Heavy Lift & Modular Installation
Moving work off the site and into factories, then putting the results back - large prefabricated modules and single heavy components delivered by sea, rail or road, transported across site and lifted into an open structure by some of the largest cranes in use anywhere.
Last updated 2026-08-25
Typical duration
Typically 2-4 years of module and heavy component installation per unit, overlapping the concrete works and paced by crane availability, design maturity and the weather windows for the largest lifts.
What is Heavy Lift & Modular Installation?
Modularisation is the single biggest change in how nuclear plants are built. Instead of assembling everything in place inside a congested, inspection-heavy structure, the project builds large sections in factories and assembly halls - reinforcement and liner modules, pipework and equipment skids, whole rooms complete with supports, cable containment and finishes - and then lifts them into position. The reasoning is simple and entirely practical. Work done in a shop is faster, safer, better controlled and easier to evidence than the same work done at height in a confined space with three other trades waiting, and it can start before the structure exists.
The construction consequence is that the sequence turns inside out. Rather than building the shell and fitting it out, the project often builds upwards and inwards at the same time, leaving the roof open so that modules can be lowered in from above. That drives everything else: the crane strategy, the laydown layout, the road widths, the assembly building positions and the order in which the concrete structures are closed. The heavy lift crane is planned years ahead, because on many schemes it is the single most constrained resource on the site, and it usually has to be erected in a position it can serve from for the whole of its stay.
Alongside the modules come the large single components supplied by the reactor supplier and the turbine manufacturer. These arrive as finished, tested items and they are large enough that the route from the factory to the final position is engineered as its own project - port, jetty, transporter, bridge assessments, temporary road strengthening and a set of storage arrangements for a component that may wait months before it can be installed. There is generally no second one on the shelf, so the handling arrangements, the lift plan and the protection regime are treated as seriously as anything else on the project.
Compare the methods at a glance
When and why is Heavy Lift & Modular Installation used?
Module installation overlaps with the concrete works rather than following them, because the whole point of the approach is to take work off the critical path. Modules are lifted in as soon as the structure below is complete and released, and the sequence is dictated by what has to go in before the roof closes rather than by trade convenience. The reason the industry went this way is cost and schedule. Nuclear construction is dominated by the assurance regime, and the more hours spent working inside a safety-classified structure the more inspection, access, coordination and rework the project buys. Move those hours into a factory and the same work is done under better conditions with tighter control, and the records come out cleaner. The reason it demands so much planning is that a module cannot be adjusted much once it is built. Its interfaces are fixed, its weight is fixed and its route is fixed, so the design has to be complete and accurate far earlier than a traditional build would require, and the survey control has to be good enough that a large assembly drops onto connections that were cast months earlier. Projects that modularise successfully commit to it early and design for it. Projects that decide to modularise late tend to get the disruption of both approaches and the benefits of neither.
Types of Heavy Lift & Modular Installation
Explore each method in depth - benefits, limitations, plant and quality control on its own page.
Structural modules
Prefabricated reinforcement cages, liner sections and composite steel and concrete panels that become part of the permanent structure once concrete is placed around or within them. They remove an enormous amount of fixing and welding from the working face and let the structure rise faster.
Mechanical and equipment modules
Skids and frames carrying pumps, tanks, heat exchangers, valves, pipework and their supports, assembled and tested in a shop and lifted in complete. The gain is that the pipework is fabricated, welded, examined and often pressure tested before it ever reaches site.
Room and building modules
Complete volumes - plant rooms, corridors, tank compartments, electrical rooms - built off site with structure, services, containment and finishes already in place. The most efficient in labour terms and the most demanding in coordination, because everything crossing the module boundary has to be agreed long in advance.
Large single components
The very heavy individual items supplied by the reactor supplier and the turbine manufacturer, delivered complete and installed as one piece. They are not modules in the prefabrication sense, but they share the same constraints: engineered transport routes, dedicated lift plans and no realistic possibility of a replacement.
Best suited for
- Repetitive, congested or labour-intensive work that is far cheaper to build in a shop than in place
- Sites with sea or rail access, where the largest components avoid the public road network
- Designs developed with modularisation in mind, where interfaces are defined early and stay stable
- Programmes building multiple identical units, where the module design and the jigs are used again and again
Heavy Lift & Modular Installation: step by step
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Step 1: Decide what becomes a module
The modularisation strategy is set early, because it changes the design rather than just the method. The project works through the plant looking for volumes of work that are repetitive, congested, labour-intensive or awkward to inspect in place, and assesses each candidate against weight, size, transport route, crane capability, interface count and the maturity of the design. A module only pays if the design is stable enough to fabricate it properly, so the decision is as much about design maturity as about physical practicality. Once the strategy is fixed, the structures, the openings, the lift routes and the crane positions are all designed around it.
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Step 2: Build and prove the module in the factory
Modules are built in dedicated facilities, either off site or in assembly halls in the site compound, under conditions closer to manufacturing than to construction. Welding, fixing, coating, testing and inspection all happen in a controlled environment, with the same traceability and record requirements that would apply on site but with far better access. Wherever possible the module is tested before it moves - pipework examined and pressure tested, electrical continuity proved, equipment function checked - so that faults are found in the shop rather than in a position where nobody can reach them. Dimensional control is checked against the survey of the interfaces the module will meet.
