Key Takeaways
- Advanced reactor designs are typically smaller than their traditional counterparts, creating opportunities for prefabrication, preassembly, and modularization (PPM).
- PPM can significantly lower construction costs and timelines but requires greater coordination between actors working in parallel.
- With their smaller size, advanced reactors can use proven and innovative techniques in concrete setting, welding, and excavation that were unavailable to past reactors.
- Some designs may require advanced construction techniques due to smaller site areas and limited storage and assembly space.
Advanced nuclear reactor designs are quickly advancing towards first-of-a-kind (FOAK) builds, with many expected in the next ten years.
As these technologies are translated into reality, there is the possibility of looming unforeseeable challenges – but EPRI is already seeking solutions. While FOAK builds are unprecedented by definition, they will still be implemented using tried and tested techniques that reduce uncertainties and risks.
EPRI researches specific existing and emerging construction techniques and technologies that can be used to make new nuclear construction easier, more economical, and faster. These efficiencies aim to help the energy industry reach net-zero emissions by 2050.
One recent EPRI white paper – the Overview of Advanced Construction Techniques for Optimizing New Nuclear Projects – provides an introduction to several proven construction techniques that will help ensure success for prospective owner-operators of advanced nuclear plants.
In This Article
What’s Different About Advanced Nuclear Reactors?
At EPRI, we define advanced nuclear reactors as fission reactors including non-water cooled designs, light water small modular reactors (SMRs), and microreactors.
Although these reactor designs vary significantly, they have some key similarities and differences compared to large-scale, traditional reactors.
Radiation and Temperature Considerations
Both advanced and traditional reactors create and sustain fission chain reactions, creating high temperatures and free neutrons, which must be considered in all aspects of construction and operation. Some design features, such as thick concrete walls for containment buildings, are required for neutron shielding rather than structural integrity.
Traditional reactors used large concrete and steel structures. Advanced reactors, on the other hand, are often smaller and with simpler safety systems, reducing their need for large-scale thick-walled concrete buildings.
Prefabrication, Preassembly, and Modularization (PPM)
Advanced reactors have greater opportunities for prefabrication, preassembly, and modularization (PPM). This means the reactor design can be divided into parts, constructed in parallel by different contractors, and then shipped to the site for significantly simpler assembly.
PPM is one of the most appealing advantages of small modular reactors (SMRs), resolving one of the nuclear energy industry’s biggest headaches: construction complexity leading to over-time and over-budget projects. SMRs hope to use PPM to easily reach cost reductions through widespread deployment, simplifying nuclear builds to assembly-line-like precision and speed.
However, PPM requires a significant amount of coordination. With many actors producing reactor parts independently of each other, any changes or errors in design are distributed and become much more difficult to correct. Timing deliveries and installation can be challenging as well, depending on the interrelated installation of various modules.
Advanced Construction Techniques to Streamline Nuclear Projects
While advanced reactors and SMRs, in particular, are being implemented for the first time, their construction methods aren’t all new. For years, EPRI has been researching relevant technologies and construction techniques – both from within and outside the nuclear energy industry – to help advanced reactors smoothly transition into reality.
Digital Twins & 3D Modeling
One such tool is a digital twin. A digital twin is a digital representation of a physical asset, with a level of connectivity between the two. A 3D model of a power plant that is updated based on photos of a construction site, or of sensors distributed throughout the constructed plant, are two examples of digital twins. Updated in real-time, these could help solve coordination challenges associated with PPM.
If any design changes or adjustments are necessary, the digital twin can be adjusted, reworked, and quickly redistributed. This will allow everyone involved in the construction to adjust much faster to any changes and have a clear path forward.
Concrete Structures
While traditional reactors were typically built at a scale with all concrete batched, poured, and set on-site, reduced concrete requirements for advanced reactors create new opportunities to accelerate and simplify construction.
For example, advanced reactors can benefit from using precast concrete, which can be shipped to the site and installed. Different types of connections using bolts, plates, and complementary geometries can significantly reduce the amount of concrete that needs to be set on site.
Many advanced reactors are smaller and have more inherent safety features, reducing their site size. This greatly limits storage space, and just-in-time shipping of precast concrete units may be beneficial. However, owner-operators may wish to limit reliance on just-in-time shipping, as it can leave them vulnerable to transportation or fabrication delays.
Welding Techniques
New nuclear builds can benefit from hot-wire gas tungsten arc welding (GTAW). Compared to traditional GTAW, this technique uses an automated wire-feed system to increase deposition rates and weld energies without increasing the required craft skills. Hot-wire GTAW is expected to save up to 20% in welding costs and increase weld strength.
Other techniques such as friction-stir welding, laser beam welding, and electron beam welding could be useful for specific areas in advanced reactor construction. Automation of these techniques could be very effective at improving deposition rates and reducing defects, especially in narrow areas.
Excavation Methods
With many advanced reactor designs requiring below-grade construction for enhanced safety, EPRI is examining the economics of different excavation techniques to improve processes and shorten timelines.
Shaft sinking is an appealing option, borrowed from tunnel boring. A vertical shaft is excavated and the borehole, up to 12 meters in diameter, can be lined with concrete. While this technique can be expensive, its speed and effectiveness are expected to significantly outweigh its costs.
Precision blasting is another option, though it has limited use cases and requires highly trained personnel. An alternative to blasting is foam expansion, which injects a rapidly expanding gas to break up large rock formations, making excavation easier.
This article is one of many developed by EPRI’s Advanced Nuclear Technology program. Stay up-to-date on the newest nuclear technologies by becoming a member today.