The activated charcoal delay bed system is today installed in several BWR power stations, in view of the great reduction obtained thereby in the reactor off-gas activity release. In this system, there will be a slow change of noble-gas activity at the outlet of the charcoal adsorber bed, corresponding to the rapid changes of the operational conditions such as off-gas flow rate, charcoal temperature and pressure.
This transient response is theoretically analyzed, taking into account local variations of the noble-gas holdup time in the adsorber bed, and non-equilibrium between dynamic adsorption and desorption. Furthermore, ¹³³Xe activity changes at the adsorber outlet are measured under rapid increase of the gas flow rate and charcoal temperature, using a test plant of actual practical size. From the fairly good agreement obtained between observed and calculated values, the reliability of the proposed theoretical model is confirmed.

View full abstract