Overcoming the Challenges Encountered in Revising the ZED-2 Reactor Safety Analysis

G. Bruce Wilkin, Senior ZED-2 Physicist Krishna R. Kumar Atomic Energy of Canada Limited, Chalk River Laboratories Station 68, Chalk River, Ontario, Canada, K0J 1J0 Phone: 613-584-3311, ext 44259 Fax: 613-584-8198 [email protected]

The ZED-2 (Zero Energy Deuterium) Reactor is a low-power critical facility owned and operated by Atomic Energy of Canada Limited and is located at the Chalk River Laboratories in Ontario, Canada. It is used to perform physics experiments in support of the CANDU® and Advanced CANDU Reactor (ACR®) programs. The reactor core is a large cylindrical vessel in which experimenters hang reactor fuel rods vertically and then pump heavy water moderator into the vessel to make the reactor critical. The design is very versatile: it can accommodate mixed fuel types in a variable number of fuel rods each with or without CANDU-type or ACR-type channels; channel coolants can be light or heavy water, or air, and can vary from channel to channel; lattices can be square or hexagonal with continuously variable lattice pitch; and some CANDU-type channels can be heated. Other items can also be placed in the core such as solid neutron absorbers, self-powered and foil-activation neutron flux detectors, and soluble neutron poisons in the heavy water. However, this versatility resulted in some challenges during the recent revision of the safety analysis. The main goal was to select an appropriate set of controlled parameters that provides a robust safety case without compromising the facility’s versatility while at the same time adhering to modern reactor licensing practice. How this goal was achieved is the subject of this paper.

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