Sketch from The Canadian Association Of Mechanical Engineers of what the Tunney’s Pasture nuclear reactor looked like.

(This information comes from an earlier OttawaRewind post written in 2014. You can read the full article here.)

Recently the National Capital Commission revealed plans to make Tunney’s Pasture the site of the new Civic Hospital campus. The current Tunney’s federal government complex is a mix of mid-century and 1970s office buildings and towers, a boring collection of grey concrete. Something that is of more excitement however, is the fact that the area was once home to a nuclear reactor.


Atomic Energy of Canada Limited Buildings located on the Tunney’s Pature Complex that housed the SLOWPOKE nuclear reactor 1971-84.

The year was 1970 and the Atomic Energy Canada Limited, or AECL, was placing a SLOWPOKE-2 class nuclear reactor at Tunney’s Pasture. According to The Canadian Society For Mechanical Engineers documents, this nuclear reactor was installed in Tunney’s Pasture at 20 Goldenrod Avenue. It was constructed as a commercial testing reactor to determine its feasibility. This nuclear reactor was in full operation after it reached critical mass in 1971 until 1984 when it was then moved to another test site located in Kanata, later decommissioned in 1992.


Aerial image showing the proximity of the Remic Bunker to the Tunney’s Pasture Nuclear Reactor site.

The reactor, nicknamed SLOWPOKE, (an acronym for Safe LOW-POwer Kritical Experiment) which used 93% enriched uranium. The reactor core sits in a pool of regular light-water, 2.5 m diameter by 18 feet deep, which provided cooling. The reactor built at Tunney’s Pasture achieved “Critical Mass” or the point at which a nuclear reaction is self-sustaining on May 1 1971 and continued operating until 1984.

The oddly shaped circular concrete bunker that remains on the shore of the Ottawa River directly opposite the old nuclear reactor site was built at the same time as the reactor in 1969-70. It was built to facilitate the increased “cooling” needs of Tunney’s Pasture, one of them you could speculate being the addition of a small nuclear reactor.


The mysterious concrete bunker at Remic Rapids has perplexed many a passerby.

The pumping station bunker and pipeline were finished in 1970 and the reactor began operating a year later. Whether or not the bunker pipeline bringing cooling water to Tunney’s Pasture was directly related to the addition of a nuclear reactor remains speculation but it is interesting to note the proximity and similar timeline of both projects.

You can follow the intake cooling water pipe by tracing a path that follows a series of manhole covers that lead from the river to the Tunney’s Pasture site.

coling trench

The buildings where the nuclear reactor once existed have since been demolished, and it is currently an empty gravel parking lot, and possibly soon to be part of the new Civic Hospital plans recently announced.


Andrew King, November 2016. 



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