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Abstract The cladding of fast reactor fuel rods, made of stainless steel, presents significant challenges in cutting due to its ductility, which leads to increased tool wear and poor cut quality with traditional mechanical methods. Laser cutting has emerged as a superior alternative, offering non-contact precision, high efficiency, and suitability for radioactive environments. This study systematically investigates the effects of laser cutting parameters—cutting speed, focal position, power, and gas pressure—on the cutting quality of simulated fast reactor fuel rods. The results show that optimal cutting is achieved with a cutting speed of 1 m/min, a focal position between − 20 and − 25 mm, a laser power between 7200 and 9600 W, and a gas pressure of 10 MPa. These parameters provide the best balance between cutting efficiency, surface roughness, and minimal slag formation. This study contributes valuable insights into optimizing laser cutting technology for nuclear fuel rod processing, with potential applications in fuel reprocessing and decommissioning.

An important factor in determining the integrity and lifetime of fuel assemblies in fast breed reactors is the fuel-cladding chemical interaction (FCCI) between MOX fuel and stainless steel cladding. This FCCI has been widely investigated through numerous in-pile and out-pile tests. Fission products (caesium, tellurium, iodine, etc.) and in-pile fuel and irradiation parameters (initial stoichiometric ratio of MOX fuel, burn-up, and cladding temperature, etc.) play an important role in the FCCI mechanism and corrosion severity of the cladding, leading to complex surface and matrix corrosion conditions. Cs- and Te-induced corrosion dominate at high and low oxygen potentials, respectively, leading to severe corrosion associated with the cladding components. However, a coupling effect of both elements is present at specific oxygen potentials. The temperature, burn-up and initial stoichiometric ratio of the fuel determine the oxygen potential at the inner surface of cladding, thus affecting the type and depth of corrosion caused by fission products. Based on these affecting factors, several prediction models applicable to different conditions have been proposed, among which the Japanese model and HEDL model are considered suitable for high and low oxygen potentials, respectively. Nevertheless, both models neglect the impacts of cladding components and properties. Finally, the differences between out-pile simulations and in-pile irradiation experiments are discussed, which need to be emphasized when analysing the experimental results. [ABSTRACT FROM AUTHOR]

Metal cladding is a process of depositing a filler material to enhance the surface properties of base material using a suitable welding process. In this work the clad specimens are produced by surfacing a layer of filler material using weld cladding process to minimize the heat loss across the walls of the pressure vessels. It is done by depositing a low thermal conductivity austenitic stainless steel grade of 316L on structural steel plates used for boiler construction using flux cored arc welding process. The experimental study is carried out as per design of experiments availed for five factors five levels central composite design using response surface methodology. The mathematical models are developed for the prediction of clad layer height, clad layer width and depth of penetration. These models are employed in formulating fitness functions for multi-objective optimization of clad layer dimensions using genetic algorithm (GA). The set of optimal solutions suggested by response surface optimizer and genetic algorithm are compared and discussed. Conformity tests are conducted to validate the prediction capability of developed models and optimum settings. Optimum clad layer dimensions have been arrived and optimized stainless steel clad specimen has been produced. The heat transfer analysis is planned to be conducted in the next phase. The findings can be used in energy efficient design of pressure vessels. [ABSTRACT FROM AUTHOR]

Jagged cracks were observed in SA240 Type 405 stainless steel cladding of Inconel 625 overlay repaired coke drums. It is found that intergranular cracking is the dominant fracture mode in the fine-grained heat-affected zone (FGHAZ) of the boat specimens. The sensitization effect from the operation and welding thermal cycles leads to the depletion of Cr with the preferential precipitation of Cr-rich M 23 C 6 carbides along the grain boundaries. The cladding FGHAZ has the largest frequency of grain boundaries with higher local strain levels and the highest fraction of grain boundary Cr-rich M 23 C 6 carbides. Thermal stress distributions predicted by finite element analysis clearly show the maximum shear stress to exhibit the typical “jagged” pattern near the cracked regions. Thermal expansion coefficient and strength mismatch among the shell base metal, cladding, and overlay is believed to have caused the unique jagged maximum shear stress distribution in the cladding HAZ of Inconel 625 overlay. The magnitude of this thermal stress can reach the yield strength of the cladding at 900 °F (482 °C) service temperature, therefore, provides the driving force for the jagged cracking formation in the sensitized HAZ. [ABSTRACT FROM AUTHOR]