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Step 3: Engineer the transport route
Getting a large module or a heavy component to site is a project in itself. The route is surveyed end to end, structures along it are assessed and where necessary strengthened, overhead obstructions are identified, and the port, jetty or rail terminal arrangements are agreed. Sea transport is common for the largest items because it avoids the road network almost entirely, with a temporary marine offloading facility built during the enabling works specifically for the purpose. Movements are planned around tides, weather and traffic, they are rehearsed, and they run under permits and escorts agreed with the highway and harbour authorities. The route is proved before the component is committed to it.
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Step 4: Receive, store and prepare on site
Arrival on site is not installation. Modules and components are received, inspected against the transport records, checked for damage, and moved to prepared laydown or storage where the ground bearing has been designed for the load. Many wait months for the structure to be ready, so preservation matters - protection from weather, controlled storage conditions where the equipment requires it, nitrogen or desiccant regimes for sensitive items, and periodic inspection to confirm nothing has deteriorated. Preparation for the lift happens here too: fitting rigging attachments, removing transport bracing at the right moment, and carrying out the final dimensional survey against the receiving structure.
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Step 5: Plan the lift
Every significant lift has an engineered lift plan produced by an appointed person and reviewed by the designers of both the module and the crane arrangement. It covers the crane configuration and standing position, the ground bearing beneath it, the rigging arrangement, the centre of gravity, the tailing and guiding arrangements, the exclusion zones, the wind limits, the communication protocol and the contingency if the lift has to be aborted part way. For the largest items the plan is rehearsed, sometimes with a dummy load. Because the same crane serves many lifts over several years, the whole crane campaign is sequenced as a programme rather than lift by lift.
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Step 6: Rig, lift and set the module
On the day, the operation runs to the plan and to nothing else. The load is rigged and checked, the crane is configured and verified, the exclusion zone is set, and the lift proceeds under a single controlling voice with wind monitored continuously. Large modules are usually landed onto prepared bearing points or shims that allow final adjustment, and the setting operation is slow and measured because the connections below were cast months earlier and have no give in them. Where the lift is over or into a partly complete structure, the loads imposed on that structure are checked in advance, because a temporary load path can be more demanding than the permanent one.
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Step 7: Connect, align and complete the interfaces
Once landed, the module is aligned, surveyed and fixed, and then the interfaces are made - structural connections, pipework welds, cable terminations, ductwork joints and supports. This is the work that could not be done in the factory and it is done in the environment the modularisation was intended to avoid, which is why the design pushes to keep the number of site connections as low as it sensibly can. Welds made on site are examined to the same regime as everything else, and the records are added to the module package so that the whole assembly has a continuous history from the shop floor to its final position.
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Step 8: Close the structure and hand over
When the last item that needs the open route is in, the openings are closed and the structure is completed above. That decision is irreversible in practice, so it is made against a verified list rather than an assumption, and it is common for the closure to be delayed while a late component is chased. Each installed module is handed over with its full record package - fabrication, examination, test, transport, lift and connection records - and with an agreed list of anything outstanding. From this point the work inside reverts to conventional access, which is exactly the constraint the whole modular strategy exists to postpone.
Plant & equipment
- Very large capacity ring or crawler cranes, erected on engineered standing and retained on site for years
- Supplementary crawler and tower cranes for the wider module programme
- Self-propelled modular transporters, skidding systems and jacking equipment for heavy moves on site
- Temporary marine offloading facility, barges and roll-on arrangements for components arriving by sea
- Module assembly halls, fabrication shops and controlled storage facilities in the site compound
- Engineered lifting beams, spreader frames and certified rigging matched to each module
- Laser scanning and dimensional metrology for fit-up verification before and after the lift
- Welding plant and non-destructive examination equipment for the site connections
- Wind monitoring, load monitoring and crane instrumentation feeding the lift control regime
Quality control & testing
- Module fabrication carried out under the same traceability and inspection regime as work built in place
- Dimensional control checked in the shop against a survey of the actual receiving structure, not against the drawing alone
- Pipework, electrical and equipment testing completed in the factory wherever it can be, and recorded
- Transport and handling monitored, with impact and condition inspected on arrival against the despatch records
- Preservation and storage regimes applied and inspected for components waiting months before installation
- Lift plans engineered, independently reviewed and, for the largest lifts, rehearsed before the day
- Post-installation survey confirming position, level and alignment before connections are made
- A continuous record package following each module from the shop floor through to final connection
Safety watchpoints
- Heavy lifting over and into partly complete structures, with exclusion zones and a single point of control
- Wind, which stops more lifts than anything else and needs a defined limit and a monitored measurement
- Load stability and rigging failure, controlled through engineered lifting equipment and a checked plan
- Ground bearing beneath crane standing and transporter routes, designed and proved rather than assumed
- Working at height on and around large modules during rigging, guiding and connection
- Transport movements on the public highway and marine operations at the offloading facility
- Stored energy in transport bracing, jacking systems and temporary supports during setting operations
- Interface between the lift operation and the trades still working in and around the structure below
Common defects to hunt
- Fit-up failure at the interface, because the module was built to the drawing and the structure was built to reality
- Module weight growth during design, pushing the lift beyond the crane arrangement it was planned for
- Damage in transit or in storage that is only found when the module is rigged and about to be lifted
- Deterioration of equipment stored for months without an adequate preservation regime
- Openings closed before every component that needed them had arrived
- Crane standing or transporter route ground bearing not designed for the actual load path
- Excessive site connections designed into a module, giving away most of the benefit of building it off site
- Record packages split between factory and site so that no single continuous history exists for the assembly
How long does Heavy Lift & Modular Installation take?
Typical duration: Typically 2-4 years of module and heavy component installation per unit, overlapping the concrete works and paced by crane availability, design maturity and the weather windows for the largest lifts..