The nuclear reactor of indigenous submarine, INS Arihant, has gone critical and was regarded by Indian Prime Minister Manmohan Singh a giant stride in the progress of India\'s native technological capabilities. The Prime Minister extended a congratulatory message to his people on Saturday following the nuclear propulsion reactor on board INS Arihant, India\'s first indigenous nuclear powered submarine, achieving criticality. When the atom-splitting reactor of a nuclear power plant is operating normally it is said to be \"critical\" or in a state of \"criticality,\" as in the context of nuclear power, \"criticality\" indicates that a reactor is operating safely. \"The development represents a giant stride in the progress of our indigenous technological capabilities,\" Singh said in a statement. He said the development was also testimony to the ability of Indian scientists, technologists and defense personnel to work together for mastering complex technologies in the service of country\'s security. While extending congratulations to all those associated with the milestone, Singh said Department of Atomic Energy, the Indian Navy and the Defense Research and Development Organization have played a critical role in developing the indigenous technology. By activating the atomic reactor on-board the indigenous nuclear submarine, India scientists have paved way for the vessel for its operational deployment in the Navy.