Preparation, testing and analysis of zinc diffusion samples, NASA Skylab experiment M-558

Transport mechanisms of zinc atoms in molten zinc were investigated by radiotracer techniques in unit and in near-zero gravity environments. Each melt in the Skylab flight experiments was maintained in a thermal gradient of 420 C to 790 C. Similar tests were performed in a unit gravity environment for comparison. After melting in the gradient furnace followed by a thermal soak period (the latter was used for flight samples only), the samples were cooled and analyzed for Zn-65 distribution. All samples melted in a unit gravity environment were found to have uniform Zn-65 distribution - no concentration gradient was observed even when the sample was brought rapidly to melting and then quenched. Space-melted samples, however, showed textbook distributions, obviously the result of diffusion. It was evident that convection phenomena were the dominant factors influencing zinc transport in unit gravity experiments, while diffusion was the dominant factor in near-zero gravity experiments

Target preparations and thickness measurements

A wide variety of isotope target preparative methods have been used, including rolling of metals, vapor deposition, electrodeposition, chemical vapor deposition, and sputtering, to obtain thin and thick films of most elements or compounds of elements in the Periodic Table. Most thin films prepared for use in self-supported form as well as those deposited on substrates require thickness measurement (atom count and distribution) and/or thickness uniformity determination before being used in nuclear research. Preparative methods are described together with thickness and uniformity determination procedures applicable to samples being prepared (in situ) and to completed samples. Only nondestructive methods are considered applicable to target samples prepared by the ORNL Solid State Division, Isotope Research Materials Laboratory. Thickness or areal density measurements of sufficient sophistication to yield errors of less than +-1 percent have been achieved with regularity. A statistical analysis procedure is applied which avoids error caused by balance zero-point drift in direct weight measurement methods. (auth

Development of cermets for high level radioactive waste fixation

A method for the solidification and fixation of commercial and defense high-level radioactive wastes, namely a cermet process, is currently under development. Chemical and physical processing techniques, as developed up to this time, and the subsequent properties of the resulting cermet bodies are described; unique and advantageous features of the cermet waste form and the conversion process are discussed

Conversion of isotope compounds to metal by reduction-distillation methods

Because isotopes in metal form provide physicists with mononuclidic targets essentially void of extraneous or interfering nuclei in two-body experiments, conversions of compounds to metals warrant extensive study. Furthermore, having isotopes in pure metallic form permits (in many cases) physical manipulations to be performed so as to convert bulk material into suitable target configurations: thin foils, wires, castings, spheres, and even colloidal suspensions. Physical properties of metals are extensively influenced by small impurity concentrations; therefore, whatever conversion method is applied, it must preserve and/or create an ultrapure product. This paper discusses the application of the reduction of a solid compounded isotope, followed by metal distillation into a noncontaminating collector vessel. A variety of isotope metal vapor condensation-collection methods and subsequent treatment of the product to form various physical forms are discussed. Unfortunately, no single collection technique is applicable to all elements. Limitations of this technique with regard to reducible cations other than those noted earlier are discussed, together with the consequences of volatilization of some metal suboxides in this process. 11 figures