Carbon dioxide emissions could be 4% higher in 2040 if all US nuclear power plants retire after their 60th year of operation, according to an analysis by the US Energy Information Administration (EIA).

In its Annual Energy Outlook 2014 (AEO2014) EIA looks at several cases that could represent conditions leading to additional coal and nuclear plant retirements, and it examines the potential energy market and emissions effects of the loss of this capacity. In 2012, coal and nuclear plants provided 56% of the electricity generated in the United States.

In the Accelerated Coal Retirements scenario EIA predicts that 110 GW of capacity, or 117% more than in the Reference case, is retired by 2040. The retirements result from assumed high fuel prices prompted by a decrease in coal mine productivity and an increase in coal transportation costs, as well as increase O&M costs as plants age.

"In the accelerated nuclear retirements scenario, 42 GW of nuclear capacity is retired through 2040"

In the Accelerated Nuclear Retirements scenario, 42 GW of nuclear capacity is retired through 2040. The scenario assumes that O&M costs for nuclear power plants grow by 3% per year through 2040; that all nuclear plants not retired for economic reasons are retired after 60 years of operation; and that no additional nuclear power plants are built after the 5.5 GW of capacity currently under construction. "This case reflects uncertainty regarding actions and costs associated with continued operation of the existing nuclear fleet," EIA says.

The EIA also examines a third case: large-scale simultaneous retirements of both coal-fired and nuclear capacity.

Emissions impacts

Projections for CO2 emissions in the accelerated nuclear retirement scenario are 4% higher compared with the reference case in 2040. Nuclear generation is replaced by natural gas (13% increase over reference case) and renewables (5% increase relative to reference case), which moderates the emissions impact.

Natural gas also makes up for most of the lost capacity in the accelerated coal retirements case (19% increase relative to reference scenario), and because using natural gas emits less CO2 than coal, emissions decrease by 20% relative to the reference scenario in 2040.

Emissions are slightly higher in the scenario that envisages accelerated coal and nuclear retirements, because natural gas-fired generation replaces some zero-emission nuclear power generation.

Graph: CO2 emissions from US electric power sector 2010-2040 (Source: U.S. Energy Information Administration, Annual Energy Outlook 2014, Issues in Focus)