• Ground surface has higher oxidation resistance than mechanically polished surface. • A fine-grained layer favors formation of dense oxide film with high Cr/Fe ratio. • Highly network Cr-bearing δ-ferrite improves the oxidation resistance. • Thermally activation enhanced self-diffusion of Cr in ferrite inhibits oxidation. • The ferrite-affected oxidation zone expands with the increase in temperature. The properties of the oxide films grown on 308 L SS cladding with various surface treatments and temperatures in simulated PWR primary water are studied. The thickness of the inner oxide layer increases with the decrease of the surface roughness. The high oxidation resistance of the ground surface is due to the thicker fine-grained layer with high dislocations density and subgrain boundaries in the near-surface. The ferrite-affected oxidation zone (FAOZ) expands with the increase in temperature, resulting from the thermally activated self-diffusion of Cr in ferrite. The effects of surface states, ferrite and temperature on oxidation performance of 308 L SS cladding are discussed. [ABSTRACT FROM AUTHOR]

The effect of the heat treatment on the residual stresses of welded cladded steel samples is analyzed in this study. The residual stresses across the plate's square sections were determined using complementary methods; applying diffraction with neutron radiation and mechanically using the contour method. The analysis of the large coarse grain austenitic cladded layers, at the feasibility limits of diffraction methods, was only made possible by applying both methods. The samples are composed of steel plates, coated on one of the faces with stainless steel filler metals, this coating process, usually known as cladding, was carried out by submerged arc welding. After cladding, the samples were submitted to two different heat treatments with dissimilar parameters: one at a temperature of 620 °C maintained for 1 h and, the second at 540 °C, for ten hours. There was some difference in residual stresses measured by the two techniques along the surface of the coating in the as-welded state, although they are similar at the welding interface and in the heat-affected zone. The results also show that there is a residual stress relaxation for both heat-treated samples. The heat treatment carried out at a higher temperature showed sometimes more than 50% reduction in the initial residual stress values and has the advantage of being less time consuming, giving it an industrial advantage and making it more viable economically. [ABSTRACT FROM AUTHOR]

Abstract: This paper highlights an experimental study carried out to analyse the effects of various gas metal arc welding (GMAW) and universal gas metal arc welding (UGMAW) process parameters on dilution in single layer stainless steel cladding of low carbon structural steel plates. Four factors five levels central composite rotatable design was used to develop relationship for predicting dilution, which enables to quantify the direct and interactive effects of four numeric factors i.e. wire feed rate, open circuit voltage, welding speed and nozzle-to-plate distance and one categorical factor preheat current. This comparative study reveals that dilution obtained in UGMAW process is significantly lower than that with GMAW process due to external preheating of the filler wire in UGMAW process which results in greater contribution of arc energy by resistive heating and as a consequence, significant drop in the main welding current values in case of UGMAW process is observed. Mathematical models developed show that dilution increases with increase in wire feed rate, open circuit voltage and welding speed, whereas it decreases with increase in nozzle-to-plate distance and preheat current. Furthermore the optimization capabilities in design-expert software were used to numerically optimize the input parameters and the optimal solutions generated indicate that for same levels of dilution, higher deposition rates were achieved in UGMAW process thus establishing that UGMAW process can prove to be a good choice for low cost surfacing applications. [Copyright &y& Elsevier]

• Oxidation and SCC behaviour of 309 L/308 L SS welds were studied in PWR primary water. • There was no indication of SCC for low alloy steel (LAS) after SSRT tests. • The oxidation resistance of 309 L SS was lower than that of 308 L SS. • 309 L SS was more susceptible to SCC than 308 L SS in PWR primary water. Oxidation resistance and stress corrosion cracking (SCC) susceptibility of A508Ⅲ-309 L/308 L stainless steel (SS) claddings were investigated in simulated pressurized water reactor (PWR) primary water following a microstructure characterization. Preferential oxidation of slip bands was observed in 309 L SS. The oxidation resistance of 309 L SS was found to be lower than that of 308 L SS due to the higher Cr- and ferrite-content in 308 L SS than in 309 L SS after cladding. There was no indication of SCC for low alloy steel (LAS) after slow strain rate tensile (SSRT) tests. The presence of type-I and type-II boundaries, composition dilution and less δ-ferrite content synergistically contributed to increasing the SCC susceptibility of 309 L SS cladding. The effect of chemical composition and microstructure on SCC performance of the SS claddings was discussed. [ABSTRACT FROM AUTHOR]