DETERMINATION OF SURFACE RECOMBINATION RATES FROM LOW PRESSURE GAS RELEASE MEASUREMENTS
Numerical codes for the calculation of the behaviour of hydrogen isotopes in the first wall of fusion reactors (recycling, permeation, inventory) need as input parameters the knowledge of bulk diffusion coefficients and surface recombination coefficients. A method is presented for the determination of recombination rates of hydrogen isotopes at metallic surfaces. This method is based on pressure increase measurements in a known volume during unloading of metallic samples which were previously loaded at gas pressures below 10 Pa. Recombination coefficients are then determined from the equilibrium hydrogen concentration in the sample and from the gas release rate at the beginning of the unloading interval. The results of protium release measurements from stainless steel 316 L samples are presented in the pressure range from 0.1 to 10**5 Pa and at two different temperatures, 648 K and 818 K. From these measurements, one can obtain the thermal desorption rate and the regions in which the hydrogen transport in the metal is recombination limited or diffusion limited. Further on, the surface recombination coefficient can be determined from the measurements at low pressures and the bulk diffusion coefficient from those at high pressure.
Bibliographic Reference: IX CONGRESSO NAZIONALE SULLA SCIENZA E TECNOLOGIA DEL VUOTO, FIRENZE (ITALY), OCT. 7-10, 1985 WRITE TO CEC LUXEMBOURG, DG XIII/A2, POB 1907 MENTIONING PAPER E 32350 ORA
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Record Number: 1989124052900 / Last updated on: 1987-01-01
Available languages: en