Overview of CNSC Approaches for Assessment and Management of Fish Mortality Resulting from the Operation of Canadian Nuclear Generating Stations

Harm to fish due to interactions with Canadian nuclear generating stations (NGS) cooling water systems is a regulatory issue and public concern, including direct mortality of adults and juveniles (impingement  IM ), larvae and eggs (entrainment  E ) from intake cooling water withdrawals, and localized warming of potential fish spawning habitat due to thermal discharge.  

The CNSC approach consists of conducting risk assessment of fish loss at operating NGS based on Environmental Assessment (EA) predictions, results of industry monitoring programs, specific research studies, and support from other federal regulatory agencies. Regulatory risk management actions set site-specific targets on NGS operators to implement mitigation measures.  The targets for a case study site were derived from US EPA criteria. The implementation of mitigation measures has resulted in a significant reduction in fish mortality due to IM&E. 

The potential risks of thermal plume on fish and fish spawning habitat are assessed with evidence from EA predictions, established thermal threshold standards, thermal plume modeling and results of industry temperature monitoring. Regulatory risk management actions consist of review of mitigation measures and options analyses, studies of thermal plume effects, fish populations and spawning habitat. Implementation of mitigation measures has reduced thermal risk to fish reproduction. Work is ongoing to validate the assessment of risk to sensitive fish species.