Tritium diffusion coefficient

All in all, the tritium data present something of a mystery, but at least they set a lower limit for the effective diffusion coefficient in the range 400-500°C, a limit rather higher than some estimates that have been given in the literature for similar temperatures but which we shall not discuss until Section 3 because thay are based on experiments in which hydrogen-acceptor complex formation was clearly important. 

Diffusion measurements169 with tritium-labelled water shows an increase of the water diffusion coefficient with water content. It reaches a plateau at 11 mole water/ mole lipid. Above 21 mole water/mole lipid D increases strongly162,169. ... 

Ichimiya, T., Furuichi, A. On solubility and diffusion coefficient of tritium in single crystals of silicon. Int. J. Appl. Rad. Isot. 19, 573 (1968)... 

Diffusion of tritium HTO Verifying the effective diffusion coefficient... 

Tritium water HjO, denoted as HTO, is non-adsorptive, so it is appropriate to check the applicability of our analysis. The diffusion coefficient of HTO in free water is reported as 2.44x10" cm /s=769.48cm/year (Klitzsche et al, 1976). 

Ramseier [/. AppL Phys. 38, 2553 (1967)] found an anisotropy of 12% for the self-diffusion coefficients of tritium in ice, but the same activation energy, in the directions parallel and perpendicular to the c-axis. His numerical results are in substantial agreement with those given in Table Vll. He favors a vacancy mechanism with entire H2O molecules diffusing. 

The release of tritium from irradiated oxide powders was studied by the method of post-irradiation annealing. At 400 to 660C, the release was a diffusion-controlled process. The diffusion coefficient of T in the two powders used was given by ... 

The effect of temperature upon the rate of release of tritium from neutron-irradiated polycrystalline and single-crystal UO2 was studied. The diffusion coefficients for... 

Imagine a system of equimolar amounts of hydrogen and ethylene containing a trace of tritium. The diffusion coefficient of tritium would not equal the diffusion coefficient of hydrogen. Explain why without using equations. 

Tables 2,3, and 4 outline many of the physical and thermodynamic properties ofpara- and normal hydrogen in the sohd, hquid, and gaseous states, respectively. Extensive tabulations of all the thermodynamic and transport properties hsted in these tables from the triple point to 3000 K and at 0.01—100 MPa (1—14,500 psi) are available (5,39). Additional properties, including accommodation coefficients, thermal diffusivity, virial coefficients, index of refraction, Joule-Thorns on coefficients, Prandti numbers, vapor pressures, infrared absorption, and heat transfer and thermal transpiration parameters are also available (5,40). Thermodynamic properties for hydrogen at 300—20,000 K and 10 Pa to 10.4 MPa (lO " -103 atm) (41) and transport properties at 1,000—30,000 K and 0.1—3.0 MPa (1—30 atm) (42) have been compiled. Enthalpy—entropy tabulations for hydrogen over the range 3—100,000 K and 0.001—101.3 MPa (0.01—1000 atm) have been made (43). Many physical properties for the other isotopes of hydrogen (deuterium and tritium) have also been compiled (44).

Permeability Experiments. Three sets of in-vitro diffusion experiments were conducted 1) identical ethanol/saline composition in both diffusion chambers, 2) ethanol/saline in the donor chamber and saline in the receiver, and 3) saline in the donor and ethanol/saline in the receiver chamber. Tritium labeled 3-estradiol was added to the donor side and samples were taken from both compartments at predetermined times and read in a scintillation counter (Beckman Inst., San Ramon, CA). Effective permeability coefficients were then calculated after steady state was reached using the following equation ... 

Several factors influence the half-time of tritium loss from the film tubes (Table 1). As size of the air space above the scintillator (and therefore the total exchange surface area of the tube) increases, the rate of loss of THO increases. This indicates that THO not only diffuses out of the tube directly from the solvent phase but from the gas phase above the scintillator as well. Solvent systems which increase the water vapor pressure in the enclosed tube by decreasing the soliiiility coefficient of water, micelle stability or micelle surface area to volume ratio would be eiqjected to decrease the half-time for THO loss. This would e q)lain the difference in half-times between the toluene and xylene derivative based scintillation solutions. 

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