Permeation Data Analysis Considering a Nonzero Hydrogen Concentration on the Low Pressure Detector Side for a Purged Permeation Experiment

Currently available diffusion constant and Sieverts constant experimental results are based on time dependent permeation experiments. The common principle is an analysis which is expecting that the permeating hydrogen is “transported” from the retentate chamber to the permeate chamber through the connecting membrane, with a vanishing hydrogen partial pressure on the permeate side. But reality shows a different behaviour caused by the fact that a nonzero hydrogen partial pressure in the permeate chamber is necessary for detection purposes. This nonzero pressure is mostly not considered by analysis. This issue is solved (approximatively) numerically by the procedure as described in this paper. This work is rooted in the field of fusion research, where so called purge gas with low partial pressure of tritium is contacting the structural materials (300-550°C) of the fusion reactor (blanket) and of process equipment, where the tritium losses are of interest. The developed algorithms are intended for the evaluation of an experiment termed “Q-PETE” (Q for any hydrogen isotope, PEermeation Transport Experiment), which abstracts the hydrogen transport conditions of the fusion blanket, and where the effect of nonzero hydrogen concentration on the permeate side is relevant. The algorithms are useful for all experiments, where the ratio of hydrogen pressures between retentate and peremeate side are far from infinite.

Rapid Fabrication of Li2TiO3 Pebbles via Microwave-Induced Combustion Process and 3D Printing

Li2TiO3 has been recognized as one of the most promising tritium breeding materials for D-T fusion reactor blanket. In this study, ultra-fine Li2TiO3 powder was prepared rapidly by microwave-induced solution combustion synthesis (MSCS) using nitrates of lithium and titanate as raw materials, citric acid as fuel. The as-synthesized Li2TiO3 powder exhibits an average crystalline size as small as 20 nm with uniform distribution. Computer-assisted 3D printing technology was employed to fabricate Li2TiO3 ceramic breeding pebbles. This computer-assisted process is precise, efficient and controllable, which offers an alternative for the mass production of Li2TiO3 pebbles. The pebbles exhibit good sphericity, relatively small grain size, preferable sinterability and crushing load strength.

Theoretical Calculation and Numerical Investigation for the Effective Thermal Conductivity of Packed Li2TiO3 Pebble Bed

Lithium titanate (Li2TiO3) in form of packed pebble bed is promising concept for breeder material in the fusion reactor blanket, and worldwide efforts have been dedicated to its R&D in the last two decade. Li2TiO3 pebble beds with the efforts of tritium breeding and thermal removing play a major role in the thermal performance of the fusion reactor blanket. Specifically, the effective thermal conductivity of Li2TiO3 is an important parameter for the design and thermal mechanical of fusion reactor blanket. The theoretical calculation and numerical simulation for the effective thermal conductivity of Li2TiO3 pebble bed are performed in this paper. The theoretical equations and modeling result for the thermal conductivity of Li2TiO3 pebble bed are given and compared with the experimental data. The results show that the effective thermal conductivity of Li2TiO3 pebble bed can be preliminarily obtained by numerical simulation and theoretical calculation.