  The mean-field rate equations have proven to be a versatile method in
simulating defect dynamics and temporal changes in the micro-structure of
materials. However, the reliability and usefulness of the method depends
critically on the defect interaction parameters used. In this study, we show
that the sink strength depends also on the detrapping or dissociation process.
The sink strength for a defect that is detrapped, is much larger than the
values usually used. We present a theory how to determine the appropriate sink
strength, and show that the rate equation method, in some cases, gives wrong
results if the detrapping dependence on the sink strength parameter is omitted.
