Apsara, India's first atomic reactor, will be upgraded with an indigenously developed core making it possible to keep it off limits to international inspectors once the civil nuclear deal with the US is through.

In its current form, the 1 MW reactor with a French core, would have invited International Atomic Energy Agency safeguards once the nuclear deal was signed, permitting inspectors on the Bhabha Atomic Research Centre's Mumbai campus, where Apsara is located.

BARC scientists said the highly-enriched uranium-fuelled French core would be replaced with an indigenous one, which will use low-enriched uranium as fuel.

The refurbished Apsara will operate at a higher power of 2 MW, enhancing the maximum available thermal neutron flux enabling it to produce radio-isotopes used to treat diseases, grow better quality vegetables and preserve food.

"With enhanced neutron flux, the radio-isotopes that are currently produced in Cirus reactor can be produced at Apsara as and when needed," they said.

The Cirus reactor, which was built with Canadian assistance, will be shut down once the Indo-US civil nuclear deal is clinched.

The Cirus was refurbished last year and could operate for another five years.

The isotope technology has helped the country grow mutant varieties of onions and potatoes, and give pulses a longer shelf-life. The technology has also made possible the use of irradiation to eliminate micro-organisms from mango and other fruits so that they could be exported.

The reactor, which turned critical on August 4, 1956 is also used for research purposes by universities and educational institutions countrywide.

The refurbished Apsara will provide enhanced facilities for studies related to material irradiation, shielding studies and neutron detector testing.

The reactor core structure of the upgraded Apsara, will be housed in the existing pool block.

Imported from France, the 'swimming pool' type reactor, which has the core immersed in light water, was given the name of Apsara by the then prime minister Jawaharlal Nehru who dedicated the research facility to the nation on January 20, 1957.

Scientists recollect that Nehru had likened the blue Cerenkov-radiation of the reactor core to the beauty of the apsaras -- the dancers in the court of Lord Indra.

The core of the upgraded reactor would be mounted on a grid plate having 64 postions arranged in 8x8 square array as against the 49 positions available at present.