Fig. 1. (a) Layout of the HiPER reactor. Reprinted with permission from J. M. Perlado et al., Proc. SPIE 8080, 80801Z (2011).¹⁸ Copyright 2011 SPIE Digital Library. (b) Schematic view of the chamber designed for the HiPER Prototype and Demo scenarios.

Fig. 2. Schematic overview of the most significant species produced in the explosion, together with their time of flight (TOF) and the depth at which they deposit most of their energy.

Fig. 3. Heat flux factor (F_HF) calculated for the different HiPER scenarios: Experimental (green dot), Prototype (yellow dot), and Demo (red dot). For comparison, F_HF values reported by Linke et al.⁷⁵ and Renk et al.⁷⁶ for surface modifications are also plotted (blue dots): roughening (R), cracking (C), melting (M), and boiling (B).

Fig. 4. Temperature of W as a function of time at different depths within the PFM for (a) HiPER Experimental scenario (first pulse), (b) HiPER Prototype scenario (steady state), and (c) HiPER Demo scenario (steady state). The steady state was reached ∼6 s and ∼60 s after the beginning of operation for HiPER Prototype and Demo scenarios, respectively. Reprinted with permission from Garoz et al., Nucl. Fusion 56, 126014 (2016). Copyright 2016 IOP Sciences.

Fig. 5. Maximum temperature calculated at the W surface and the maximum steady-state temperature. For comparison, the recrystallization and melting temperatures for W are indicated with dashed lines.

Fig. 6. Transverse stress (left) and axial strain (right) in W as a function of time for different depths. (a) HiPER Experimental scenario (first pulse). (b) HiPER Prototype scenario (steady state). (c) HiPER Demo scenario (steady state). Reprinted with permission from Garoz et al., Nucl. Fusion 56, 126014 (2016). Copyright 2016 IOP Sciences.

Fig. 7. Scanning electron microscopy images of the surface of a W sample after exposure to 1600 pulses of (a) a nitrogen beam and (b) a helium beam. Reprinted with permission from Renk et al., Fusion Sci. Technol. 61, 57–80 (2012). Copyright 2012 Taylor and Francis the American Nuclear Society (http://www.asn.org/).

Fig. 8. [(a)–(c)] Ratio of He retained to total implanted He for W samples irradiated with He at 3 keV under different conditions: (a) Continuous irradiation at a dose rate of 2 × 10¹² cm⁻² s⁻¹. (b) Pulsed irradiation, with 2 × 10¹² cm⁻² per pulse at a repetition rate of 1 Hz. (c) Comparison of continuous and pulsed irradiation at 1300 K and for different fluxes. In all cases, the number of He ions per cm² averaged over 1 s is the same (2 × 10¹² cm⁻² or 2 × 10¹³ cm⁻²). [(d)–(f)] Fraction of He retained in trapping sites for W samples irradiated with He at 3 keV under different conditions. (d) Pulsed irradiation at 700 K, with 2 × 10¹³ cm⁻² per pulse at a repetition rate of 1 Hz. (e) Pulsed irradiation at 1300 K, with 2 × 10¹³ cm⁻² per pulse at a repetition rate of 1 Hz. (f) Continuous irradiation at a dose rate of 2 × 10¹³ cm⁻² s⁻¹. Reprinted with permission from Rivera et al., Nucl. Instrum. Methods Phys. Res., Sect. B 303, 81–83 (2013). Copyright 2013 Elsevier.

Fig. 9. Top view (a) and cross-sectional (b) scanning electron microscopy images of pure α-phase nanostructured W coatings deposited by sputtering at the Instituto de Fusión Nuclear Guillermo Velarde following the procedure described in Ref. 152. The coating is made of columns with an average diameter of ∼100 nm, which grow perpendicular to the substrate.

Fig. 10. Depth distribution of vacancies for nanostructured (NW) and monocrystalline (MW) W samples sequentially irradiated in continuous mode at room temperature by C and H ions at energies of 665 keV and 170 keV, respectively, as calculated by the Object Kinetic Monte Carlo (OKMC) code MMonCa at 300 K (black), and after annealing for 30 min at 473 K (green) or at 573 K (blue). Data taken from Ref. 113.

Fig. 11. Implantation profiles of H calculated by the SRIM code for unannealed W: (a) nanostructured and (e) monocrystalline. Experimental (measured) and MMonCa simulated (calculated) depth profiles of H and vacancies for nanostructured W (left) and monocrystalline W (right) samples irradiated in continuous mode sequentially by high-energy C and H ions (665 keV and 170 keV, respectively) both at room temperature and at a fluence of 5 × 10 ²⁰ m⁻²: [(b) and (f)] unannealed, [(c) and (g)] after annealing for 30 min at 473 K, and [(d) and (h)] after annealing for 30 min at 573 K. The shaded region between 0 nm and 150 nm is not considered in the analysis because it is highly influenced by surface contamination. Data taken from Ref. 113.

Fig. 12. Cross-sectional transmission electron micrographs of a section of (a) a Mo-coated W needle (a) unirradiated, (b) exposed to 1600 He pulses. (c) Scanning electron microscopy image of a Mo-coated W needle after exposure to 1200 He pulses in RHEPP-1. Reprinted with permission from Renk et al., Fusion Sci. Technol. 61, 57–80 (2012). Copyright 2012 Taylor and Francis the American Nuclear Society (http://www.asn.org/).

Fig. 13. Nano-turf-coated tungsten foam. (a) 50×, (b) 200×, and (c) 2500× magnification. The ligaments are coated with single tungsten crystals and have characteristic lengths scales of the order of 5 µm. Reprinted with permission from Sharafat et al., J. Nucl. Mater. 347, 217–243 (2005). Copyright 2005 Elsevier.

Table 1. HiPER operating conditions for the three HiPER scenarios (Experimental, Prototype, and Demo) together with the main operating parameters and the predicted lifetimes based on purely thermomechanical considerations and on synergistic effects (combined effect of pulsed thermal load up to 10⁵ MW m⁻² and high-flux high-energy He irradiation).

Table 2. Neutron flux, average power density, damage rate, and transmutation rates caused by neutron irradiation in W in the HiPER Demo scenario. fpy stands for full power year.

Table 3. Brief overview of the type of W, annealing time and temperature, fraction of retained H obtained from experiments and simulations and main path for H release for nanostructured tungsten, and for monocrystalline samples. Prior to the analysis, all samples were first irradiated with 665-keV C ions and then with 170-keV H ions, both at room temperature and at a fluence of 5 × 10²⁰ m⁻². Identical irradiation parameters were used for computational simulations. Data taken from Ref. 113.