[ RadSafe ] Kr-85

[Hal C]

BWR charcoal beds are placed on the exhaust of the steam jet air ejector.  But after the air ejector and before the charcoal beds there is a system of condensers to remove all condensable gases and moisture.  The charcoal is then used to delay the release of the noble gases prior to being exhausted to the vent system.  Some beds are cooled to low temperatures but this can lead to maintenance or other problems and the more common practice today is to use ambient temperature charcoal and a series of large charcoal tanks.  The Krypton isotopes are held up for periods of 12 -24 hours depending on the technical specification flow rate and system design and the Xenons are held up for approximately eighteen times the krypton hold up period.  For rough estimations see NUREG-0016 and any modern BWR FSAR chapter 11.


Hal Careway