Westinghouse Electric Company successfully completed zero-power criticality testing for its eVinci microreactor on August 24, 2026. The milestone validates key design assumptions and advances the company’s strategy for deploying resilient nuclear technology in remote and challenging environments.

The test concluded at 10:39 am PT at the National Criticality Experiments Research Center (NCERC), a National Nuclear Security Administration (NNSA) facility located at the Nevada National Security Site (NNSS). Westinghouse conducted the exercise in partnership with Los Alamos National Laboratory and Idaho National Laboratory.

Technical Validation and Design

The achievement confirms the models and core design assumptions underpinning the eVinci technology. This step is part of Westinghouse’s rapid product development philosophy, which integrates testing, modeling, simulation, and design improvements to accelerate technology maturation while reducing technical risk.

The eVinci microreactor utilizes a compact architecture combining advanced heat pipe technology, TRISO fuel, graphite core materials, and control drum components. The design aims to provide continuous electricity for eight years without refueling, targeting applications in defense and space sectors.

Strategic Implications

Dr. Lou Martinez Sancho, Westinghouse Chief Technology Officer, stated that the milestone reflects the company’s heritage of innovation and its push toward the next frontier of nuclear energy. He acknowledged the collaboration with the U.S. Department of Energy, NNSA, and partner laboratories.

Future phases will focus on integrated prototype testing and demonstrations to further validate performance, operability, and manufacturability. Learnings from each stage will guide subsequent development and prototype improvements.

What the Numbers Show

While no financial figures were disclosed, the operational timeline indicates a structured validation process. The completion of zero-power criticality testing serves as a binary gate: it confirms physical adherence to theoretical models before capital-intensive high-power demonstrations proceed. This reduces downstream technical risk by verifying core physics assumptions early in the development cycle.

Westinghouse Electric Company and Amentum (NYSE: AMTM) have entered into a series of agreements to support the Westinghouse APX technology platform, aiming to augment capabilities for the fleet-scale deployment of its AP1000 reactor while advancing the development of the AP300 small modular reactor (SMR). This strategic collaboration strengthens Westinghouse’s operational framework for large-scale nuclear projects and accelerates innovation in smaller reactor technologies, addressing growing global demand for firm baseload power.

Strategic Partnership Details

The agreements focus on enhancing technical and engineering support for Westinghouse’s nuclear portfolio. By leveraging Amentum’s expertise in advanced engineering and technology solutions, Westinghouse seeks to improve its capacity for deploying the AP1000 reactor on a fleet scale. Dan Sumner, President and Chief Executive Officer of Westinghouse, stated that the company is pursuing a disciplined APX technology strategy built on the proven AP1000 reactor and extended through the AP300 SMR.

"We continue to make investments to strengthen our proven APX platform, and our ongoing collaboration with Amentum is expected to accelerate the licensing of the AP300 SMR with the NRC," Sumner said. "Separately, our two companies will work together to enhance our engineering and execution capabilities for delivering 1-gigawatt reactors at scale."

Key Objectives

The primary objectives of the agreement include:

• Augmenting Westinghouse capabilities for fleet-scale deployment of the AP1000 reactor.
• Advancing the development of the AP300 small modular reactor (SMR).
• Collaborating to obtain regulatory approval for the AP300 SMR by the U.S. Nuclear Regulatory Commission (NRC).

Market Implications

This partnership underscores the increasing importance of collaborative efforts in the nuclear energy sector. John Heller, Amentum Chief Executive Officer, noted that Amentum’s expertise spans the full spectrum of the nuclear project lifecycle, accelerating the development and deployment of advanced nuclear solutions. He highlighted an expanding global market for firm baseload power, stating that the collaboration will enable them to help meet that demand.

The Westinghouse APX strategy offers a single technology platform enabling the fleet delivery of the AP1000 reactor and the AP300 SMR. The APX platform is based on the proven innovations and technology of the AP1000 plant, including validated engineering, components, licensing strategies, fuel design, and supply chain. Amentum’s engineering capacity and nuclear experience will strengthen the industrial base and delivery model, enabling the repeatable deployment of the APX technology suite.

What the Numbers Show

While specific financial figures were not disclosed in the announcement, the strategic alignment between Westinghouse and Amentum suggests a significant investment in technology and engineering resources. The emphasis on fleet-scale deployment indicates a long-term commitment to expanding nuclear infrastructure, which could drive future revenue growth and market share for both entities. The focus on both the AP1000 and AP300 reactors highlights a balanced approach to addressing diverse market needs, from large-scale power generation to more flexible, modular solutions.