Vapor pressure tritium

For vapor-only tritium recovery, 99% of the tritium production (or 19.3 mg/s) must be processed by the vacuum system, and the required pressure is 100 times the allowable pressure for liquid-only recovery. Therefore, with a laser driver, tritium vapor pressure between 3.5 and 350 mPa (2.6 x 10 5 and 2.6 X 10 3 Torr) requires tritium recovery from both the liquid-circulation and the vacuum systems. For the heavy-ion-... 

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).

In addition to H2, D2, and molecular tritium [100028-17-8] the following isotopic mixtures exist HD [13983-20-5] HT [14885-60-0] and DT [14885-61-1]. Table 5 Hsts the vapor pressures of normal H2, D2, and T2 at the respective boiling points and triple points. As the molecular weight of the isotope increases, the triple point and boiling point temperatures also increase. Other physical constants also differ for the heavy isotopes. A 98% ortho—25/q deuterium mixture (the low temperature form) has the following critical properties = 1.650 MPa(16.28 atm), = 38.26 K, 17 = 60.3 cm/mol3... 

Properties of Light and Heavy Hydrogen. Vapor pressures from the triple point to the critical point for hydrogen, deuterium, tritium, and the various diatomic combinations are Hsted in Table 1 (15). Data are presented for the equiUbrium and normal states. The equiUbrium state for these substances is the low temperature ortho—para composition existing at 20.39 K, the normal boiling point of normal hydrogen. The normal state is the high (above 200 K) temperature ortho—para composition, which remains essentially constant. 

Calculated vapor pressure relationships of T2, HT, and DT have been reported (10) (see Deuteriumand tritium,deuterium). An equation for the vapor pressure of soHd tritium in units of kPa, Tin Kelvin, has been given (11) ... 

Davanloo and Wai studied the reaction of hot tritium from the He(n, p)T reaction with gaseous cyclopropyl bromide. Table 6 gives the ratio of the yields in the presence of I2 as a scavenger. Due to the low vapor pressure of c-CjHsBr at room temperature, the effect of stabilization was observed by the addition of CHjBr. It acts both as a stabilizer and as a moderator, thus reducing the yields of all hot products, and the important results are the ratios of the yields of the various organic products. 

The DT reactor needs several kg tritium as starting material. A likely technique involves the irradiation of a Li-Al alloy in a high flux thermal fission reactor which produces both tritium and He (17.43) These can be separated on the basis of their different vapor pressures, different permeability through palladium, or through their different chemical reactivities. 

Saturated hydrocarbon mineral oils (for example, Duo-Seal) require frequent changes in tritium service because of vapor pressure increases (offgassing) and liquid viscosity increases. Silicone oils are rapidly polymerized or solidified. Polyphenyl ether oils last for years in similar service, but are expensive and may absorb significant amounts of tritium. 

Figure 3 was constructed as mentioned previously from Fig. 2 by cross-plotting isotherms of reduced conductivity vs. A. The thermal conductivity data for carbon monoxide were not used. Then from Fig. 3 the values of k for tritium (A = 1.00) were obtained to predict the temperature dependence of the thermal conductivity of tritium along the vapor pressure curve as shown in Fig, 2. Lastly, it may be pointed out that an extension of the Ne data of Ldchtermann P ] to the critical-temperature locus would appear to give some values of the thermal conductivity which would be very near to those predicted for tritium, and would also require an S-shaped curve, which seems improbable in view of the value of T for neon, i.e, 1.247. A curve for the thermal conductivity of Ne predicated upon behavior similar to argon and tritium is also shown. Derivation of the thermal conductivities of the unsymmetrical isotopic species of hydrogen—HT, HD, and DT— is a triviality and can easily be obtained from Fig. 3. Note that de Boer s theory does not distinguish between the behavior of HT and D2 P ]. For the unsymmetric isotope HT the value of A should be computed after Friedmann [ ] as...

Figure 3 again shows the nonuniformity among the diflFerent types of species considered toward the heavy-molecule terminus of the triple-point loci. In addition, the double-valued thermal conductivity behavior is evident from the isotherms which lie above the diatomic molecule triple-point locus. The crossover is seen to occur at reduced temperatures so that tritium should be the heaviest molecule exhibiting a thermal conductivity maximum along its vapor pressure curve. 

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. 

Carson et al. 20) measured the temperature variation of the vapor pressure of a tin tetraphenyl sample labeled with tritium by a modified Knudsen effusion technique AHy at 25°C = 15.85 kcal/mole. Consequently,... 

Hydrogen Pressure Ranges for Liquid-Only or Vapor-Only Tritium Recovery for IMW IGF Reactors. For a 2700-MWf IGF reac-tor with a 600-m chamber, a 30% tritium bum fraction and a 1.75 tritium breeding ratio, 19.5 mg/s of tritium are added to the reaction chamber. If tritium is to be recovered from only the liquid, a maximum loss through the vacuum system of 1% (0.2 mg/s) is assumed to be acceptable. With a laser driver (26), the vacuum system might operate at a 1.3 Pa (10 2 Torr) with about 10% of the vapor being pumped per second. Then, about 3.5 mPa (2.6 x 10 Torr) of tritium, or 10 times the pressure associated with 0.2 mg tritium, is allowable. 

With a heavy-ion-beam driver (26), the vacuum system might operate around 0.13 Pa (10" Torr), with about 50% of the vapor being pumped per second. Then, about 0.7 mPa (5 x 10 Torr) of tritium, or twice the pressure associated with 0.2 mg tritium, is allowable if only the liquid is to be processed. 

Tritium in water vapor has also been utilized in the study of meteorology. Kigoshi and Yoneda observed daily variations in the tritium content of atmospheric moisture (water vapor) collected in Tokyo. High tritimn contents indicate the arrival of continental air masses from the north, and the low contents in tropical low-pressure air masses are nearly equal to that of surface ocean water. 

The leakage of heavy water from hot, pressurized reactor circuits presents problems both on account of the economic penalty and the associated escape of radioactive tritium which is formed by neutron capture in the deuterium. Early experience with the Douglas Point CANDU reactor, for example, indicated the need foi sealing of building volumes around the coolant circuit, and the extraction and recovery of the D2O vapor which had leaked into them. 

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