Nuclear Power

Over the next three years, researchers from the Faculty of Applied Science & Engineering will lead projects that could shift how and where nuclear power is used

Small modular reactors (SMRs) represent a new paradigm that could change how and where nuclear power is used to meet our energy needs – and research from the ��Ƶ's Faculty of Applied Science and Engineering could help point the way forward.

Professors Greg Jamieson in the department of the department of mechanical and industrial engineering, Oh-Sung Kwon in the department of civil and mineral engineering and Assistant Professor Yu Zou in the department of materials science and engineering, recently received funding from the NSERC-CNSC Small Modular Reactors Research Grant Initiative.

Over the next three years, each of them will be leading a project that seeks to improve the design of SMR technology, from the materials used in manufacturing to the ways in which they are operated.

“Canada has a long history in the nuclear space, and a lot of experience building and operating nuclear power plants,” says Jamieson, who holds the Clarice Chalmers Chair of Engineering Design and is co-director of the Cognitive Engineering Laboratory.

“So far, these have all been large facilities designed to meet the needs of major population centres. But we also have many communities and natural resources that are located hundreds or thousands of kilometres away from these big cities. With a geography like that, SMRs start to make a lot of sense.”

While there are currently no SMRs in commercial operation, several companies and organizations around the world are working on pilot facilities to demonstrate proof of concept. For example, Ontario Power Generation has begun site preparation activities for an SMR project at its existing Darlington site in the Greater Toronto Area.

These plants would be small – producing less than 300 megawatts of power, as compared to two or three times that amount from Canada’s existing plants – and built with pre-fabricated components that could be shipped to remote locations and assembled on site.

Since they operate without producing any greenhouse gas emissions, SMRs are seen as a potentially cleaner replacement for the diesel generators that are currently the industrial standard in remote locations – and electricity isn’t all they produce.

“Like all nuclear plants, SMRs generate heat, which produces the steam that is used to run the turbines,” Jamieson says.

“But you could also use this heat in other ways – for example, district heating, or for industrial processes such as hydrogen generation or the early stages of oil sands processing. There are a lot of possibilities.”

(L-R) Greg Jamieson, Oh-Sung Kwon and Yu Zou are all leading new research projects that look at various aspects of small modular reactors (supplied photos)

As a human factors researcher, Jamieson will be focusing on how the plant’s operators will monitor and control the technology. His project builds on some of his previous experience with the nuclear industry, but also represents a contrast to current industry standards.

“Large nuclear plants have operating procedures oriented around a single crew of operators monitoring a single reactor,” Jamieson says.

“But small modular designs open up new possibilities – such as a single crew monitoring multiple reactors – which raises questions about how you distribute human attention.”

Many proposed SMR systems also include what is known as “inherently safe design.” This means that systems are designed to passively shut down if operating conditions deviate from normal.

“Inherently safe design is a good idea, but we want to understand if there are situations where operators, possibly as a result of misinterpreting data, might mistakenly override those systems,” Jamieson says.

“This is something that was a factor in previous nuclear accidents, such as at the Three Mile Island facility in the U.S.”

In addition to differences in their potential modes of operation, SMRs might also require the use of different materials than current reactors – those that can stand up to harsher working environments. This aspect is the focus of Zou’s research project.

“In today’s reactors, water is usually used as the cooling fluid,” says Zou, principal investigator of the Laboratory for Extreme Mechanics & Additive Manufacturing.

“But many SMR designs use molten salts as the coolant, which can be more corrosive than water. Other designs use water, but they operate at much higher temperatures and pressures than traditional reactors. This means that the pipes, heat exchangers and other components need to be able to stand up to much harsher conditions.”

Zou and his team are working with collaborators at Natural Resources Canada and Dalhousie University to study how various materials might react to these tougher conditions. These might include nickel or iron-based alloys in common use today, but they will also consider new materials – such as high-entropy alloys – that haven’t been used for these applications before.

