Nuclear power has long been a core component of the Illinois energy sector. A new law seeks to enable nuclear power to play an increased role in the energy transition by allowing construction of new “small modular reactors” in the state.

In December 2023, Governor J.B. Pritzker signed a bipartisan bill permitting the construction of certain smaller nuclear power plants in Illinois, authorizing a study of nuclear power, and directing state agencies to adopt new rules for nuclear plants. The smaller, “advanced” nuclear facilities allowed by the new law have not yet been constructed in the United States or received all required federal authorizations. But the new law may be an early signal to the industry that Illinois remains fertile ground for the next wave of nuclear development.

In 2022, Illinois generated more nuclear energy than any other state, with its six existing nuclear plants producing 52% of the state’s power. These six plants host 11 large nuclear reactors, with nameplate capacities of about 900-1200 megawatts (MW) each. However, no new nuclear power plants have been constructed in Illinois for more than 30 years. In fact, since 1987, construction of new nuclear plants has been effectively prohibited by a state statute that required federal approval of nuclear waste disposal technologies before new plants could be built. Still, the state has acted to preserve its existing nuclear fleet, adopting two ratepayer-funded support programs for the plants, first in 2016 and again 2021. Most recently, as part of PA 102-0662 (commonly referred to as the Climate and Equitable Jobs Act), the Illinois General Assembly declared that “nuclear power is necessary for the State’s transition to 100% clean energy.” 20 ILCS 3855/1-75(d-10)(1)(C).

In May 2023, the Illinois General Assembly passed a bill — SB 76 — that would have allowed construction of any “advanced nuclear reactor.” That term, incorporating a definition from federal law, includes no size limitations or specific technical requirements. 42 U.S.C. 16271. Governor Pritzker vetoed the bill, stating that the authorization was too broad, and could have allowed the construction of large new nuclear plants in Illinois which would be “so costly to build that they [would] cause exorbitant ratepayer-funded bailouts.”

In November 2023, the legislature passed a more comprehensive bill, authorizing construction of “small modular reactors” beginning in 2026. Governor Pritzker signed that bill into law on December 8, 2023, as PA 103-0569. The “small modular reactors” authorized by the law are limited to 300 MW, much smaller than the existing reactors in the state. However, the law allows more than one reactor to be constructed at the same site.

The law also allows the governor to commission a wide-ranging study regarding the role and impacts of nuclear power in the state, including permitting issues, water use, energy market impacts, and health risks. That study must be commissioned by January 1, 2025. Additionally, the law requires the Illinois Emergency Management Agency and Office of Homeland Security, in consultation with the Illinois Environmental Protection Agency, to adopt new rules for small modular reactors by January 1, 2026, addressing topics including decommissioning, environmental monitoring, emergency preparedness, inspections, and fees.