Additively manufactured stainless steels could help build the next generation of nuclear reactors, but a new review finds that their radiation performance is far from guaranteed. The analysis, published in Frontiers in Nuclear Engineering, compiles the scattered irradiation data collected to date on 3D-printed 304 and 316 stainless steels and concludes that the same microstructural features that can protect these alloys from radiation damage can also become weak points under the wrong conditions. The authors, from Utah State University and Idaho National Laboratory, argue that the existing database remains too sparse and fragmented to qualify printed components for reactor service, even as the field moves from small test coupons toward actual hardware.
The motivation comes from the extreme demands of Generation IV reactor concepts, which include molten salt reactors, sodium fast reactors, lead fast reactors, supercritical water cooled reactors, very high temperature gas reactors, and gas fast reactors. These designs push operating conditions beyond the experience of today’s light water fleet. The review notes that maximum irradiation damage is estimated to rise from 80 displacements per atom in pressurized water reactors to 200 displacements per atom in molten salt and sodium fast reactors, while molten salt coolants also create more corrosive environments. The authors set an upper-bound screening envelope of 600 degrees Celsius and 200 displacements per atom for components where stainless steel is relevant, and they use that envelope as the benchmark against which all available printed-steel irradiation data are judged.
Additive manufacturing appeals to reactor designers for reasons that go beyond materials performance. Laser powder bed fusion and directed energy deposition can fabricate complex geometries such as heat exchangers, valves, and pump housings that are difficult or impossible to machine conventionally, consolidate multi-part assemblies to reduce failure-prone joints, and cut lead times by eliminating specialized tooling. The processes can also vary properties spatially, allowing a component’s surface to be optimized for radiation resistance while its core is tuned for structural toughness. But the review emphasizes that printed metals are not simply conventional alloys in a new shape. Rapid solidification produces fine cellular sub-grain structures, high dislocation densities, small melt pools, and sometimes nano-oxide particles, and these features act as sinks that can absorb the vacancies and interstitials created by radiation.
On irradiation hardening, the compiled evidence is cautiously favorable. Under xenon ion irradiation, selective laser melted 304L showed a normalized hardness increase of roughly 37 percent at 10 displacements per atom, compared with 76 percent in traditionally manufactured material, a difference linked to smaller and fewer dislocation loops in the printed alloy. Iron ion studies on printed 316L showed consistently lower hardening than wrought counterparts for the same reason. Adding dispersed titanium carbide to printed 316L suppressed hardening further at low doses, with a 4 percent TiC condition showing the lowest hardening rate, although the benefit became less consistent at higher damage levels, hinting at possible sink saturation. The review stresses, however, that the advantage is conditional: heat-treated printed 316L can respond comparably to wrought material, and irradiation temperature matters, since raising the temperature from room temperature to 450 degrees Celsius reduced loop density and weakened hardening in one selective laser melting study.
Build orientation adds another layer of complexity. One study of laser additive manufactured 316L found that irradiation hardening was lowest parallel to the build direction and highest perpendicular to it, with nanoindentation showing a progression from 19 percent hardening in vertical builds to 24 percent in 45-degree builds and 26 percent in horizontal builds. Electron backscatter diffraction revealed corresponding differences in crystallographic texture and Taylor factor, giving a crystallographic basis for the anisotropic response. The review concludes that hardening in printed 316L depends not only on how many defects accumulate but also on grain structure, texture, and defect morphology relative to the loading direction, which means qualification testing must characterize components in multiple directions rather than relying on a single coupon orientation.
Irradiation-assisted stress corrosion cracking results tell a similar story of conditional benefit. Hot isostatic pressing emerged as a standout: printed 316L samples treated with HIP showed no cracks after constant extension rate testing, while wrought 316L samples developed intergranular cracks at the same strain levels. Notably, the HIP printed material had nearly identical chromium depletion at grain boundaries compared with the cracking-prone wrought samples, and it actually exhibited about 30 percent more radiation hardening, yet it resisted cracking better. The authors attribute this to broader dislocation channels and reduced strain localization near grain boundaries, a finding that moves the field beyond the traditional framework in which radiation-induced segregation and hardening alone predict cracking susceptibility. Micro-alloying with tiny amounts of hafnium also improved cracking resistance by suppressing hardening and strain localization.
