Modular power in the nuclear industry

There are a multitude of roles for mobile power generation in the nuclear sector in both short and long-term scenarios, argues Marcus Saul

Mobile power is an essential player during all phases of a nuclear plant’s lifecycle

Credit: Aggreko

Changing attitudes towards nuclear power plants (NPPs) are continuing to have an impact on the global utilities industry and evolving energy mix.

Nearly 70 reactors are currently under construction. However, countries like Sweden, Switzerland and Germany are continuing to phase out nuclear generation to an extent that more plants have closed than opened in recent years.

While the debate continues, the construction, operation and decommissioning of nuclear power plants (NPPs), including processes that all have their own specific power needs, is ongoing.

One key requirement at all stages of the NPP lifecycle is a reliable, efficient and flexible energy source, which modular power achieves easily. Whether it’s filling the gap during planned or unplanned maintenance, load testing a newly commissioned turbine or substation, or providing ancillary power for heat exchangers and cooling technology, for example, the adoption of mobile power generation in the short and long term can mitigate the risk of disruption to end users and contribute to a more efficient operation.

Involving energy specialists early in the process is vital to avoid delays and disruptions during later stages. However, the true demands of the project are often not realized until a full review has been conducted. The flexibility of modular power enables generation technology to be tailored to these very specific needs, even if they exceed initial expectations.

While energy demands continue to grow and more fossil fuel plants and NPPs close, either as a result of changing political and environmental agendas or because they’ve reached a certain age, this widening generation gap needs to be filled. According to the Nuclear Energy Institute, one nuclear reactor will need to be built every year to meet rapidly growing energy demands in the US alone.

Mobile power plays an important role before and during the construction process, supporting feasibility studies in often remote locations and allowing both equipment and workers to function safely at full capacity.

Often, an ‘island mode’ approach to energy is adopted, which sees generation distributed across the NPP site, creating a more efficient source and reducing the overall cost of power production, as well as minimizing any environmental risks. Providers have a responsibility to deliver reliable and effective power, but a big part of their role is allowing operators or sub-contractors to meet goals and deadlines, which saves costs in the long run.

Similarly, during the decommissioning process, adopting modular power can allow operators to come off-grid earlier and, as a result, save significant costs. Operators are charged for access to the grid based on their overall capacity rather than actual demand; however, once they have decommissioned, say, three or four sections (and reduced capacity), they can adopt mobile power for the remaining processes.

Modular generation equipment can be rented on a short-term basis to avoid the need to invest hundreds of thousands when costs are already high. For example, if a plant has access to power from the grid but no transformer, it can hire one for six months or longer if required. Renting rather than buying reduces the up-front costs and mitigates the risk of expensive maintenance fees.

NPPs aren’t designed to handle additional operational ‘parasitic power’ needs. An increase in capacity demand that hasn’t been accounted for, such as elements of the construction process and maintenance requirements aside from planned shutdowns, can cause significant strain on a plant’s resources.

Small, localized generators offer a unique benefit in this case as they address the parasitic power, but also avoid the need to lay comprehensive cables on-site and the associated health and safety risks. The flexibility and mobility of modular power makes it a great fit, as generators can be easily moved to an on-site location when needed.

‘Refeeding’ power from the grid is often required where NPPs need to conduct short-circuit testing of protective devices for first use and on a regular basis to ensure a smooth working process. Not only does this create considerable expense, but it also depends on free grid capacity, which doesn’t particularly allow for flexible operation.

Regular, planned maintenance of key processes in an NPP operation, whether this is during or outside its annual shutdown, reduces its ability to contribute to the grid, and so any downtime needs to be kept to a minimum. As well as adopting technology that maintains a high level of efficiency and productivity, reliability is central to mitigating the risk of prolonging this downtime.

Load bank testing for backup power equipment

Credit: Aggreko

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Regular load testing of NPP equipment can help anticipate and prevent disruptions

Credit: Aggreko

The type of maintenance and upgrades required can depend on the age and characteristics of the NPP. During the annual shutdown, for operators to access the reactor area significant cooling needs to take place, which creates high parasitic power demands.

For example, Aggreko was required to rapidly cool a steam turbine to allow operator access. Rather than directly applying cool air to the turbine, which might have cracked or damaged it, we built a surrounding marquee and cooled the air around it in a process that took three or four days and required reliable on-site power to ensure the process was efficient and productive.

Another example of the importance of a continuous energy supply is during the treatment (cleaning) of transformer oil, which is necessary every two to four years. The cleaning process requires a reliable source of power to supply pumps and heat oil to around 75oC. Due to time restraints and the specific requirements of the process, an uninterruptible power source is essential, so an unreliable grid can be a concern. Backing this up with additional on-site generators ensures there would be no disruptions should it fail. By making the NPP independent of the grid, it avoids the risks associated with it being compromised.

Another component of planning ahead to anticipate and prevent disruptions is the regular load testing of equipment throughout a NPP, whether this has been recently commissioned or replaced. For one customer, we tested an auxiliary stand-by turbine and a new Rolls Royce turbine after replacement, as well as the performance and stamina before and after maintenance on all other parts of the turbine installation, using our standard load bank fleet. By incorporating specific technology, the system allowed for a more accurate result by capturing voltage, current and frequency as generated.

As utilities continue to operate under increased pressure to fill energy gaps while reducing end-user costs and environmental impact, improving reliability, productivity and efficiency of a plant is key. This applies to all processes throughout the lifecycle.

Changes in the nuclear sector in particular mean that meeting objectives is ever more important, whether that’s during the construction, operational or decommissioning stages. As the energy agenda continues to evolve, it’s clear that mobile power remains an essential player in achieving these both in the short and long term.

Marcus Saul is Aggreko Business Development Manager for Marine Renewables & Nuclear

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