Minimization of Entropy Generation Rate in Hydrogen Iodide Decomposition Reactor Heated by High-Temperature Helium

The thermochemical sulfur-iodine cycle is a potential method for hydrogen production, and the hydrogen iodide (HI) decomposition is the key step to determine the efficiency of hydrogen production in the cycle. To further reduce the irreversibility of various transmission processes in the HI decomposition reaction, a one-dimensional plug flow model of HI decomposition tubular reactor is established, and performance optimization with entropy generate rate minimization (EGRM) in the decomposition reaction system as an optimization goal based on finite-time thermodynamics is carried out. The reference reactor is heated counter-currently by high-temperature helium gas, the optimal reactor and the modified reactor are designed based on the reference reactor design parameters. With the EGRM as the optimization goal, the optimal control method is used to solve the optimal configuration of the reactor under the condition that both the reactant inlet state and hydrogen production rate are fixed, and the optimal value of total EGR in the reactor is reduced by 13.3% compared with the reference value. The reference reactor is improved on the basis of the total EGR in the optimal reactor, two modified reactors with increased length are designed under the condition of changing the helium inlet state. The total EGR of the two modified reactors are the same as that of the optimal reactor, which are realized by decreasing the helium inlet temperature and helium inlet flow rate, respectively. The results show that the EGR of heat transfer accounts for a large proportion, and the decrease of total EGR is mainly caused by reducing heat transfer irreversibility. The local total EGR of the optimal reactor distribution is more uniform, which approximately confirms the principle of equipartition of entropy production. The EGR distributions of the modified reactors are similar to that of the reference reactor, but the reactor length increases significantly, bringing a relatively large pressure drop. The research results have certain guiding significance to the optimum design of HI decomposition reactors.

Size-Dependent Liquid Crystal Behavior of Graphene Oxides for Preparation of Highly Ordered Graphene-Based Films

We report the preparation of a highly-oriented graphene-based film prepared from liquid crystal dispersion of graphene oxides (GOs). We observed that the liquid crystal behavior of GOs is highly affected by the lateral size of GO flakes: the critical concentration for liquid crystal formation decreased with the increase of the lateral size of GO flakes, which is in a good agreement with Onsager’s theory. As a result, we were able to obtain highly-ordered graphene assemblies with large-sized GO flakes (150 ± 29 μm) at relatively low concentrations. By applying the shear force, we were able to obtain highly-oriented films from liquid crystal GO flakes. After hydrogen iodide (HI) reduction, GO films showed excellent mechanical strength and electrical conductivity, which were 278% and 283% higher, respectively, than those of films made from smaller sized GO flakes (28 ± 24 μm).

Sensitivity Analysis for Release and Transport Behavior of Radionuclide of the 1F Unit-1 Accident Using SAMPSON

To support the 1F decommissioning project, the Institute of Applied Energy has been analyzing the course of the accident using the SAMPSON code with an aim to grasp radionuclide distribution in 1F NPP. The present study has mainly focused on molybdenum release from a fuel pellet and chemical forms of iodine during the early phase of the accident because a release rate of semi-volatile FPs has various uncertainties. The present simulation set the detrimental factor of molybdenum used in FP release model as a sensitive parameter. The simulation results indicate that more molybdenum release causes more generation of hydrogen iodide and more deposition of iodine inside Reactor Pressure Vessel (RPV) because the adsorption velocity of hydrogen iodide is comparatively higher than deposition velocities of another FPs.