Decommissioning of Research Reactors - Canadian Nuclear Laboratories

Abstract

Canadian Nuclear Laboratories (CNL), manages Canada's nuclear legacy liabilities on behalf of Atomic Energy of Canada Limited (AECL) and the Government of Canada. Operating under a Government Owned - Contractor Operated (GOCO) model, CNL has accelerated its environmental clean-up mission, the largest and most complex decommissioning and environmental remediation program of work in the country.

CNL is currently executing clean-up work at six different sites across Canada. The largest site and the main campus of CNL is in Chalk River, Ontario and is home to four experimental reactors in various stages of the decommissioning lifecycle.

The National Research eXperimental (NRX) reactor at the Chalk River site was Canada's first large-scale research reactor and commenced operation in 1947. The NRX operated for over four decades, enabling research and medical isotope production and also playing an important role in developing CANDU reactor technology. The NRX was shut down in 1992 when placed in a safe shutdown state. In 2019 the Canadian Nuclear Safety Commission (CNSC) approved CNL's Detailed Decommissioning Plan (DDP), enabling the first phase of decommissioning activities to commence.

The National Research Universal (NRU) reactor, also at the Chalk River site, went critical in 1957. The reactor was an improved design of the NRX and ten times more powerful. During several decades of operation, NRU served the science and medical communities by producing medical isotopes, neutron beam research and nuclear power research and development. NRU was permanently shutdown in November 2018 and is currently within a phase of Post Operational Clean-Out (POCO) activities. Within this phase, materials and equipment that supported facility operations are characterized and safely disposed of. The team is also developing strategies for delineating the scope and defining stages for developing and submitting DDP's.

The Multipurpose Applied Physics Lattice Experiment (MAPLE) was a dedicated isotope-production facility built by AECL and MDS Nordion. The facility contains two identical reactors (MAPLE 1 & MAPLE 2), as well as isotope-processing facilities designed to produce a large portion of the world's medical isotopes, especially molybdenum-99, medical cobalt-60, xenon-133, iodine-131 and iodine-125. MAPLE 1 went critical for the first time in 2000. However, it was never fully commissioned, and the project was terminated in 2008. CNL has started POCO work in the buildings, and decommissioning activities which begin in the near term with a focus on characterization in support of the development of the DDP to ensure its safe decommissioning. This presentation highlights CNL's experience and strategies with respect to decommissioning research reactors.