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BackgroundLiquid molten salt reactors that use chloride salts as fuel are characterized by the high solubility of heavy metals and a hard energy spectrum, hence are ideal for transmuting transuranic nuclides (TRU). A small modular reactor exhibits the characteristics of a modular design and construction, which is one of the future development directions for nuclear energy.PurposeThis study aims to investigate the TRU incineration characteristics of a small modular chloride fast reactor (sm-MCFR) that can be refueled online and applied to the disposal of TRU in nuclear waste produced by pressurized-water reactors.MethodsFirstly, a 50-MW sm-MCFR scheme was proposed, and its neutron properties, as well as the performance of TRU incineration, were explored using the Monca program TMCBurnup (TRITON MODEC Coupled Burnup Code), a combination of the SCALE 6.1 (Standardized Computer Analyses for Licensing Evaluation) and the high-precision point burn-up program MODEC (Molten Salt Reactor Specific DEpletion Code). Then, the analysis of critical parameters, burn-up evolution, and the transmutation efficiency of both TRU mixed with Depleted Uranium (DU) and TRU combined with 232Th were investigated, using a straightforward post-processing approach.ResultsThe findings of this study indicate that using TRU as fission fuel in the sm-MCFR requires the online addition of TRU. When the heavy metal balance is maintained, the effective multiplication factor (keff) is less than 1. Conversely, when the balance is not maintained, keff > 1, allowing continuous operation. When operating at full power for 40 years, the core's residual TRU content will be significantly higher than the initial fuel load, with 657 kg remaining for the TRU+Th mix and 725 kg for the TRU+DU mix. Notably, the sm-MCFR demonstrates efficient transmutation when TRU is added online without maintaining the heavy metal balance. Over 40 years at full power, the transmutation rates will be 41% for TRU+DU and 49% for TRU+Th, effectively reducing the production of long-lived small-actinide elements.ConclusionsThe sm-MCFR can effectively incinerate TRU and provide a feasible scheme for minimizing spent fuel.

BackgroundMolten salt reactors, one of the important types of fourth-generation advanced reactors, use high-boiling-point molten salt as a nuclear fuel carrier after melting, hence have the characteristics of high-temperature output and normal-pressure operation. A heat-pipe molten salt reactor based on thermoelectric power generation has the advantages of its components, that is, high output temperature, high thermoelectric conversion efficiency, simple structure, safety, and reliability. Therefore, the reactor of heat-pipe molten salt has significant advantages in the field of energy systems as it is an ideal energy source for outer space and deep-sea exploration missions. However, because of the low thermal conductivity of the molten salt in the core, the dense arrangement of heat pipes complicates the heat transfer design of the thermal power generator in the condensing section of the heat pipes.PurposeThis study aims to design a heat-pipe–thermal power generation coupling system structure suitable for molten salt reactors, and analyze its heat transfer characteristics on the basis of design requirements of the reactor.MethodsFirstly, the condensing section of the core heat pipe was designed using a tower thermoelectric power generation system. A thermoelectric generator was placed between the outer wall of the hot-side tower and the inner wall of the cold-side tower, and the gap between the generators was made of an insulating material to reduce heat leakage. Then, a heat transfer simulation of a four-layer tower thermoelectric power generation system suitable for a heat-pipe molten salt reactor was performed using the ANSYS Workbench. Finally, temperature distribution and variation under different power values at each layer of the thermoelectric generator and every thermoelectric generator, etc., were analyzed.ResultsThe analysis results reveal that, when the system is running with maximum heat-pipe temperature of 696 ℃, the temperature distribution in the overall tower is uniform, the effective heat utilization rate is >96%, the system leakage heat is 490 ℃, which is conducive for improving the thermoelectric conversion efficiency.ConclusionsThe structural design of this study is feasible and conducive for promoting the application of thermoelectric power generation in a heat-pipe molten salt reactor.

Safety valve is an important guarantee for nuclear power plant system. Its working environment is harsh, and medium is high-temperature corrosive. It is important to study the dynamic characteristics of nuclear safety valve under unsteady condition to improve the stability and safety of nuclear power plant piping system. Using the finite element method, mass simplification and Rayleigh method, the frequency response analysis of the safety valve and the spring is predicted to predict the seismic capacity under the earthquake load. Based on the verification of the dynamic characteristics of the valve body, the stress and strain analysis of the spring is carried out. To explore the failure condition of the safety valve spring, the lateral deviation linearity of the spring was tested and analyzed by setting up the offset test bench. The results show that the safety valve with the above analysis method can meet the working requirements under the shaking condition. The research results provide an important theoretical basis for the design and analysis of nuclear safety valves.

In order to design a safety valve with a high safety factor, on the basis of theoretical calculations and ANSYS analysis, stress analysis is performed on the key components of the new nuclear A48 safety valve under open and closed conditions to detect whether the safety valve fails. The natural frequency of the safety valve and the spring are respectively analyzed and tested for seismic performance. The spring parameters are calculated through spring design specifications to determine the method of spring failure calculation and analysis. A lateral deflection measurement bench was built to verify the correctness of the design method through experimental data and provide a reliable theoretical basis for the design of safety valves with high safety factors.

Femtosecond laser direct writing is a powerful technique for fabricating micro‐nano devices as it can modify the interior of transparent optical materials in a spatially selective manner through nonlinear multi‐photon absorption. In this context, laser‐induced nanogratings, i.e., a sub‐wavelength assembly of nanolayers (≈20 nm in width, ≈200 nm period), are ultrashort self‐organized structures created by light in the bulk of transparent materials. These have been intensively explored over the last two decades opening a novel era of micro photonic devices due to their unique physicochemical properties, like orientable form birefringence, anisotropic light scattering, highly selective chemical etching, optical chirality, and extraordinary thermal stability. This review provides a throughout overview of the advances in this field, specifically focused on the formation of nanogratings, optical properties that can be exploited in various transparent solids, and the related main applications. Also, the fundamental characteristics, formation mechanism, tuning methods of nanogratings are reviewed. [ABSTRACT FROM AUTHOR]