Inside every nuclear reactor is an invisible orchestra of particles at work. Neutrons collide with heavy atoms, splitting them apart in a chain reaction that powers cities, produces medical isotopes, and drives nuclear innovation. To keep that reaction steady—and to better understand the impact of the reaction, scientists are honing in on sensitive detectors that measure the flow of neutrons.
Canadian Nuclear Laboratories (CNL) began exploring this research back in 2022 to better understand how these tiny detectors can offer real-time vibration monitoring technology that has the potential to transform the way reactors here in Canada, and across the globe, are maintained and monitored, enhancing safety and reliability of the nuclear industry.
That said, the concept of real-time monitoring isn’t new, the idea was conceptualized in the 1970s. This golden era of nuclear science saw the CANDU™ reactor become commercially scaled – lighting up Ontario with reactors in Pickering and Kincardine, the ZED-2 reactor in its research-prime at Chalk River Laboratories (CRL), and the groundwork for modern reactor diagnostics and online monitoring in its founding days. And since that time, the nuclear industry has been leveraging conventional vibration monitoring; a process completed during hot functional testing, before any fission had even taken place.
What is hot functional Testing? Hot functional testing is part of reactor commissioning, when coolant systems are brought to operating temperature and pressure before startup, allowing engineers to check for vibration and thermal performance—without any nuclear reaction taking place.
Today, researchers like Dr. Salim El Bouzidi, P.Eng., and the team at the Dynamics, Measurements, and Analytics Section of the Fluids Engineering Branch at CNL, with funding from the Atomic Energy of Canada Limited (AECL) Federal Nuclear Science & Technology Work Plan, are looking beyond this conventional way of monitoring, diving into in-reactor experiments that will enhance neutron noise analysis techniques for vibration monitoring.
Dr. El Bouzidi explains, “we want to bring a new monitoring capacity to our reactor fleets, not just at the outset of a reactor’s life, but as it ages and evolves. A reactor will change, for example the fuel channels grow in length and spacers migrate over time while a reactor is in operation; they are truly a living thing if you think about it.”
By conducting this research and exploring new ways to monitor reactors, the team at CNL will create a new generation of technology ready to survive the harsh elements of a reactor for the long-term. Inside the reactor, powerful pumps and coolant flows create subtle vibrations that can reveal early signs of wear or mechanical stress. Understanding these vibrations is essential for detecting potential failures before they happen, but conventional vibration sensors aren’t equipped to survive for long periods of time in the intense radiation and heat of a reactor core. This leaves operators without a way to continuously monitor a reactor’s internal “heartbeat” during operation. The team’s research aims to change that—exploring new ways to listen to and interpret the natural signals inside a reactor, offering a path toward earlier detection of issues, safer operation, and longer equipment life.
To put their idea to the test, the team designed and carried out a first-of-its-kind experiment inside the ZED-2 research reactor at CRL. Selected for its rare combination of flexibility and scale— ZED-2 is low enough in power for researchers to safely enter and reconfigure the vessel, yet large enough to mimic the complex neutron flux patterns found in commercial reactors. The team installed a custom metal plate and miniature shaker assembly directly onto one of the reactor’s fuel channels to generate precise, controlled vibrations under real operating conditions. Using the reactor’s ultra-sensitive neutron detectors, they measured how those mechanical vibrations translated into tiny fluctuations in the neutron field—essentially capturing the reactor’s response in real time. The work brought together specialists in mechanical vibrations, reactor physics, and instrumentation, demonstrating the level of precision and interdisciplinary collaboration needed to conduct such a delicate experiment in an active reactor environment.
“This experiment brought together experts from across disciplines to do something that had never been attempted at this scale,” added Dr. El Bouzidi. “By creating and measuring these controlled vibrations inside the ZED-2, we were able to watch how the reactor responds—offering a new window into the health and behaviour of a reactor at work.”
From these tests, the team confirmed that the neutron detectors already built into reactors can do more than track the fission process—they can also act as remarkably sensitive vibration sensors. By analyzing subtle patterns, or “neutron noise,” within the detector signals, researchers can trace how mechanical disturbances ripple through the reactor system. This breakthrough led to the development of a transfer function—a kind of mathematical map that shows how a known vibration in one part of the reactor translates into a measurable neutron response elsewhere. Together, these findings point toward a new way to monitor the physical health of a reactor continuously, without adding new instruments or exposing sensitive equipment to extreme conditions.
“What we’ve shown is that the detectors we already rely on to control the reactor can also tell us how it’s moving and responding, adds Dr. Bhaskar Sur, Senior Scientist with the Advanced Fuels & Reactor Physics team. “By understanding how a vibration propagates through the neutron field inside the reactor – what we call the transfer function—we can start to read the reactor’s natural signals as indicators of its mechanical state.”
The results from ZED-2 are more than proof of concept—they mark an important step toward a new era of reactor monitoring. By defining how vibrations appear in neutron signals, this research lays the groundwork for “reverse-engineering” vibration events in operating power reactors. In the future, if an unusual neutron noise pattern is detected, engineers could use these findings to trace it back to a specific source—pinpointing which component is moving, how much, and why.
Beyond the scientific achievement though, the implications for reactor safety and performance are significant. Continuous monitoring through existing detectors could allow operators to identify emerging issues long before they lead to wear, damage, or costly downtime. This means earlier detection, fewer unplanned outages, and an improved understanding of how reactors evolve over time—ultimately strengthening safety margins and extending the lifespan of key components.
“Our goal is to turn every reactor’s existing instrumentation into a kind of built-in diagnostic system,” says Sur. “With this research, we’re getting closer to a future where reactors can tell us, in real time, when something doesn’t sound quite right.”
With the experiment complete, the team is now turning its focus to modeling and real-world application. Using the data gathered, CNL’s team is building detailed computational models to predict how similar vibration patterns would appear in full-scale power reactors. These models will help translate laboratory findings into tools that utilities can use to interpret neutron noise signals from their own plants. Further collaborations with industry partners are planned to validate and refine the approach, bringing this research one step closer to implementation in Canada’s CANDU™ fleet and other reactor designs around the world.
Beyond its immediate technical benefits, this work reinforces Canada’s reputation as a leader in nuclear innovation and safety. From the development of the CANDU™ reactor to ongoing advances in reactor monitoring and maintenance, Canadian researchers continue to push the boundaries of what’s possible in nuclear science. By pioneering new ways to “listen” to reactors and understand their behavior, CNL’s team is helping to shape the next generation of intelligent, data-driven nuclear systems—making operations safer, more efficient, and more sustainable for decades to come. The research team looks forward to continuing this work into 2027, with additional reactors testing planned for the year ahead.
“Canada has always been at the forefront of nuclear technology,” shares Dr. El Bouzidi. “This project carries that legacy forward using the tools we already have in smarter ways to make reactors safer and more reliable for the future.”
“In the end, this work is about learning to listen,” explains Sur. “Through the subtle rhythm of neutron noise, CNL scientists are uncovering the signals that have always been there—turning invisible data into meaningful insight.”
By listening to the heartbeat of our reactors, this research opens the door to a safer, smarter, and more responsive nuclear future—one where every vibration tells a story, and every signal helps safeguard the systems that power our world.
This research is funded by Atomic Energy of Canada Limited’s (AECL) Federal Nuclear Science & Technology (FNST) Work Plan, which connects federal organizations, departments, and agencies to the nuclear science expertise and facilities we have at Chalk River Laboratories.
Under the FNST Work Plan, researchers at Canadian Nuclear Laboratories (CNL) carry out projects to support the Canadian government’s core responsibilities and priorities across the areas of health, safety and security, energy, and the environment.
