The 60 MWt WR-1 was designed and built by Canadian General Electric, and first achieved criticality in 1965. The reactor was built at a cost of $14.5 Million CDN. The original purpose of the unit was as a test reactor for a proposed organic-cooled CANDU power reactor. When that program ceased in 1972, WR-1 was used for irradiation, experimentation and heating the WNRE site. WR-1 was shut down for the last time in 1985, was defuelled, and is now undergoing decommissioning.
The reactor had vertical fuel channels, was cooled by an organic liquid (an oil) rather than water. The neutrons were moderated by cool heavy water in a large calandria vessel surrounding the fuel channels. The reactor did not use conventional control rods, but relied on control of the level of the heavy water moderator to adjust the power output. The reactor could be shut down quickly (SCRAM) by rapid dumping of the moderator. The organic liquid, called OS-84, that was selected as a coolant in WR-1 is a mixture of terphenyls treated catalytically with hydrogen to produce 40 percent saturated hydrocarbons. The terphenyls are petrochemical derivatives that were readily available and were already in use as heat transfer media. Using an organic coolant meant the reactor was run at low operating pressures, and had very low corrosion rates. The low corrosion rates allowed it to use metallic uranium and uranium carbide fuels, which corrode in water. The metallic fuel conducts heat better, so that a higher power core could be used in the same space.
The organic coolant also meant the reactor could be run at high temperatures, with outlet temperatures up to 425°C.
In November 1978 there was a major loss of coolant accident . 2,739 liters of coolant oil leaked, most of it into the Winnipeg River. The repair took several weeks for workers to complete. There was another leak in 1980 of 680 liters said Robert Pollock, the environmental officer. 
WR1 was shut down for the last time ostensibly for economic reasons, on May 17, 1985 although it was the youngest of AECL's large research reactors. The reactor is currently in an interim decommissioning stage, defuelled and largely disassembled. The site will be returned to Green Field status at the end of decommissioning.
- "Manitoba's forgotten nuclear accident" Dave Taylor. March 24, 2011
- "Nuclear leak into river Negligable " Winnipeg Free Press. Ritchie Gage July 30, 1981
- The Canadian Nuclear FAQ
- AECL - Atomic Energy of Canada Limited
- Atomic Energy of Canada Limited
- Whiteshell Reactor No. 1
- WR-1, UNIQUE AMONG RESEARCH REACTORS
- Canadian Nuclear Association