A 200-tonne safety vessel was successfully lowered into the reactor vault of the 500 MW Prototype Fast Breeder Reactor(FBR) in Kalpakkam in a "historic moment" for the country's indigenous nuclear programme.

The vessel--the first to be fabricated on site--for the country's first indigenous FBR at Kalpakkam marked a crucial step in achieving criticality in September 2010 and start generating cheap power six months later.

"It is a historic moment in the right direction" in developing nuclear power in the country, SK Jain, chairman of the Nuclear Power Corporation of India Limited (NPCIL), told reporters after witnessing the installation of the most crucial component in a PFBR in ideal weather conditions.

The scientists put in place the indigenously built vessel with precision into the reactor vault that houses the entire radioactive sodium coolant. The power from PFBRs could be sold for a price as low as around Rs 2.50 per unit, Jain said.

The vessel whose design has advanced features will prevent any "unlikely leakage" of the sodium from the vault and is filled with nitrogen for a tighter grip between the vessel and the vault, scientists at the Bharatiya Nabhikiya Vidyut Nigam Limited, a special purpose vehicle formed for the construction and commissioning of PFBRs, said.

"The safety vessel is the most crucial component in the PFBR and its successful installation is a march towards India reaching a technological maturity," Jain said of the significant milestone coming against the backdrop of a stalled Indo-US nuclear deal. The Indira Gandhi [Images] Centre for Atomic Research (IGCAR), Kalpakkam, had designed the vessel while the Indian industry had fabricated it despite "some early apprehensions," over the successful implementation of the design, Jain said.