"If any of you are under the impression that it made contact with water with an actual reactor fitted inside its hull you are mistaken," the scientist told IANS.
The scientist echoes a report in Defence Professionals Daily, a German online publication, which says Arihant "currently is little more than a floating hull" without nuclear propulsion or weapons systems. The scientist, who did not want to be named as he was not authorised to speak to the media, was clarifying media reports implying that Arihant is propelled by nuclear power and that India has become the sixth nation to operate nuclear subs.
"I think the media did not correctly report what was told to them by the Bhabha Atomic Research Centre (BARC), or the officials deliberately did not want to be explicit beyond a point," he said.
The reports had said that Arihant is fitted with a nuclear power plant that is a replica of the secretly built 80-MW reactor at Kalpakkam near Chennai that was shown to the media Aug 2.
Building this land-based power plant -- for demonstration and training the naval personnel -- is no doubt a creditable achievement of BARC considering that "making the fuel tubes were a real challenge", the source said.
Besides, he said, it has proved India's ability to produce enriched uranium necessary for designing small enough reactors that can fit inside the submarine.
The higher the enrichment, the smaller the size of the reactor and, according to the source, the Indian design uses 15 to 20 percent enrichment. The commercial Tarapur nuclear power plant, on the other hand, uses about three percent enriched imported uranium.
"However, to say a duplicate of this land-based reactor is already inside Arihant and working is not correct," he said. He pointed out that the official statement that Arihant's reactor will take at least a year to go critical is another way of saying there is no reactor core right now inside the hull since making a reactor critical only takes days, not months.
The scientist said several steps are involved after achieving criticality and the reactor must be fully tested before it is sent to the sea. Integrating the ballistic or cruise missiles will take time and a few more years are needed to prove the platform and its systems, first in harbour, then at sea and lastly, under water, at increasing depths.
"Therefore, announcement of India's entry into the nuclear submarine club with a half-baked product without the nuclear reactor -- let alone the weapons systems -- is perhaps premature," the scientist said.
"After all the project had remained under wraps for over 20 years and another few years would not have made a difference."
In contrast, although India was the fifth country to set up a nuclear reprocessing plant in 1964 even before Germany and China, the late Homi Bhabha, father of Indian atomic energy programme, announced the achievement only after it was commissioned and started to produce plutonium, he pointed out.
Nataraja Sarma, former BARC physicist and co-author of "Nuclear Power in India: A Critical History", says it makes safety sense to first check out the seaworthiness of the basic submarine without the reactor core and then assemble the reactor.
"Once big components like reactor vessel, heat exchangers and the lead shielding (for protecting crew from radiation) are transferred to the submarine before closing its shell, the remaining smaller components including the fuel assembly can be introduced later to complete the construction," he said.
Arihant is far from reaching operational status but the coconut breaking that released it from the Visakhapatnam dry dock was nevertheless an important day for India, the scientists say.
"What is significant about the launch is that now India has publicly acknowledged its quest to acquire a nuclear submarine and has shown it has the ability to design and build such a platform," Uday Bhaskar, a former naval commander and now head of the National Maritime Foundation, is quoted as saying in the journal.