IL HB3603

Amends the Public Utilities Act to expand the types of nuclear reactors that can be constructed in Illinois, replacing the previous limit of reactors with 300 megawatts or less nameplate capacity with authorization for "advanced nuclear reactors" of any size

Defines "advanced nuclear reactor" as a nuclear fission reactor with significant improvements and additional inherent safety features compared to reactors operating in the U.S. prior to December 27, 2020

Allows construction of advanced nuclear reactors beginning January 1, 2026, provided the entity obtains all required federal and state permits, licenses, and demonstrates adequate decommissioning funding assurance

Maintains existing requirements that construction can proceed if the Illinois Emergency Management Agency finds the federal government has approved a technology for high-level nuclear waste disposal, or if specifically approved by the General Assembly

Preserves exemptions for existing nuclear power reactors that began operation prior to June 1, 2024, allowing license uprates, renewals, or subsequent renewals without meeting these new requirements