It generated radionuclides used to treat or diagnose over 20 million people in 80 countries every year (and, to a lesser extent, other isotopes used for non-medical purposes).
It was the test bed for Atomic Energy of Canada Limited to develop fuels and materials for the CANDU reactor.
[1] It was built as the successor to the NRX reactor at the Atomic Energy Project of the National Research Council of Canada at Chalk River Laboratories.
[2] NRU started self-sustained operation (or went "critical") on November 3, 1957, a decade after the NRX, and was ten times more powerful.
The fire was extinguished, but a sizeable quantity of radioactive combustion products had contaminated the interior of the reactor building and, to a lesser degree, an area of the surrounding laboratory site.
Care was taken to ensure no one was exposed to dangerous levels of radiation and staff involved in clean-up were monitored over the following decades.
[6] A corporal named Bjarnie Hannibal Paulson who was at the clean up developed unusual skin cancers and received a disability pension.
In 1994, Bertram Brockhouse was awarded the Nobel Prize in Physics, for his pioneering work carried out in the NRX and NRU reactors in the 1950s.
[10] In 1996, AECL informed the Canadian Nuclear Safety Commission (then known as the Atomic Energy Control Board) that operation of the NRU reactor would not continue beyond December 31, 2005.
The technique of Neutron Reflectometry is capable of providing unique information on materials in the nanometre length scale.
This shutdown was voluntarily extended when AECL decided to install seismically qualified emergency power systems (EPS) to two of the reactor's cooling pumps (in addition to the AC and DC backup power systems already in place), as required as part of its August 2006 operating license extension by the Canadian Nuclear Safety Commission (CNSC).
On December 11, 2007, the House of Commons of Canada, acting on what the government described as "independent expert" advice, passed emergency legislation authorizing the restarting of the NRU reactor with one of the two seismic connections complete (one pump being sufficient to cool the core), and authorizing the reactor's operation for 120 days without CNSC approval.
Prime Minister Stephen Harper accused the "Liberal-appointed" CNSC for this shutdown which "jeopardized the health and safety of tens of thousands of Canadians".
Others viewed the actions and priorities of the Prime Minister and government in terms of protecting the eventual sale of AECL to private investors.
With the construction of the earlier NRX reactor, it was possible for the first time to commercially manufacture isotopes that were not commonly found in nature.
The NRU reactor continued the legacy of NRX and until it was decommissioned March 31, 2018 produced more medical isotopes than any facility in the world.
The fundamental knowledge gained from NRU enabled the development of the CANDU reactor, and is the foundation for the Canadian nuclear industry.