Small Modular Reactors and the future of nuclear power
17 February 2019
Thomas Fink, General Manager of the Nuclear Safety Division at SCHOTT Electronic Packaging, looks at the emergence of modular reactors and the intriguing benefits they present for safe, flexible power generation. High-quality component development and integration as well as ambitious development projects in China are pushing the way forward for a new generation of nuclear power that could prove to be a low-carbon emissions answer for the future.
According to the World Nuclear Association, there has been a ‘revival of interest in small and simpler units for generating electricity from nuclear power.’ The physical footprints of traditional, large nuclear power plants – coupled with substantial construction and operation costs – have presented challenges to the energy generation sector, while fossil fuel-based energy sources pose significant concerns in regards to pollution and overall environmental impact.
The combination of these factors has led to the rapid development and deployment of modular nuclear reactors.
Modular reactors are a new-generation breed of nuclear reactors that provide economic affordability and flexible power generation. A common type of modular reactor found today is the small modular reactor (SMR), defined by the International Atomic Energy Agency (IAEA) as a unit of 300 MWe or less. Modular reactors and SMRs are suitable for a wide range of users and applications and utilize high-quality components that deliver enhanced safety performance.
Most modular reactors and SMRs are amply-equipped to replace the power generation capabilities of “traditional” power plants, such as coal-fired units. Thanks to their efficient designs and the ability for components to be factory produced, additional modular reactor units can be added to a site incrementally should a capacity increase be required.
Examples of potential applications include remote sites in the far reaches of the world, such as maritime shipping locations and military installations, where a single SMR could power an entire community. More recent development projects, particularly in China, are slated to bring larger modular reactors to the forefront as a commercial-scale power generation option to meet growing energy demands.
Small Modular Reactors offer substantial benefits
SMRs are an attractive option for power generation in a wide variety of instances, particularly in remote or unusual environments. Factory-made designs are efficient and cost-effective as they enable offsite manufacturing in a controlled environment. SMR production is faster than that of larger scale reactors and due to their compact size, they are easier to place on site. Factory production capability also means high quality control measures can be implemented that were not previously possible with largely on-site based construction methods. In financial metrics, the quick construction track and small modules create the opportunity for a fast recuperation on initial investments in SMRs.
The application flexibility provided by SMRs is exceptional. They can be used in areas where conventional nuclear power plants cannot typically be constructed, such as remote locations lacking the network infrastructure for a large plant, sites without access to bodies of water for cooling, and areas requiring a small supplementary power source to assist the existing power grid, among others. Their modular design allows additional units to be added as and when required. For example, if a small town was to rely on one SMR for its energy supply and that town was to grow as the area develops, additional units can easily be added to the existing infrastructure to meet these demands. SMRs also have the potential to be used in both civil and military settings. A small reactor could be fitted to power a submarine or surface vessel, giving it an almost infinite range.
In order to deliver high-output power generation in a small package, SMRs must operate at a higher temperature than typical nuclear reactors. To create the highest possible level of safety, engineers have taken steps to address any points of concern in the SMR operating environment. An example of this comes through bolstering the strength and durability of the electrical penetration assemblies (EPAs) that supply power and data transmission into the reactor’s first loop. Rather than using polymer-sealed assemblies that cannot withstand high temperatures, SMR engineers have made glass-to-metal sealed EPAs a standard in SMRs. Glass-sealed assemblies can withstand temperatures of several hundred degrees Celsius without issue and handle extreme pressure levels. This makes them ideal for supporting reliable day-to-day SMR operation while also providing maximum protection to maintain infrastructure integrity and mitigate any potential severe accident scenario.
In addition to bolstering safety, glass-sealed EPAs offer a factor of simplicity that is well-aligned with the overall benefits of SMR construction and usage. Advanced EPAs on the market today utilize strong connectors that can join 140 electric compactors together in a single step. It is simply plugged in, securely locked, and then ready for operation. Supplying individual wires to a junction box can take hours of strenuous work. By choosing a connector-based plug and play option, the process can be completely streamlined to prevent any slowdowns or missteps stemming from an otherwise complicated installation.
