Commission: impossible
Tony Anderson, CTO of the Commissioning Specialists Association, and former HVAC Commissioning Manager at the 1,600MW Olkiluoto 3 nuclear reactor, explains why commissioning in the nuclear sector is not fundamentally different from other building services projects – but comes with significantly higher levels of scrutiny, regulation and responsibility.
Most engineers agree that the fundamental process of building services commissioning is the same regardless of the project type, whether it is a mixed-use office block or a healthcare facility. Yet many hesitate when confronted with a nuclear project. This hesitation often stems from the perception of increased complexity and stricter regulations in nuclear facilities.
Same process, higher stakes
Commissioning for a nuclear facility starts with the same basics. Engineers verify that building systems deliver the required design flows, ensure all equipment is fit for installation and commission each system to meet or exceed industry standards. From HVAC systems to electrical installations, the core steps remain familiar: reviewing design specifications, checking compliance with building regulations and logging all test results. These are the bread-and-butter tasks of any commissioning project.
For nuclear projects, every step carries added gravity. The Office for Nuclear Regulation (ONR) sets a high bar for safety, traceability and risk management. Its strict oversight makes the process robust and often extremely thorough. In effect, the same commissioning steps are followed, but the stakes are higher and each step faces much closer scrutiny.
Rigour, red tape and realities
One key difference in nuclear projects is regulatory compliance. The ONR recognises the importance of commissioning as the final check gate to verify and validate achievement of the design intent prior to entering service – so much so one of the Conditions is dedicated to Commissioning: LC21. Inspectors may review plans, challenge practices and even pause progress to ensure risks are kept ‘As Low As Reasonably Practicable’ (ALARP).
For commissioning engineers and managers, this often means additional protocols and documentation to demonstrate compliance. In practice, every pump closed-head test or damper adjustment is scrutinised, and maintaining a complete commissioning ‘audit trail’ is critically important.
Tighter performance tolerances can also set nuclear commissioning apart. Engineers familiar with standard tolerances from industry guidelines (British Standards, CIBSE, BSRIA, BESA, etc.) should note that some nuclear projects impose stricter limits. For example, an air-handling unit (AHU) set to 110% airflow might pass most standards, but a nuclear site could require it to operate in a narrow 100% to 102% range with no individual room exceeding 102%. These tight tolerances help ensure uniform environmental control across sensitive areas.
Similarly, building management system (BMS) controls may demand greater precision. Local control deadbands for heating and cooling are often minimised or removed entirely, allowing tighter temperature and humidity control in each room or zone.
Security and access protocols introduce another layer of requirements. Nuclear facilities have stringent entry controls, which can include:
- Strict prohibition of personal mobile phones and laptops on-site – this can be a direct issue as this is typically what engineers use for test records – via company automated test sheets/online portals
- Permanent escorts for site visitors or contractors – plan for what equipment and tools you need for the day ahead of time
- Restrictions and prohibition of personal or work vehicles on-site. As above, plan for what you need and schedule your day accordingly
- Thorough background checks for personnel – standard process for this type of facility
- Mandatory visitor badges or lanyards
- Tracking of personnel movements with RFID badges
Moreover, site restrictions and security restrictions also apply to new and existing plant and equipment and tools:
- Reluctance to use process plant and equipment with Bluetooth or other connectivity capabilities (pumps that are designed to be set up using a portable electronic device connected via Bluetooth tend to be a problem in nuclear)
- There is often a hesitance to use complex software systems in lieu of simple hardwired systems when it comes to safety systems, due to the difficulty to substantiate all failure modes of a complex software based systems
Because of these measures, engineers typically rely on handwritten forms to record commissioning activities. Paper logs might seem antiquated or tedious compared to automated digital systems, but they are often required for compliance. Some projects provide specialised secure devices (for example, tablets without SIM cards, cameras or voice recorders) to access commissioning portals and record test data. However, these devices and systems vary by project. Engineers should confirm in advance which devices are allowed and which methods are required to record test results.
Meeting ONR demands
In nuclear projects, commissioning must satisfy not only the client but also the ONR and other government bodies. Before any safety-critical system can be commissioned, the licence holder must demonstrate that ‘adequate arrangements’ are in place. This means having proactive, transparent and fully documented protocols. Documentation requirements are exhaustive: every step must be logged, often with independent review.
Such thorough requirements can initially feel overwhelming, but commissioning engineers mainly need to understand their specific role. In practice, most nuclear safety activities are managed by dedicated project teams that design, plan and execute each step. The commissioning team then integrates its tasks into this framework, rather than handling every aspect independently.
Meeting ONR demands typically involves thorough pre-commissioning preparations. For example, engineers may need to submit blank test sheets for each system well in advance, complete with design drawings, schematics, risk assessments and method statements. These forms can be reviewed for compliance weeks or months before actual commissioning begins. During commissioning, engineers often upload results daily into a project quality assurance/quality control (QA/QC) system.
Witnessing and demonstrating a commissioned system in a nuclear project is similar to working with multiple stakeholders in other sectors, but with a twist. In addition to client representatives, one or more witnesses might be from the ONR or an independent assessor. Organising these witness tests requires significant advance notice (often four to eight weeks), making scheduling and planning crucial.
Shared expertise, shared solutions
Despite the unique challenges, many core commissioning skills and practices transfer to the nuclear context. Teams experienced in healthcare, office or education projects can bring valuable expertise: clear communication, transparent documentation and methodical verification are essential in any setting. The main differences lie in context and collaboration. Security protocols are stricter, and working effectively requires close cooperation among diverse stakeholders (including regulators).
Ultimately, everyone in the project shares the same goal: systems that are installed and operated safely, with no surprises at handover.
A major lesson from nuclear commissioning is the importance of preparation. Constraints such as access protocols, systemisation (room by room versus system by system), communication restrictions and reporting obligations should be identified and planned for early, ideally during the design and construction phases. For instance, if permit requirements for each system are known and budgeted from the start, scheduling them becomes a routine task rather than a last-minute challenge.
Looking ahead, the upcoming roll-out of small modular reactors (SMR) underscores the need for early engagement. Involving regulatory and site project teams in the planning process can help streamline commissioning once construction is underway. By getting everyone aligned early, many potential obstacles can be addressed proactively.
Conclusion: Not too hot to handle
For seasoned commissioning engineers, nuclear commissioning remains fundamentally similar to other projects, but the stakes are higher. The core process stays the same, while controls are stricter and record-keeping is far more detailed. Teams that value precision and careful planning will find the challenge rewarding.
Successful building services commissioning requires diligence and adaptability. With thorough planning and respect for rigorous safety processes, commissioning in this environment can be manageable and highly rewarding!
