A Study Of Prohibiting Permeation Of Hydrogen With Cr-C Film Electroplated On The Surface Of The Zirconium Hydride

In nuclear reaction piles, zirconium hydride has become one kind of ideal moderator materials in space piles and small nuclear reaction piles and has been put into use in not only reaction piles which has little weight and little volume but also hot neutron reaction piles which are cooled by liquid metal.But 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°C and 750°C 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 lower 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 Preparation of hydrogen permeation barrier with Cr-C film electrodeposited on Zirconium hydride (ratio of H and Zr is 1.801) was studied.(l) The influence of experimental craft preparing hydrogen permeation barriers on performance of prohibiting permeation of hydrogen is studied. (2) The crystal phase, surface, ingredients of hydrogen permeation barrier on the surface of zirconium hydrogen is studied with the help of X-ray Diffraction (XRD) ,Scanning Electronic Microscope (SEM) and X-ray Photoelectron Spectrum (XPS ) respectively. (3) The performance of hydrogen permeation barrier on the surface of zirconium hydrogen at 700°C is discussed when the material co-exist which is able to adsorb hydrogen. With the help of X-ray Diffraction (XRD) the structure of the hydrogen permeation barrier are tested.(4) The mechanism of hydrogen permeation barrier at 700°C is studied when hydrogen permeation barrier works in atmosphere of a lot of CO₂ or a little CO₂ respectively. With the help of X-ray Photoelectron Spectrum (XPS) the valence of the element on the hydrogen permeation barrier surface is tested and with the help of Scanning Electronic Microscope (SEM) the surface of the barrier is studied. The problem is explained.The experiment results suggest that: (1) 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 ZrO₂,electrodeposited coating Cr-C and Cr₂O₃. The XPS results suggest that the C and O with H would form more C-H and -OH bonds in the oxide film to stop permeating H, when heated at 700°C for many hours. (3)At 700°C the permeating hydrogen prefer to react with carbon. With time going and more permeating hydrogen both carbon and oxygen have the tendency to destroy O-C or C-O to arrest hydrogen. (4) The hydrogen permeation barrier works hardly at 700°C when the material which is able to adsorb hydrogen co-exists. (4) The hydrogen permeation barrier does not work well when excessive CO₂ exists while a little CO₂ does not harm hydrogen permeation barrier at 700°C.