46°3′15.53″N 77°21′52.12″W / 46.0543139°N 77.3644778°W The National Research Universal (NRU) reactor was a 135 MW nuclear research reactor built in the Chalk River Laboratories, Ontario, one of Canada’s national science facilities. It was a multipurpose science facility that served three main roles. 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 neutron source for the NRC Canadian Neutron Beam Centre: a materials research centre that grew from the Nobel Prize-winning work of Bertram Brockhouse. It was the test bed for Atomic Energy of Canada Limited to develop fuels and materials for the CANDU reactor. At the time of its retirement on March 31, 2018, it was the world's oldest operating nuclear reactor.