In this technical note we examine a method for self-sustainable (in-situ) deuterium production in a fusion reactor, using a very different approach to those considered in previous studies. Here, instead of pursuing the production of deuterium via neutron capture (H + n ! D) inside and/or outside the fusion chamber, the deuterium is obtained by ionization induced by the neutronic flux in an ionization chamber and then electromagnetically separated. Using conservative modelling assumptions, an estimate of the amount of deuterium obtainable per day is made. The results show the feasibility of this approach, encouraging further research. Using the proposed method in combination with the use of lithium blankets for tritium breeding opens a new possibility for integral in-situ production of all the nuclear fuel required for fusion.