Assystem
Assystem is a France-based engineering and project-management group specializing in complex industrial infrastructure, particularly nuclear power and aerospace.
Last updated August 22, 2026
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Overview
Assystem is an independent engineering group headquartered in Paris, France, and established in 1966. The company provides technical and project-management services for complex industrial programs, with a strong concentration in nuclear energy. Its work spans design, construction support, project supervision, commissioning, operational support, safety, quality, and engineering coordination across the life cycle of major infrastructure. The group is best known for its role in the civil-nuclear sector. Assystem has participated in the construction programs for all of the European Pressurized Reactor projects identified in the reference material: Flamanville in France, Taishan in China, and Olkiluoto in Finland. Its involvement reflects a business model centered on engineering expertise, systems integration, project controls, and the management of technically demanding programs rather than the manufacture of a single standardized consumer product. Assystem also has aerospace activities. In 2005, it acquired the Atena subsidiary of German aircraft-engine manufacturer MTU Aero Engines, expanding its engineering capabilities in aerospace and propulsion-related work. From 2018, the group was involved in the engineering of Flying Whales, a proposed large airship project. These activities illustrate the company’s broader experience in highly regulated industries requiring advanced design, certification, industrialization, and program management. During the 2010s and early 2020s, Assystem deliberately narrowed its strategic focus. The group reduced or exited substantial parts of its participation in sectors such as automotive engineering and increasingly concentrated resources on nuclear projects and related energy-transition infrastructure. This repositioning was associated with a reduction in both revenue and employee numbers compared with the earlier part of the decade. The supplied reference material reports revenue of more than EUR 470 million in 2020, compared with EUR 871.4 million in 2013, and more than 7,100 employees in 2021, compared with more than 11,000 in 2013. A major organizational change occurred in February 2019, when the Assystem Technologies division was renamed Expleo Group. The change separated that activity under a new identity while Assystem continued to emphasize nuclear engineering and other strategic industrial programs. Today, Assystem is primarily positioned as a specialist engineering partner for nuclear operators, technology providers, contractors, and public or private infrastructure developers. Its value proposition is based on technical depth, knowledge of regulated industrial environments, and the ability to support projects from early design through construction, commissioning, and operations.
History
Assystem was created in 1966 in France as an engineering company serving complex industrial and infrastructure programs. Its business developed around the provision of technical expertise, design support, project coordination, construction supervision, commissioning, and operational assistance. Rather than being identified with a single manufactured product, the company built its position through participation in major engineering programs where safety, reliability, regulatory compliance, and coordination among multiple contractors are critical. Nuclear energy became the defining area of Assystem’s development. The group contributed engineering and project expertise to European Pressurized Reactor programs in France, China, and Finland, including the projects at Flamanville, Taishan, and Olkiluoto. Its work in these programs placed it within the international network of engineering companies supporting reactor design, plant construction, industrial integration, commissioning, and related project controls. Nuclear engineering also gave Assystem a long-term role in services connected with plant operations, safety, quality, maintenance, and life-cycle management. The company expanded beyond nuclear engineering during the following decades. Aerospace became an important adjacent field, and in 2005 Assystem acquired Atena, a subsidiary of the German aircraft-engine manufacturer MTU Aero Engines. The transaction added aerospace engineering capabilities and strengthened the group’s participation in technically complex programs involving aircraft systems and propulsion. Assystem later participated in the engineering of the Flying Whales airship, beginning in 2018 according to the supplied reference material. This project represented an application of the group’s systems-engineering and advanced industrial-design experience to a novel aerospace platform. Assystem also operated in other engineering markets, including automotive. Over time, however, the group reassessed the breadth of its portfolio. Its strategic direction shifted toward nuclear energy and a smaller number of specialized industrial domains. This recentering involved reducing its participation in several non-core sectors and contributed to a decline in overall revenue and employee numbers relative to the beginning of the 2010s. The supplied reference material gives revenue of EUR 871.4 million for 2013 and more than EUR 470 million for 2020, while employment declined from more than 11,000 people in 2013 to more than 7,100 in 2021. A significant identity and organizational milestone came in February 2019, when Assystem Technologies was renamed Expleo Group. The change distinguished that business from the continuing Assystem organization. Assystem subsequently remained associated primarily with engineering and project services for the nuclear sector, while retaining selected aerospace and other advanced-industry capabilities. In its current form, Assystem is positioned as an engineering partner for complex, capital-intensive, and regulated infrastructure. Its services cover multiple stages of the asset life cycle, including early design, industrial engineering, construction support, supervision, commissioning, safety, and operations. The company’s history is therefore characterized by a progression from broad industrial engineering toward a more focused specialist model built around nuclear expertise, supported by aerospace and other high-technology capabilities.
