To replace the ageing nuclear reactors used today for radio- isotope production, research and industrial applications, we propose to use a spallation neutron source, with neutron multiplication by fission. A 150 MeV cyclotron will be used to produce a proton beam hitting a molten Pb-Bi primary target producing about 0.8 primary neutron per incident proton. The primary spallation neutrons, moderated, strike a number of secondary targets containing a subcritical amount of 235U. Typical neutron fluxes at the targets location will be around 6.1013n/cm2s. Such a systems can be used, for example, to supply more than 50 percent of the world demand in 99Mo, the most frequently used radio- isotope in nuclear medicine. The non-critical nature of the system makes it more acceptable for the public than a nuclear reactor and simplifies the licensing process. The foreseen investment and operational cost, including radiowaste and decommissioning, of such a system are more favorable than for nuclear reactors. In extra, the licensing procedure is considerably simplified and the time from planning to commissioning might be shorter than four years. This paper discusses the current status of the ADONIS- project and more particularly one of its applications: the optimization of this system as a dedicated 99Mo production plant.