Study Of Preparing The Hydrogen Permeation Barrier On The Surface Of Zirconium Hydride With CO₂ Reaction Method

Followed as the increasing need for nuclear-power in the word, requirements for materials used in nuclear reactors also improved. Zirconium hydride has become a kind of ideal moderator materials in space piles or small nuclear reaction piles due to its many excellent properties including its small thermal neutron absorption cross section, low density, high content of hydrogen, high working temperature, high thermal conductivity, etc. And it has been put into use in impulse pile.As moderator in pile zirconium-hydride works at temperature from 650℃to 750℃, however, zirconium-hydride begins to loses its hydrogen at 550℃.The escaping of hydrogen would enlarges the pressure in the room and lower the hydrogen density, that lead the lost of neutron moderating ability. So to prevent or to block the hydrogen disperse from zirconium hydride are main parts for its using in small nuclear power reactorsThe research materials at home and abroad indicate that use surface treatment, especially to build a protective layer, is the best economical and effective way to improve the corrosion-resistant capability and hydrogen-preventing capability. The method that studied in the article has simple procedures and little requirement for equipments and would not be restricted by shape of workpiece, to develop a compact oxide film in zirconium hydride's surface at the premise of keeping total characters in structure materials. Through analysis for the morphology and element in oxide film which obtained by the method of CO₂ gas-solid reaction, analysis for oxide film's corrosion-resistant capability to carbon-dioxide in 700℃, Hydrogen discharging experiment in 700℃, chemical tests for different oxide films, the article answered the following questions: the relationship for oxide-dynamics, characters, organize and defaults; and the relationship between the stress-characters and corrosion-resistant capability; and the infections of time parameter and inhibiter; and the infection of lattice to hydrogen preventing character.The experiment results suggest that: the gas-solid reaction of CO₂ method can develop a compact oxide film in zirconium hydride's surface, and the principle for its hindering hydrogen permeation is that ,in lattice of ZrO₂ of baddeleyite structure, the average distance between Oxygen-iron and zirconium-iron is from 0.05nm to 0.09nm,that is shorter than 0.105nm which is the hydrogen-atom's diameter, so, the hydrogen is not easily to permeate the well compacted oxide film. But in the different atmosphere with carbon-dioxide simulate experiment at 700℃, the oxide film will grow into chemical-computation ZrO₂ in whose lattice Oxygen- atom's diameter, then the negative ion prove a good way for hydrogen-atom's permeation ,and the phase change in ZrO₂ may lead to the oxide film's mechanical broken.The experiment has do some analysis about phosphorus as the inhibiter and the anti-acid&alkali character of zirconium oxide films, and the probability of using Gas-solid Reaction of CO₂ to prepare the protect films in zirconium alloy.