For a ring with 1, we show
that every proper kernel functor generates a proper torsion radical if and
only if the ring is a finite subdirect product of strongly prime (also called
ATF) rings. This is equivalent to every essential right ideal containing a
finite set whose right annihilator is zero. We use this characterization to
quickly prove a number of properties of rings satisfying this condition, and
apply the results to the problem: when is every kernel functor a torsion
radical.