CC: Reactor Committee SPECIAL HOLDING SYSTEM FOR GASES
The holding tank system proposed by
number and sizes of tanks needed to achieve the desired attenuation of fission gas
The method is described by the diagram below:
The pressure in the Pitot tube at the stack is approximately 7" of water, (assuming
a 25,000 ft³/min blower and a 10' diameter stack) which should provide a
An attenuative of activity of the principal hazardous isotope, Xe133 of a factor of
25, to bring its concentration in the stack gas down to 10-6 [mu]c/cm³ of air, can be
achieved with reasonably-sized tanks. A discharge rate of 100 cm³/min, principally
residual H2 and O2 was assumed to arrive at these figures:
|Number of tanks||Dimension (or cubical tank)|
The only difficulty with the scheme is that the concentration of H2 and O2 builds up
in the tanks, so that at equilibrium, it will be pure. The "half life" for the
build up is given by tH = 0.693/v/V where v is the discharge rate (1.33 cm³/sec)
and V is the individual tank volume (for the case of 3 tanks, 1.26 x 106 cm³).
A typical half life (for the above figures) is l8 hours.
A possible solution is to install a valve after the concentrator that bleeds in
enough air to increase the half life to a safe value, and to operate alternate
systems. This requires that the storage volume be increased further, however, both
by number and size of tanks.
Suggestions are requested from other members of the Committee.