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Crack initiation and propagation under creep is one of the main failure modes of service equipment made of plastic. This paper explores the feasibility of using the creep C* integral approach to deduce creep crack growth data obtained for a polymeric material, specifically an acrylonitrile butadiene styrene polymer, which exhibits nonlinear mechanical behavior. Experimental creep crack growth data, measured at 60 and 80 °C, was used to obtain the relationship between the time rate of crack growth, da/dt, due to secondary creep and the applied value of C*. A master-curve could be determined, which describes experimental data at both temperatures. These promising results suggest that C* integral approach can be used as powerful and convenient tool to describe crack propagation of polymeric materials under secondary creep conditions. The approach may also be of interest for the prediction of creep lifetime for ductile polymers.

The main purpose of IFMIF-DONES facility is to provide a neutron source for irradiating small specimens and producing experimental data of material properties for the construction of DEMO fusion power plant. The Test Cell (TC) of the DONES is a confined and well-shielded room, where the strong irradiation environment is created. The biological shielding of the TC mainly consists of several meters thick concrete walls and shielding plugs, and a stainless-steel liner. The TC liner and the concrete walls are actively cooled by water because of the high volumetric heating coming from nuclear reactions. Although, the TC is designed to be fully functional for the complete life span of the facility, still there is a very low probability of defect of the TC biological shielding due to their exposure of intense neutron and gamma irradiation. Therefore, the original TC configuration, which was a monolithic approach, had to be revised. Due to this reason, at the end of 2019 the project team has changed the TC concept from the monolithic design to the so-called Maintainable TC Concept (MTCC) design, which allows a maintenance possibility in case of unexpected damage.

During the Engineering Validation and Engineering Design Activities (EVEDA) phase (2007-2014) of the International Fusion Materials Irradiation Facility (IFMIF), an advanced engineering design of the High Flux Test Module (HFTM) has been developed with the objective to facilitate the controlled irradiation of steel samples in the high flux area directly behind the IFMIF neutron source. The development process addressed included manufacturing techniques, CAD, neutronic, thermal-hydraulic and mechanical analyses complemented by a series of validation activities. Validation included manufacturing of 1:1 parts and mockups, test of prototypes in the FLEX and HELOKA-LP helium loops of KIT for verification of the thermal and mechanical properties, and irradiation of specimen filled capsule prototypes in the BR2 test reactor. The prototyping activities were backed by several R&D studies addressing focused issues like handling of liquid NaK (as filling medium) and insertion of Small Specimen Test Technique (SSTT) specimens into the irradiation capsules. This paper provides an up-todate design description of the HFTM irradiation device, and reports on the achieved performance criteria related to the requirements. Results of the validation activities are accounted for and the most important issues for further development are identified.

The necessity of a neutron source for fusion materials research was identified already in the 70s. Though neutrons induced degradation present similarities on a mechanistic approach, thresholds energies for crucial transmutations are typically above fission neutrons spectrum. The generation of He via 56Fe (n,α) 53Cr in future fusion reactors with around 12 appm/dpa will lead to swelling and structural materials embrittlement. Existing neutron sources, namely fission reactors or spallation sources lead to different degradation, attempts for extrapolation are unsuccessful given the absence of experimental observations in the operational ranges of a fusion reactor. Neutrons with a broad peak at 14MeV can be generated with Li(d,xn) reactions; the technological efforts that started with FMIT in the early 80s have finally matured with the success of IFMIF/EVEDA under the Broader Approach Agreement. The status today of five technological challenges, perceived in the past as most critical, are addressed. These are: 1. the feasibility of IFMIF accelerators, 2. the long term stability of lithium flow at IFMIF nominal conditions, 3. the potential instabilities in the lithium screen induced by the 2×5 MW impacting deuteron beam, 4. the uniformity of temperature in the specimens during irradiation, and 5. the validity of data provided with small specimens. Other ideas for fusion material testing have been considered, but they possibly are either not technologically feasible if fixed targets are considered or would require the results of a Li(d,xn) facility to be reliably designed. In addition, today we know beyond reasonable doubt that the cost of IFMIF, consistently estimated throughout decades, is marginal compared with the cost of a fusion reactor. The less ambitious DEMO reactor performance being considered correlates with a lower need of fusion neutrons flux; thus IFMIF with its two accelerators is possibly not needed since with only one accelerator as the European DONES or the Japanese A-FNS propose, the present needs >10 dpa/fpy would be fulfilled. World fusion roadmaps stipulate a fusion relevant neutron source by the middle of next decade, the success of IFMIF/EVEDA phase is materializing this four decades old dream.