Modular reactor projects and advanced components deliver intrigue for the future
While small modular reactors offer terrific promise and intrigue for efficient and flexible nuclear power generation, new projects in China are aiming to ambitiously utilize modular technology on an even larger scale as they look towards a low-carbon emissions future.
A natural progression can be seen in the work of the ongoing partnership between Chinergy Co., Ltd, and Jiamusi Electric Machine Co., Ltd. The companies cooperated to develop and construct the Shidaowan twin high temperature reactor (HTR) in the Shandong province of China. The reactor is slated to be connected to the power grid and go online this year.
The current Shidaowan HTR, as with all high-temperature gas-cooled reactors, fell under the classification of being a small modular reactor because of its power generation capability of less than 300MWe: the twin reactors at Shidaowan will power a single steam turbine capable of producing 210 MWe. However, the benchmark has already been set higher. Chinergy and Jiamusi Electric Machine are working towards a new undertaking known as the HTR-PM600 project. Here, the modular reactor is getting added muscle and will emerge as an intriguing option for large-scale commercial power generation. A total of six identical modules will be coupled to a single steam turbine.
While the HTR-PM600 project is in the early stages, Chinergy has begun preliminary development work at a site in Wan’an, Fujin province. Location selection for a second HTR-PM600 unit is ongoing and has a list of potential sites that includes Sanmen in Zhejiang, Xiapu in Fujian, and Bai'an in Guangdong. The first units are planned to be built in pairs for a total output of 1200MWe and completion is currently scheduled for 2022-2023.
A common thread between the projects is the use of glass-to-metal sealed electrical penetration assemblies in the primary loop of the modular reactor infrastructure for information and control signal transmission. Supplied by glass specialist SCHOTT AG from southern Germany for both projects, the successful integration of glass-to-metal sealed EPAs in the Shidaowan project paved the way for planned repeated integration in the HTR-PM600 units.
As with all modular reactors, the Shidaowan twin-reactor HTR facility and HTR-PM600 units differ from regular reactors because their components are manufactured or replicated in-plant for fast replacement and greater long-term cost-efficiency. SCHOTT provided design recommendations and technical consultation as they worked in close collaboration with the teams at Chinergy and Jiamusi Electric Machine. The result was the achievement of a tailored solution that meets the unique installation requirements and can withstand the high temperature, high pressure environment of the HTR’s primary loop.
The incorporation of glass-to-metal sealed EPAs in the primary loop of these new HTR units is a promising step forward for shaping the future of next generation nuclear power. Glass-sealed EPAs already represent a superior solution for “traditional” nuclear power plants, as they maintain uncompromised seal integrity for a qualified lifetime of 60 years. In comparison, polymer-based seals are organic and age naturally, resulting in degradation and the need for multiple replacements over the lifetime of the reactor. This presents both a cost burden and potential safety risk. In HTR applications, glass-sealed EPAs are the only viable feedthrough option for the primary loop as polymer cannot withstand the high temperature and pressure of the working environment.
As advancements continue to be made in modular reactors across a wide range of applications, the combination of unique and innovative assembly and operation of SMRs along with the superior safety and performance of glass-to-metal sealed EPAs represents a viable option for the advancement of nuclear power in the years to come.
With carbon emissions mitigation becoming a topic of greater importance with each passing day, utilities and governments cannot afford to brush aside nuclear power as an energy option of the past. The nuclear industry worldwide will be watching as advanced modular reactor projects in China aim to take significant steps towards delivering commercial-scale power generation with modern nuclear technology.
About the author
Thomas Fink is General Manager, Nuclear Safety Division of SCHOTT. He is a recognized authority for glass-to-metal sealing technology, especially with respect to its use in nuclear applications, and has written a number of published works about nuclear safety and learnings from the Fukushima accident. His paper “Post-Fukushima Technology Enhancements to Improve Safety Margins” has been presented at expert conferences internationally, including events hosted by the American Nuclear Society and the China Nuclear Energy Association.
He also is an Advisory Board Member of the Ohio State University Nuclear Engineering Program in the United States.
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