None

Calculations indicate that it is impossible, even at high oxygen injection rates, to insure an excess of oxygen in the HRT fuel solution if the bubble letdown rate is more than 1 or 2 liters per minute. If, on the other hand, no bubbles are allowed to form, a reasonable excess oxygen concentration can be maintained with an oxygen injection rate which would not tax the capacity of the off-gas system. The xenon poison will be reduced to less than 2% by liquid letdown alone, and if an iodine absorption bed is installed below the catalytic recombiner, the xenon poison should be less than 1% without any bubble letdown. Therefore, it is recommended that sufficient copper be added to prevent the formation of gas bubbles and that the oxygen injection rate be limited to a value which would permit adequate holdup times in the present charcoal adsorption beds, assuming this quantity is sufficient to meet corrosion requirements.