The need of a neutron source for the qualification of materials to be used in future fusion power reactors have been recognized in the European (EU) fusion programme for many years. The construction and exploitation of this facility is presently considered to be in the critical path of DEMO. This issue prompted the EU to launch activities for the design and engineering of the IFMIF-DONES (International Fusion Materials Irradiation Facility-DEMO Oriented Neutron Source) facility based on and taking profit of the results obtained in the IFMIF/EVEDA (Engineering Validation and Engineering Design Activities) project, presently conducted in the framework of the EU-Japan Bilateral Agreement on the Broader Approach to Fusion. These activities and R&D work for the IFMIF-DONES Plant are presently taking place in the framework of a work package of the EUROfusion Consortium, in direct collaboration with the Fusion for Energy Organization. The main objective of these activities is to consolidate the design and the underlying technology basis in order to be ready for IFMIF-DONES construction as early as possible. The paper presents the main engineering results for a generic site obtained during the first years of design work, as indicated in the recently released IFMIF-DONES Preliminary Engineering Design Report, making emphasis on the design evolution from previous phases and on the critical issues to be further developed in the near future. The proposed European site to host the facility (Granada, Spain) is briefly introduced as well. [ABSTRACT FROM AUTHOR]

The need of a neutron source for the qualification of materials to be used in future fusion power reactors has been recognized in the European Union (EU) fusion programme for many years. The construction and exploitation of this facility is presently considered to be critical to the construction of the DEMOnstration Power Plant (DEMO). This issue has prompted the EU to launch activities for the design and engineering of the International Fusion Materials Irradiation Facility-DEMO Oriented Neutron Source (IFMIF-DONES) facility based on and taking profit of the results obtained in the Engineering Validation and Engineering Design Activities (IFMIF/EVEDA) project, presently conducted in the framework of the EU–Japan Bilateral Agreement on the Broader Approach to Fusion. These activities and research and development work for the IFMIF-DONES plant are presently taking place in the framework of a work package of the EUROfusion Consortium, in direct collaboration with the Fusion for Energy organization. The main objective of these activities is to consolidate the design and underlying technology basis in order to be ready for the start of the IFMIF-DONES construction as early as possible. In this paper, an overview and the present status of the IFMIF-DONES engineering design is presented for a generic site, making emphasis on the recent design evolution from previous phases. [ABSTRACT FROM AUTHOR]

IFMIF, the International Fusion Materials Irradiation Facility, is presently in its engineering validation and engineering design activities (EVEDA) phase under the Broader Approach Agreement. The engineering design activity (EDA) phase was successfully accomplished within the allocated time. The engineering validation activity (EVA) phase has focused on validating the Accelerator Facility (AF), the Target Facility and the Test Facility (TF) by constructing prototypes. The ELTL at JAEAc, Oarai successfully demonstrated the long-term stability of a Li flow under the IFMIF’s nominal operational conditions keeping the specified free-surface fluctuations below  ±1 mm in a continuous manner for 25 d. A full-scale prototype of the high flux test module (HFTM) was successfully tested in the HELOKA loop (KIT, Karlsruhe), where it was demonstrated that the irradiation temperature can be set individually and kept uniform. LIPAc, designed and constructed in European labs under the coordination of F4E, presently under installation and commissioning in the Rokkasho Fusion Institute, aims at validating the concept of IFMIF accelerators with a D+ beam of 125 mA continuous wave (CW) and 9 MeV. The commissioning phases of the H+/D+ beams at 100 keV are progressing and should be concluded in 2017; in turn, the commissioning of the 5 MeV beam is due to start during 2017. The D+ beam through the superconducting cavities is expected to be achieved within the Broader Approach Agreement time frame with the superconducting cryomodule being assembled in Rokkasho. The realisation of a fusion-relevant neutron source is a necessary step for the successful development of fusion. The ongoing success of the IFMIF/EVEDA involves ruling out concerns about potential technical showstoppers which were raised in the past. Thus, a situation has emerged where soon steps towards constructing a Li(d,xn) fusion-relevant neutron source could be taken, which is also justified in the light of costs which are marginal to those of a fusion plant. [ABSTRACT FROM AUTHOR]

