The Chemical Engineering and Materials Testing Building (B250) is a 13,500‑square‑foot multi-purpose laboratory constructed in three phases between 1950 and 1953. Historically, it supported research involving solutions with significant radioisotope activity and housed numerous laboratories, fume hoods, glove boxes, and hot cells. CNL began actively decommissioning this complex facility in 2019.
Chemical Engineering and Materials Testing building (B250)
After years of planning and detailed fieldwork, the project team has reached a major milestone. The hot cells within B250 have now been fully remediated—an essential step toward eventual demolition of the building.
“Because of their structure and purpose, decommissioning hot cells is among the most complex and high-risk activities in nuclear decommissioning,” said James Miller, CNL’s Vice-President of Decommissioning and Waste Management. “High radiation fields, contamination embedded within structural materials, and limited access and visibility present significant challenges.”
Hot cells are heavily shielded, lead-lined rooms that allow nuclear workers to safely conduct experiments involving high‑radiation materials. Operators use externally mounted robotic manipulator arms to handle materials that emit significant radiation or contain elevated contamination levels. Controlled negative air pressure, maintained by a complex ventilation system, ensures safe atmospheric conditions inside and outside the cells.
Operators use the manipulator arms to perform work inside the hot cells
Designed for nuclear fuel experiments, the hot cells feature two-storey interior heights, walls made of poured concrete, and front walls reinforced with interlocking lead bricks. Four manipulator arms and thick, square glass windows enabled operators to perform delicate work while maintaining visibility.
During their operational life, the hot cells supported a range of activities, including dissolving irradiated fuel for isotopic analysis and, more recently, testing irradiated pressure tube specimens. They were shut down in 2019 and remained in a safe shutdown state until CNL began comprehensive decommissioning in 2020.
Two sets of manipulator arms were carefully withdrawn from the hot cell ports in mid-2022. The radiologically contaminated ends were encased in plastic throughout the entire removal process, ensuring contamination control. The manipulators were refurbished for future use at Chalk River Laboratories
Weighing approximately 376 kg each, the 20-centimetre-thick square glass windows of the hot cells were safely removed in 2023. The windows are being safely stored for potential reuse. Workers sealed the openings into the hot cells with a poly cover glass.
Figure 1: Workers completed concrete scabbling, a crucial step to reduce the radiological footprint of the hot cells by removing surface layers that may have been contaminated with radioactive particles
Figure 2: Workers dismantled the stainless-steel door liners and the floor liner and installed protective covering on the surfaces
Workers safely removed over 22,000 kg of interlocking lead bricks embedded in the front walls of the hot cells.
Between 2020 and 2025, CNL safely removed approximately 30,000 kilograms of low-level waste, 26,000 kilograms of lead waste, and 4,000 kilograms of equipment and material waste—achieving a substantial reduction in radiological dose during the remediation of the hot cells.
“This is an incredible milestone for our team,” said Project Director Josh Carolan. “Over the past five years, they’ve tackled this technically demanding work with relentless drive and determination. Seeing this scope completed safely—and significantly reducing hazards in the facility—is a major win. This achievement speaks to the expertise and dedication of our talented D&ER team, and we’re energized to bring this same momentum into the next phases of the project.”
The team is now focused on decommissioning the building’s ventilation systems, fume hoods, and other complex service systems as they prepare for full facility demolition.
Chalk River Laboratories has long been a Canadian leader in nuclear medicine, research, and technological innovation. Today, as Canada’s national nuclear science and technology organization, CNL is transforming the Chalk River site into a modern, state-of-the-art campus that will support advanced nuclear research and contribute to the global nuclear renaissance. As part of this transformation—and in keeping with CNL’s mission to restore and protect the environment—legacy infrastructure such as B250 is being carefully decommissioned to enable site revitalization while honouring the facility’s significant role in Canada’s scientific history.
