Hydrogen and deuterium in Pd-25 pct Ag alloy: Permeation, diffusion, solubilization, and surface reaction
- PDF / 303,970 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 17 Downloads / 287 Views
I.
INTRODUCTION
THE Pd-25 pct Ag alloy is the candidate material for the International Thermonuclear Experimental Reactor (ITER) permeator for the recovery of tritium and deuterium from all reactor exhaust streams.[1,2] Both the plasma exhaust gas and the blanket sweep gas with the bred tritium include impurities such as water vapor, hydrocarbons, ammonia, oxygen, and inert gases. The cleanup process proposed for the recovery of molecular tritium and deuterium is based on the combination of hydrogen permeation through palladium/silver membranes with catalytic process steps involving the thermal decomposition of hydrocarbons and the reduction of water vapor by carbon monoxide. The objectives set for the work are to obtain the hydrogen and deuterium inventory and transport parameters (permeability, diffusivity, and solubility) in Pd-25 pct Ag alloy and then to obtain experimental values for the constants describing surface reactions in Pd-25 pct Ag alloy: i.e., the constants characterizing the release rate of hydrogen and deuterium from the surface and the rate at which adatoms move into the subsurface layer. Although the hydrogen permeability, diffusivity, and solubility in Pd-25 pct Ag alloy have been studied by many authors, no data are available for the constants describing surface reactions. To study this alloy, besides a permeation technique, a microgravimetric experimental technique has been used. II.
EXPERIMENTAL
The samples, with measured composition (wt pct) Pd75 and Ag25, were obtained from a thin sheet of the material supplied by KfK Karlsruhe.
E. SERRA, formerly Doctoral Fellowship with the European Commission, JRC-Ispra Site, Institute of Advanced Materials, is Ph.D. Scientific Collaborator with ENEA CR Brasimone, 40032 Camugnano, Bologna, Italy. M. KEMALI, Assistant Professor, Joule Laboratory, Department of Physics, and D.K. ROSS, Director, Science Research Institute, are with the University of Salford, Salford M5 4WT, United Kingdom. A. PERUJO, Head of Research Group, is with the Institute of Advanced Materials, JRC-Ispra Site, Institute of Advanced Materials, I21020 Ispra (Va), Italy. Manuscript submitted July 2, 1997. METALLURGICAL AND MATERIALS TRANSACTIONS A
A. Permeation Measurements The Pd-25 pct Ag samples used for the hydrogen and deuterium permeation measurements consisted of discs 7.82z1023 m in diameter and 0.198z1023 m in thickness. The method chosen for the high pressure (0.1 to 100 kPa) measurements during the current investigation is a gasphase technique, where after evacuating the apparatus to a ultrahigh vacuum so that both sides of a sample are initially in contact with vacuum, one side of the sample (the ‘‘high pressure side’’) is instantaneously exposed to hydrogen gas at a known, fixed pressure. Gas permeates through the sample and is released at the other side (the ‘‘low pressure side’’), where it causes a pressure rise in an initially evacuated, calibrated volume. The pressure rise is measured using a Baratron capacitance manometer with a full scale reading of 1000 Pa (10 m
Data Loading...