- 2021
Workforce exceeds 7,100 employees
[1]The group has more than 7,100 employees, after reducing its presence in several non-core sectors compared with the earlier decade.
- 2020
Reported revenue exceeds EUR 470 million
[1]Assystem reports revenue of more than EUR 470 million for 2020, following a strategic shift toward nuclear activities.
- 2019
Assystem Technologies becomes Expleo Group
[1]The Assystem Technologies division is renamed Expleo Group, separating its identity from the Assystem brand.
- 2018
Involvement in Flying Whales engineering
[1]Assystem becomes involved in engineering work for the proposed Flying Whales airship project.
- 2005
Acquisition of Atena
[1]Assystem acquires Atena, a subsidiary of German aircraft-engine manufacturer MTU Aero Engines, strengthening its aerospace engineering activities.
- 1966
Assystem is established
[1]Assystem is created in France as an independent engineering group serving complex industrial and infrastructure programs.
Products and positioning
A specialist engineering and project-management partner for complex, highly regulated industrial programs, with nuclear energy as its central area of expertise and aerospace as an additional capability.
Nuclear engineering
Nuclear engineering services
Assystem’s principal offering is engineering and technical assistance for nuclear-power programs. Services can cover design coordination, systems engineering, safety and quality support, construction oversight, commissioning, operational assistance, and life-cycle engineering. The company has participated in European Pressurized Reactor projects in France, China, and Finland, giving the nuclear business an international project footprint.
Industrial engineering
Industrial project and infrastructure services
The group supports complex industrial facilities and infrastructure through design management, project controls, construction supervision, commissioning, and coordination among engineering and construction disciplines. These services are intended for large, technically integrated programs where schedule, safety, regulatory, and quality requirements must be managed across the full asset life cycle.
Aerospace engineering · 2005
Aerospace engineering
Assystem has aerospace engineering capabilities that expanded through its 2005 acquisition of Atena from MTU Aero Engines. The activity has included work associated with aircraft and propulsion-related engineering, as well as participation in the development engineering of the Flying Whales airship project from 2018.
Brand decisions
2020
Recenter the business on nuclear engineeringStrategyBackground
Assystem reduced its participation in sectors such as automotive and redirected attention toward nuclear energy and selected complex industrial programs.
Action taken
The group pursued a narrower strategic portfolio centered on nuclear engineering and related infrastructure services.
Aftermath
The repositioning was associated with lower reported revenue and employee numbers than in 2013, while reinforcing Assystem’s identity as a nuclear-sector engineering specialist.
Revenue. EUR 871.4 million → More than EUR 470 million (2013 versus 2020)
2019
Separate Assystem Technologies under the Expleo nameStrategyBackground
Assystem was increasingly concentrating its activities on nuclear engineering while managing a broader portfolio of technology and industrial engineering activities.
Action taken
In February 2019, the Assystem Technologies division was renamed Expleo Group.
Aftermath
The rebranding created a separate identity for the former Assystem Technologies activity, while Assystem continued to develop its nuclear-focused engineering position.
Recent events
- Unconfirmed
Assystem acquires Schofield Lothian[2]
Reported:
Assystem acquired Schofield Lothian Ltd, a London-based consultancy with 80 consultants specializing in rail project consents and engagement, environmental services, project management, and commercial management.
Assystem acquires Corporate Risk Associates[3]
Reported:
Assystem acquired 100% of the shares in Corporate Risk Associates (CRA), a UK-based risk, safety, operations and human factors consultancy.
Sources3 sources
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