ATHENS, Ala. (AP) — The Tennessee Valley Authority says it's completed a $475 million upgrade at its oldest nuclear power plant in a move that helped boost the amount of electricity it produces without carbon emissions.

The Times Free Press reports modifications to reactors at Browns Ferry Nuclear Plant in Alabama added power and expanded service to almost 300,000 more homes.

CEO Jeff Lyash said the upgrades, coupled with increased use of solar power, will help TVA reduce carbon emissions by 70% of 2005 levels by 2030.

The newspaper reports solar energy is a small part of TVA's overall generation. Although nuclear power is expected to produce about 40% of TVA's electricity, its plan for the next 20 years shows about 15% of power will still come from coal and 20% from natural gas.