Layers of Protection When Adapting Modern Technologies to Enable Remote Handling of Radioactive Materials

Abstract Canadian Nuclear Laboratories (CNL) is planning to decommission the Waste Management Area (WMA) standpipe and bunker structures at the Whiteshell Laboratories (WL) site located in Pinawa, Manitoba. The decommissioning activities will include retrieving historical radioactive waste from standpipes and bunkers. The waste stored in standpipes and bunkers ranges in activity from Low-Level Waste (LLW) to Intermediate-Level Waste (ILW). The standpipes and bunkers include radioactive solid waste stored in containers of unknown integrity and radioactive liquid waste, a byproduct of water ingress into the waste storage structures. The unknown integrity of waste containers presents a high risk of worker exposure to radiological hazards. In recent years, CNL has conducted extensive research developing automated systems for handling radioactive waste during decommissioning activities. Adopting modern technologies and tooling to reduce human interaction with radiological material minimizes worker exposure. The design concept of these systems is based on the operational experiences and lessons learned (internal and external) from the WL Hot Cell Facility. When implementing modern technologies and tooling to handle radioactive materials remotely, it is important to implement defence-in-depth in the system design (multiple layers of protection) to ensure the safety of workers, the public, and the environment. These layers of protection act as barriers to prevent a Postulated Initiating Event (PIE) from progressing into a severe accident. The more independent the layers are, the more robust the defence. Layers of protection in the design of a system include inherently safe design, control and monitoring of the system, alarms requiring operator intervention or critical alarms with safety interlock to prevent an accident, passive or active protection to mitigate the consequence of the hazardous event, and emergency response. The system designs were conservative, with safety margins between normal operations and abnormal conditions. This paper outlines some of the recent efforts of CNL in radioactive waste management, particularly in designing systems for radioactive waste handling activities involving historic solid waste. These activities include retrieving, characterization, sorting, segregation, and repackaging of radioactive waste. A high-level hazard identification methodology is used to identify hazards and PIEs associated with the design and operation of these remotely operated waste retrieval and handling systems. These hazards and PIEs are assessed and compared with the non-automated retrieval method to demonstrate that remotely operated waste retrieval and handling systems reduce the risk of radiological exposure to workers and protect the environment.