Influence of Helium on Swelling of Steels

Abstract

In this work, we have studied the effect of helium and its injection mode on the microstructure of Type 316 and titanium-modified Type 316 stainless steels, both in their solution-annealed and cold-worked states. Irradiations have been conducted in a dual-beam accelerator to doses up to 150 dpa in a wide range of temperatures, from 550 to 750°C. Different injection modes have been investigated: cold preinjection, hot preinjection, and dual beam. The results show that the effect of helium on swelling is largely dependent on the injection mode and also on the chemical composition of the alloy considered. In Type 316 steel, the presence of helium decreases swelling, the major effect being observed when helium is preinjected at room temperature. In titanium-modified steels, if a high density of tiny helium bubbles are present in all the specimens containing helium, void swelling only occurs for dual-beam irradiations. In conclusions, this work shows that the effect of helium on void swelling depends on its injection mode, but also that the sense of this effect is clearly different when comparing the behavior of a low and a high swelling alloy.

Monitoring of the microstructure of ion‐irradiated nuclear ceramics by in situ Raman spectroscopy

“…Moreover, some studies show that sequential single beam or simultaneous multiple beam irradiations do not produce the same type of microstructural evolution. For example, Lévy and coworkers clearly demonstrated that sequential dual‐beam irradiation of 316 steel (using Ni and He ions) could lead to substantially different results in terms of swelling amplitude. More recently, Thomé and coworkers performed at JANNUS‐Saclay sequential single and dual‐beam irradiations of oxides (ZrO 2 , MgO and Gd 2 Ti 2 O 7 ) and carbides (SiC) to study combined effects of nuclear stopping power S n (using 900‐keV I ion) and electronic stopping power S e (using 36‐MeV W ions).…”

An assessment of the available alternatives for fusion relevant neutron sources

“…The length scales of relevant processes range from ~1 Å to ~10 m of structural components, and relevant timescales are covering 22 orders of magnitude, with the shortest time-scale being in the femtosecond range [44]. The threshold energy of 3.7 MeV for the impacting neutron in the reaction 56 Fe(n,α) 53 Cr limits to 0.3 appm/dpa of He generation in RAFM even in fast fission reactors, compared with the 12 appm/dpa of the 14.1 MeV of fusion neutrons [21,45]. In turn, fusion neutrons generate H through 56 Fe(n,p) 56 Mn reactions at a rate of 45 appm/dpa compared with the 0.7 appm/dpa of fission neutrons.…”

“…The threshold energy of 3.7 MeV for the impacting neutron in the reaction 56 Fe(n,α) 53 Cr limits to 0.3 appm/dpa of He generation in RAFM even in fast fission reactors, compared with the 12 appm/dpa of the 14.1 MeV of fusion neutrons [21,45]. In turn, fusion neutrons generate H through 56 Fe(n,p) 56 Mn reactions at a rate of 45 appm/dpa compared with the 0.7 appm/dpa of fission neutrons. Nevertheless, the high permeation of hydrogen makes the potential degrading impact of hydrogen less relevant as already pointed out by Birrs in 1969 [11].…”

“…Averback first studied the simulation of neutron induced damage effects in irradiated materials by means of ion beams in 1978 [55]. However, the validity of the reproduction of the He generation concurrently with the recoiling atoms from ion impacts was only accepted as practical by middle 80s, after the understanding of the role of He in the incubation period for void swelling through its induced thermodynamic stabilization of vacancy clusters [56,57]. Triple beam irradiation facilities allow studying synergies of recoiling atoms in the presence of H and He production as well as other transmuted elements for fusion materials research.…”

JANNUS: A multi-irradiation platform for experimental validation at the scale of the atomistic modelling

“…Then, Farrell, Lewis and Packan showed that during the dual or triple irradiation of steel, hydrogen synergistic effects are rather limited on the evolution of microstructure [2]. In France, Lévy, Gilbon and Rivera clearly demonstrated that sequential and dual beam irradiation of 316 steel (Ni and He ions) could lead to substantially different results in terms of swelling amplitude [3].…”