Nuclear power plant has reached critical mass, will be powered up within weeks, Salehi says, echoing statements of senior Russian diplomat.

As we have previously announced, Bushehr power plant has reached the criticality stage, meaning it has been successfully launched," Salehi reportedly said.
Criticality is the stage in a nuclear reaction when the fissile material is self-sustaining. "This stage lasts for two months. We hope the plant will gain some 40 percent of its power within the next one or two months," Salehi added.

The United States and other Western nations for years urged Russia to abandon the project, fearing it would help Iran develop nuclear weapons. But an agreement obliging Tehran to repatriate spent nuclear fuel to Russia eased those concerns.
Iranian FM says Bushehr nuclear ... JPost - Iranian Threat - News