In November 2007, Atomic Energy of Canada Limited (AECL), acting upon the advice of the CNSC that it was in violation of its site operating licence for Chalk River Laboratories (CRL), voluntarily chose to extend a routine shutdown of the NRU nuclear reactor pending completion of safety upgrades. The issue involved two of NRU's eight coolant pumps which, upon completion of several safety upgrades, would be credited as being able to withstand severe external hazards such as a major earthquake. Before and after the awarding of CRL's October 2006 operating licence to CRL, AECL reported that these two pumps had not yet been connected to a seismically-qualified backup power supply (separate from NRU's normal backup power supplies); however, in November 2007, this fact was recognized by the CNSC as evidence of a licence violation, leading AECL to extend the NRU's maintenance shutdown until the seismically-qualified backup power connection could be completed. These two pumps are the last line of defence in the event of an earthquake or other primary power system failure in order to continue to provide cooling to the reactor fuel and prevent a meltdown of the reactor core.