Simulation of first wall damage: Effects of the method of gas implantation

Abstract

Cavity formation in an austenitic alloy of similar composition to type 3(6 stainless steel has been explored with regard to various methods of gas implantation. Irradiations were conducted at 900 K to doses of 1, 10, and 70 dpa with helium injection levels of 20 appm/dpa. Highest swelling (18%) was exhibited by the unimpUnted reference material; a lesser amount by simultaneous helium injection (11%). Greatly reduced swelling due to profuse cavity nucleation was the result of the preinjection of 1400 appm He, either at room temperature (S-1%) or at 900 K (*%). The dirlocation density was not sensitive to helium injection technique. Simultaneous injection of SO appm H/dpa, along with the He, nay have caused a modest increase in the cavity and dislocation concentrations at higher doses. The observations are compared with a theory of void growth kinetics to estimate the relative influence of voids and dislocations as point defect sinks.

Helium trapping in carbide precipitates in a tempered F82H ferritic–martensitic steel

“…The application of NFAs for this purpose is predicated on the ultra-fine-dispersion of nano-scale precipitates distributed throughout the matrix acting as effective nucleation sites for nano-scale He bubbles, rather than the random nucleation of larger He bubbles typically observed in traditional steels that do not contain nano-scale precipitates [11][12][13][14][15][16].…”

Transmission electron microscope study of fusion-environment radiation damage in iron and iron-chromium alloys

“…As in the current study, Packan and Farrell [132] have found that, for irradiations of an austenitic alloy similar to 316 stainless steel, room-temperature pre-injection of helium followed by 4 MeV ^1++-bombardment to 10 dpa at 898 K caused a reduction in the dislocation density compared to triple-beam ion-irradiation (10 dpa, 200 at.…”

Void swelling in high dose ion-irradiated reduced activation ferritic–martensitic steels

“…According to the critical bubble-to-void and rate theory [19][20][21][22][23], helium facilitates nucleation of voids by lowering the critical radius required for bias-driven void growth, and it usually increases the concentration and reduces the size of voids. Helium encourages the formation of voids and assists swelling, and it is also possible to depress the growth of voids and thereby retarding swelling if voids become the dominant sink [19,20,24,25].…”

“…Farrell and Packan [19,25] investigated the effects of the method of gas implantation on void formation, including implanting helium at room temperature prior to irradiation, preimplanting helium at the irradiation temperature, and implanting helium during irradiation. They found that the cold-preimplanted helium is much more effective in increasing the void concentration and reducing void size than hot-preimplanted helium and simultaneous implanted helium.…”