Editorial on the Research Topic Editorial: Mechanical Property Characterization and Radiation Res... more Editorial on the Research Topic Editorial: Mechanical Property Characterization and Radiation Resistant Design of Nuclear Structural Materials Under Ion Irradiation The development of advanced structural materials which can withstand the harsh and complex environments, such as high energy particle irradiation, high temperatures and cyclic stresses, encountered in nuclear power systems, either fission or fusion reactors, requires the understanding of the neutron radiation effects on the mechanical properties of the materials. The neutrons produced by either fission or fusion reactions create lattice damage and transmutation products. The irradiation induced defects cause or accelerate the degradation of the mechanical properties threatening the safe operation of the reactors. Moreover, the transmutation products, such as hydrogen (H) or helium (He), act synergistically with the lattice damage and degrade further the performance of the materials. The lattice damage is not produced by the neutron per se, but by the primary knock-on atoms. As a result single-or multiion irradiation, i.e., heavy ion + He + H, is used to emulate the effects of neutron irradiation, offering many advantages such as low cost, short irradiation duration, absence of radioactivity, well defined and easily controlled conditions in terms of ion energy and irradiation dose. On the other hand, small-scale mechanical testing can be used as a tool for material screening. However, the analysis of the mechanical test data at nano-or micro-scale, especially of the ion irradiated materials, is challenging and sometimes debatable. The current Research Topic is focused on the small-scale mechanical characterization of ion and neutron irradiated metallic structural materials. The review article of Mei et al. focuses on the research progress on the application of smallscale mechanical property tests for investigating the mechanical properties of ion-irradiated materials, i.e., radiation-induced strengthening/hardening, embrittlement, as well as the creep and fatigue. The advantages and shortcomings of the currently used techniques and data analysis models are discussed as well as the consistency and reliability of them are overviewed. Das et al. focus their research on the effect of the ion energy on the hardening of pure Fe, ferritic Fe-9Cr, martensitic Fe-9Cr and ferritic-martensitic reduced-activation steel Eurofer 97 using depth sensing nano-indentation. Through empirical models they describe the hardness increase versus contact depth taken into consideration the profiles of the displacement damage and the implanted ions in combination with indentation size effects. An approach is suggested to separate the displacement damage contribution in hardening in order to make it comparable to
This paper compares the gyrokinetic instabilities and transport in two representative JET pedesta... more This paper compares the gyrokinetic instabilities and transport in two representative JET pedestals, one (pulse 78697) from the JET configuration with a carbon wall (C) and another (pulse 92432) from after the installation of JET's ITERlike Wall (ILW). The discharges were selected for a comparison of JET-ILW and JET-C discharges with good confinement at high current (3 MA, corresponding also to low ρ *) and retain the distinguishing features of JET-C and JET-ILW, notably, decreased pedestal top temperature for JET-ILW. A comparison of the profiles and heating power reveals a stark qualitative difference between the discharges: the JET-ILW pulse (92432) requires twice the heating power, at a gas rate of 1.9×10 22 e/s, to sustain roughly half the temperature gradient of the JET-C pulse (78697), operated at zero gas rate. This points to heat transport as a central component of the dynamics limiting the JET-ILW pedestal and reinforces the following emerging JET-ILW pedestal transport paradigm, which is proposed for further examination by both theory and experiment. ILW conditions modify the density pedestal in ways that decrease the normalized pedestal density gradient a/L n , often via an outward shift of the density pedestal. This is attributable to some combination of direct metal wall effects and the need for increased fueling to mitigate tungsten contamination. The modification to the density profile increases η = L n /L T , thereby producing more robust ion temperature gradient (ITG) and electron temperature gradient driven instability. The decreased pedestal gradients for JET-ILW (92432) also result in a strongly reduced E × B shear rate, further enhancing the ion scale turbulence. Collectively, these effects limit the pedestal temperature and demand more heating power to achieve good pedestal performance. Our simulations, consistent with basic theoretical arguments, find higher ITG turbulence, stronger stiffness, and higher pedestal transport in the ILW plasma at lower ρ * .
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2018
Measurements of neutron streaming through penetrations in biological shields are being carried ou... more Measurements of neutron streaming through penetrations in biological shields are being carried out at JET fusion device by means of thermoluminescence (TL) detectors with the objective to validate the neutronics codes and nuclear data widely applied in ITER nuclear analyses in a real fusion environment. TLDs response due to the neutron component of the radiation field is related to the neutron fluence in a well-defined neutron energy spectrum. Therefore, a TLDs calibration in real fusion radiation fields is necessary to allow neutron fluence from TL measurements at JET to be more precisely calculated. Hence, a MCP-N and MCP-7 TLDs produced at the IFJ PAN in Kraków were calibrated at the ENEA facilities of Frascati and Casaccia laboratories. The obtained results have been analysed and new calibration factors are proposed. The detection system based on TLDs developed and calibrated for JET experiments can then be generally applied not only to fusion neutron fields, but also to ITER to monitor the neutron fluence outside the biological shield.
The recently developed Monte-Carlo code ERO2.0 is applied to the modelling of limited and diverte... more The recently developed Monte-Carlo code ERO2.0 is applied to the modelling of limited and diverted discharges at JET with the ITER-like wall (ILW). The global beryllium (Be) erosion and deposition is simulated and compared to experimental results from passive spectroscopy. For the limiter configuration, it is demonstrated that Be self-sputtering is an important contributor (at least 35%) to the Be erosion. Taking this contribution into account, the ERO2.0 modelling confirms previous evidence that high deuterium (D) surface concentrations of up to ∼ 50% atomic fraction provide a reasonable estimate of Be erosion in plasma-wetted areas. For the divertor configuration, it is shown that drifts can have a high impact on the scrape-off layer plasma flows, which in turn affect global Be transport by entrainment and lead to increased migration into the inner divertor. The modelling of the effective erosion yield for different operational phases (ohmic, Land H-mode) agrees with experimental values within a factor of two, and confirms that the effective erosion yield decreases with increasing heating power and confinement. 2. The ERO2.0 code The physics basis of the ERO1.0 code, on which ERO2.0 is based, is
Corrigendum to "Thermal desorption spectrometry of beryllium plasma facing tiles exposed in the J... more Corrigendum to "Thermal desorption spectrometry of beryllium plasma facing tiles exposed in the JET tokamak" [Fusion Eng. Des. 133 (2018) 135-141]
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