improvements, TH calculations will be performed including also uncertainty quantification relevant to PTS assessment. Benchmark calculations for both deterministic and probabilistic RPV integrity assessment will be performed with the goal to establish the impact of LTO improvements and TH uncertainties on the overall RPV integrity margins.