Cracking behavior in printed alloys can also diverge qualitatively from wrought material. Directed energy deposition samples showed a unique intragranular cracking mode, with cracks forming inside grain matrices away from boundaries, attributed to delta-ferrite particles, and other work documented intergranular, intragranular, and transgranular cracking coexisting in stress-relieved printed 316L under proton irradiation. Anisotropy appears here too, but with a twist: one study found stress-relieved directed energy deposition samples more crack-resistant when loaded perpendicular to the build direction, while laser powder bed fusion studies found better resistance when loading was parallel to it, a discrepancy the review attributes to differences in powder composition and build technique. All current cracking studies used simulated boiling water reactor chemistry, which the authors caution may not translate to the non-aqueous coolants of Generation IV designs.
Void swelling data are the most contradictory. Some studies found printed 316L in as-built or stress-relieved states swelled more than recrystallized or hot isostatically pressed conditions, with one reporting roughly twice the swelling rate for as-built versus solution-annealed and fully recrystallized samples at 500 degrees Celsius and 50 displacements per atom. Others found printed material outperformed wrought alloy, attributed to sub-grain boundaries and nano-oxide inclusions acting as trap sites. Hafnium doping repeatedly helped, reducing void size, density, and swelling rate, with doped as-built samples reaching about 1 percent peak swelling versus 3.75 percent for undoped recrystallized samples under helium irradiation. Yet one study reported slightly reduced swelling resistance in HIP samples due to larger cavities, and another found as-built samples swelled before wrought material at room temperature. Calculated steady-state rates of 0.15 percent per displacement per atom for stress-relieved and 0.1 percent for HIP printed samples, well below the roughly 1 percent per dpa established for wrought austenitic stainless steels, are encouraging but rest on limited dose ranges.
A recurring complication is that almost all of these results come from accelerated ion irradiation rather than neutron exposure. The review explains that ion beams can reach dose rates many orders of magnitude higher than reactor neutrons, which alters defect accumulation, segregation, and swelling kinetics. Heavier ions also differ in their efficiency at producing freely migrating defects, so equal displacements per atom do not guarantee equal degradation. Neutrons additionally produce transmutation helium and hydrogen inside the metal, gases that accumulate at grain boundaries and voids and can accelerate swelling; single-ion experiments that omit these effects may underestimate degradation. The authors point to the absence of swelling in some heavy-ion studies at 100 displacements per atom alongside void formation at 2.5 displacements per atom under proton irradiation as evidence that dose rate effects can mask or reveal damage depending on the technique used.
The review closes with a research agenda aimed at qualification rather than demonstration. The authors call for head-to-head comparisons of laser powder bed fusion, directed energy deposition, and wrought references using closely matched chemistry and identical irradiation conditions; systematic irradiation-response maps spanning low to high damage levels at fixed temperatures with well-reported dose rates; paired ion and neutron campaigns on the same material heats, including dual- and triple-beam experiments that capture transmutation gas effects; and long-term stability testing of cellular structures, oxides, and engineered interfaces at reactor-relevant exposures. They also urge statistically designed sampling across multiple builds to address anisotropy and property scatter, and coupled studies treating cracking, hardening, swelling, creep, and corrosion as linked outcomes. Recent milestones, including successful neutron irradiation of printed 316H capsules at Oak Ridge National Laboratory, the NUCOBAM qualification project, and ASME qualification efforts for printed 316H, suggest the community is already moving toward component-level deployment, but the authors conclude that the irradiation database for printed stainless steels is still not systematic enough for design use.
Subject of Research: Irradiation damage behavior of additively manufactured 304 and 316 stainless steels for Generation IV nuclear reactors
Article Title: A review of irradiation damage in additively manufactured stainless steels for next-generation nuclear systems
Article References: Adhikari, M., Anwar, T. U., Kamboj, A., & Kouraytem, N. (2026). A review of irradiation damage in additively manufactured stainless steels for next-generation nuclear systems. Frontiers in Nuclear Engineering, 5, Article 1870147. https://doi.org/10.3389/fnuen.2026.1870147
Image Credits: AI Generated
DOI: 10.3389/fnuen.2026.1870147
Keywords: additive manufacturing, stainless steel, irradiation damage, Generation IV reactors, void swelling, irradiation hardening, IASCC, hot isostatic pressing, ion irradiation, nuclear materials, microstructure, radiation-induced segregation
News Source: Denise Maddox. (November 5, 2026). 3D-Printed Stainless Steels Show Uneven Radiation Resistance in Nuclear Reactor Review. Scienmag.
