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

Moderators are applied to moderate neutron in nuclear reaction piles. Zirconium hydride has become one kind of ideal moderator materials in space piles and small nuclear reaction piles due to its many excellent properties including its low density (~5.6g/cm~3 ),high content of hydrogen(H/Zr atom ratio can reach 1.80),high working temperature(<600℃),little thermal neutron absorption cross section, high thermal conductivity and high thermal mechanical strength. Zirconium hydride has been put into use not only in reaction piles which have small weight and volume but also in hot neutron reaction piles which are cooled by liquid metal.One important problem about zirconium hydride must be resolved is its working temperature's influence when it is used in reaction piles. As moderator, Zirconium hydride works at temperature between 650℃ and 750℃ in space piles, in this case, zirconium hydride (atom ratio of H/Zr >1.8) loses its hydrogen easily. The escaping hydrogen enlarges the pressure in the room and lowersx the neutron moderating ability. Therefore something must be done about zirconium hydride to prevent hydrogen from dispersing from its inner part. Some domestic and overseas research materials indicate that hydrogen permeation barrier can be prepared on the surface of the construction materials in order to stop the hydrogen from escaping.In this paper Electroplating and CO2 Reaction Method has been used to build hydrogen permeation barrier on the surface of zirconium hydride in this experiment. (1) The craft and influence of preparing hydrogen permeation barriers is studied, for example time, current density and precondition.(2) Through heating zirconium hydride, high purityC02 and red phosphorous, the gas adsorbs, desorbs, scatters and finally forms the compact film on the surface of zirconium hydride.(3) The mechanism of permeation of hydrogen permeation barrier at 700*C on the surface of zirconium hydrogen is studied. With the help of Scanning Electronic Microscope (SEM) the joining interfaces of the films and their substrates are studied, of X-ray Photoelectron Spectrum (XPS) the valence of the element on the hydrogen permeation barrier surface is tested, of X-ray Diffraction (XRD) the constitutes of the hydrogen permeation barrier are tested.The experiment results suggest that:(l) there are many C-H bonds and -OH groups in the film.(2) The hydrogen permeation barrier which is prepared with electroplating method is composed with baddeleyite ZrC^ electrodeposited coating Cr-C and Cr2O3.(3) The film obtained by the method of CO2 reaction primarily consists of ZrO2 (which possesses the structure of baddeleyite ) ,this kind of ZrO2 belongs to one of zirconium's suboxide and is very compact and able to capture hydrogen which tries to escape.(4) The XPS results suggest that more C-H and -OH bonds are formed in the oxide film, when heated at 700'C for many hours.In a conclusion, it is that carbon and oxygen capture H in the course of keeping high temperatures.