Helium Sweep Gas Research Articles

Desorption of H 2O and H 2 from steel and LiAlO 2 by temperature programmed desorption

Temperature programmed desorption (TPD) measurements with a steel sample tube and helium sweep gas are in progress to provide data describing the kinetics of desorption of H 2O(g) and H 2(g) from ceramic tritium breeders. Preliminary blank experiments indicated that the steel can be a reactive participant with H 2O being consumed and H 2 being evolved. There is also evidence of some dissolution of H 2 in the steel. However, it is possible to stabilize the steel in the absence of added H 2 so that useful desorption measurements with H 2O(g) can be made. Initial work was on the LiAlO 2-H 2O(g) system. Fresh samples of LiAlO 2 bear large amounts of adsorbed H 2O. TPD spectra were measured for LiAlO 2 that had been equilibrated in a helium stream with 200 ppm H 2O(g) at temperatures from 473 to 773 K. Several techniques of data analysis were applied, questions of possible peak overlap still remain to be resolved. An activation energy for desorption of H 2O(g) of approximately 120 kJ/mol appears to be associated with the sample equilibrated at 673 K. This result agrees with the value reported in the literature for decomposition of LiOH, and suggests that some sites on LiAlO 2 might resemble sites on Li 2O in their adsorptive properties. For a 773 K equilibration, the activation energy of desorption appears considerably higher.

A Two-dimensional analysis of membrane thickness in a hollow-fiber-contained liquid membrane permeator

For theoretical calculation of effective liquid membrane thickness in a hollow-fiber-contained liquid membrane gas permeator, a two-dimensional diffusion equation model is presented. Four possible feed-sweep fiber configurations have been investigated. Pure component permeation and multicomponent gas mixture separation have been modelled, taking into account the pressure variation inside the feed and the sweep fibers. Using water as liquid membrane, pure CO 2 permeation and three-component gas separation experiments with a number of CO 2-N 2 feed gas mixtures and a pure helium sweep gas have been carried out to verify the mathematical models. Effects of hollow fiber size and packing density on the liquid membrane thickness have been analyzed.

The effect of fusion neutron irradiation on tritium recovery from lithium salts

The effect of 14 MeV neutron irradiation on tritium recovery was studied from the lithium salts LiF, LiCl, LiBr, Lil, LiF-BeF 2 and LiF-PbF 2. The chemical state distribution of tritium formed in the irradiated lithium salts was found to depend on the neutron fluence. The dependence was explained by taking into account the interactions of tritium with radiation defects. In the tritium recovery experiments, the effects of irradiation were apparently observed with the highly irradiated samples; the TX recovery with a helium sweep gas and the HT recovery with a hydrogen-containing sweep gas were well described by the reaction kinetics in which F centers play an important role. In the case of the less-irradiated samples, on the other hand, the tritium recoveries were found to follow a diffusion-controlled kinetics and were explained on the basis of atomic theory of diffusion.

The effect of 14 MeV neutron irradiation on tritium recovery from lithium oxide

Post-irradiation experiments were performed to study the effect of 14 MeV neutron irradiation on the recovery of tritium from sintered lithium oxide. The chemical state distribution of tritium produced in the lithium oxide was found to depend on the neutron fluence because of the influence of radiation defects. When the lithium oxide was heated with a helium sweep gas, tritium was recovered mainly as HTO and its recovery was controlled by bulk diffusion of tritium in the T+ state except in an early period of recovery. The diffusion coefficient was expressed as D = 4.4 exp [−143 (kJ mol−1)/RT] cm2 s−1. When hydrogen was added to the sweep gas, on the other hand, a considerable amount of tritium was recovered as HT. The HT recovery was analyzed with first-order kinetics using the activation energy of 137 kJ mol−1. The reactions of tritium with F+ centers may be responsible for the observed behaviour.

The TRI0-01 experiment: In-situ tritium recovery results

The TRIO-01 experiment is a test of in-situ tritium recovery from γ-LiAIO 2 with test conditions chosen to simulate those anticipated in fusion power reactors. A status report is presented which describes qualitatively the results observed during the irradiation phase of the experiment. Both the rate of tritium release and the chemical forms of tritium were measured using a helium sweep gas which flowed past the breeder material to a gas analysis system.

Water adsorption on lithium oxide pellets in helium sweep gas stream

Water adsorption on lithium oxide pellets in helium sweep gas stream

Reactor loop for continuous production of gaseous fission product radioisotopes— I. 235U-loaded molecular sieve target

The development of high surface area fissile targets by the deposition of 235U on molecular sieves and silica gel provides a matrix from which the gaseous fission products readily diffuse. Collection of the fission product gases by helium sweep gas circulated through such a target installed in a reactor neutron flux constitutes a loop system for the continuous production of fission product gases, e.g. 135Xe. This system has provided 135Xe for medical diagnostic clinical evaluations and mixed fission product gases for study of reactor stack monitor systems performance.

Online Monitoring of Specific Radionuclides in Gaseous Effluents

A feasibility study of automatic online monitoring of specific radionuclides in nuclear plant gaseous effluents is being conducted at the Georgia Tech Research Reactor (GTRR). An inpile loop experiment has been designed, built, and operated in the GTRR to simulate gaseous effluent mixtures anticipated for a variety of reactor situations. The gaseous fission product mixture may be altered by varying the flow rate of the helium sweep gas over the uranium-235 loaded microporous target, the neutron flux and temperature at the target, and the configuration of the cryogenic trapping system external to the reactor. The loop is used for experiments in remote monitoring of specific radionuclides to be experienced for normal, minor malfunction, and accident conditions at a nuclear plant. As a means of evaluating the practical aspects of automatic online monitoring, a remote monitoring system has been designed and built to measure nuclear and meteorological data at the GTRR, and to transmit the data to a central computer on either a routine "record keeping" or on an emergency-interrupt basis. The measurement system can be adjusted from the remote location to allow live time probing of conditions at the monitored location.