In this work, we discuss the possible uses of accelerator driven thermal nuclear reactors both for production of energy and isotopes. We consider accelerator driven thermal thorium reactors. This study indicates that such system can produce 2-15 times the energy, its accelerator consumes. The energy gain depends on the speed with which it burns fuel. For example, a slow reactor, which burns .9% of thorium per year, and has a neutron loss of 4% would have an electrical efficiency 70-79%. Neutron loss is the proportion of neutrons absorbed by reactor itself rather than material within it. The wide range in reactor efficiency is due to the fact that the number of neutrons produced per GeV accelerator energy has not yet been accurately determined. This system should also be relatively safe among the reactors commonly in use.