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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - MEACTOS (Mitigating Environmentally Assissted Cracking Through Optimisation of Surface Condition)

Teaser

Summary

The goal of the MEACTOS project is to improve the safety and reliability of Generation II and III Nuclear Power Plants (NPPs) by improving the resistance of critical locations, including welds, to Environmentally-Assisted Cracking (EAC) through the application of optimized surface machining and improved surface treatments. EAC is one of the major failure modes occurring in Light Water Reactors (LWRs)), affecting our safe, reliable and economic nuclear energy production. The condition of surfaces exposed to the primary coolant plays a main role on the susceptibility of components to EAC. However, many national and international guidelines and standards do not address surface condition of critical components in NPPs.

MEACTOS project will take advantage of advanced machining procedures developed by the aeronautical industry that have shown beneficial effects in the cracking mitigation, increasing the service life of the machined components.

Selected machining and treatment techniques applied to specimens of representative alloys used in LWRs will be exposed to accelerated testing conditions for screening purposes. Later, the more suitable will be tested in simulated operating conditions of LWRÂ´s.

EAC initiation models developed by the consortium members in the framework of NUGENIA are considered an adequate tool for the extrapolation of lab results to plant components.

It is expected that the results of the MEACTOS project contribute to the establishment of surface finished requirements guidelines for LWR components.

Work performed

- A workshop, named SOTA workshop, was held, as foreseen, during the first months of the project, organized by VTT. The objective of SOTA workshop was to set the technical actions to be carried out in the project, with specific decisions regarding materials surface modification techniques and testing protocols. An open discussion took place among the attendees, coming from both the industry and the laboratories, which allowed us to advance in achieving the objective of the workshop. At the same time, some open points were identified that have been subsequently discussed in different meetings and telephone calls. Workshop Minutes (WP3/D3.1 and WP9/D9.4a): â€œWorkshop on latest knowledge on EAC initiationâ€.

- Selected materials for testing have been the weld metal 182 and the austenitic stainless steels 316 L cold worked up to 15% by cold rolling. Weld metal 182 has been deposited simulating weld overlays conditions by ENSA. Cold work application to 316L has been carried out by ACERINOX, a Spanish stainless steel manufacturer. After applying the classic surface treatments to these materials, they have been sent to NAMRC to apply the advanced surface machining and the final manufacturing of the specimens with the different geometries defined.

- Crack initiation tests procedures including specimens geometries, load/deformation types and environments has been extensively discussed to fulfill all the requirements of both experimental phases of MEACTOS .

- The optimization of the parameters of the EAC models that will subsequently be used has been started. For this purpose information and results from previous projects such as NUGENIA MICRIN + are being compiled and processed.

- A project data management plan has been established and contacts have been initiated to include the results of the project in the database managed by JRC (MatDB).

- Dissemination of the project has been addresses from the beginning with the design of a new multifunctional web page, put into operation for the project. (https://meactos.eu/) with general information related to the project contents, linked information to other related EU projects as well as an internal area that serves as internal communication for the consortium members.

- The project has been presented by the consortium members in both national and international forums. This dissemination activity will be maintained and encouraged based on the technical results obtained during the experimentation, as well as the presentation of these results in scientific / technical publications.

- The Advisory Board Group (AB) and the End User Group (EUG) have been established. AB is formed by five member from non- consortium organizations with recognized expertise in the topics covered by the project. Several non-consortium organizations participate in the EUG.

Final results

The anticipated results of this project will lead to a proactive approach for dealing with materials degradation, greater reliability for the existing plants as they age, and reliability for plants that will be built. Some of the expected benefits are:

- Improving the service lifetime of the austenitic weld alloys by reducing microstructural and stress related factors that contribute to EAC.

- Reducing the scheduled in-service inspections and maintenance costs through the use of more EAC resistant components.

- Ecological benefits, due to the reduction or possible elimination of lubricating fluids based on petroleum products.

- Other additional benefits include (i) potential reduction in machining costs by reducing machining time and increasing the cutting tool lifetime and (ii) cross-cutting benefits, as these improvements in manufacturing processes can be applied to other industries such as food, petrochemical and pharmaceutical.

The project is aligned with the expected impacts detailed in the NFRP1-2016-2017 Work Programme:

- To help industrial stakeholders to develop efficient solutions in response to the new requirements of the amended Nuclear Safety Directive.

- Reinforcement of the safety features of the Generation â€“II and â€“III EU nuclear reactor fleet.

- Improve the market profile of EU-based reactor designs and strengthen the competitiveness of the EU nuclear sector through promoting an excellent level of safety in response to market requirements and trends.

MEACTOS will contribute to tackle the obsolescence of the machining practices used in the nuclear field with direct application to the construction of the new plants.