Components for SMRs could be made via additive manufacturing, also known as 3D printing. This method, which Zou’s team has expertise in, can significantly reduce the time from the development to the production.

The team will conduct physical experiments in the lab to test the mechanical properties of these materials, then feed the results into a set of computer simulations. Those simulations, in turn, will inform the development of future lab experiments in an iterative approach.

“Our goal is to build up a database that could be consulted by the designers of future SMRs,” Zou says. “It would also help regulators, as the lack of data about material behaviour under the relevant conditions makes it hard to assess safety.”

For their part, Kwon and his team are looking at how SMRs might react to seismic activity.

“Seismic analysis involves looking at how vibrations caused by seismic waves will affect a structure, including whether or not there are resonances that would amplify the effects of these vibrations,” Kwon says.

“In the case of a nuclear plant, we are interested not only in how vibrations might affect the building itself, but also the equipment within the building.”

One of the factors that Kwon and his team are focusing on is the properties of the soil underneath the reactor and containment buildings.

“Today’s plants undergo a lengthy site selection process that ensures they are seated on stiff, compacted soil that will not liquify in the case of a seismic event,” he says.

“But SMRs are designed to be shipped to remote locations, where there is less choice about where to situate them, so they may have to be designed to work on softer soils. In Canada’s North in particular, they might be seated on permafrost. If climate change causes that permafrost to melt, it could affect the seismic resilience of the facility.”

While SMRs are still a long way from widespread application, research from projects such as these can inform their development and keep Canada at the forefront of innovation in the sector.

U of T researchers help design the future of nuclear waste management

Christopher.Sorensen — Wed, 15 Feb 2023 16:27:55 +0000

U of T researchers help design the future of nuclear waste management

Christopher.Sorensen Wed, 02/15/2023 - 11:27

Cutline

Flex-time PhD researcher Grant Minor, a senior engineer at the Nuclear Waste Management Organization, holds a CANDU fuel bundle replica (photo courtesy of NWMO)

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Researchers at the ��Ƶ are collaborating with the Nuclear Waste Management Organization (NWMO) to optimize the design and layout of a new plant for processing used nuclear fuel packages.

By leveraging a technique known as multidisciplinary design optimization, the project aims to further enhance Canada’s long-term management of used nuclear fuel.

“The Used Fuel Packaging Plant will be the first of its kind in Canada,” says Grant Minor, a senior engineer at NWMO and a flex-time PhD candidate in the lab of Kamran Behdinan, a professor in the department of mechanical and industrial engineering in the Faculty of Applied Science & Engineering. “It is a huge infrastructure investment for Canada.”

At present, 19 Canadian deuterium uranium (CANDU) reactors provide about 15 per cent of Canada’s electricity. The proportion is even higher in Ontario, which is home to three out of Canada’s four operating nuclear plants and currently sources 56 per cent of its electricity from nuclear power.

Canada’s nuclear waste management plan, called Adaptive Phased Management, is being implemented by the NWMO, a not-for-profit organization formed in 2002 through the federal government’s Nuclear Fuel Waste Act. The organization is responsible for designing and implementing Canada’s plan for the safe long-term management.

CANDU reactors are fuelled by a reaction using natural uranium, which is moderated by deuterium, a constituent of heavy water. The fuel goes into pressure tubes that are held by a large cylindrical vessel called the calandria, which holds approximately 5,000 fuel bundles when it is operating, depending on reactor configuration. Each CANDU fuel bundle — around the size of a fireplace log — contains about 20 kilograms of uranium and can power 100 homes for a year. These bundles stay in the reactor for 15 to 18 months.

Once the used fuel is removed from the reactor, it first goes into wet storage where it sits for seven to 10 years before being moved to dry storage. There are about 3.2 million used CANDU nuclear fuel bundles in Canada, which are distributed between the nuclear reactor sites.

