A new system proposed for the generation of radioisotopes with accelerator neutrons by deuterons (GRAND) is described by mainly discussing the production of ⁹⁹Mo used for nuclear medicine diagnosis. A prototype facility of this system consists of a cyclotron to produce intense accelerator neutrons from the ^natC(,) reaction with 40 MeV 2 mA deuteron beams, and a sublimation system to separate ^99mTc from an irradiated ¹⁰⁰MoO₃ sample. About 8.1 TBq/week of ⁹⁹Mo is produced by repeating irradiation on an enriched ¹⁰⁰Mo sample (251 g) with accelerator neutrons for two days three times. It meets about 10% of the ⁹⁹Mo demand in Japan. The characteristic feature of the system lies in its capability to reliably produce a wide variety of high-quality, carrier-free, carrier-added radioisotopes with a minimum level of radioactive waste without using uranium. The system is compact in size, and easy to operate; therefore it could be used worldwide to produce radioisotopes for medical, research, and industrial applications.