4D PLANNING | IT & DIGITAL
meticulous preparation. Significant documentation is required to ensure adherence to health and safety legislation on site and through the supply chain. Increasingly, it is recognised that ‘4D’ planning, which
integrates the static 3D model of the built asset with its construction schedule, is necessary for improving safety, cost-effectiveness and speed of progress in nuclear construction projects. The most obvious benefit of 4D planning is that, by adding a time dimension, project teams can better visualise how construction will be sequenced. However, the latest 4D tools, powered by artificial intelligence, offer several additional capabilities, beyond visualisation, that are proving fundamental to smooth project planning. Updateable in real-time, and providing transparency about status and costs, a 4D plan supports decision-making as well as being an effective communication tool. These capabilities include:
● Validation of constructability – a mechanism for determining how to build without errors
● Virtual rehearsals of difficult, hazardous tasks ● Real-time status monitoring and proactively responding to changing circumstances
● Scenario simulation – exploring probable consequences of changes to the plan
● A communications tool for aligning workforces and building trust with external stakeholders
● A central source of truth, integrating further fields of information including cost data and compliance documentation
Validating constructability A 4D planning tool allows stakeholders to explore how tasks interact in time and space, and thus identify ‘risks’ – clashes of people, materials and equipment – that are invisible in static models. In a complex project, there are thousands of interface points that cannot be seen on a 3D model or the typical gantt chart. These may show that a wall is required, but not how to access the point of work with large equipment, deliver materials, or complete the task safely and at the appropriate point in the sequence. For example, consider how an import route, blocked by a beam, prevents vehicles or mechanical equipment from accessing a works location. Left undetected, fixing such a problem may require breaking down walls, rebuilding, reordering materials – which also incur administrative, transport and storage costs – and extra worker hours.
During pre-construction, the 4D planner will run through the design to spot clashes, find a solution that is suitable for the installation teams, and convey desired changes to designers before work begins. For example, as part of a programme to build a waste retreatment facility at the UK’s Sellafield site, exceeding £1bn (US$XXbn) in value, integrated 4D workflows helped identify and remedy over 160 risks, avoiding 500 days of rework that could have cost £80m (US$XXm).
Virtual rehearsals for risky operations A common cause of accidents is misunderstandings of risk assessments relating to hazardous activities such as major lifts, tunnel breakthroughs, or works adjacent to live assets. 4D planning tools that can integrate data with gaming software such as Unreal Engine, can enable virtual rehearsals of such hazardous operations. The tasks can be rehearsed in immersive, virtual reality (VR) environments that give site workers a view identical to what they would see when performing them in real life. For instance, a crane operator may learn how to avoid hazards such as losing line of sight of a heavy load – which can be as much as 5,000 tonnes nowadays – or twisting of taglines, to perform a lift safely. Such rehearsals build team confidence and support clear safety briefings.
Status monitoring and proactively responding At any time in the construction phase, hundreds of tasks will be in progress simultaneously. If there is any delay in updating the model or it cannot adapt to changes in the schedule, the model would become redundant: stakeholders will neither use nor trust it, because it will not reflect reality. However, its ability to work with multiple data
sources means that a 4D plan can reflect the project’s actual status. Here, the 4D planners can play a key role in keeping the schedule up-to-date and reflecting reality on the ground. Data may be collected through laser scans or cameras fitted to safety helmets. Data or footage taken on a site tour can be uploaded and the model may be automatically updated. A frequently updated status in turn allows the development of simple-to-understand dashboard presentations, highlighting discrepancies between what is completed and what was planned at any point in the schedule. A commonly held myth that drives resistance to
change is that digital planning makes project managers ‘redundant’. In fact, with access to reliable, relevant,
www.neimagazine.com | June 2026 | 19
An advanced 4D plan, integrated with documentation and cost data, can also provide the basis for a digital twin. Source: US NRC
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