Powering cancer treatment and protecting workers

Bruce Power is at the forefront of medical isotope production, playing a critical role in supplying lutetium-177 (Lu-177), a cancer-fighting isotope. While the focus is often on the remarkable medical advancements enabled by these isotopes, behind the scenes, meticulous work is done to ensure the safety of the workers producing them.  

A recent study, led by Bruce Power’s research team in collaboration with Ontario Tech University and Ontario Power Generation (OPG), sheds light on how neutron radiation levels are monitored and managed in the Lu-177 production area. 

Lutetium-177: A powerful tool in cancer treatment 

Lutetium-177 is a medical isotope used in targeted radionuclide therapy, particularly for treating prostate cancer and neuroendocrine tumors. It delivers precise radiation to cancerous cells while minimizing damage to surrounding healthy tissue.  

Historically, commercial power reactors have not been used to produce short-lived medical isotopes such as Lu-177, which has a half-life of just 6.7 days.

However, in 2022, Bruce Power accomplished a groundbreaking milestone by obtaining regulatory approval from the Canadian Nuclear Safety Commission to operate an isotope production system within their commercial reactor. The ability to produce Lu-177 at large scales allows for widespread availability of this promising treatment, improving patient outcomes worldwide. 

Balancing worker safety and efficient production 

Unlike in research reactors, where isotope production is often done on a smaller scale, production within a commercial reactor comes with unique radiation protection challenges. 

When working in environments where radiation is present, safety is paramount. Bruce Power workers have strict dose limits to ensure their long-term health, meaning that if their cumulative radiation exposure exceeds certain thresholds, they must be replaced with another qualified worker.

An accurate understanding of the radiation levels is key: underestimating the dose could pose a safety risk, while overestimating the radiation exposure can impact efficiency, requiring additional personnel and logistical planning.  

“The isotope production system at Bruce Power is designed to work within the constraints of a commercial CANDU reactor,” explains Andrei Hanu, a senior scientist in dosimetry at Bruce Power and co-author of the study. “One of the challenges is that workers have to be in a radiation environment to produce this isotope. It’s not a dangerous environment by any means—but you do have to understand it.” 

To address this, researchers undertook a study to map the neutron radiation levels in the Lu-177 production area.  

Measuring neutron exposure in the workplace 

The main radiation concern for workers near the isotope production system comes from photoneutrons. These are neutrons that are ejected from an atomic nucleus when that nucleus absorbs a high-energy photon, like an X-ray or a gamma ray.  

Unlike charged particles, neutrons have no electric charge, which means they can penetrate deep into biological tissue before interacting. When the neutrons collide with atomic nuclei in the body, they can cause indirect ionization, leading to cellular and DNA damage.  

One of the primary heat transfer pumps, a source of neutron exposure to workers, and the shielding wall that is used to reduce neutron dose rates.

Photoneutrons are especially important in the context of Lu-177 production because they are produced when the reactor is at power. After they are produced, they quickly scatter in the heat transport water and the surrounding area. To reduce worker exposure to neutrons, a shielding wall was erected between the heat transport pumps and the isotope production area. The next step was to measure just how many neutrons to expect at various areas of the facility. 

“The closer you are to the primary heat transport pumps, the higher the neutron dose,” says Hanu. “Workers spend time in this area, operating the system, harvesting the lutetium, and packaging it for transport. We needed to understand the dose rates and apply any necessary corrections to optimize worker safety.” 

The team used a specialized tool called the Nested Neutron Spectrometer (NNS) to measure neutron radiation levels at different distances from the source. These measurements were compared with standard survey meters used for official dosimetry on-site. The key finding? The standard instruments tended to overestimate the radiation dose behind the shielding wall, where workers are standing when working at the isotope production system. 

“It’s good to be conservative, but being overly conservative means using up dose limits faster than necessary,” Hanu says. “We identified a correction factor that allows us to more accurately measure the dose, meaning we can produce lutetium-177 in larger quantities without increasing the number of workers required.” 

Leading the way in radiation safety 

The insights from this study not only optimize safety protocols at Bruce Power but can also provide a reference for other nuclear facilities looking to improve their dosimetry practices. 

“One of the things we realized is that while we talk a lot about isotope production at a high level, there’s less discussion about what’s happening on the ground—the people doing the work and the environment they operate in,” Hanu notes. “This study provides a glimpse into that environment.” 

While peer-reviewed research is not traditionally common in the nuclear industry’s operational practices, Bruce Power and its partners have embraced it as a way to validate and improve safety standards. 

“We’ve started to introduce peer review into more regulatory discussions,” Hanu says. “It strengthens our case when we implement new safety measures, ensuring transparency and credibility.” 

The findings from this study are already being applied at Bruce Power, ensuring that workers remain safe while maintaining the efficiency of Lu-177 production. As demand for medical isotopes grows, research like this will continue to be essential in balancing production with best-in-class radiation protection standards. 

At the Nuclear Innovation Institute and funded by Bruce Power, the Environment program within the Bruce Power Nexus Research Centre is also committed to research on radiation and human health. By studying the impacts of radiation and improving measurement techniques, this work supports the broader goal of ensuring that nuclear technologies are developed with safety and sustainability in mind.  

For those interested in the technical details, the full study is available here. 

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Dr. Stephanie Keating is Director, Environment, part of the Bruce Power Nexus Research Centre.