ZEEP Reactor

In the Fall of 1945, a small low-power (1 watt) prototype reactor named Zero Energy Experimental Pile or ZEEP was developed at the National Research Council of Canada’s newly constructed Chalk River Laboratories in Ontario. It was built with the purpose to help Canadian researchers better understand the physics and material problems of heavy water moderated nuclear reactions.  This marked a major milestone in Canada’s participation in nuclear research, becoming only the second country in the world, other than the United States, to use a reactor to control the nuclear fission process.

The ZEEP reactor was built primarily as a simplified prototype for the larger, more complex National Research Experimental reactor (NRX) that the NRC was planning to build at the Chalk River site. In later years, ZEEP was used for important research on the behaviour of neutrons in reactors and to provide data for the design of other reactors.

ZEEP
Close-up of ZEEP reactor core.
ZEEP
View of ZEEP prior to upgrading in 1956.
ZEEP
ZEEP in February 1954 with NRX and NRU (under construction in the background).