Ti, Zr, Er Tritium Aging Effect Of Compound Research

Tritium is a hydrogen isotope of considerable interest and has important technological applications, especially in the nuclear industry. However, the radioactive nature of tritium imposes many conditions on its handling and storage. It has been recognized for a long time that the best way to store hydrogen is in the form of a hydride, which has the advantage of safety, easy recovery, and also much larger quantities of hydrogen can be stored per unit volume than in its liquid form, Therefore, it is quite natural to propose the storage of tritium in the form of a tritide, and metals such as titanium, zirconium, erbium are commonly used for this purpose.Helium release from titanium tritide, zirconium tritide and erbium tritide at room temperature have been studied. The evolution of lattice defects in long-aged three kinds of metal tritides are also investigated by X-ray diffraction (XRD). Thermal helium desorption spectrums (THDS) of these three kind of metal tritides have been used to investigate the3He release from titanium tritide film. Results of XRD, TD and helium release were synthesized. A continuum-scale evolutionary model of helium for aging titanium tritide, zirconium tritide and erbium tritide are described which accounts for major features of the tritide experiment data. Key parameters which could affect the helium evolution in metal tritide have been validated and the eigenvalue which could evaluate the3He retention in metal tritide has been found.The samples were stored at room temperature in an ultravacuum metal system with a vacuum of10-5Pa and the release behavior of3He from titanium tritide films were analyzed by a quadrupole mass spectrometer (QMS). The amount of helium released from titanium tritide, zirconium tritide and erbium tritide during the aging time were measured. Typical3He release characteristics indicate most3He generated remains in lattice. The rapid3He release values of these three kinds of metal tritides are different, the value from higher to lower are fct zirconium tritide (0.50-0.533He/Zr), fcc erbium tritide (-0.303He/Er), titanium tritide (0.25～0.283He/Ti). The initial atom ratio and phase composing are found have effect on rapid3He release value.Experiments were carried out for thermal desorption measurement of3He from metal tritide with linear temperature increase and constant temperature in vacuum condition, and3He measurement were performed on line by a Quadrupole Mass Spectrometer (QMS). Thermal helium desorption spectra (THDS) were obtained by He partial pressure vs temperature. THDS has been used to investigate the3He release from titanium tritide with 3He/Ti atom ratio from0.006to0.325and indicated that there are four3He states in titanium tritide. THDS of zirconium tritide and erbium tritide in special aging time have been compared with titanium tritide. An effective helium diffusivities of0.04-2.39×10-20m-2/s in fct zirconium tritide.0.36-1.51×10-20m-2/s in fce titanium tritide and0.88-31.39×10-19m-2/s in fcc erbium tritide at300K have been found by helium release on constant temperature.The evolution of lattice defects in long-aged titanium tritide, zirconium tritide and erbium tritide are investigated by X-ray diffraction (XRD) and changes in the positions, intensities and line shapes of diffraction peaks have been determined. The results show that finite defects retention and twin stacking faults of these three kinds of metal tritides are different, the infinite defects change behavior are all depend on (hkl). The initial atom ratio and phase composing are found have effect on the evolution of lattice defects.Based on XRD, SEM. Helium release test and THDS, the microscopic structure of titanium film deposited by resistively-heated evaporation and electron gun evaporation respectively have been studied. And the effect of microscopic structure on helium retention has been revealed. It found that helium retention in the films which have strong texture, small grain size, and a lot of defects is lower. The effect of microscopic structure of zirconium tritide were also studied.A continuum-scale evolutionary model of helium release for titanium tritide, zirconium tritide and erbium tritide are described which accounts for major features of these three kinds of tritide XRD, helium release and THDS experiment data. There are six helium evolution stages in titanium tritide and zirconium tritide:helium atom migration and the formation of isolated tetrahedral interstitial3He atoms or3He clusters, nano-cracks (Griffith) evolution, dislocation dipole expansion by plate bubble, dislocation loop punching by sphere bubble, inter-bubble fracture and linked-bubble network generation. The combined stress-assisted-block loop punching growth for sphere bubble arrays and an average ligament stress criterion predicts an onset of inter-bubble fracture in good agreement with the3He/M ratio observed for rapid He release. There are five helium evolution stages in erbium tritide: helium atom migration and the formation of isolated tetrahedral interstitial3He atoms or3He clusters, nano-cracks (Griffith) evolution, dislocation dipole expansion by plate bubble, inter-bubble fracture and linked-bubble network generation. The combined platelet area projections in a fracture plane and an average ligament stress criterion predicts an onset of inter-bubble fracture in good agreement with the3He/Er ratio observed for rapid He release.Comparative analysis of three kinds of metal tritide3He evolution behavior of similarities and differences, the characteristic index evaluating3He retention of metal tritide is the turning point3He/M when the unit cell volume of metal tritide have changed during aging.It is concluded from the continuum-scale evolutionary models of these three kinds of metal tritides that the main characteristic parameters which control of He retention are helium bubble density and mechanical properties (Young’s modulus, shear modulus, theoretical fracture strength). And control of3He retention can be accomplished through control of bubble nucleation and improving the mechanical properties of metal tritide.