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Improving the CNSC Technical Reactor Safety Group for the EOC

Abstract of the technical presentation presented at:
3rd International CNS Technical Meeting on Fire Safety and Emergency Preparedness for the Nuclear Industry
October 27–30, 2019
Ottawa, Ontario

Prepared by:
Sam Gyepi-Garbrah
Canadian Nuclear Safety Commission


During a reactor nuclear emergency, the Reactor Safety Group (RSG), as part of the Canadian Nuclear Safety Commission (CNSC) Emergency Operations Center (EOC), performs an independent assessment of the reactor state that includes a diagnosis of the current status of the radioactive release barriers and a prognosis for the status of these barriers in the future. If the prognosis assessment predicts that there is a potential for radioactive release to the environment, the RSG predicts the release characteristics. This independent CNSC assessment of the on-site conditions and potential off-site consequences is a critical input for the federal government response, as well as for other stakeholders.

From an accident diagnosis/prognosis perspective, CANDU reactors can be considered to have four main barriers to prevent/reduce the release of fission products into the environment. The RSG uses CANDU 4D/4P methodology, which presents a road map for performing a systematic diagnosis and prognosis process during a reactor nuclear emergency. The RSG uses the 4D/4P grid in assessing the status of the fission product barriers, to characterize the actual and/or possible release characteristics.

To support the CANDU 4D/4P methodology, the RSG uses a suite of tools developed in-house to promptly assess the fission barriers status and timing of possible release(s) into the environment. This toolset includes the Source Term Database for Canadian Nuclear Power Plants (NPPs), the Technical EOC Assessment Tool, the Accident Handbook, the Computational Hydrogen Assessment Tool (CHAT), the Reactor Assessment Product (RAP), and fast-running tools (VETA and URI). The RSG also performs MAAP-CANDU simulations, as required, to support the accident diagnosis and prognosis. The current tool for 4D/4P analysis is in the form of Microsoft Excel spreadsheets, which are manually filled by RSG personnel and used to track plant status information based on the data sent by the licensee and to obtain the information needed to produce the RAP.

Currently, RSG is working in developing a new automated tool that can be used to increase the efficiency of processing the data received from the plant and used as an input into the 4D/4P grid. In this presentation, an update of the automation of the CANDU 4D/4P accident assessment will be discussed in addition to its linkages with the in-house toolsets and the RAP tool that would be shared with the IAEA during a reactor nuclear emergency.

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