The US Nuclear Regulatory Commission (NRC) has received an application from Westinghouse Electric Company to renew and update the design certification for its AP1000 reactor, incorporating construction and operating experience from recently completed US reactors. The application seeks to align the certified AP1000 design with the as-built configuration of Vogtle NPP units 3&4, which entered service in 2023 and 2024.
The submittal would establish a validated baseline that could facilitate streamlined licensing for future applicants to replicate, which could lead to faster licensing approvals, lower regulatory uncertainty and costs, and increased deployment of new nuclear plants to meet the rising electricity demand.
NRC said it is evaluating the application to determine if it is complete and acceptable for processing. If the application is determined to be sufficient, the staff will docket it and begin a detailed technical review.
Future applications referencing the updated AP1000 should benefit from efficiencies introduced through standardised, nth-of-a-kind licensing and the incorporation of lessons learned from Vogtle’s licensing, construction, and startup.
The planned amendment process is part of the NRC’s broader effort to streamline design certification updates and combined licence application reviews for reactors referencing approved designs, enhancing regulatory predictability while maintaining the agency’s high safety standards.
NRC first certified the AP1000 design in 2006, and it is valid to 2046. Westinghouse’s application requests a 40-year renewal of the certification while incorporating design changes approved during the construction and licensing of Vogtle 3&4. During the construction of those units, Westinghouse and the licensee identified design changes requiring NRC review and approval through licence amendments. Many of these changes represented departures from the original certified design.
During the construction of Vogtle 3&4, the licensee (Southern Nuclear Operating Company) and Westinghouse identified numerous design changes that departed from the original AP1000 Certified Design, requiring NRC approval through License Amendment Requests (LARs).
These changes addressed structural inconsistencies, layout optimisations, and updated safety regulations. Key departures included major structural redesigns. The original design of the shield building had to be significantly modified to use “modern but not-yet-tested construction techniques” to comply with updated safety standards. Amendments were required to the nuclear island basemat to revise the upper tolerance on basemat thickness and structural criteria for anchoring headed shear reinforcement bars.
Changes were approved for shear stud size and spacing and for switching certain reinforced concrete structures to steel-plate composite construction. The licensee requested exemptions to depart from the certified gap distance between the Nuclear Island and adjacent buildings.
There were also building and layout modifications. Significant changes to the annex and radwaste buildings involved internal configuration updates, such as converting rooms into battery rooms, increasing floor thicknesses for structural loads, and moving fire area walls. Approvals were granted for changes to the turbine building bracing (eccentric and concentric) and general layout adjustments. Amendments resolved wall thickness inconsistencies and structural floor details of the auxiliary building.
Adjustments were also required to the safety and electrical system. An additional non-safety-related battery was added to support uninterruptable power supply (UPS) loads. A temporary reduction in minimum boron concentration for unit 4 was approved for its initial operating cycle. Changes were made to the Radiologically Controlled Area ventilation system and containment cooling strategies. The project had to incorporate design changes to account for potential commercial aircraft impacts, which was not part of the original design when it was first conceived.
The methodology for instrument setpoints was updated to prevent licensing delays while instruments were still being selected. Multiple amendments removed unit-specific language or modified conditions that became non-applicable as construction reached completion.
The Vogtle units were significantly delayed and over-budget. The timeline spanned 15 years from initial design selection to full commercial operation. The project was originally projected to take roughly seven years but faced a 14-year construction period due to design finalisation issues, supply chain challenges, and the 2017 bankruptcy of Westinghouse.
The expansion of Plant Vogtle reached a final cost of approximately $36.8bn, more than double the original 2009 estimate of $14bn. These overruns were driven by a combination of systemic project failures and acute technical issues that emerged late in construction.
Work began before the AP1000 design was 100% complete, leading to the massive volumes of design changes and “rework”. Westinghouse filed for bankruptcy after absorbing billions in losses, forcing Southern Nuclear to take over project management directly. Prefabricated modules often arrived at the site incomplete or with incorrect dimensions, requiring expensive and time-consuming on-site modifications. Because the project took 14 years instead of the planned seven, interest on loans compounded significantly, adding billions to the final price tag.
In 2021, the NRC increased its oversight after identifying critical quality control failures at unit 3. Inspectors found over 600 cases where safety-related and non-safety-related cables were not properly separated. This separation is a regulatory requirement to ensure a single event (like a fire) cannot disable redundant safety systems.
During the final stages, component test failure rates reached as high as 40% to 80%. Many parts had been left exposed to the weather for years without proper protection or chain of custody, leading to degradation. Late-stage testing revealed excessive pipe vibrations in the cooling systems, which required structural reinforcements and further delayed the startup of both units.
In October 2025 the US government signed a strategic partnership with the current owners of Westinghouse Electric Company – Brookfield Asset Management and Cameco Corporation – to deploy at least $80bn in new nuclear reactors across the US utilising the AP1000 and the AP300 small modular reactor (SMR). The US government undertook to facilitate financing, permitting, and regulatory approvals.
Westinghouse’s application to renew and update the design certification for the AP1000 reactor is clearly a very necessary first step to implementation of this ambitious project.
