The role of a Quantitative Health Objective (QHO) in emergency preparedness and risk management of a severe nuclear accident

Nuclear emergency management is a shared responsibility in Canada. The Canadian Nuclear Safety Commission (CNSC) is responsible for overseeing licensee emergency preparedness and response, maintaining its own emergency preparedness program, as well as supporting provincial and federal partners. Various provisions including safety concepts, goals, objectives, principles, criteria, among other means, are in place to ensure that both the frequency and consequences of severe accidents are mitigated.

As the nuclear regulator, the CNSC can strengthen emergency management by describing how potential short- and long-term impacts of nuclear accidents are included in the regulatory framework, and by considering where appropriate improvements could be realized. In light of this, the CNSC has developed a new safety objective called a Quantitative Health Objective (QHO).

A QHO is a numerical value with an associated dose value that aims to describe the potential health impacts directly related to a nuclear accident with off-site releases. The QHO represents an increase of less than 0.5% in the lifetime probability of developing cancer in Canada, corresponding to approximately 100 mSv of dose (average dose received either acutely or chronically).

The QHO reflects a broader definition of health, which is aligned with international guidance. As such, the QHO value is set at level low enough where radiological health effects (i.e., cancer) are unlikely, but also set high enough to minimize the mental health and psychosocial consequences associated with potential long-term or permanent relocation. The purpose of this presentation will be to provide a holistic picture of CNSC’s existing safety concepts and to introduce the QHO, exploring its usage in facilitating regulatory decision-making, as a risk communication tool, and in informing emergency risk management in the unlikely event of a nuclear emergency. The CNSC is also seeking comments on an upcoming discussion paper and encourages feedback from all interested parties.