Removal of Fission Product Noble Gases from the Helium of a High Temperature Gas Cooled Reactor Using Charcoal at Low Temperatures.Dragon Project Report

After the technical problem is outlined the initial results obtained from a study on the removal of fission product noble gases from helium by low temperature adsorption technique are reported. The results of break-through experiments on laboratory and technical scale are reported, after a description of the techniques and equipment used. Adsorption equilibrium and rate data at the temperatures of interest are presented. It is shown that not only ''dynamic'' and ''static'' equilibrium data are in good agreement with each other, but that they fit into the Dubinin extension of Polanyi's thermodynamic considerations. As a result it will be possible to use a ''characteristic curve'' of a particular adsorbent for predicting adsorption equilibrium data for other gases and other temperatures. A conclusive interpretation of the adsorption rate data for xenon on charcoal is not yet possible. Rate determining seems to be surface migration (solid phase diffusion). There are strong indications that at low temperatures the rate equation with a linear driving force relationship gives the best fit. In the last chapter the various break-through curves obtained are analysed, making use of the equilibrium data and adsorption rate data obtained. It is concluded that the adsorbers of the plant constructed for the Dragon Reactor Experiment will amply meet their specifications. A considerable margin for optimisation seems available. For a more accurate interpretation of the shapes of break-through curves from technical scale experiments more experimental work with the Pilot Plant is needed. As far as the optimisation of the process itself is concerned further laboratory scale experiments are necessary and in particular with respect to the adsorption of gas mixtures.