Study On The Hydrogen Isotope Effect Of ?-aged Palladium

For huge energy releasing and an abundance of fuel storage in nature, fusion of deuterium and tritium is considered to be one of the future energy source. Commonly, the main Fuel of fusion is deuterium and triton. However, when hydrogen presence, the reaction of deuterium and deuterium or deuterrium and tritium will slow down. Thus, reducing the content of protium is needed. Metal separation method is the common method used in hydrogen isotope separation. Due to some excellent properties, such as resistance to poisoning, remarkable hydrogen isotope effect, appropriate rate of hydrogen absorption and desorption, palladium is chosed using widely as hydrogen separation.The basis of hydrogen isotope separation is the isotope effect in the palladium hydrogen system. Investigations indicate that the isotope effect is caused by the difference of physics and chemistry property between isotopes or their compounds, which origining from mass and spin dissimilitude. As the lightest element in natural, hydrogen has the largest isotope effect, changing mass number will bring the greatest relative mass alter. Up to now, the study of Pd-H and Pd-D system is already abundance and perfect. However, due to a ? emitting radionuclides of tritium, the disintegration production 3He and ? radial will have an infaust impact on the substrate. For instance, form structural defects in palladium, such as clusters of selt-interstitial, dislocations and dislocation loops. Those defects may lead to changes in the thermodynamics properties, mechanical properties, microstructure and application performance of the material, resulting in tritium aging effect. Up to now, some literatures have reported the works mainly concentrating on the thermodynamic property of Pd-T system. Howerver, It's rare to survey the study of palladium protium and palladium deuterium systems after tritium aging and there is few publication reports of isotope separation factor(a) in tritium aged palladium hydrid.How tritium aging affects the applied properties of palladium? It is an issue we concern. In this paper, the XRD analysis of tritium aged palladium powder(with an original T/Pd of 0.65) were carried out. At the same time, the thermodynamic and isotope separation factor were dicussed.The fresh palladium,1.6 years and 3.5 years aged palladium were characterized by XRD analysis. The results indicate that the XRD graphs of the unaged Pd and the aged Pd have the similar shape. At the same time, aging did not alter the crystal structure, with a face centere cubic (FCC) structure. It is shown that peaks go wider, and shift to larger 2? after tritium aging, resulting in the tritium aging product'He induce crystal lattice aberration. Also shown that the lattice constant of virgin palladium is 3.8904 A, after 1.6 and 3.5 years tritium aging, they are 3.8899 A and 3.8862 A separately. Corresponding particles size from 39.05 nm reduced to 23.05 nm and 21.13 nm. And strain of tritium aged palladium samples increases compared with unaged one.Introducing Sieverts decice experimentized thermodynamics experiment of palladium hydrid, after 0,1.6,3.5 and 6.5 years tritium aging respectively, in the ranging of 30??75 ?. The plateaus pressure of aged Pd-H and Pd-D systems are evident to decrease compared with the fresh one. Based on the thermodynamics, helium from tritium decay prior occupy vacancies, dislocation, grain boundary in palladium, and it contributes to the orderliness of palladium hydrogen system, which was confirmed by enthalpy changes and entropy changes of the formation in palladium hydride. In addition, absorption-desorption enthalpy and entropy changes and hysteresis coefficients were extracted from PcT digrams. The results indicate same absorption-desorption enthalpy changes and different entropy changes and hysteresis coefficients. For helium atoms are prone to band together with substitutional vacancy in palladium, while hydrogen is mostly limited in the interstitial site, there is little effect on enthalpy changes of palladium hydrid. The variation of the other parameters in aged Palladium can be contributed to 3He retention which changes the microstructure and reducing the interstitial sites.The separation factors in fresh Pd-H-D system and aged Pd-H-D system which had been tritium storaged up to 3.5 and 6.5 years respectively, were experimentally measured at different temperatures ranging from-25? to 155?, different deuterium concentrations in solid phase ranging from 5% to 90% and different hydrogen concentrations in solid phase, which can be indication by atomic ratio of hydreogen to palldium, ranging from 0.05 to 0.7, by quarternary mass spectrum. Results show that the separation factor decreases with temperature and increases with deuterium concentration and hydrogen concentration in solid phase. In addition, there is an inverse relationship between In a and reciprocal of temperature. Further more, the hydrogen isotope effect in aged palladium-hydrogen system is remarkably varied compared to the unaged one at the same conditions. Further analysis on the hydrogen-deuterium separation factor for aged palladium-hydrogen system gives unambiguous evidence of tritium aging effects, which is correlated to temperature, hydrogen/palladium ratio and hydrogen concentration in solid phase for palladium hydride.