The EUROfusion materials property handbook for DEMO in-vessel components—Status and the challenge to improve confidence level for engineering data

The development of a specific materials database and handbook, for engineering design of in-vessel components of EU-DEMO, is an essential requirement for assessing the structural integrity by design. For baseline in-vessel materials, including EURFOER97, CuCrZr, Tungsten as well as dielectric and optical materials, this development has been ongoing for several years within the Engineering Data and Design Integration sub-project of the EUROfusion Materials Work Package. Currently the database is insufficient to ensure reliable engineering design and safety or hazard analysis and mostly does not yet exist in established nuclear codes. In this paper the current status of EU-DEMO database and handbook for key in-vessel materials is provided. This comprises practical steps taken to obtain the raw data, screening procedures and data storage, to ensure quality and provenance. We discuss how this procedure has been utilized to produce materials handbook chapter on EUROFER97 and the critical challenges in data accumulation for CuCrZr and Tungsten, planned mitigations and the implications this has on structural design. Finally, key elements and methodology of our strategy to develop the materials database and handbook for the in-vessel materials are outlined, including concepts to accommodate sparse irradiated materials data and links to EU-DEMO engineering design criteria

Multiscale modelling for fusion and fission materials: the M4F project

The M4F project brings together the fusion and fission materials communities working on the prediction of radiation damage production and evolution and its effects on the mechanical behaviour of irradiated ferritic/martensitic (F/M) steels. It is a multidisciplinary project in which several different experimental and computational materials science tools are integrated to understand and model the complex phenomena associated with the formation and evolution of irradiation induced defects and their effects on the macroscopic behaviour of the target materials. In particular the project focuses on two specific aspects: (1) To develop physical understanding and predictive models of the origin and consequences of localised deformation under irradiation in F/M steels; (2) To develop good practices and possibly advance towards the definition of protocols for the use of ion irradiation as a tool to evaluate radiation effects on materials. Nineteen modelling codes across different scales are being used and developed and an experimental validation programme based on the examination of materials irradiated with neutrons and ions is being carried out. The project enters now its 4th year and is close to delivering high-quality results. This paper overviews the work performed so far within the project, highlighting its impact for fission and fusion materials science.This work has received funding from the Euratom research and training programme 2014-2018 under grant agreement No. 755039 (M4F project)

Technology readiness assessment of materials for DEMO in-vessel applications

A dedicated procedure was developed to categorize the technology readiness of materials for specific DEMO in-vessel fusion reactor applications. This methodology was employed to assess the technological maturity of materials under development within the EUROfusion materials work package (WPMAT). This covers materials intended for structural, high heat flux, optical and dielectric applications in the European DEMO fusion reactor (breeder materials and barrier coatings are not covered here). The baseline materials have been assigned DEMO Material Technology Readiness Levels (MTRLs) of 4 (EUROFER97), 3 (conventional tungsten) and 4 (Copper-Chromium-Zirconium). In addition, a further 28 candidate materials (and groups of materials) were also assessed. These were generally assigned DEMO MTRLs in the range of 2-3. This process has highlighted the wide range of materials under development within WPMAT. However, it has also brought into focus the many challenges facing DEMO materials development. While the lack of technologically ready materials is clearly a source of risk to DEMO, the introduction of a biennial review of technology readiness within WPMAT is intended to facilitate more effective planning and targeted materials development, in line with the strategic plans of EUROfusion. This paper highlights the methodologies for fusion specific material technology readiness levels, their application for EU-DEMO and the effectiveness of these in strategic materials development

Choice of a low operating temperature for the DEMO EUROFER97 divertor cassette

One of the fundamental input parameters required for the thermo hydraulic and structural design of a divertor cassette is the operation temperature range. In the current design activities to develop European DEMO divertor in the frame of EUROfusion, reduced activation steel EUROFER97 was chosen as structural material for the divertor cassette body considering its low long-term activation and superior creep and swelling resistance under neutron irradiation (You et al., 2016) [1]. For specifying an operation temperature range (i.e. cooling condition) various, often conflicting requirements have to be considered. In this article the lower limit of allowed operation temperature window is defined for EUROFER97 for structural design of DEMO divertor cassette body. The underlying rationale and supporting experimental data from a number of previous irradiation tests are also presented. The motivation of this survey study is to explore the possibility to use EUROFER97 for water-cooled divertor cassette at temperatures below 350 °C which has been regarded as limit temperature to preserve ductility under irradiation. Based on the literature data of FTTT (Fracture Toughness Transition Temperature) calibrated by Master Curve method, it is concluded that EUROFER97 at the envisaged maximum dose of 6 dpa will have to be operated above 180 °C taking the embrittlement due to helium production into account

Present Status of the Fractesus Project:Round Robin on Unirradiated Materials

The present paper provides a summary of an inter-laboratory round robin on the fracture toughness testing and Master Curve application on unirradiated materials. First, a validation exercise was performed on the analysis of a given forcedisplacement curve. Then, a validation exercise was performed on the application of the Master Curve procedure on a given data set of fracture toughness results. Finally, the preliminary results of the Master Curve application on mini compact tension (MC(T)) specimens by 13 different labs on six different materials (four base materials and two welds) are presented. The validation exercise on fracture toughness data evaluation showed the need for a uniform conversion from front face displacement to load line displacement. The validation exercise on application of the Master Curve approach to obtain the reference temperature proved the equivalence between the T0TEM software and in-house developed softwares. The interlaboratory round robin showed the equivalence between T0 obtained by MC(T) and larger specimens, except for A533B JRQ and 73W. The reasons for the deviations of A533B JRQ and 73W are under investigation. As a general comment, it can be stated that the results from MC(T) specimens often indicate material inhomogeneity as compared to the result from larger specimens. This is likely the consequence of the small sampling volume of the MC(T) specimens.</p

The European ITER Test Blanket Modules: EUROFER97 material and TBM’s fabrication technologies development and qualification

The paper overviews activities focused on qualification of EUROFER97 structural material, introduced under a probationary phase in the nuclear components design and construction code RCC-MRx, and identification/analyses of gaps in the respective material database to be filled in. Additionally the available design rules in the code are reviewed to verify their applicability to the specificities of EUROFER97 steel and to the TBM design and fabrication. Progress achieved in development of fabrication technologies and procedures applied for manufacturing of the TBM sub-components, like, HCLL and HCPB cooling plates, stiffening plates, first wall and side caps, and for TBM structure sub-assembly is described. The used technologies are based on fusion (laser and TIG) and diffusion (HIP) welding techniques taking into account specificities of the EUROFER97 steel. With help of the agreed notified body, an appropriate approach/methodology for qualification of the developed, TBMs-related preliminary welding procedure specifications has been identified and future steps established