The Adaptive Phased Management plan – funded by Ontario Power Generation, Atomic Energy of Canada Limited, Hydro-Québec and NB Power – requires used fuel to be contained and isolated in a deep geological repository. But before that can happen, the used nuclear fuel needs to be received from nuclear reactor sites, inspected and repackaged into used fuel containers. This will happen at the Used Fuel Packaging Plant – a key surface facility at the repository site.

Minor’s PhD research is focused on finding an optimal design and layout for this facility, where employees will control every aspect of the process using remote handling techniques, robotics and automated systems.

“The key operation in the Used Fuel Packaging Plant is the handling of highly radioactive nuclear material, so it will have to operate very reliably,” says Minor. “Protection of the environment, public safety and worker safety is and will be NWMO’s highest priority during design, development, construction, commissioning and future operations and maintenance.

“I saw an opportunity to apply multidisciplinary design optimization to a nuclear facility. Professor Behdinan, a leading expert in [multidisciplinary design optimization], has many years of experience in this technique.” 

Professor Kamran Behdinan holds the Natural Sciences and Engineering Research Council of Canada Chair in Multidisciplinary Engineering Design (photo by Ray Cheah)

Multidisciplinary design optimization is a methodology that is used to create systems where multiple engineering disciplines are integrated, such as mechanical, electrical, controls and automation, manufacturing, process, and reliability engineering. It provides a holistic approach to solving multidisciplinary design problems.

Over the past few decades, multidisciplinary design optimization has traditionally been used in the aerospace and aviation industry and has proven crucial in the structural design of aircraft and their many parts. More recently, Behdinan has applied the approach to automotive, advanced manufacturing and biomedical designs as well.

“This method is very effective when you are dealing with a very complex system,” says Behdinan, who holds the Natural Sciences and Engineering Research Council of Canada Chair in Multidisciplinary Engineering Design.

“It is a structured way of interacting between these engineering disciplines – not only for optimization, but to see how design variables within these disciplines interact and affect each other. This allows us to analyze and assess the parts that will be integrated into the overall design of a big system like an aircraft.”

In the case of an aircraft, where every gram of weight matters for fuel efficiency and to maximize the payload – passengers, baggage and cargo – engineers use MDO to evaluate each of their design decisions.

By exploring the mathematical optimization equations used by different engineering disciplines simultaneously, researchers like Behdinan and Minor can see how they relate to each other to create safe and reliable designs that operate as efficiently as possible.

“NWMO is accountable to the public for the safe and reliable design and operation of this Used Fuel Packaging Plant,” says Minor.

“The plant has to process about 120,000 used fuel bundles each year. It has to operate for 250 days a year, while being reliable and cost effective. The facility design must also comply with Canadian Nuclear Safety Commission regulations, other applicable laws, regulations, codes and standards, and engineering best practices.” 

Minor has developed an initial framework for a simplified study of the processes that will take place in the Used Fuel Packaging Plant, looking at three disciplines: radiation analysis, cost analysis and reliability analysis.

For example, there will be remotely controlled machinery in the packaging plant to close the used fuel containers and that machinery will have to operate sequentially to perform the processes on each container. The team is looking at the best way to split the equipment in the processing cells – from setups where all the equipment is in one line to every single piece of equipment in its own isolated enclosure.

The design targets include minimization of the risks associated with management of the used nuclear fuel in the plant – for example, reduction of unnecessary fuel handling steps and unnecessary transfer of used fuel between environments would be a focus.

Minor and Behdinan will be collaborating to create new optimization techniques for nuclear fuel disposal facilities that aim to increase safety, improve operations and relability and cut costs.

“We haven’t seen the application of [multidisciplinary design optimization] in the nuclear waste management field,” says Behdinan.

“But there are so many disciplines involved in the overall design of the nuclear waste management system, and this creates many design variables. We want to optimize them because we want to get the best out of the plant. Optimization is always about better solutions.”