For several reasons the challenge to keep the loads to the first wall within engineering limits is substantially higher in DEMO compared to ITER. Therefore the pre-conceptual design development for DEMO that is currently ongoing in Europe needs to be based on load estimates that are derived employing the most recent plasma edge physics knowledge. An initial assessment of the static wall heat load limit in DEMO infers that the steady state peak heat flux limit on the majority of the DEMO first wall should not be assumed to be higher than 1.0 MW m−2. This compares to an average wall heat load of 0.29 MW m−2 for the design assuming a perfect homogeneous distribution. The main part of this publication concentrates on the development of first DEMO estimates for charged particle, radiation, fast particle (all static) and disruption heat loads. Employing an initial engineering wall design with clear optimization potential in combination with parameters for the flat-top phase (x-point configuration), loads up to 7 MW m−2 (penalty factor for tolerances etc not applied) have been calculated. Assuming a fraction of power radiated from the x-point region between 1/5 and 1/3, peaks of the total power flux density due to radiation of 0.6–0.8 MW m−2 are found in the outer baffle region. This first review of wall loads, and the associated limits in DEMO clearly underlines a significant challenge that necessitates substantial engineering efforts as well as a considerable consolidation of the associated physics basis. [ABSTRACT FROM AUTHOR]

The International Fusion Materials Irradiation Facility (IFMIF), presently in its Engineering Validation and Engineering Design Activities (EVEDA) phase under the frame of the Broader Approach Agreement between Europe and Japan, accomplished in summer 2013, on schedule, its EDA phase with the release of the engineering design report of the IFMIF plant, which is here described. Many improvements of the design from former phases are implemented, particularly a reduction of beam losses and operational costs thanks to the superconducting accelerator concept, the re-location of the quench tank outside the test cell (TC) with a reduction of tritium inventory and a simplification on its replacement in case of failure, the separation of the irradiation modules from the shielding block gaining irradiation flexibility and enhancement of the remote handling equipment reliability and cost reduction, and the water cooling of the liner and biological shielding of the TC, enhancing the efficiency and economy of the related sub-systems. In addition, the maintenance strategy has been modified to allow a shorter yearly stop of the irradiation operations and a more careful management of the irradiated samples. The design of the IFMIF plant is intimately linked with the EVA phase carried out since the entry into force of IFMIF/EVEDA in June 2007. These last activities and their on-going accomplishment have been thoroughly described elsewhere (Knaster J et al [19]), which, combined with the present paper, allows a clear understanding of the maturity of the European–Japanese international efforts. This released IFMIF Intermediate Engineering Design Report (IIEDR), which could be complemented if required concurrently with the outcome of the on-going EVA, will allow decision making on its construction and/or serve as the basis for the definition of the next step, aligned with the evolving needs of our fusion community. [ABSTRACT FROM AUTHOR]

In the European fusion roadmap, ITER is followed by a demonstration fusion power reactor (DEMO), for which a conceptual design is under development. This paper reports the first results of a coherent effort to develop the relevant physics knowledge for that (DEMO Physics Basis), carried out by European experts. The program currently includes investigations in the areas of scenario modeling, transport, MHD, heating & current drive, fast particles, plasma wall interaction and disruptions. [ABSTRACT FROM AUTHOR]