Kalpakkam (Tamil Nadu), Aug 2 - INS Arihant, India's first indigenously designed and built nuclear powered submarine launched a week ago, is energised by a power pack that was developed from a land-based prototype version, a nuclear scientist revealed here Sunday.

The scientists' team was given the mandate to develop a land-based prototype power pack for a submarine and development and construction of a nuclear steam generating system for the sea-going version,

There is a sea of difference between designing a nuclear power pack to propel a submarine and a land-based atomic power station, Srikumar Banerjee, director of the Bhabha Atomic Research Centre (BARC) and member of the Atomic Energy Commission (AEC), told reporters here.

The 82.5 MW nuclear reactor for submarine has been designed here by PRP Centre - PRP originally stood for Plutonium Reprocessing Project - under the BARC.

The PRP Centre is located inside the Kalpakkam nuclear enclave, 45 km from Chennai, housing various atomic energy related entities.

'While a land-based atomic power plant gets support from the grid and others, a nuclear power pack in a submarine does not have such fallback systems,' Banerjee said.

He said the major challenges were miniaturisation of the land-based plant to fit into the confined space of a submarine and also making it lightweight but strong enough to endure the shock due to depth discharge.

'The reactor while withstanding the pitch and roll of a submarine should also be capable of accelerating and decelerating at a quick pace - unlike a land-based power plant which would ramp up speed in a gradual manner,' he added.

To generate power, the steam turbine should be operated at 3,000 revolutions per minute (rpm) whereas the nuclear submarine propulsion turbine will be operated at variable speed of 0 to 4,000 rpms.