Molten salt reactors are one of the technologies developed under GEN IV nuclear research. The mol-ten mix of LiF and BeF2, LiF, NaF nad KF, or NaBF4 and NaF act both as a reactor coolant both in primary and secondary loop. The combination of m...

The presented paper is focused on laser shock-peening technology for hardening the metallic material surface. The material surface hardening improve fatigue performance, static properties, and resistance to stress corrosion cracking of metallic material, which is achieved by creating a pressure residual stress with. The hardening is achieved by shock waves, which are generated by confining the laser-induced plasma to cause a large pressure shock wave over a significant surface area. In the present study, effects of laser shock peening (LSP) on static and dynamic mechanical properties of austenitic stainless steel for nuclear industry were investigated. The tested material was austenitic stainless steel GOST 08CH18N10T (AISI 321H-UNS S32109) for nuclear industry (water–water energetic reactors).

One of the concepts behind Generation IV reactors is a molten salt coolant system, where the materials for the reactor itself and for the primary and secondary circuit components are subjected to extreme chemical and thermal stresses. Due to the unavailability of these materials, a nickel–molybdenum alloy known as MoNiCr has been developed in the Czech Republic. This paper discusses the manufacturing process for the MoNiCr alloy, covering conventional casting technology, forming, powder atomization, additive manufacturing (AM) using the directed energy deposition (DED-LB) process, and final heat treatment. Special attention was given to the quality of the input powders for additive manufacturing, particularly regarding the optimization of the chemical composition, which significantly influenced the quality of the additively manufactured components. AM enables the realization of complex structural designs that are critical for energy applications, despite the high susceptibility of the MoNiCr alloy to solidification cracking. Through AM, a test body was successfully produced with a maximum defect rate of 0.03% and the following mechanical properties: a yield strength (YS) of 279 MPa, an ultimate tensile strength (UTS) of 602 MPa, and an elongation (El) of 51%.

A custom low-chromium MoNiCr alloy produced by wire-fed laser directed energy deposition (W-DED) was exposed to eutectic LiF–BeF₂ (FLiBe) at 750 °C for 1000 h to assess corrosion of the retained deposition surface. A nominally 100 × 100 × 100 mm cube was divided into as-built (AB) and hot-isostatically pressed (HIP) portions. Two coupons were extracted from each of the X–Y, Z–X, and Z–Y surface layers of each portion, giving 12 coupons. Each coupon was fully immersed in a separate nominally equal salt charge within a graphite crucible enclosed in an individually sealed AISI 304 capsule. Characterization focused on the original W-DED face. Optical profilometry compared exposed coupons with adjacent unexposed reference regions. Cross-sectional scanning electron microscopy and energy-dispersive X-ray spectroscopy assessed microstructure and near-surface chemistry. The topography measurements showed substantial spatial variability and did not establish a consistent dependence on orientation or material condition. Backscattered-electron images and semiquantitative elemental profiles indicated a shallow near-surface region associated with Cr depletion, without establishing a quantitative penetration depth or corrosion rate. The results provide descriptive screening observations for retained W-DED surfaces under the specific static exposure conditions. Unmeasured salt redox potential and impurity concentrations, together with the limited replication, constrain their use in material qualification.

A Hastelloy N-like MoNiCr alloy produced by wire-laser directed energy deposition (W-DED) was exposed to eutectic LiF–BeF₂ (FLiBe) at 750 °C for 1000 h to assess the effects of manufacturing-generated surface states on corrosion response. Surface-skin coupons were extracted from as-built (AB) and hot-isostatically pressed (HIP) portions of a W-DED cube while preserving either the deposited surface or a wire electrical-discharge-machined (wire-EDM) surface. High-purity LiF and BeF₂ powders were mixed to the eutectic composition (66 mol% LiF–34 mol% BeF₂), melted at 700 °C under nitrogen, and the salt was subsequently remelted and poured over specimens in individual graphite crucibles before hermetic enclosure in laser-welded AISI 304 capsules. Optical profilometry compared exposed coupons with adjacent unexposed reference regions; metallography, SEM, and EDS evaluated microstructure and near-surface chemistry. Preserved deposited surfaces largely retained their orientation-dependent topography, whereas exposed wire-EDM surfaces had lower height-related roughness parameters than the unexposed references and developed a more uniform chromium-depleted region. HIP altered internal microstructure more strongly than macroscopic surface morphology. Because redox potential and a complete material balance were not measured, the results are interpreted as comparative static-screening data for MSR service. Mean chromium-depletion depth was approximately 8 ± 2 µm for preserved W-DED surfaces and 11 ± 1 µm for wire-EDM surfaces.