Addressing a press conference, Navy Chief Admiral D K Joshi also said the issue of imposition of air defence regulations by China over East China Sea was under its "close examination".
"The nuclear propulsion plant of Arihant had attained criticality on August 10. There are a series of activities that it will be put through before it is brought to 200 per cent loading. After loading, there will be series of physics experiments which are essentially rehearing for emergencies that could occur while its loading.
INS Arihant is the first of the Arihant class submarines of the Indian Navy and it has been developed in collaboration between the DRDO and public and private sector industries with the help of Russian scientists.
The Navy chief said the harbour trials of the vessel were complete.
Asked whether the submarine would be without much potent weaponry, Joshi said, "The boat will not be toothless. It will have what it needs to have.