Chalk River Information Bulletin

ZED-2 Heavy Water Loss

Chalk River, 2016 May 05 – The following information bulletin is in accordance with Canadian Nuclear Laboratories (CNL) ongoing commitment to voluntary public disclosure of events related to the Chalk River Laboratories (CRL).

The quarterly inventory of the ZED-2 Research reactor’s  heavy water determined a shortfall of approximately 300 kilograms.  While the facility does experience routine loss of heavy water through evaporation, this amount was higher than expected.  The heavy water used in ZED-2 does not contain fission products and has a minimal tritium content.

The source of the event has been linked to a small portion of ZED-2 heavy water inventory overflowing one of its storage tanks, which occurred on 2016 January 29.  At that time, heavy water overflowed the storage tank and flowed into the heavy water system ventilation ducts.  The 300 kilogram loss of heavy water occurred over the three-month period since the initiating event through evaporation of the heavy water trapped in the system’s ventilation ducting. 

On discovery of the loss of heavy water, CNL reported to the Canadian Nuclear Safety Commission on April 26.  This event is currently under further investigation. 

CNL confirms that there is no threat to workers, the public, the environment or nuclear safety related to this event. 



Patrick Quinn
Director, Corporate Communications
CNL, 1-866-886-2325 

About ZED-2 

CNL’s Zero Energy Deuterium (ZED-2) reactor is a versatile tank type, heavy water moderated low power research reactor that achieved first criticality in 1960. The variable pitch of the reactor and ease of access to the core, along with associated counting facilities, make the reactor an ideal tool for performing reactor physics measurements and fuel studies. The clean, extremely low activity, moderator means that neutronic equipment calibrated in the reactor can be returned to the customer within a day of irradiation.  

To learn more visit: ZED-2 Research reactor.