Retaining tritium in the structural materials of future fusion reactors constrains the fuel cycle and safety: the regulatory limit for ITER is about 1 kg of tritium in the vacuum vessel. Neighboring studies in the archive show how irradiation changes magnetic properties, how hydrogen embrittles steel, and how boron coatings protect walls, but the atomic mechanism linking radiation-induced segregation to hydrogen isotope trapping at high temperatures remained unclear. This article fills that gap by connecting experiments and calculations.
Samples of F82H-IEA steel were simultaneously irradiated with iron (5 MeV), hydrogen (390 keV), and helium (2.85 MeV) ions at 500 °C to doses of 50 and 150 dpa. The chemical composition of cavities was examined using transmission electron microscopy with energy-dispersive X-ray spectroscopy. Then, density functional theory was used to model iron (100) and (110) surfaces with helium clusters and Cr, Ta, W impurities at coverages from 0.1 to 1 monolayer; hydrogen binding energies and migration barriers were calculated using the CI-NEB method.
Experiments revealed pronounced segregation of chromium and tantalum on helium cavity surfaces, while tungsten remained uniformly distributed. Calculations showed that Cr, Ta, and W generally strengthen hydrogen binding compared to pure iron: on the (100) facet tantalum has the largest effect, while on the (110) facet chromium wins at high coverages. Helium acts oppositely: at He/V = 1 the hydrogen binding energy drops due to lattice compression and reduced charge transfer, but segregated Cr and Ta preserve the traps. Electronic analysis revealed two mechanisms: strong hybridization of H 1s with d-orbitals of Ta and W, and a shift of the surface d-band, which for Cr brings it closer to the Fermi level and enhances adsorption.
This work differs from neighboring studies in that it is the first to link observed radiation-induced segregation of alloying elements to enhanced hydrogen retention at the atomic level. Neighbors studied the effects of irradiation on magnetic properties, hydrogen embrittlement, and protective coatings, but did not consider the combined action of helium, impurities, and hydrogen at cavity surfaces. Here it is shown that cavity surface chemistry is governed not only by helium but also by segregated elements, opening a path to managing tritium inventory through alloy composition.
The topic could develop toward multiscale modeling, from electronic structure to kinetic models of tritium accumulation under realistic irradiation conditions. It would be interesting to test how Cr and Ta segregation affects deuterium and tritium trapping at higher temperatures and doses, and to investigate other elements such as vanadium or manganese. Optimizing RAFM steel composition to reduce tritium retention without losing mechanical properties is a possibility.
The results will influence the design of materials for fusion reactor blankets and divertors, as well as the assessment of the fuel cycle and safety.
The next step is to verify the predictions of the calculations using thermal desorption spectroscopy on samples with known segregation, and then incorporate the obtained binding energies into kinetic models of tritium accumulation.
This work directly addresses the unresolved problem of quantitatively predicting tritium retention in irradiated steels: until now it was unclear how radiation-induced segregation changes the hydrogen binding energy at interfaces. The obtained data allow refining fuel cycle models and tritium breeding requirements.
This section is addressed to the author of the paper and their colleagues. Neighbouring works were found by meaning-based search across our archive, not by word overlap. We do not review: we show the field around the work.
What the work does
The study experimentally detected segregation of Cr and Ta on the walls of helium cavities in F82H steel after triple irradiation at 500 °C. DFT calculations showed that these impurities enhance hydrogen binding, while helium weakens but does not eliminate the effect. The mechanism is linked to hybridization of H 1s with metal d-states and a shift of the d-band.
Where its strength is
The work connects observed radiation-induced segregation with atomic-scale calculations, showing how the local chemistry of cavity surfaces governs hydrogen retention. This provides a concrete basis for managing tritium inventory through alloy composition.
Where it could go next
Worth trying
Why this may matter
Understanding how segregation of alloying elements on cavity surfaces affects tritium retention could help develop steels with reduced tritium accumulation, which is critical for the safety of future fusion reactors.
Nearby works in our archive
The archive is sparse around this work: the closest review is only 0.50, against a usual 0.64. It looks like few have drilled nearby.
The binding energy of hydrogen on a tantalum-decorated surface reaches 1.2 eV, comparable to the binding energy in a water molecule; meanwhile, the hydrogen release barrier can increase by 0.3 eV, meaning that freeing an atom requires a temperature roughly 350 degrees higher than for pure iron.