Westinghouse begins Bohunice AP1000 engineering study

Westinghouse Electric Company has begun a six-month front-end engineering and design (FEED) study for a proposed AP1000 nuclear reactor at Jaslovské Bohunice in Slovakia. The company signed an agreement with project developer Jadrová energetická spoločnosť Slovenska (JESS) on 28 October 2026, establishing a programme of engineering, licensing preparation and project planning intended to inform the next development decisions.

The agreement follows civil nuclear cooperation between Slovakia and the United States, formalised through an intergovernmental agreement in January. Funding for the study is being provided in part through the US Department of State’s Foundational Infrastructure for Responsible Use of Small Modular Reactor Technology (FIRST) programme. The reactor under assessment is Westinghouse’s large-scale AP1000 design, rather than a small modular reactor.

JESS is responsible for preparing the new nuclear power plant project at Bohunice. It became wholly owned by the Slovak state through Jadrová a vyraďovacia spoločnosť (JAVYS) on 8 October, following the transfer of the former ownership interest held by Czech utility ČEZ. The ownership change places the project company entirely under Slovak state control as its technical preparations continue.

Westinghouse will assess whether the AP1000 configuration is suitable for the proposed site and develop more detailed engineering and project documentation. The work is expected to produce a preliminary construction schedule and budget, alongside information needed to progress the relevant licensing activities. These deliverables will provide an initial basis for evaluating technical and economic feasibility before further design and investment commitments are made.

The AP1000 is a Generation III+ pressurised water reactor incorporating passive safety systems. Heat produced by nuclear fission is transferred through a pressurised primary coolant circuit to steam generators, where it is used to produce steam in a separate secondary circuit. The steam drives a turbine connected to an electrical generator, while cooling and supporting systems manage the remaining thermal energy.

Its passive safety arrangements use physical processes including gravity and natural circulation to perform specified cooling and safety functions. The design reduces dependence on powered equipment for certain emergency responses, although a completed nuclear station still requires extensive electrical, mechanical, instrumentation and control systems. The performance and operating requirements of those systems must be addressed in the applicable engineering and safety assessments.

Jaslovské Bohunice already accommodates nuclear power infrastructure, but an established nuclear location still requires detailed assessment before another reactor can be constructed. Ground conditions, seismic characteristics, cooling arrangements and the available site area influence how the proposed unit can be positioned. Existing roads, utilities and industrial facilities also affect the routes available for transporting large equipment and carrying out construction work.

Civil engineering requirements must be coordinated with the reactor’s structural design and equipment layout. The foundations and supporting structures need to accommodate substantial loads from the reactor building, containment arrangements and associated machinery. Ground investigation and structural analysis establish the assumptions used to design those elements, with further detail required as the project progresses towards construction.

Cooling infrastructure is another consideration because electricity generation produces substantial quantities of residual heat. The selected cooling arrangement must be capable of transferring that heat under the operating and environmental conditions applicable to the site. Water availability, temperature limits and the design of associated cooling equipment can influence both the plant configuration and its permitted operating conditions.

Electrical integration will require assessment of the proposed generator’s connection to Slovakia’s transmission system. A large generating unit changes the power flows and operating conditions of the network to which it connects. Connection studies must consider the generator’s intended output, voltage regulation, fault behaviour and the arrangements needed to maintain system stability during changes in generation or network conditions.

Transformers, high-voltage switchgear and protection systems will provide the interface between the generating station and the external network. Protection settings must allow faults to be detected and isolated while coordinating the responses of equipment within the plant and on the transmission system. The design must also establish how station auxiliaries receive electricity during normal operation, shutdown and other specified conditions.

Those auxiliary supplies serve equipment including pumps, monitoring systems and plant controls. Safety-related electrical arrangements require particular attention because their performance must be demonstrated against the conditions considered in the reactor’s safety case. The engineering study will help define the infrastructure and interfaces that require further examination, although detailed equipment specifications will be developed during subsequent stages.

Licensing preparation will proceed alongside the engineering work. JESS will need documentation describing the proposed reactor, site characteristics and technical arrangements to support the requirements of the relevant Slovak authorities. Experience from AP1000 projects elsewhere can provide an engineering reference, while the proposed Bohunice installation must satisfy the regulatory conditions applicable to its own location and design.

Westinghouse has operating AP1000 units in China and the United States, and the technology has been selected or is under consideration for other nuclear projects. Existing reference designs and operating experience can inform the proposed Slovak development, including component specifications and construction planning. Site-specific engineering and the required national approvals remain necessary before construction can proceed.

The FEED programme will also establish preliminary information on project costs and delivery periods. Nuclear construction budgets depend on civil engineering, equipment manufacturing, installation, labour, infrastructure and commissioning requirements. The assumptions used at this stage will need to be refined as the design develops and suppliers establish the commercial terms governing individual work packages.

Construction planning must account for the interfaces between equipment procurement and site works. Major reactor components can require lengthy manufacturing periods, while their installation depends on the availability of completed structures and suitable lifting arrangements. Coordinating these activities during engineering development can identify sequencing requirements before detailed procurement and construction contracts are finalised.

Slovakia already relies substantially on nuclear generation, with operating reactors at Bohunice and Mochovce. The proposed additional unit forms part of the country’s longer-term electricity supply planning. Its eventual contribution will depend on the selected generating capacity, technical performance and the programme required to bring a new reactor through construction and commissioning.

JESS chief executive Tomáš Vavruška said the FEED results would provide the project company with more detailed technical documentation, a preliminary timetable and budget to support its next decisions. The study is expected to conclude approximately six months after the October agreement, providing a defined engineering assessment for consideration before the project advances further.