A simple plasmalike model that describes the time behavior of the deuteron-deuteron (d-d) fusion reaction rate as a function of charging time is presented. When used to describe the experimental shape of d-d neutron production rates averaged over broad time intervals, the model gives reasonable agreement. The fusion rates obtained from this comparison are of the order of the magnitude of effects that could be expected by the combination of electron screening and fluctuation enhancement. The model allows predictions of the conditions under which d-d fusion neutrons in condensed matter might be observed and explains why, in many cases, no effects are observed.